At 10:36 AM 12/31/98 -0500, you wrote:
>For our vintage group, CVAR, replacing the front suspension with the Caterham
>a-arm system results in removal from the vintage group.
>Harold Pace
>CVAR Regulations Committee
>
Rick, and others:
VARAC also frowns on such radical changes to the suspension setup. Our guys
tend to use stock suspension, maybe going to tighter bushes and stiffer
front bar, but retaining the stock design. One would think that the roll of
the car is almost a design feature to ensure that the tires are as lightly
loaded as possible. they also tend to run open diff's (keep in mind that
they also run the 1.1 Litre engine to fit into our Vintage class). I
suspect that Seven's would react well to using the best shock absorbers, I
would look into Penske single adjustables, as they are working well on my
car and they look great (the single adjustables don't have the remote
reserviors, are adjustable for low speed rebound, which theoretically is
important for controlling roll, and car be rebuilt and revalved to suit
anything).
Duncan Baker had a hugh crash at Mosport in their Series Two Seven a few
years ago. The front suspension failed as he was entering Turn One at
Mosport, and how he survived without injury is beyond me (the engine was in
the passenger seat). So check this: The front lower A-arms are attached
with pickup points that use a bolt placed in single shear, the same as many
small British cars. On Baker's car, the front-most bolt failed, allowing
the lower A-arm to fold under, a resulted in a total loss of steering.
Three things to consider, per Dick Baker's review of the causes:
1. The suspension bushing was nylon or polyurethane, rather than the stock
metalastic bushing, which put greater shock loads into the pickup point. In
his opinion, the stock bushing would be totally adequate given the tires
that we use, and the joint would be stronger.
2. The bolt was what actually failed. Check the bolts often, and use the
best possible bolts for the application. On my Merlyn, these bolts are
7/16" grade eight SAE, I don't know what size they are on the Seven, but if
they're 3/8", maybe upgrade them to 7/16"???
3. The design is single shear. According to Carroll Smith, this is an
offence again nature and the racing gods, however Lotus and others did this
to most of their cars for years. Design new brackets that put these points
into double shear.
Cheers, Brian
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