Archive | Issue 8 RSS feed for this section

The Luvax-Girling Damper

2 Aug

A NEW DEVICE AND HOW IT WORKS

Original MG TC Maintenance Instruction BookletEd’s Introductory Note: Each new TC was issued with a little pocket sized booklet as per the scanned copy shown (it will be noted that mine has seen better days!). Inside my copy I found two inserts; one is a single sheet which gives hints on care and maintenance of Dunlop synthetic tyres, the other is a quarto size pamphlet of four pages (including front and back).

The front of the pamphlet has the MG Octagon and the Safety Fast! logo and a note in the bottom right hand corner, which states “The M.G. Midget “TC” Series cars are equipped with Hydraulic Dampers incorporating the “Pressure Recuperation” feature. This reprint from ‘The Light Car’ explains, in non-technical language, how they operate.”

The back of the pamphlet says “WITH THE COMPLIMENTS OF THE M. G. CAR COMPANY LTD.,” plus address, telephone number and telegraphic address. “PRINTED BY TEMPLE PRESS LTD., LONDON E.C.1” is in the bottom left hand corner.

The two inside pages of the pamphlet explain how the hydraulic dampers work and the re-printed article from ‘The Light Car’ starts with a sketch of a section of a double-acting unit.

Section of a complete double-acting unit, showing the cam-operated pistons, and the baffle (D) which seals off the recuperating chamber above it, except for a “pre-determined leak” past the extension of the filler cap (E).

“You’ve read a good deal already about the Luvax piston-type pressure recuperating shock-absorber in the descriptions of new cars that have appeared in “The Light Car.” What is it? What does the term mean? How does it work?

Well, first of all, you must forget the term “shock-absorber”; it is considered to be a misnomer: the road springs are the shock-absorbers. Damper is a better term. Next, an amplification of the name: the result is the Luvax-Girling Damper and that is the name by which this particular commodity will be known in future. We must stress the fact that it is an entirely new and improved version of our old friend the Luvax shock-absorber.

The secret of the Damper is wrapped up in the term “pressure recuperating”. In essentially non-technical language, this means that when the piston returns to its “neutral” position after its initial damping movement, the cavity thus formed in the end of the cylinder is filled with oil-completely filled-for the simple reason that the oil has nowhere else to go. This is important. The piston must be “fully armed” for the next damping stroke, and it can’t be unless the cavity or chamber is fully replenished.

Now let us see how it works, assuming, for the sake of simplicity, that there is only one piston (the double-acting type shown in the sketch has two opposed pistons).

Deflection of the chassis frame partially rotates an arm, one end of which actuates a cam. In turn, that cam forces a piston outwards in a cylinder. The speed with which the piston can move outwards, however, is governed by the speed with which oil can be transferred from one side of the piston to the other. This is controlled by (A) a relief valve and (B) a “bleed,” the area of which is fixed by a restrictor pin. Both valve and “bleed” are part of the piston. The “bleed” is formed by a small flat on the top of the piston and a hole through which the restrictor passes.

A section of one of the pistons. (A) is the relief valve. (B) is the “bleed” and (C) the disc-type recuperator valve. The curved member on the extreme left is a steel spring which keeps the valve assembly in place.

On the return or inward stroke of the piston (as the chassis frame rises again) a disc-type recuperator valve permits the oil to be quickly transferred back again to the other side of the piston.

The transference is complete, because the body of the Damper, which is of course, filled with oil, is sealed by a lid or (to give it its technical term) a baffle.

The baffle has one important peculiarity in the shape of a “pre-determined annular leak,” which does, in fact, permit oil to pass to the recuperation chamber above it. The leak permits a slow flow, but is too small to accommodate a rapid flow such as that which movement of the piston tends to generate. Its object is to take care of volumetric increases due to expansion by temperature and to permit the oil to pass back again to the main oil chamber when the temperature falls.

To sum up, then, the piston moves backwards and forwards, the displaced oil on one side being squeezed via the appropriate ports and valve into the space on the other side. The manner of its regulation governs the ease, and therefore the speed, with which the piston can move, and the operating arm of the Damper can oscillate. That regulation of movement provides the damping action which enables you to drive over bumps and potholes as though they weren’t there.

These Dampers are not adjustable. The best setting is obtained during actual road tests of each make (and model) of car and this setting is adopted on the standard production model.

The new Luvax-Girling Damper is good for 25,000 miles without attention. It is not an afterthought, so to speak, but an integral part of the springing assembly: a scientific device which is the outcome of much thought, knowledge and experiment: and it has a stern task, for pressures up to 1,000 lb. per sq. in. may be generated.

It’s nice to think that you haven’t got to worry about it, but it’s worth knowing how it works”.

Ed’s note: I rather liked the reference to being able to drive over bumps and potholes as though they weren’t there! The roads must have been in better condition in the 1940s than they are now.

I spoke to Derek Stevenson of Stevson Motors in Birmingham about reconditioning of dampers. His company, founded in 1944, has been reconditioning vintage and classic lever arm and telescopic types for many years.

Derek told me that the dampers are neglected for maintenance purposes on many cars with the result that sludge forms in them and blocks the valves. A split casing renders the damper un-repairable and new casings are not currently available.

Derek’s website is at www.stevsonmotors.co.uk. He also sells flexible steel braided fuel hoses, brake hoses and brake pipes and accessories.

The Editor

1 Aug

Welcome to Issue 8!

I’m putting this issue ‘to bed’ in the middle of August to ‘sleep’ until the middle of September because my IT man (son, Stephen) is off at the end of this week on his travels to Japan and Taiwan for six weeks. Due to the shorter time interlude between the preparation of this issue and the last one I’ve struggled a bit with sufficient copy but we’ve just about made it.

A healthy supply of copy is vital to keep a magazine like this going and I feel for Vernon Byrom, Editor of the MG Octagon Car Club magazine The Bulletin, who, just lately, has had to make a number of requests for copy and indeed, has had to write some of the articles himself to fill the magazine. I’m in the same boat with Vernon this month in having to write some of the articles; I don’t mind doing this but it does consume more time when I could be in the garage ………dreaming up more articles!

In editing a magazine it is desirable to strike a balance between types of articles featured; in the case of this magazine, which is unashamedly biased towards the technical side of ownership of our cars, I strive to cover every T-Series model and therefore strike a balance between the beam axle models and those with coil spring independent front suspension. I have to say that I feel uncomfortable with the lack of coverage I am able to give to the TD and TF models, but I can only include what I am provided with. Perhaps TD and TF owners would like to take the hint!

Speaking of the MG Octagon Car Club, I attended the Club’s ‘Wings’ Run at the end of July. It was held at Westonbirt Arboretum in Gloucestershire, which is a mere 25 miles from me. I was a little apprehensive (as the photograph taken by Steve, just before setting off shows) but this was the first time I had used the car this year.

MG PB

Steve, my passenger ‘shot’ a couple of short videos on the journey; the first, taken shortly after after setting off:

The second is a bit longer and is ‘shot’ in the countryside. Apologies for the squeaky brakes in both videos and don’t forget the PB has a ‘crash’ gearbox!

Encouraged by the performance of the car on the ‘Wings’ Run I took it to David Lewis’ Wiltshire ‘natter’ at Lacock a week later. Even though it entailed a drive back home in the dark, I was glad I attended because there must have been a record number of M.G.s there – at least 20. T-Types were a plenty, but also MGAs, MGBs, V8, YA and ZA,

On 11th August we posted a news item on the website to say that we had reached the landmark of 1400 email subscribers to this magazine. To have attained this number in just under a year (the website was officially one year old on 20th August!) is no mean feat. At the rate that new subscriptions are coming in (current number at 17th August is 1430) we shall soon hit the 1500 mark. Thank you all for your support!

On 14th August we launched a new section of the website for our visitors: the T-Database. Part gallery, part T-Type “wiki”, the T-Database is an opportunity for MG T-Type owners to showcase their cars on the site. Through the T-Database you may upload multiple photos of your T-Series car, and add limited non-personal information about your vehicle. Alternatively, you may simply wish to browse the records of the cars that have already been added to the T-Database.

In order to post information and photos to the T-Database you need to be a member of ttypes.org; membership is quick and most importantly totally free, and can be obtained by filling out the registration form here. Once you have logged in, you will be able to update your car’s record on the T-Database by searching for your car by chassis number and then by clicking “Edit this Car’s Details”.

Not ones to let the grass grow under our feet, there are more enhancements planned for the website, more suppliers and more items for the Technical Publications section – just need the time!

In the December issue I’ll publish the up to date financial situation. However, I can say with certainty that the sum total of donations is very healthy and the ‘hard’ copy account is in surplus, both due to lots of generous donations.

Just enough space left to thank Fred Weber, Bart Vandonk, Tom Thompson and Trad Harrison for identifying Denis Dunstan’s mystery item. All said that they were fitted to the tappet chest plate – more details in ‘Bits and Pieces’ later in this issue.

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.