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Thursday, January 31, 2008

Rock 'n' Rollers: Suspense Again

The Roller Mount as installed. Picture: J.J.Hildreth

Silentblocs™ and rubber are, as I remarked earlier in this little series, an effective solution to many production and geometrical problems. And they are cheap. Rubber can be extremely effective as a suspension medium as in the original Mini, but in other places it is not quite so good.

One of rubber’s properties is hysteresis, but in our optimised suspension we would like to see unrestricted movement so that the road wheels, springs and dampers can all work effectively together without winding and unwinding pieces of rubber.

This brings me to the famous connection between the upper wishbones and the front spring. I have already drawn your attention to the rather nasty goings-on that must occur when the suspension is working. It was of course the works that originally attacked this problem. They used a roller (actually a lower suspension pin) mounted in a simple steel fixture that was bolted to the upper wishbone. There is plenty of pre-load in the Fulvia’s set-up so the spring is always in contact with the roller and with the freedom of movement (i.e. without the interference of the rubber) the suspension works much more effectively.

I never liked the rubber installation, and had been studying the transverse spring installation on a FIAT 130TC as a possible solution. It was at that time that I read somewhere that the works used a roller arrangement, but I was unable to find a picture of it. At the very next Surrey meeting of the Lancia Motor Club, I mentioned the idea to Doug Ellis (who owns a magnificent SI 1.3S) and we discussed the likely improvements that might result. The following month Doug turned up as usual and placed in my hands an exquisite piece of machining: a superbly finished aluminium mount fitted with a Nylatron roller running on a stainless steel pin. “Something you were talking about” he said. Neither Doug’s nor my car were running at the time so it was Justin (he has the Kugelfischer car I have written about here) who was the guinea pig. He reported a distinct improvement in handling, notably turn-in.

Unfortunately, the Nylatron roller soon wore out, the load from the spring being too much. Doug of course came up with the solution: a pair of ball races together with hardened steel pads that bolt to the spring. The system has been totally reliable: I have covered over 40,000 miles on mine and I still have the original ball races fitted. Doug wrote up the story in Viva Lancia (the LMC magazine not the web site) in 2006.

Justin has made drawings of the units, which I reproduce here. I have to say that I should think that they would be expensive to make. The Factory version would be much cheaper to fabricate – there is a photograph in Carlo Stella’s Zagato book for those who would prefer to take this route. A nice feature of the works design is that with rallying in mind, the mounts were designed to provide two height settings.

À bientôt


8 comments:

Anonymous said...

Hi

Always was interested in this particular improvement of the front suspension. The articles I've read and persons I spoke were all consistent: or the bearing-roller is worn out of the leaf spring gets to thin. This all happening whitin a few thousand kms.
Your (friends) system keeps working for 40K kms? That is a good mileage for an improvement of that kind. If this is the replacement interval, more people would be interested in this mechanism.
You wrote it would be expensive to make. What is expensive? 100€/each or ...
The rubber mounts aren't that cheap anyway, and if replacement comes up...
By the way, there is no such a thing as a cheap Fulvia part. (eg. wheelbearings, waterpump, bodyparts)

greetings from Belgium
Bart Verbeek

Paul said...

Thanks Bart. I agree about "cheap Fulvia parts". I am in no position to make these mounts. They would be much more costly than €100 I would say: the mount is machined from solid HE30, then there is the stainless steel pin to make. Admittedly the bearings would be cheap though! best option is to copy the works version which could easly be fabricated I think.

William said...

Hi paul, Ive fabricated a sollution in between the two you described. It is basically a 'Stella' U-frame. Mine is a cast aloy unit, but from steel, one can fabricate a copy quite simple.
The bolt is a normal 10mm bolt on were I have stacked 5ea 8mm wide bearings giving a 'roller of 40mm wide. exactly the width of the leafspring. First I discovered early cracking of the bearing outer race after about 5000Kms but that was due to a 7-leaf berlina spring fitted to my light car. That spring was so stiff it crashed more than that it absorbed. Now i've changed back to the original 6-leaf coupe spring and no more cracking whatsover! You can publish the picture if you wish.

Paul said...

Thanks William. I am sure you agree that Rollers make a big difference.

And yes, send me the picture I'll be delighted to post it.

Steve said...

Hi Paul,
I would really like to investigate having some of these rollers made here in South Africa. Would you be able to send me some better quality images as I cannot read the dimensions on the images posted here ?
Many thanks
Steve Archer
sjarcher@iafrica.com

Paul said...

Hello.

All you have to do is click on the image to get full size

Rob and Cailin said...

How much did this setup drop the suspension compared to the standard rubber setup?

I have heard rollers can be loud when driving, have you found this?

Paul said...

Hullo.

I cannot remember - and anyway that's up to you - you can always add spacers if necessary.

As for the noise, I don't see why there should be any. My car had no interior trim and quite a loud exhaust, so I wouldn't have heard any difference anyway. The handling is improved so any noise would be well worth it - the original idea of the rubber was truly horrible!

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