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by Brit-Car-Nut » Tue 22.08.2017, 14:16
That seems strange.
They aren't 4 of each thickness so they get one of each at each arm? It would be nice if you had a stock suspension and you could measure to get the right spacing and then match that with the poly parts. Easy enough to turn, but I would ask Steve as he isn't that careless and you might have a rogue or defective kit. Time doesn't matter here since wrong is wrong and you trusted his parts to bolt in without thought.
I think I have a couple of stock upper wishbones off a car that I could measure the total spacing and details so you can match them. I am concerned the bushes are correct and the distance tubes are wrong so modifying the bushes would be the wrong solution. I could see thicker flanged bushes on the insides and thinner on the outsides, but never really gave it much thought before today.
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by lotusflasherman » Tue 22.08.2017, 16:09
chrisP wrote: I may try machining the pu inserts, in a lathe, to the correct thickness
Have you considered copying them the correct size in PTFE by machining from PTFE rod?
It's something we did in the 70's on race Mini's to replace the lower arm inboard metalastic bush and rubber bushes on front tie rod. (The guy who drove the other car worked at ICI Plastics Research in Welwyn Garden City so he made them at work as 'research' ). Under braking the OE bushes used to 'wind up' and cause judder around the point the tyres were losing grip and it cured that. Some competitors spent an awful lot of money on a 'rose joint conversions' to achieve the same result. PTFE is quite hard & 'self lubricating' but is supposed to suffer 'creep' (will slowly change shape) so we had spare sets of bushes - but never used them as the originals proved more durable than 'rose joints' . The only problem we had was trying to keep the PTFE painted black so nobody noticed our 'Demon Tweak' and copied it ..
It's something I've thought about for the Elan after reading in the Hughes' book that the wishbone inboard bushes are 'much stiffer than normal' (page 146). The raft mounting bushes provide insulation from road noise so don't think it will have an adverse effect on noise. Stainless steel tube inserts probably best as any rust would act as abrasive & wear the PTFE away ...
Phil
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by Brit-Car-Nut » Tue 22.08.2017, 17:12
When we were racing the MG Midgets, we looked at Teflon bushes but because of their "flow under pressure" ratings, we went to Delrin which is more structurally rigid. Today, I would look more at Acetal (more stable and less hygroscopic) but would need to do a lot of research as to compression and flow under stress.
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by dapinky » Tue 22.08.2017, 17:54
On my track/race cars we went down the rose-joint route - gave great results and could be adjustable for each track we used....
.... but that's the issue for a road car, you really need the elasticity of 'softer' components to avoid your fillings rattling use on the way to Tescos.
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by lotusflasherman » Wed 23.08.2017, 00:35
dapinky wrote:On my track/race cars we went down the rose-joint route - gave great results and could be adjustable for each track we used....
... but that's the issue for a road car, you really need the elasticity of 'softer' components to avoid your fillings rattling use on the way to Tescos.
Rose joints great for track use as they add an easy geo' adjustment too but expensive and harsh, though PTFE bushes are harsh too - much harsher than rubber. M100 has raft bushes too so at least your fillings should stay in ...
Benefits of PTFE are - easily available, dirt cheap, easy to machine on a lathe, fairly durable - but make some extra sets so you can swap them when needed, they always come out easily so doesn't take long...
Phil
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by chrisP » Wed 23.08.2017, 11:53
I have stock parts as well, so I have already measured the bushes against stock, the stainless tube in the SJ kits is the same length as the original metalastic central tube. So the PU is too thick. What i am not sure is, how much if anything the PU should be thicker than the insert. I will have a chat with sj's as soon as I can. Thanks for the comments people.
Chris
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by chrisP » Tue 03.10.2017, 11:44
Just to update on this story.
I sent an email to Steve at SJ Sportscars regarding the noises coming from the front upper wishbone bushes, with a picture or two he was able to identify that the 'tophat section' was not machined to the correct thickness and has sent a new set to me for fitting. So the problem should be fixed over the annual SORN (avoid salt covered roads) winter break.
Chris
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