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Bits and Pieces

7 May

Manchester XPAG Project – Progress May 2016

Some of you may remember that in 2013 we sponsored a group of students at the School of Mechanical, Aerospace and Civil Engineering, University of Manchester (MACE) to run tests on a XPAG engine to try to understand why classic cars had running problems with modern fuels. Unfortunately, time constraints and problems prevented the students from finding anything useful.

The good news is that after lengthy negotiations and with the help of MACE and Dave Haughton, we were able to access the facility and spend one week running the tests ourselves. All made possible by additional funding from the MGCC.

The first task was to improve the instrumentation that was fitted to the engine, this included installing thermocouples on the carburettors, fuel pump and cylinder head as well as vacuum gauges, etc. In all, 24 different parameters were measured for each of the 180 tests using a range of different fuels. A lot of data to be analysed.

Thanks must also go to the Anglo American Oil Company Ltd who supplied additional test fuels. With technical advice and a grant from the FBHVC we have identified the causes of the problems we all see with modern fuel. Furthermore, the tests have not only dismissed some of the myths, they have provided valuable information on ways we can mitigate the problems of running classic cars on modern fuel.

At the moment, I am testing one of the possible solutions on my 1949 MG TC to assess its effectiveness before writing an article.

One of the most demanding challenges faced by my car is the Ipswich to Felixstowe run organised by the Ipswich Transport Museum. This run is a victim of its own success with over 350 vehicles, 25 or more years old, and a great number of visitors travelling to Felixstowe, the 13.5 mile run is, in practice, a 13.5 mile stop-start traffic jam. Needless to say, there are numerous classic car casualties stopped at the side of the road, bonnets open to allow the engines to cool. Fortunately, this year the weather was kind. While it was a sunny day, cold winds from the sea kept ambient temperatures to around 13C, not a very challenging test for my car. Even so there were still a significant number of broken down classic cars at the roadside.

So how did my TC perform? Like many other T- Types, the sender for my temperature gauge is in the header tank for the radiator. With a thermostat fitted, the radiator temperature effectively gives an indication of excess heat generated by the engine. Going downhill when the engine is doing less work, the temperature drops, conversely it rises when going uphill. In practice, during normal running, this has proved a very useful means of determining how efficiently the engine is running on a given fuel, typically running around 72C on a super grade fuel and 75C on a standard 95 octane fuel. On the Ipswich to Felixstowe crawl, the temperature gauge barely reached 68C, normally running around the 65C mark. Considering our average speed was around 5mph, this is very low.

Does this mean the fixes have worked? Still more tests needed on hotter days. Watch out for the full report.

Paul Ireland

Right to the Core

I’ve noticed something interesting within Issue 33 of TTT 2, brass core plugs fitted to overcome the rusting experienced when fitting steel plugs.

Now that all sounds very good – as we know, brass will not rust but consider my article in Issue 24 of TTT 2 entitled ‘A Negative View’.

This article explained the phenomenon of electrolytic corrosion caused by dissimilar metals in contact with each other acting as electrodes of an electrical cell under the presence of moisture.

So on original manufacture we have steel core plugs in a cast iron block with no shortage of moisture from within the engine cooling galleries. Steel has a potential of -0.75V and cast iron a potential of -0.44V when acting as electrodes of an electrical cell in the presence of moisture.
With the more negative potential the steel will corrode in preference to the cast iron and this is clearly illustrated by core plug failures experienced by many owners of T-Types.

Now consider the fitment of brass core plugs. Brass has a potential of -0.30V and cast iron a potential of -0.44V when acting as electrodes of an electrical cell in the presence of moisture. The original design intent of the material interface has now been reversed as the cast iron block has the more negative potential.

Whilst the difference is well within the recommended maximum -0.25V, the cast iron will still be the material that will corrode in preference to the brass and that corrosion would affect the plug counterbore.

The internal cooling galleries of an engine will always be prone to corrosion and inhibitors present in anti-freeze reduce the tendency but why make changes that will compound the issue?

When the engine for TC0894 is rebuilt I will be opting for steel core plugs to be the sacrificial component of the engine assembly rather than the ageing and increasingly rare XPAG block.

Steve Cameron TC0894 (under full restoration)

Ed’s note: The use of brass core plugs has recently been discussed on the Triple-M forum. I noted that one contributor concluded that “the soft (little risk of damage to the block) brass core plugs, IF insulated from the iron block using a sealant, which you would do anyway (bath sealant) work fine, and will last far longer.”

TD12010 – Request for details of previous owners

John Gilks in New Zealand is looking for help in tracing previous owners of his car. John has owned TD12010 for 36 years and had details of previous owners as these were listed on the registration certificate. Unfortunately, the certificate was lost during a house move many years ago. He has subsequently tried without success to establish the names of previous owners.

John says that although he cannot be certain he is fairly sure that the car was exported to N.Z from new as very few pre-owned cars were imported to N.Z. in the 1950s. Under an arrangement with the previous owner back in 1982/84 he travelled to Wellington and picked up the car from a car park. From there he took it across Cook Straight by ferry and drove down the South Island to Dunedin where he lived. The car had recently been fully restored, probably late 1970s or early 1980s.The Transport Authority in New Zealand kept a very good history of vehicle ownership until the time when they transferred to a computer based system. Regrettably that history was eliminated on conversion to the replacement system. Ed: Where have we heard that before!

John’s e-mail address is johng(at)dbay.co.nz {please substitute @ for (at)}

TC7631 – Registration Mark JAD 513

Barry Robinson (Triple-M owner) has contacted me on behalf of Stephen Stewart Smith who owned this car when he was just 18 years of age, having spent the previous two years riding motorcycles ranging from a Triumph Tiger Cub to a BSA DBD 34 500 cc Gold Star.

Stephen, at 16. was employed by IMI Kynoch at Witton, Birmingham as an engineering apprentice. He used to see the TC being driven to and from work through the site and longed to own the car, never ever expecting that he would.

As part of his apprentice training he was regularly seconded to different departments on the site and one day ended up in a work area known as ‘Steam, Water and Gas’. He found himself working with a skilled fitter, who, by a stroke of luck, owned the TC. The fitter, Alan Radford, took young Stephen out for a ‘spin’ in the car with the hood down and he was hooked on the TC. When Alan said that he was going to sell the car, Stephen just had to buy it. At the time he had not even passed his driving test as he was learning to drive in his dad’s Sunbeam Rapier, so the car stayed on his parents’ drive until he passed the test.

Having passed his driving test, Stephen used to drive the TC to work and back on a daily basis and at every opportunity he would have the hood down with the tonneau cover fitted; he says it was just like riding a motorcycle!

As Stephen became a more experienced driver he wanted to go faster and found the TC to be quite a handful, especially keeping it in a straight line, which was becoming more and more difficult.

Stephen eventually sold the car (he can’t remember to whom, or for how much) and bought a Mini which his brother ‘souped up’, so much so that with wide wheels, SP tyres and a set of Koni’s it became a desirable target and was ‘nicked’.

The car is on the DVLA website so hopefully, the owner will see this and learn a little of the history of his or her TC.

Stephen can be contacted via Barry Robinson at bsjrobinson(at)tiscali.co.uk {substitute @ for (at)}.

Replacement Ignition Capacitors

6 May

It’s now generally recognised that the quality of the internal bonding and construction of replacement distributor capacitors is lamentable. A supplier of replacement capacitors has gone to some trouble to commission capacitors made to the original Lucas specification. Unfortunately, not the best of places to start!

Lucas capacitors used beryllium-copper wavy washers to spring load connections to the capacitor element, whilst the replacements use a “bee-hive” spring of zinc plated steel to make its electrical connections (see photo 1).

Photo 1 – Internal construction of distributor capacitors.

Both approaches fall well short of industrial standards and introduce significant series resistance; in the replacement sample that John James obtained, the series resistance measured 3.65 ohms. Whilst initially this is not high enough to affect the capacitor’s function, it is significant in that it predisposes the capacitor to failure in much the same way as the old Lucas capacitors.

The spring loaded electrical connections deteriorate with time, possibly due to localised heating from the high pulse currents, which would tarnish the surface. As the series resistance increases, so too do the very conditions that cause the connections to degrade. This represents a “runaway” situation, leading to series resistances up to 100 ohms and above.

As previously mentioned in the article on ignition systems (Issue 31, August 2015), the increasing series resistance shortens the contact-breaker life and then eventually the ignition fails due to insufficient energy at the spark plug to ignite the fuel-air charge.

Possibly, the only real improvement in the new replacement capacitors over some previous replacements, is the use of an epoxy-like potting compound to seal the wire-link end. Some previous replacements relied on a “rubber bung” to both seal and tension the electrical connections to the capacitor element. The types of connections detailed above are in stark contrast to the plasma welded connection of the recommended pulse capacitors (see photo 2).

Photo 2 – Pulse rated capacitor with plasma welded connection.

A meaningful test for these capacitors would measure their series resistance, but as this requires special equipment, its relevance seems to have been understated. The construction techniques used are so misconceived as to defy comprehension in this advanced age. Is someone taking the originality issue too far?

The case of the replacement capacitor was zinc plated steel, but traces of corrosion existed inside, not an issue with the Lucas unit which was made of tin plated brass, so some quality aspects of the Lucas unit are unique.

Eric Worpe

Ed’s note: The replacement sample which I obtained and sent on to Eric was purchased from Martin Jay, who is better known as ‘The Distributor Doctor’

.

I thought it only fair to forward Eric’s article to Martin for his comments; these are reproduced below preceded by the text of a covering e-mail from him.

Text of an e-mail sent by Martin Jay to John James dated 28th April, 2016.

Thank you for the opportunity to see the article on industrial capacitors, which I am familiar with. Please see the attached document in response to concerns over our products.

I would like to summarise in saying that the original Lucas specification & method of construction, which is the same as ours, has stood the test of time.

Only the relatively recent inferior copies over the last 15 years or so have given the capacitor an unreliable reputation.

We make all our capacitors to the same exacting standards and have sold over twelve thousand with just two reported failures.

I need say no more.

“Attached document” follows………

Replacement Ignition Capacitors / plasma welding technique.

With hindsight, it looks good to criticise the old Lucas capacitor or any near replacement, but how long have they served the industry well?

OK if new techniques come along like Plasma welded connections that can only be a good move forward. Plasma welding of the connecting wire to a capacitor has now been a standard in the wire-ended types (as shown in Photo 2, which is not an ignition capacitor) destined for printed circuit use for some time, but the ignition capacitor is a little bit different.

One of the main requirements of a conventional ignition capacitor is the means to keep a good intact connection between the foil element and the case housing allowing for expansion caused by heat between the foil capacitor element and the case. These connections must be flexible necessitating; the need for the internal connection springs used to keep the connection between the foil element and the case. Hence the Beryllium / copper wavy washer used by Lucas. As long as a replacement capacitor uses a spring, or any means of keeping the connection intact that will not corrode, then the result is the same. The same applies to the case that Lucas used which was a brass tin plated case, but a replacement steel zinc plated case is OK as long as it does not corrode. Another major criterion in the Lucas design is the fact that the foil element must be a loose fit in the case so that the spring methods used for keeping the connections at the lowest possible resistance can be effective.

If the new plasma welding technique can be done on a flexible braid to connect the case to the foil element and the foil element to the insulated wire end, the allowance for expansion is not so critical because the plasma welded flexible braid takes the place of the conventional spring designed to keep the connection as low as possible. The same applies to the insulated wire end if this can be connected direct to the opposite end of the foil element then a spring connection here is not required meaning a better product. The foil element, in my opinion, must still be a loose fit in the case to allow for longitudinal and lateral expansion.

Another improvement must be an epoxy seal on the insulated wire end instead of a ‘rubber bung’, but I would have thought no one building replacement capacitors relies on a rubber seal to keep out damp and corrosion!

In conclusion.

1) The old design has stood the test of time for many years and cannot be so poor that a panic change should be implemented.

2) If a plasma weld can be used on an ignition capacitor (not as shown in photo 2 a wire ended type) then this will remove many elements such as the spring-loaded connections, which can only improve the product.

3) If an epoxy seal can also be used to replace the ‘rubber bung’ then a good product can only result.

Ed’s further note:

I copied Martin’s e-mail and attachment (his document) to Eric.

Eric has come back, saying that continuing the discussion may only serve to confuse the issue even more, but makes three main points, which are:

  1. a primitive spring-loaded connection is unsuitable when a reliably low resistance capacitor is needed

  1. traces of corrosion found on the inside of the zinc plated steel case leaves a question mark about quality control

  1. there doesn’t seem to be any sound reason why a modern capacitor such as the one suggested could not be used as they are heavy pulse duty rated to 85 degrees centigrade and the very low series resistance precludes internal heating.

Eric has indicated that he is willing to write an article on how to fabricate replacement capacitor modules.

Low Oil Pressure switch for a TA engine

5 May

David Ralph (TTT2 24 – June 2014) described his solution to fitting a low oil pressure warning system to his MPJG engine. I have had similar concerns recently and decided to come up with a system fitted directly to the engine and with an audible as well as visual warning.

The threads on the block for brass unions (line to oil pressure gauge, block and cylinder head oil line and the block tap) are 1/8BSP-28. This turns out to be a standard thread used in pneumatic equipment, so a range of fittings is readily available. To clear the oil pump I used a 40mm extension piece, then a Y-connector. One port was used for a low oil pressure switch (3-6 psi) and the other for the relocated oil gauge union. Electrical supply was taken from my auxiliary fuse box under the dash, to a combined buzzer/red lamp (eBay, from Hong Kong) then to the oil switch. Earth is via the oil switch. Photo 1 shows the arrangement.

Photo 1 – Low oil Pressure Switch installed

All parts (Photo 2) were sourced via eBay, costing under £20, including the Dowty washers which are much better than fibre washers. In the event I did not use the plastic switch panel as too modern and instead made a matching panel to the additional under dash switch panel. Please note the 16mm dimension in the photo for the hole should be 20mm.

Photo 2 – Low Oil Pressure Switch components

Now I only have to concentrate on the speedometer and the water temperature when driving.

Ian Linton

TC10178 – saved from sitting on bricks since 1967 in a Sheffield lock up garage (Part 6)

3 May

I got on with the radiator grille on 1st December. I coated it in paint remover (you know the stuff, it burns holes in your bum). I jet washed it off and did it again. Then I rubbed each slat down with wet and dry. I left it to dry under the arc lamps. I gave the grille another two coats of Reno Red and left it to dry under the arc lights.

Today (02/12) I’ll finish the grille and then strip the spare wheel for sandblasting as soon as it’s a dry day.

(Left pic) The slats drying under two 2,000 watt arc lamps. (Right pic) the grille now painted with 4 coats of primer and about 5 or 6 coats of red. I haven’t looked at it close up but it looks smooth but flat. I’ll leave it at that and see if it will polish when its fully dry, like January.

The radiator painted and rebuilt and protected.

(Left pic) The tyre is nearly off the spare wheel – very difficult with 50 year-old hard rubber! (Right pic) and two new spokes fitted; the old ones were damaged because the spinner had been wired to the spokes.

I started at 0820 on 3rd December and welded the side screen frame. Good news is I can see much better since yesterday and was able to do a better job than the first attempt. It’s not perfect but OK. I then set up the sand blaster. I have two sacks of sand in the back of the Land Rover so backed the LR in front of the workshop. Cut a box to use for collecting the sand and got the airline, the blast gun, the vacuum cleaner and.. oh yes, the wheel! Cut a slot in the top of one of the bags and pushed the pick-up pipe in. Started blasting but it stopped. Went to the sack to wiggle the pick-up and realised the sand was very damp. Oh well that will have to wait for next summer to dry out.

The wheel blasted up well but not the areas with oil and grease. I then washed out the large cleaning tray, poured some petrol in and washed the wheel thoroughly. I then set up the jet wash, got another cardboard box (not short of them) and, in the middle of the field, jet washed the wheel. I took the wheel into the house, put the new gas fire on, and dried the wheel. Only took about 10 minutes whilst I had a coffee. I then gave the wheel another blast with the sand and it was as good as it was going to get.

Placed the wheel on the bench and gave it the first coat of primer. Had lunch and half an hour later, went back and gave it a second coat. Then watched the rest of Bargain Hunt and, at 1400, gave it the third and final coat of primer.

I now started to rub down and prepare to paint the side screen frames. I have an aerosol tin but I’m spraying it into the lid and brushing it on. Before starting to paint the frame I took the vacuum cleaner apart as it was making loud clanging noises and whistling. Got it apart and found the fan has disintegrated. Oh well, a new vacuum cleaner tomorrow. I then applied the first top coat of silver to both sides of the wheel. I did not overspray so it wasn’t fully covering the primer. I carried on brush painting the frames. I would paint one side with it laying on the bench then string it up and, holding the frame with mole grips on one of the brackets, paint the other side. After two frames I gave the wheel a second coat of silver. When the last frame was completed I gave the outside of the wheel a third coat.

I’m now writing this up (I do state the obvious sometimes, don’t I) and will go back in an hour to fit the new tyre and inner tube. Well, in an hour and a half, which will be 1800.

(Left pic) Welded frame (Right pic) the piece I welded on. The slot will be cut later. I also have the rivets to drill out of the rear frames. But it was painting day so I’ll finish the metalwork later and touch up round it.

(Left pic) just starting the sand blasting ……(Right pic) …..a close up.

Two ‘shots’ of the finished spare wheel – looks OK, well I think so …. and that’s what matters.

One of the frames hanging from a bit of string. I know it’s sideways but it looks the same the correct way round, believe me.

A member of the TABC group has a TC just 22 chassis numbers from mine. His car doesn’t have a body serial number plate. As his engine is also 22 more than mine he’s assuming, probably correctly, his body is 22 more than mine. So here it is…….

Left for the bodyshop at 0730 on 4th December with the wheel, the radiator, tools in a box and a nut for the track rod ends and the lower link on the front shock absorbers. On arrival, jacked car up onto axle stands whilst one of the lads took the tyre off the wheel to repair the inner tube. By the time he’s finished I had the other four wheels by his machine and he then took the tyres off those. Much easier than with tyre levers. I then took the incorrect nuts of the TRE’s off and fitted the correct ones. Problem! the 5/16″ Whitworth socket didn’t fit; it was too large. I borrowed a 13 mm and 14 mm spanners but they weren’t right either. I’ve made a note to take some AF spanners when I go back. I then went to fit the nuts on the lower shock absorber links but needed some spring washers. They only had Citroen concave washers but the largest they had was too small. Note to take two 7/16″ spring washers next visit.

I called in to Brico on the way back and bought a new vacuum cleaner, a roll of masking tape and 2 tins of primer. The plans of mice and men…. the mice may get it right – I never do. I’d planned on getting the 4 wheels blasted clean by tonight and apply the primer inside the rim tonight so it would be dry and I could paint the wheels tomorrow. Read on…… Got home at 1030, set up the sandblaster and washed all 4 wheels in petrol to get the oil and grease off. Started sand blasting the first wheel. When the compressor needed time to catch up (the sand blaster used huge volumes of air) I washed the wheel I’d painted yesterday as I needed to paint the rim again. I’d got some of the primer I used for the inside well on the rim and it was “lumpy”. I wet and dried it smooth and gave it a coat of silver. Back to blasting. I carried on for about 45 minutes and then broke for lunch. Fell asleep until 1400. Carried on with the sand blasting but ran out of sand. So, at 1530 went to Chateaubriant for 3 more bags of sand. I carried on sand blasting with the new sand. I bought medium grade instead of the usual fine. It does get the paint off quicker but leaves the surface black and rough. It also stings a lot more than fine when it hits hands and cheeks. Not worried about it being rough, the primer will fill that. I have enough fine left to go over it again to get it grey. I did about 20 minutes and then had to stop because the light was going.

So, I’ve got to finish the sand blasting tomorrow as it may rain on Sunday. If I can get the wheels blasted by tomorrow night and the inner wells primed I’ll be happy as I can paint on Sunday morning. It won’t take that long with all four wheels being painted at the same time. I’ve left the camera in the workshop so pictures tomorrow.

Started at first light on 5th December. The medium sand isn’t very good. I may have to get more bags of fine. Put a tea towel around my face held together with a bulldog clip and have donned gloves. This medium sand really stings when it hits your face and hands. It’s about 1 or 2 degrees outside and the goggles steam up as soon as I put them on. I’ve stopped to let the compressor catch up, it has almost run out of pressure. So, a coffee and I’ll start again. At 0930 I gave up and went back with the two unused bags of medium sand to replace them with 3 bags of fine. The medium just wasn’t getting the wheel down to metal. I get back at 1030 and start blasting with the fine. It’s much better but this wheel is taking ages. Unlike the others, this one has good paint with little rust. I can blast for about 6-8 minutes then have to stop for ten whilst the compressor catches up. Whilst waiting I fit the fuel filter bought from Doug Pelton in the States. This entails removing the soldered extension pipe I fitted to bring the outlet above the bottom of the tank. No problems, it came out easily and the filter went in.

I have lunch in one of the 10 minute breaks and paint the inner rim of the second wheel which was finished about 1430. It’s now 1540 and I’m onto the third wheel. I’ll finish this one tonight leaving the fourth to do in the morning and then to paint all four. The final session, before it got too dark to see, got both wheel rims blasted clean. The centre is done as is the outer outside rim. All that needs doing is the inner outside rim. However, this enabled me to get the rust-proofing primer brushed on the wheel well. So, three are painted and will be dry in the morning. I have the third to finish and the fourth and final wheel to blast. If I can get finished blasting by 1100 I will be able to get all four painted by the evening. I will lay all four on the floor outside facing up. I can then spray all four wheels together. Three coats of primer and two coats of silver then turn them over and do same. If I do this every half hour I will be finished by 2100. I can then take them back to the bodyshop first thing Monday morning, get the tyres put back on and refit the wheels.

The work area.

The fuel filter from Doug Pelton of ‘From The Frame Up’ in the USA.

It has a raised section, so it will leave some fuel in the bottom of the tank along with all the ‘crap’.

Ed’s editing of activity on 6th December: Norman started before first light as he had fallen behind schedule in getting all the wheels sandblasted by the previous night due to getting the sand changed. He had also wanted to get all the wheel wells painted because the paint he was using took ages to dry. In the event he still had one wheel to finish sandblasting and one wheel well to paint, after which all the wheels would need to have two coats of primer and three coats of silver paint. The reason for the rush? Norman wanted to get the finished wheels to the bodyshop by the next day to have the tyres fitted and have the wheels back on the car.

The finished wheels.

Ed’s note: back to Norman……….. In the workshop at 0715 on 7th December and loaded the wheels, tyres, tubes and tools in the car. Left at 0730 and arrived at the bodyshop dead on 0800. No one there, which is unusual. However, the forecourt is full of new cars which reminded me that they had an open day over the weekend. They had an automated phone system inform every customer by phone. Jean-Luc turned up at 0830, opened the doors to the workshop and I drove in. The workshop was full of new and a few second hand cars and a large table with nibbles and wine. Never mind, I take the wheels, tyres and tubes to the tyre machine and the tools to the chassis. I tighten the track rod end nuts, they’re 9/16″ AF and split pin them. Fit the lower link nuts and spring washers and all done in 15 minutes. I say goodbye and agree to return Wednesday afternoon to refit the wheels to the chassis. I want to rub down the inner and outer surfaces of the hubs so there’s no paint between the wheel and hub and the spinner and wheel.

I didn’t mention it but Monday (8th December) saw me finish (apart from some very minor jobs) the car. I’ll now have to wait until I get the chassis back and refit all the mechanicals and interior trim. In the meantime I’ll catch up on jobs in the house, lay the new floor in the garage and fix the Mini, Land Rover and Caterham, all of which need work. I guess I should be delighted but I feel a bit “flat”. I’ve really enjoyed working away in the garage with Radio 4 playing….. The results look good to me. I hope the finished car doesn’t look over-restored. I’ve tried hard to keep as much of the original as possible. However, I suspect it looks a bit blingy as you cannot tell the chrome plater not to do a good job and make all the re-chromed parts look a bit old. Likewise, with the interior trim, the seats are good as I restored them but the trim was beyond repair. It had gone brittle and was tearing as I took it off. The new trim looks lovely, but far better than when the car was built. The paint is being done in the correct colour cellulose so will be very shiny, but original. The bodyshop owner wanted to do it in two pack but I insisted on using the type of paint it had when it left the factory.

I started at 0700 on 9th December by taking TC rad to the workshop. The rad needs to have the casing lowered on the rad as the cap won’t fit. Looks like I’ll have to elongate the holes.

January 2016

Left at 0830 on 21st January and picked up the chassis. Back here by 0930, unloaded and pushed it into the workshop. Took the deparnage (flatbed trailer) back.

22nd January: You’ve all been there. It’s 0530 and you’re wide awake but it’s too early to get up. So I read another few pages of The Lord of The Rings and….. wake up at 0910. In the workshop by 1000. Clear the bench and floor area and lay out all the boxes and cabinets of fixings. Then get the chassis lined up ready for the engine to go on. First I spend some time finishing the handbrake and fitting it. Then the pedals go in. Lastly the engine and gearbox assembly goes in. Only problem is the rear plate on the gearbox is stopping the gearbox mounting bolt going through. Solved it by running a drill through and grinding a flat off one of the bolts. Then the prop shaft goes in.

So, at 1645 I have the engine, gearbox and prop in. The pedals are on as is the handbrake. A good day’s work.

I have the split pins to fit into the prop shaft flange bolts, the handbrake to adjust and the brakes to bleed. Also I’ve to fit the front engine mounting bolts when they arrive, probably Tuesday. I’ve searched for them but can’t find them so NTG are sending me a set.

Chassis in the workshop, up on stands, the engine in place to refit.

Engine now fitted.

Started at 0800 on 23rd January and did the following: Locked the prop shaft bolts with split pins. Checked all fluid levels and greased all the grease points. Topping up the diff took ages, 140 grade oil is like pouring grease. I then cleaned up one of the pipes that fit on the handbrake cable for greasing. Got it all cleaned and fitted and pumped some grease in but most was coming out the joint. I looked for the other pipe but can’t find it. If I can’t find the pipe it’s £96 for a new kit. 

The wheels were next. I used some sandpaper to remove the paint where the wheel touches the hub and, on the outside, where the spinner makes contact. I fitted the handbrake stop bar, which I’d forgotten and then filled the engine with a mixture of water and phosphate to loosen any rust/silt left in the block. Problem was the bottom hose, which I’d blanked off with some plastic bin liner material and rubber bands leaked. So I put a jubilee clip over the bands and it stopped most of it. It’s dripping a bit, so I’ve got the oil drain can under it.

Time to bleed the brakes. Lynne came and helped and I ran into trouble straight away. The pedal still had the old actuating arm on it and it doesn’t have any threads left as they’ve rusted away. So, I had to remove the pedal shaft to fit the new pushrod. Took about half an hour and then my little darling worked the pedal and kept the cylinder topped up whilst I went round bleeding. We bled twice, had to unblock the new bleed valve on one of the front wheel cylinders and we now have a brake pedal that operates the brakes.

The handbrake now fitted with the stop bracket.

In the workshop at 0730 on 25th January (aren’t I keen), wheels off (again) and drums painted gloss black. Then moved the earth strap to the correct bolt (bell housing rather than gearbox mounting), changed split pin in pedal shaft. Then tried to fit the heat shield to the master cylinder. It won’t fit because the cylinder has different width ends. So I file/grind the cut outs on the shield to suit. Still won’t fit as the new master cylinder is in the way of the shield fixing to the chassis. So I wrapped a piece of heatshield material around the cylinder. Then fitted the exhaust front pipe, which meant I had to heat up one of the studs to bend it straight so the copper and asbestos (or whatever they use now) will fit (as well as the downpipe flange). It went on OK and I then tried to fix the bracket to the bell housing bolt. No chance. I had to remove the pipe and grind the top of the bracket to be half round. Fitted it all back. Then for the silencer. I can’t find the ring that fits between the silencer and the front pipe or the U clamp. I re-organise all the bits into boxes and have a good clear up but still can’t find them. I do have a clamp for the rear tailpipe. I fit the silencer but leave the 4 fixing bolts – silencer to chassis – loose as I’ll have to remove it to fit the ring. Then I find the rear clamp is too small. I’ve ordered parts, last night, for my friend’s TC from Moss Paris so I come in and ring them to add the exhaust parts. They don’t open until 1400 on Monday so I go back to work.

Let the car down and push it out so the front is outside the workshop. I turn the water hose on and set the engine flushing. I’ve already slackened the dynamo so I can use the electric socket gun turning the water pump. Whilst it’s flushing I look for the missing parts for the O/S handbrake greaser. I have the pipe and find the union on the old handbrake cable. Then I find the other union, bleed nipple and triangular bracket in one of the boxes of bits. So I clean it all up and fit it. Pump some grease in and I’m happy. Turn the tap off and blow the water off the engine and chassis and then leave it all to dry in the sun whilst I have lunch. At 1400 I ring Moss Paris and add the exhaust parts to the order. They have it all except the rear clamp. Never mind I can fit that later. I’m hoping it will be here on Thursday so I can go back to the bodyshop to finish the exhaust and fit the front engine mounting bolts which are on the way from NTG. At 1415 Lynne helps me search for the missing exhaust bits but we can’t find them.

Up at 0645 on 26th January – out to the bodyshop at 0720 and arrive at 0755. It was foggy hence a bit slower than normal. Left with the flatbed at 0830 and got back loaded the MG with Lynne’s help, she is a darling, got up early to help me push the chassis to the flatbed. I can’t get the flatbed to the workshop as the ground is too soft. Returned, got the chassis off and then had a search for the engine bolts and found them. So have cancelled the new ones from NTG.

The stuff I ordered yesterday from Moss Paris arrived. I now have the parts to fit the exhaust properly so I’ll go over on Thursday and do all the little jobs I haven’t done. Like fit the engine mounting bolts, refit the dynamo, fit the exhaust and fit some grease nipples to the track rod ends. I’ve also got a bit of the tub to prime and paint.

Off to the bodyshop on 28th January (after a visit to the blood testing laboratory) where I pick out the chassis numbers stamped on the chassis (which I masked off) in yellow paint. When that dried I sprayed the area with a clear lacquer. Then fitted the newly found and cleaned front engine bolts and refitted the dynamo. Removed the silencer, located the two studs in the silencer flange into the flange of the front pipe, positioned the joint and tightened the two nuts.

Went to fit the new U clamp on the silencer to tailpipe joint and find it’s too small. Would I be out of order to complain to Moss that their parts are wrong? Won’t bother as they probably won’t do anything about it. Swapped the clamp I had for a larger one the bodyshop has in stock and fitted it. Then removed the rear clamp, which is too small and reshaped it, cut a bit off and drilled a new hole. It fitted perfectly. So exhaust now finished.

Kept spraying more lacquer on the chassis and fitted the grease nipples to the drag ling and track rod joints. I’ll have to re-visit this when I get the chassis back here as one TRE doesn’t seem to have a hole for the nipple and one I did fit won’t let the grease gun lock on. As it’s a bit dark where the chassis is I couldn’t see very well. Lastly, I masked the tips of the fan blades and sprayed the tips yellow so no silly bug*er, i.e. ME! puts their fingers into the blades when the engine is running.

Got home at 1230 and took the tools out the car. Then sorted out the windscreen frame parts. I have the old bottom corner brackets to drill out and fit new ones and build the frame onto the screen, Only problem is that I seem to have forgotten to order new corner brackets. Ring Linda at NTG and they’re on their way. So, after lunch I drill out the four seized screws and then clean the tacho and speedo cables and lightly oil them ready for refitting. Tomorrow we’re off to St Bruieac to collect the hood and side screens.

Up at 0800 on 30th January and bring the two front side screen frames and screens (collected yesterday) and the strips and special screws into the house along with some tools. Now, I’m worse than useless at doing mitred edges so, of course, I bug*ered the cutting up. The edges don’t meet correctly and I’ve ended up cutting the strips short. Fitting the frame was a nightmare. The screws don’t come through enough to get the nut on. After a lot of struggling and pulling the screws through with a small pair of long nose pliers I get all but two nuts on. The two that I can’t get on will have to remain ‘nutless’, one is by the weld and the other just hasn’t enough thread showing to pull it through. After lunch I started on the other side. This time I decided not to mitre but just butt the edges together. I also got all the screws into the channels and stuck matches under the head so the thread will go through enough to get a nut on. I marked the edges and then slid the trim forward a bit so I could raise it from the screen and cut it off with the Dremel and a cutting disc. I then got all the nuts on and tightened them. Much easier this time.

You can see the gaps on the mitred side (left). The right hand one has the butted edges.

Up with the lark, well 0900, on 31st December – lazy larks. Had breakfast and went into the workshop. Got the old loom laid out and the new one in the same orientation. Then marked with a piece of tape where the armour should go on the new loom. I cut the old loom to get the armour off and then cleaned it on the wire brush. I cut the ferrules so that they will fit over the new loom, the intention is to solder the cut joint. Then I unwound the armour coil. Took the ends, coil and tools inside. Sat in my chair with a cover over me, I proceeded to wind the armour on to the new loom. Having done a few turns I realised I had started at the wrong end and was winding it on with the next bit going under the previous. So I unwound it and started at the other end, with the next coil winding over the previous. It was very hard to do with my arthritic fingers but got there by 1245. Put the ferrules on and pinched them together, I’ll solder them in the morning. Lunch and then I cut the smaller section armour off the old, cleaned it, and onto the new. All done by 1445.

Two looms laid out like a nest of snakes.

The section of armour that has to be removed from the old and fitted to the new.

Cutting the old loom to get the ferules and armour coil off.

The coil, ready to be unwound.

The coil unwound.

And started. Only problem is this is being wound on the wrong way, so after about 8 coils I unwound it and started at the other end.

Nearly there!

The whole picture, over half way.

Done, now for lunch!

The smaller section…..

..getting there.

……………and finished.

And that’s the end of January. How time flies……

I’ll solder the ferrules in the morning.

You can read the whole blog at www.frenchblat.com and click the shortcut to MG TC.

Panelling a TC ash frame – Part 2

2 May

In Part 1 of his article (see Issue 35) Bob Lyell started on the front quarter panels to (as he put it) “gain experience and confidence”. Part 2 sees him moving to the rear quarter panels. Over to Bob……………

With the front quarter panels successfully completed, it was time to tackle the rear ones and whilst the same metal working principles applied, achieving the more pronounced curves would prove significantly more challenging, but still possible.

However before getting started I took the opportunity to trial fit each rear wing to check for gaps between it and the wheel arch cut out in the ash frame, particularly in the rear corner where the body curves over the crown of the wing to follow its inner face. So visible and attractive on the finished car the best possible fit must be achieved now either by sanding to remove high spots or gap filling by adding small strips of wood, wing piping will only disguise so much.

Checking for rear wing to tub fit.

Actually I went so far as to fully pre-fit and drill the holes for the wing securing screws because it was so much easier to clamp, adjust and align the wing without the inner wheel arch or outer skin in place. I figured I would be able to find the holes again.

Continuing without an inner wheel arch, for ease of clamping, I lightly block sanded the outer faces to check for lumps or hollows (there were none) and to get a feel for the shape. Then I made a paper pattern about 1 inch oversize which for my body measured exactly 1 metre from front to back, allowing the blank to be cut from the width of an Aluminium sheet whilst leaving the wheel arch cut out to provide material for a door skin.

Next I jig sawed another clamping strip from 9mm plywood, shaped to exactly follow the top edge of the flat vertical face from the top hinge to the side screen slot. Once satisfied that the Aluminium was correctly positioned I clamped it in place and added 2 location screws in excess material. One just below the bottom door hinge, the other, to locate the top of the panel, into a wooden block screwed into an existing hole, drilled for a hood tacking fixing screw. These screws would allow the panel to be located now whilst flat and exactly repositioned throughout most of the panel forming process. Being in excess material, the holes would disappear when the panel edges were trimmed back to their finished size.

Panel location screws; additional block for upper/rear one and lower/front location screw in place.

The final preparatory job was to make and fit a tubular steel cross brace between the tip of the bull horn where it could share the 2 mounting screws and the opposite body iron corner below the door hinge, secured with a G clamp. Without it the ash frame flexed when I hammered against it.

I decided to start with the complex shaped top edge between the door aperture and the side screen slot and to anneal the Aluminium before striking the first blow. At least by attempting the most difficult part first, if I failed I would not be throwing away any other hard work. I roughly cut out the side screen slot to split the gentle curve into 2 more manageable lengths and then worked forwards each time along the curved top which wants to roll straight, through the external corner which required a lot of shrinking, then down the easy straight slope to finish through the tight internal corner with much stretching.

I found it very important (and difficult) to identify exactly where the flat face ended and the curved edge started so I could clamp the plywood with its edge no more than a couple of millimetres back. This prevented the Aluminium from bulging back out behind the hammer blows whist trying to work the metal forwards. As the shape was progressively formed the Aluminium had to be worked to fit tight against the Ash, so the first run of blows with a plastic headed mallet had to be as close as possible to edge of the plywood, not easy. I found that it helped to also pull the panel edge over with a mole grip whilst striking and to listen for the reassuringly hard sound of striking against wood as opposed to a hollow sound when it is not touching.

From the side screen cut out to the external corner it was easy to roll the metal over, however like a rolled up paper it wanted to form a straight line and lift away from the gently curved top edge of the wood at each end. I resorted to clamping both ends down hard with soft faced G clamps in order to achieve a tight fit which forced the centre portion to ripple. After annealing, these were removed by shrinking with a slapping tool before working the metal over the sharp edge and down the inner face, with more shrinking. This finished profile was then sufficiently rigid to hold its shape without springing back.

Forcing the panel to follow the curve of the Ash.

For the external corner, by progressively striking from the start of the curved edge I was able to force the panel to gradually curve hard against the wood without a push back bulge forming. Due to the amount of aluminium to be shrunk, the small ripples formed by striking out from the clamping strip needed to be encouraged to grow by simultaneously working them from the open edge into folds with round nosed pliers or a similar tool. It became a continuous process of forming ripples and then shrinking them back with frequent annealing because this amount of manipulation quickly work hardened the metal. Trimming the metal back as soon as I could determine where the finished edge would be, also helped by simply reducing the volume. On one side I greedily formed a ripple so large that I could neither shrink it nor re-form it into two smaller ones. The only way out was to lose it by cutting out a wedge of material and forming a butt joint for welding after the panel was finally secured in place, an annoying but fortunately not disastrous mistake.

Butt joint ready for welding.

Fortunately, the next part, the edge down to the internal corner is straight, making the job much easier. For the internal corner my technique was simply to keep the metal soft by frequent annealing, to not be greedy and to keep checking that the Aluminium really is hard against the Ash, as it is so easy to fool yourself and bridge the corner. Again, trimming back as early as possible helped. I didn’t worry about the rebate at this stage, I just left sufficient material.

To complete the sharp fold down the inner face I annealed the panel and clamped it down tight with G clamps and small strips of wood along the top edge and worked it over with a plastic mallet. The additional stretching next to the internal corner presents a high risk of splitting because the Aluminium is now getting very thin and any cut or nick in the edge can quickly propagate into a split.

For the rebate I decided to intentionally make a (junior hacksaw) cut in the Aluminium to leave a flap of metal, form the rebate and then fold the flap back over to make a butt joint around its edge ready for welding, I just couldn’t see any other way. To my surprise, persuading the Aluminium to follow the rebate proved easy after annealing by using a homemade hardwood (Lignum Vitae) tool shaped like a chisel but with a soft tip and by using slightly heavier hammer blows.

Working the Aluminium into the rebate before cutting and folding over a flap to finish.

To finish this area, I formed the vertical fold between the hinges and was pleased to find that the panel could still be removed.

Back to the top rail, from the side screen cut out rearwards to the sharp square step (although I have now seen bodies without this feature) was a combination of serious panel clamping against the side, soft faced G clamps on top and my new hardwood chisel tool to work the metal into the corner of the step. Afraid of wrecking the panel and all of my hard work and being committed to welding for other reasons I had considered making another saw cut and filling the gap by welding in a small triangle of metal, but I decided to be brave and go for it.

The rear corner’s simple curve could be pulled around by hand before clamping it tight against the flat rear plywood panel. By using the cut edge of the Aluminium to draw a pencil line on the plywood it was easy to measure back to the edge of the rebate and allowing 1/8 inch for a flange mark where to cut and fold. As I was still able to remove the panel I formed the corner in my hand operated folder.

Cut, folded and a snug fit in the rebate.

To form the curved top fold which goes under the hood tacking corner I first made a simple clamping strip from 25mm x 4mm mild steel. After annealing the Aluminium this strip was aligned with the top edge, the temporary panel locating block removed and the metal progressively worked over to form ripples which could be shrunk back to leave a smooth face for the tacking corner to sit on.

After the first run of hammer blows it looks scary, but it will shrink down flat.

I had now reached my last opportunity to remove the panel, so it was a case of marking the final cut edge around the wheel arch, down the back panel and across the bottom door hinge. Removed and cut to final size, the order of assembly was inner wheel arch, front quarter panel, rear quarter panel and finish its return edges. Then mark out and drill for nails and try to rediscover the wing securing screw holes.

With both rear quarter panels secured in place I was able to finish on an easy note by just measuring the panel edge to panel edge gap to determine where to guillotine and fold the flat rear panel (exactly as described in Sherrell’s book) to give a tight edge to edge fit with no gaps or visible fixings, but noting that the top fold is less than 90 degrees.

Edge to edge. Clean, tight, flush and ready for nailing.


TABC Brakes

1 May

So, why the change from mechanical braking systems to hydraulic? Even in the mid-1930s, hydraulic brakes were viewed with some suspicion due to poor rubber compounds and brake fluids, barely one generation away from water and glycerine. A failure in just one part of the system could result in total failure with only the mechanical handbrake left.

What were the disadvantages of the mechanical system that pushed the development of hydraulic brakes?

A. The need to balance the braking effort of all the brake drums by mechanical adjustment, both initially and throughout the life of the linings.

B. Complexity in assigning the correct braking effort between the front and rear brakes. *

C. Lost braking effort due to friction in the cable and rod linkages.

D. Wear in pivot points and actuating cams, leading to inconsistent braking amongst the brake drums.

E. The need for essential regular maintenance such as cleaning and lubrication.

F. The cost of producing a robust system that worked reliably. **

* When braking, the weight transfer to the front increases the adhesion of the tyres at the expense of rear tyre adhesion. Typically, the braking effort at the front should be 60% to the rear’s 40%. Balance compensators were available but at increased complexity and cost.

** The high cost of robust mechanical brakes encouraged some manufacturers of cheap cars to opt for hydraulic systems, maybe those who could only afford cheap cars were seen as expendable. Rolls Royce tried a combined system with hydraulic front brakes and mechanically operated rear brakes.

Hydraulic Systems

Main advantage is that the hydraulic pressure is evenly distributed throughout the system and any need for differences in applied force or braking effort can be accomplished by varying the surface area of the pistons in the wheel cylinders. In the case of the TA/B/C, the front wheel cylinder’s piston is 1 inch in diameter, giving a surface area of 0.785 sq. ins. The rear wheel cylinder’s piston is 0.875 inches in diameter, giving a surface area of 0.60 sq. ins. This gives an applied force ratio of 57% to the front and 43% to the rear.

Hydraulic systems are almost frictionless and able to produce increases in mechanical advantage easily. However, in the case of the TA/B/C, the main mechanical advantage is achieved through the brake pedal. The foot pedal section is 10 inches long, whilst that of the master cylinder operating lever is only 2.5 inches, giving a mechanical advantage of 4.

Foot pressure on the pedal can reach 100 lbf under hard braking, producing a force of 400 lbf at the master cylinder piston of cross sectional area 0.6 sq. ins. resulting in a pressure of 670 psi. Such a hydraulic pressure gives a braking force of 525 lbf at the front shoes and 400 lbf at the rear shoes. Pedal pressure might well double in an emergency and I’ve even heard of the brake pedal bending in a crash situation, so a minimum burst pressure rating of 2,000 psi for the brake pipe work is a starting point.

Figure 1 – Brake system schematic.

Modern brake fluids are synthetic and based on Glycol-Ethers, whose main disadvantage is their hygroscopic nature; they readily absorb moisture causing corrosion and forming deposits, which can clog systems, hence the need to change fluids frequently. Expensive mineral based brake fluids were sometimes used on Rolls Royce and Citroen cars.

Brake fluids in wheel cylinders can be exposed to high temperatures from the brake linings, so they need to have a high boiling point temperature to avoid vaporization. The gaseous nature of a vaporized brake fluid is compressible and would cause a serious reduction in applied braking force. Any ingress of moisture through the vented master cylinder under the floor board, would disperse throughout the whole system and reduce the boiling point of the fluid in the wheel cylinders.

Brake fluids are defined by their DOT grade in relation to their boiling temperature for both dry and wet states. Whilst DOT 4 would seem to be better than DOT 3, its rate of boiling point degradation due to moisture content is greater than DOT 3. This would imply that if brake fluids are not frequently changed, one might benefit from use of the lower spec. DOT 3.

DOT (Department of Transport) grading system.

Note 1: The WET specification is for a water based content of about 2%.

Note 2: DOT 5 is a silicone based fluid.

One survey found more than 20% of old cars exceeded a water content of 5% in their brake fluid, which had probably never been changed.

Brake fluid must have a consistent viscosity over a wide temperature range. Corrosion inhibitors are added, but these degrade with time and combined with accumulating moisture levels necessitate frequent changes of non-silicone based fluids.

Water is immiscible with silicone, so any water entering a silicone based system forms pockets, which sink to the bottom. Due to the surface tension of silicone, small water pockets are unlikely to penetrate through any film of silicone that has wetted the base surface of say the Master Cylinder. However, this may not be the case for easily visible pockets of water, which could cause localised corrosion and freezing.

Silicone fluid should only be introduced to a system that is either new or has been flushed out and had new rubber seals and hoses fitted. Due to the fact that it should never be mixed with non-silicone fluids, it is coloured purple.

Liquids are not appreciably compressible, thus brake fluids would need pressures over 20,000 psi to produce a compression of 1 to 2%.

In this respect, Silicone is slightly more compressible, which seems to have justified some complaints about “spongy brakes”. The real issue could be about trapped air bubbles due to poor pouring techniques and a surface tension that resists air bubbles combining, which would have helped when purging the system of air. To avoid introducing air bubbles the following points should be observed:

A. Leave the container of Silicone fluid to stand for a while and do not shake the bottle.

B. Use a funnel, whose end is dipped into any existing fluid in the master cylinder.

C. Pour directly onto the side of the funnel to minimise entrapping any air.

Several attempts at bleeding the brakes may be needed.

Figure 2 – Silicone pouring technique.

Silicone is more compressible than Glycol based fluids particularly at the higher temperatures where Glycol based fluids would have vapour-locked anyway.

Graph 1 – Compressibility of brake fluids.

Only part of the brake system experiences high temperatures whilst the rest of the system remains cool, so the typical compressibility of silicone is less than 1% and that of Glycol based fluid about 0.3%.

The techniques for bleeding brakes can be confusing, the often advised slow pumping of the brake pedal may not sweep air bubbles away from high spots in the system. On the other hand, somewhat surprisingly, vigorous pumping is claimed to induce cavitation, so somewhere between the two speeds seems sensible. Consider using a Gunson Eezibleed kit at about £17 to £18.

Bleeding usually necessitates extra-long strokes of the piston in the master cylinder. The initial strokes should be done cautiously as the piston seals may encounter unpolished sections of the M/C bore.

Brake System Design.

Braking effectiveness is considerably reduced if the wheels are allowed to “lock up” and induce skidding. Maximum braking force is obtained when there is between 10% to 20% slippage between the braked wheel’s circumferential velocity and the road surface. One exception is on loose gravel where a wedge of material builds up in front of the tyre. Avoidance of “locking up” becomes a significant criterion in brake design, as a system powerful enough to be effective at high speeds could result in the wheels “locking up” at modest and low speeds. A proportionate system, where for a given pedal force, the braking effort increases with velocity, is therefore needed.

This is achieved through the self-servo action of the leading brake shoes. The “drag” of the revolving brake drum on the leading edge of the friction lining, causes the leading shoe to be pulled into the drum. The trailing shoe is pushed away, resulting in approximately a 4 to 1 ratio between the braking effects of the shoes.

Figure 3 – Schematic of self-servo action.

If the leading and trailing edges are considered as the tips of levers, rotating about a common focal point, then the frictional force on the leading lever A pulls the lever into the drum, whilst that on B pushes the lever away. This amplification of the braking effort by the self-servo action is not without drawbacks. Any deviation from the assumed coefficient of friction of the linings could result in either “grabbing” of the brakes or a hazardous braking underperformance.

Types of friction lining.

Difficult to find information that isn’t influenced by commercial self-interests; such is the enthusiasm shown by the marketing fraternity that one bit of “puffery” even described their linings as having low wear and anti-friction properties. Original type asbestos based linings were banned in 1998 due to the alarming numbers of garage mechanics suffering from asbestos related diseases, sometimes taking up to 40 years to develop.

Initially, organic fibres such as those from coconuts, bonded by high pressure and resin based adhesives were used. Since then, synthetic linings have been introduced using fibre-glass and Aramid fibres.

Manufacturers tend to keep quiet about their recipe, as up to 20 ingredients may have to be blended to produce an inexpensive high friction material that’s strong, yet flexible enough to be shaped, capable of withstanding high temperatures without fading, non-abrasive to brake drums yet resistant to wear, able to work when wet and not squeal. Some linings include a thin wire mesh of brass, zinc and even steel to stabilise the friction value by conducting heat away from the operating surface and also to strengthen the lining material.

Woven linings with their characteristic hexagonal pattern have been largely augmented by moulded linings, which are easier to produce, although possibly less robust.

There’s no clear indication that brake linings are more suitable for cast iron drums than for steel ones, as the only recommendations that I’ve found suggest that cold-rolled steel harder than Brinnell 180 and close-grained cast iron are equally suitable. However, cast iron is the preferred material due to its greater dimensional stability and hence freedom from warping due to heat; cast aluminium with cast iron linings are also recommended.

Take care when following recommendations on internet Forum sites, for example one recommendation for “Green Gripper Linings” with a higher coefficient of friction u was countered by a warning that such linings wear the drums out.

Dynamic friction coefficient u for most linings is in the range 0.35 to 0.42. Codes on modern linings identify the hot and cold values of u. E is up to 0.35, F is up to 0.45, G is up to 0.55, H is greater than 0.55. These codes do not address the hardness or wear rates.

Soft linings tend to have a higher u, but are more prone to fade at high temperatures, hence being suitable for normal driving. Hard linings suitable for “sporty” driving resist fade, but inherently have a lower u which can be enhanced by adding metal particles. These particles, being abrasive, are bad news for drums no longer being made.

Look out at auto-jumbles for MO/27/1 which could be an asbestos based soft lining. Soft linings need occasional inspection of the front leading shoes as these account for 45% of the braking effect and wear down heavily. Clean drums with a damp rag and then dispose of rag in a plastic bag. Avoid the use an air-line to blow dust out.

There’s a bewildering choice of linings, as some suppliers offer linings intended for industrial uses, such as wind turbine speed brakes. Being able to specify a specific soft lining material, that others have found effective, would need the collective input of many fellow classic car owners whose choice would have been guided by knowledgeable brake lining suppliers. Is this an “action” point?

Figure 4 – Master brake cylinder.

When the piston is pushed forward, fluid is pumped out to operate the wheel cylinders. On the release of the piston, the brake shoe return springs force fluid to return the piston back to its origin. However, if any fluid were to leak out under pressure, the piston would not fully return (the return displacement of the shoes is limited by the adjustment cams) and thus any volume “compensation” of the fluid through the By-Pass port would be prevented. Adding an internal spring pushes the piston right back, creating a partial vacuum that draws fluid past the master cup via the piston’s chamber.

When the piston is at rest against the circlip, the By-Pass port is only just uncovered, allowing the free flow of fluid to and from the reservoir to allow for volume changes due to temperature, which could cause dragging brakes.

Figure 5 – Master cylinder piston.

The larger port enables fluid to enter the piston’s chamber, forming a low pressure fluid seal behind the master cup, with the rear secondary cup sealing against any fluid leakage, whilst the rubber boot guards against any contamination.

However, a problem arises when bleeding the system as any fluid forced out will be drawn back in, air bubbles and all. This is overcome by a dual role check valve.

Figure 6 – Check valve.

When the piston is operated, fluid is forced through the side holes in the check valve cup, displacing the internal rubber sealing cup washer and flowing out through the extension tube. Fluid is then returned by the brake shoe’s return-spring pressure and lifts the cup off the end sealing washer against the pressure of the master cylinder’s internal spring. When the two opposing spring pressures balance, the check valve returns to sit on its sealing washer, leaving a slight back pressure in the system. This helps splay out the sealing cups in the wheel cylinders, reducing leakage and restricting any moisture diffusing through the seals and hoses. It might help to occasionally pump up the brakes during storage.

When bleeding the brakes, the back pressure falls to zero, preventing any fluid passing the spring loaded check valve on the return stroke.

Figure 7 – Push-rod’s knuckle joint.

This may look odd because of the angled adjusting screw, but is well thought out. The crucial issue is the position of the actual ball of the joint. This should be “plumb” or just forward of the pedal spindle, when the knuckle screw is adjusted to give a “free play” of ½ inch at the brake pedal. Limited movements of the ball-end produce a near horizontal thrust vector and displacement of the push-rod. The height of the master-cylinder should be adjusted to be slightly above the ball, as the ball tends to rise up if its displacement is extended due to slack brake shoe adjustment. Check that the push-rod is a suitable length, straight, almost horizontal and not touching the sides of the hollowed out section of the piston over the likely travel of the brake pedal. Some after-market push-rods and master cylinders may deviate from the original dimensions.

Important, check that the ball is secure in its housing. Check brake switch operation, especially after adjusting brakes, as the limited pedal movement may not operate the mechanical switch.

Consider installing a hydraulic switch and LED brake light placed inside the spare wheel. Use a modified banjo bolt on the 3-way adaptor on the end of the master cylinder extension, for the brake switch.

Checking the fluid level in the master cylinder could be made easier if a remote reservoir was located in the engine bay and connected to the screw top of the master cylinder by a tube and elbow adaptor.

Bronze master and wheel cylinders are available with stainless steel pistons, although it’s still possible to sleeve old wheel cylinders.

Handbrake

MOT testers sometimes comment on how effective this is, hardly surprising, given its 10 to 1 mechanical advantage. However, dried-out old grease in the cables can be a problem causing sluggish brake release. In which case, remove the cables and heat up in hot water or with a hot air gun and then pump paraffin through to flush out the old grease. Try 140 grade oil to re-lubricate.

Check the correct assembly of the cable support flanges on the back plate. (see Fig. 8).

Figure 8 – Assembly of cable support flanges on back plate.

Check that the operating arms on the handbrake cross-shaft are nearly vertical when the cables are in tension, otherwise the threaded rods can be bent by being pulled around the cross-shaft. Strangely, there’s no information on adjustment in the “Brown book”.

New rachets and pawls are available from Roger Furneaux and Digby Elliott.

Lining renewal.

Partially drill through the old rivet with a 1/8 inch drill and then punch out with a pin punch. Avoid opening out holes in the brake shoes. After cleaning and degreasing the shoes, inspect for cracks.

Figure 9 – Flaring rivets.

Start riveting from the centre and loosely flare rivets with special “roll-set punch” working outwards. The lining surface can be kept clean by temporarily covering with masking tape. Use a tool clamp to hold down lining and then secure rivets working outwards again to minimise air gaps between the shoe and lining.

Chamfer the leading and trailing edges of the linings. De-grease drums and remove any glaze with emery cloth. Any high spots on the lining can be found by chalking the inside of the drum, and after rotating the drum with a light application of the brakes, the witness marks on the lining can be removed with a rasp type file.

Check points

1. Shoe pivot stud is secure, if loose it can tend to

elongate the hole.

2. Adjustment cams are not loose. (internal spring rusts and breaks; grind away the bit of the shaft that’s been peened over the cam, dis-assemble, fit new spring then clamp cam to the shaft and MIG weld over to retain cam.)

3. Assembly of shoes onto pivot stud. Should be:

Back plate, double coil spring washer (Thackeray type), shoes (offset ends assembled such that the flanges are in line), horse shoe circlip.

Figure 10 – Pivot assembly.

Pipe replacement.

The original pipes were ¼ inch dia. copper. These need to be well supported at regular intervals to avoid the vibration or flexing that causes work hardening, metal fatigue and possible fracture.

Consider using ¼ inch KUNIFER tube, a copper-nickel alloy which resists fatigue and corrosion.

The original pipes had single flared ends. Double flared ends are more effective in sealing, but need two operations using a special flaring tool.

Photo 1 – Flaring tool and bending former.

Figure 11 – Flared ends.

Use a bending former to avoid kinking the tube and remember to put the flare clamping nuts and protective spring over tube before flaring ends. The thread form used on our brakes is 7/16 inch UNF as the system is based on Lockheed. Brass nuts, to avoid corrosion and a special ring spanner are well advised. Pipe lengths and layout are detailed in Doug Pelton’s “From The Frame Up” and stainless steel protective springs are supplied by Roger Furneaux.

Check the pipes are supported by rubber/plastic lined clamps on bare sections of pipe and that the rubber grommets are not worn or perished where the pipes go through the chassis.

Good practice would be to replace synthetic brake fluids every few years and also renew brake hoses. MOT tests on brake rolling roads can show up imbalances due to oil or brake fluid leaks, the calculated efficiency should be in the order of 100% if you give the weight of the car as 787 kg. (Brown book).

I think 100% means the deceleration of the car is numerically equal to the acceleration due to gravity. However, this won’t stop you falling off a cliff!

Vehicle’s total braking force = F. Test weight for vehicle = Gp

Braking efficiency Z = (F / Gp) x 100%

Such an efficiency is not really achievable as the additional weights of fuel, oil, water and the person driving have not been taken into account.

Ed’s Note: Yet another of Eric Worpe’s superb technical articles. The source document for this article was a bundle of flip charts which Eric produced to illustrate his presentation to the T Register’s ‘Rebuild’ seminar held in March. Eric must have spent several hours in writing up his notes and in taking photographs of the flip charts.

As a matter of interest I had occasion to contact Eric recently about the thickness of brake lining material for TA/B/C brakes. I had received an enquiry from a TC owner who was experiencing difficulty in getting his new linings to fit – the drums were getting hot, even after a short run.

My advice to the owner, admittedly based on my Triple-M experience was, 3/16” but I said I would check with Eric. After measuring some different samples, including some original Raybestos linings we came up with a thickness of 4.8mm (3/16” = 4.7625mm). This information was relayed onwards and using this measurement solved the problem.

The Editor

1 May

It is fitting that a TA should grace the front cover of the June 2016 issue. Eighty years ago (June 1936) the first batch of TAs rolled off the production line in Abingdon*. On 25th June 1936 ten cars (chassis numbers TA0253 to TA0262) were built and by 29th June University Motors had a demonstrator.

Jarvis of Wimbledon had also managed to acquire one for their Showrooms in Victoria Crescent London SW19.

*Clausager lists TA0251 and TA0252 as prototypes; their build dates were 3rd March and 3rd April 1936 respectively.

The car on the front cover is Mick Pay’s ‘Primrose’, chassis number TA2073. In the background is Chillenden windmill, a Grade II listed open trestle post mill situated north of Chillenden (near Canterbury), Kent, England. It is the last post mill built in Kent.

Life has been more hectic than usual of late. A contributory factor is the appearance of Windows 10 on my computer; it is driving me to distraction. I’m afraid that you can’t teach this old dog new tricks (he doesn’t want to know about them!). All these ‘bells and whistles’ are superfluous as far as I’m concerned and get in the way of doing my job; End of moan!

Pictured above is the rally plaque for the Tour of the Forest of Dean and Wye Valley later this year. The photograph (which I know will be quite small in the printed version) is of the Horseshoe Bend of the river Wye, taken from high up on Yat Rock. This will be one of our stopping places on the Tour and if you haven’t been there before, the view from the observation point is quite breathtaking.

Whilst we are on the subject of Tours, next year’s is based on the Chichester Park Hotel, West Sussex. The Tour organisers are Vanessa and Peter Cole who have reserved 50 of the hotel’s 81 rooms. Booking details are as follows:

Telephone number of the hotel is 01243 817434. Booking reference is GA000367. The hotel will ask for your credit card details to confirm the booking, but nothing will be deducted until your arrival. An acknowledgement of booking will be e-mailed which includes the hotel’s cancellation policy.

When you have booked, Peter would appreciate an e-mail advice from you to let him know that you have booked. Peter’s e-mail address is as follows: pcoleuk(at)gmail.com {substitute @ for (at)}.

For some time now Steve (Webmaster and all things technical) and me (Editor) have been contemplating how we should take the website and the TTT 2 magazine forward. From a zero base in 2010 we have grown the circulation of TTT 2 to over 4,000 ‘subscribers’ worldwide (copy below of recent advice from our commercial e-mail forwarder).

The campaign Issue 35 Newsletter has been sent to 4,064 recipients, with the subject of ‘Totally T-Type 2 Issue 35 Published’

A recent feature on the TA in Classic Car Weekly listed all the UK MG Clubs at the end of the article but TTT 2 did not get a mention – probably because it does not have a discernible identity. We believe that we should be up there on equal terms with the other Clubs because we are constantly told that our services are valued and we have the largest on-line T-Type magazine circulation in the world. We have therefore decided that we will apply to Companies House to be incorporated as a Company Limited by Guarantee and be known as The MG ‘T’ Society Limited. There is some work to be done in submitting the necessary forms and then there is a much larger task of asking members to register and agree to act as guarantors by giving an undertaking to contribute a nominal amount (1 GBP) in the event of the winding up of the company.

Finally, subscribers to the printed copy of TTT 2 will receive a subscription renewal letter with this issue. The cost for six issues is 15 GBP (UK), 25 GBP (EU), 30 GBP (Rest of World). Apologies for the high non-UK subs due to high postal charges.

I would welcome more printed copy subscribers.

JOHN JAMES


DISCLAIMER BY THE EDITOR

Totally T-Type 2 is produced totally on a voluntary basis and is available on the website www.ttypes.org on a totally FREE basis. Its primary purpose is to help T-Type owners through articles of a technical nature and point them in the direction of recommended service and spares suppliers.

Articles are published in good faith but I cannot accept responsibility or legal liability and in respect of contents, liability is expressly disclaimed.