Formula Vauxhall Lotus - Technical

[schomosport]

The mainshaft concentric clutch slave cylinder used by the Reynard Formula Vauxhall Lotus (amongst others) is derided in many quarters since it is only sealed by O rings. Once wear has caused the assembly to score it either leaks fluid or sucks air - effect is the same, drags like hell.
2 options -
1) replace all as new and wait for it to happen again (possibly not in my lifetime seeing as I don't get out that often)
2) bin it and engineer a better solution,. SAAB 99 series slave cylinder is the favorite but requires some one off engineering since I am not aware of any truly bolt on adapters.
Anyone out there BTDT or recommend a way forward?
Sorry if wrong forum but there are a lot of FVLs in mono and a lot of mono contributers in this forum.

Cheers

[kickstart]

Cannot help but have you contacted Douglas Mclay at the Mono club - he runs a FVL and should be able to point you in the right direction.

[bella]

best place for this would be the techie forum, there's loads more brains to pick on there

[Bruce Shingle]

The problem with the seals on FVL is that most people use the wrong grade of material. Viton is often quoted as being what you want because it is the dearest which indeed it is. However it reacts to brake and clutch fliud. What was specified by Reynard when they built the cars and will do the job is EPDM one of the cheaper rubbers but resistant to brake fluid. According to my build list you need 1 BS224EP, 1 BS218EP and three BS227EP. The EP reference in the Reynard pt no being EPDM. Hope this helps.

[Barny]

I bought a repair kit from Alan Cornock, but that was some years back, so wouldn't know if he still hase them.

[schomosport]

Thanks, that's really interesting! I had succumbed to Carroll Smith's version of events and switched to Viton. That said, on my car both piston and cylinder are heavily scored and are probably as much the cause of the problem as the seals. However I have just acquired an unused pair so that should sort out that problem. I am interested in the viton reacts to oil and brake fluid bit because I had always been lead to believe that the whole point of viton was that it was resistant to petro chemicals - or perhaps it's just petrol?

Thanks especially for the O ring part nos. - I spent quite a lot of time with a vernier measuring used rings and the grooves in the piston/cylinder assembly but it's quite difficult to decide just what size rings to buy on that basis - nothing seems to be quite the right size. Cost wise, I procured Viton rings quite easily from a bearing stockist at a price that was peanuts.

[schomosport]

Further to above, I am using synthetic clutch fluid on the recommendation of other FVL drivers 'because it makes the seals last longer' I have absolutely no idea of the compatability or otherwise of the various o-ring materials and synthetic clutch fluid!!!Again, thanks for the input.

[Bruce Shingle]

Synthetic fluid will eat the gearbox casing in which the clutch fluid runs. Just as you should not use AP 600 in the clutch but AP 550. An ordinary road fluid will do if you use the EPDM seals. Look at www.jameswalker.co.uk You can get the corrcet EPDM seals from Wyko Seals in Halesowen. Why do you think that Reynard in the FVL manual make a particular point of stressing use EPDM.You do not need to measure they are sold by by the BS number which I gave you.

[schomosport]

Nothing in any Reynard information I have specifies the oil seal material. I have nontheless on your advice ordered EPDM O-rings and I will see how I get on. And yes, I understand how o-rings sizes are defined but at the time I last had to obtain seals I was left to my own devices. For the record, I correctly identified the sizes for myself because I bought exactly the same sizes as the numbers you gave me (only I specified Viton).

I am however a little surprised at your assertion that synthetic clutch fluid is incompatible with the gearbox casing and will damage it. Perhaps you could provide further details?

[Bruce Shingle]

Forgive me but I cannot remember if the FVL case is magnesium or not. Long time since we had one. If it is then it will be eaten by the fluid where the fluid runs through the casing. You can see this warning on a can of AP 600 as well. A good sign is the fluid looking 'milky'.

If you have a build list or a parts list for the FVL does it not give the part nos for the seals with an 'EP' at the end signifyiny EPDM.

Hope this helps.

[Bruce Shingle]

Schomosport,

When I look at last reply but one again it reads a little terse. Not meant to be............the Aussie in me!! Who mentioned Rugby World cup??

Bruce

[schomosport]

Bruce,

No worries. On re-reading the Reynard manual it does indeed state BS227EP, BS224EP and BS218ED - hopefully the last ones a typo and they mean EP else I'm really confused. What actually happened is that I was let down by a supplier who was going to send me an O-ring set. His catalogue just identifies them as 'O-ring'. The seals never turned up so I measured up what I had and went off down the bearing supplier without ever thinking to go back to the Reynard manual to check if there was any further information. By then I had already bought the (incorrect) idea that Viton just had to be the way to go so I would probably have ignored the EP reference anyway! We live and learn.

I had a suspiscion magnesium was about to raise it's head with regard to clutch fluid - the FVL is L155 aluminium so shouldn't be a problem with this casing. Again, synthetic fluid and magnesium not being compatible another thing to add to my list of 'I never new that'. Thanks again for your help and advice.