Bits and Pieces

Polybushes

The following was received from Barrie Jones:

“When visually checking my TF recently I noticed some blue particles under the rear end. The polyurethane bushes fitted to the rear spring shackles were flaking at the edges.  These are usually regarded as “fit-and-forget” so it came as a surprise to me.  I raised the rear end and dismantled one of the shackles. This is what I found (above photo).  All 8 bushes had turned crystalline and were no longer doing their job properly.

I keep detailed maintenance records so I looked up when I fitted them.  It was 17 years ago! 
So, they do last longer than rubber bushes, but they are not everlasting”.

The following from Michael Sherrell who received it from John Canty:

XPAG CROSSFLOW ALLOY HEAD

“The other day some interesting information arrived from TC owner John Canty in the UK.

He has an 8 port, alloy, crossflow, XPAG head made by Robert Cowell (later Roberta Cowell), the origins of which are unknown to me, but in 1954 Mike Costin acquired one whilst working with Colin Chapman on the Lotus 8, Frank Costin’s first streamliner SAR 5. The original heads had a small ‘Cowell’ cast in the side, but the Chapman ones did not!

John came across the head at a motor spares place when he went looking for a pair of SU air rams. We could be so lucky! His head does not have the ‘Cowell’ cast in, so it might be a Chapman one. John was a TC racer (TC/1403) back in the days when TCs filled the grids in the UK. He could have done with the head then!

The story gets more intriguing: with the letters and photos John sent me, came a photocopy of a letter addressed to him from Keith Duckworth himself (of Cosworth Engineering) dated 10/05/91. In it he outlined some of the history of these heads and it goes like this: It was Mike Costin who was with Colin Chapman at the time – 1954 – He had just returned from holiday. They used a crossflow aluminium head, which was made by Robert Cowell – who incidentally became Roberta Cowell by the assistance of the odd operation or two. Some heads had a small COWELL cast on the side of the head. The Lotus had not got the Cowell name (and we all know why!). Had a leak from pushrod hole to exhaust port, which Mike Costin lined with a copper tube. Mike and I think the heads were very rare… Best Wishes, Keith Duckworth.

Looking at the photos, one can see the spark plugs have been shifted to the off side to be with the four individual inlets and enter the (minimal) combustion chambers over the inlet valves. There appears to be little of no water flow block to head and minimal oil drain head to block. One can only guess at the compression ratio (high) and it would be pretty difficult to blow a head gasket with all that  flat area. Exhaust ports are round, as are the inlets. The whole design looks vert appealing, pity they are so rare.

I believe these heads may be the source of some confusion over the Laystall Lucas alloy heads, sometimes thought of as crossflow heads, which they were not. I would like to thank John Canty for going to trouble and expense to share this interesting bit of XPAG history with us.

Almost as interesting as the heads themselves is the story of Robert Cowell, who later became Roberta Cowell after a series of operations, becoming a forerunner of gender change. It’s worth looking up Roberta Cowell on line. Spitfire pilot, racing driver, talented engineer and pioneering transgender person, just a bit ahead of her time”.

TC gearbox end covers

The following from Paul Busby:

“Thought you would like to see my latest efforts to suitably improve one of the weaknesses in TC’s design. Other people have remanufactured the gearbox end cover or offer steel splint plates but I have re-visited the issue. Clearly failure occurs through the engine/gearbox combination moving forward through normal traction and braking loads, accident, soft and perished mounting rubbers, flexure in the engine mount plate and chassis mount brackets which do not offer much resistance to longitudinal movement.

Hence the need for additional ribbing around the cantilever section of the end cover.  In addition to increasing the stiffening rib arrangement around the common failure line, I have enlarged the output shaft spigot to accept a modern lip seal. The seal runs on the original, reverse scroll section of the drive flange which is covered by a SKF ‘super sleeve/shaft repair sleeve’. A 36mm repair sleeve is a perfect fit. – see photo. If needed, the end cover can be left bored as original to run the reverse scroll. 

Second photograph includes one of an original end cover (un-broken, pretty rare). Due to making the outer rib parallel, the arrangement needs the M10 studs to be longer and for ease of availability the M8 csk bolt is replaced by a M8x30 Allen cap screw.

I have so far only made end covers for my own use but if there is enough interest shown (Minimum of10), I would make a batch. Alloy is LM25 heat treated to TF condition.” pyb.7(at)tiscali.co.uk [please substitute @ for (at)].

Also available from Paul are these gearbox remote top covers, as these break and wear at the gear lever ball causing the lever to drop through the actuator arm.

Thin steel gaskets for tappet chest cover

All 20 of these have now been sold, along with the 40 nitrile cork gaskets.

I have recently ordered some spare nitrile bonded cork gaskets. Whist they are not to hand at the time of typing this, they should be available by the time that this appears.

I have yet to fit my steel and nitrile bonded cork gasket set (been too busy refitting the back axle on my TF) but when the time comes, Paul Ireland has sent me the following ‘instructions’ on how to do it:

“To fix, I would recommend using a good quality gasket sealant such as red Hermetite or Loctite SI 5980 Gasket Sealant Paste. Put a thin coat on one side of one of the cork gaskets then press it onto the steel plate.

Put a thin coat of gasket sealant onto the exposed side of that cork gasket and offer the steel plate up to the cover, using two of the fastening bolts to locate it.

You can then put a thin coat of sealant on one face of the final cork gasket face and put it onto the steel plate. Coat the final face and offer the cover and steel plate up to the engine, using the fastening bolts to keep everything aligned.

It’s probably easier than fitting the original cork gasket.

However, please be aware it’s not a magic fix to the oil leaks, it just helps to reduce them.”

Loctite SI 5980 (other brands are available).

2 thoughts on “Bits and Pieces

  1. Geoff P says:

    I was under the impression that the cause of TC gearbox end cover mount breakage was primarily due to chassis flexing. I base this reasoning upon the observation that a ‘boxed’ TC chassis has no gearbox end cover issues. Either way, the improved gearbox end cover offered by Paul is a major improvement on the original.

  2. Tony O'Reilly says:

    Fascinating article on the crossflow XPAG cylinder head. I didn’t even know such a thing existed. I’m now wanting one for my Cooper MG, although I’m not sure if it would work with my XPEG block!
    Probably unlikely that I’d ever fine one, but nice to contemplate the possibility.
    Robert Cowell, or Roberta was also a great read. What a character. Thanks so much for sharing. Great article.

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