I've got a question for all the suspension experts out there....
I'm thinking of how I'm going to sort out my rear suspension. I'm building a mid engined car (NOT a 7) and would like to use a similar
rear suspension design to that of the book front. However with the drive shafts going through the middle of the wheel mounting the damper is going to
be a problem.... is there any reason I can't mount the damper on the top wishbone instead of the lower?
Good question! I'm doing the exact same thing at the rear(with the shock coming from the top A arm). I just hope the transit track rod is up to
it. I think it'll be perfectly ok, the only thing is I'm only going to have 3 1/2" travel on my shocker which should be enough
it'll just have to have a stiff spring on it.
As I say I would like to hear what everyones opinions are on this.
Mike
Not a very good idea... track rod ends are not designed for bending, only longitudinal loads. Maybe you should mount the track rod end to the lower
arm instead. Itīs simple and safer.
Gustavo
i see nothing wrong with it myself, at least the TRE is getting pushed down, not apart.
One alternative is to run a push rod off the lower arm, and mount it to avoid the driveshaft.
If you arent happy with a TRE taking the load, just use a different upper ball joint.
Copying a front suspension for a rear is a really bad start -- even more so when it is the book front suspension with its massive bump steer
problems.
A better start would be adapting MK style rear IRS.
what engine are you using, and are the hubs the matching ones? And are you using an insert to replace a strut?
The transit rod end works at the front of the car because it only has to resist sideways forces from braking. Even so, it's not really designed
for this application and the conclusions from previous discussions on here suggest is that there isn't a very large safety factor as the thread
is stressed in bending rather than tension/compression (though the failure rate would suggest it's strong enough).
However, putting suspension forces through it is a very bad idea, not only from the strength issue, but because force transfered through the balljoint
in that direction will compress the internal spring that keeps the ball tightly in it's socket. This means the ball will be free to float
around, giving unwanted movement in your suspension.
As you are presumably designing something from scratch, why not use a ball joint designed for this application, from e.g. a metro?
[Edited on 18/9/05 by MikeRJ]
Ok well if the problem is in the TRE what about if I reveresed things? using a ball joint facing downwards at the top and a TRE facing up at the
bottom? or is this an even worse idea?
The other option would be as someone pointed out working in a mounting for a push rod and having a cantilevered suspension.
am i missing something here? if it is the rear suspension you dont need balljoints at all.
just bushes or spherical bearings for up/down movement. no point copying the whole front suspension design. youd probably be better off modifying your
upright with a bracket and using a polybush, or prefferably 2.
Russ.
i think he's using a FWD setup at the back, hence the hubs will be steerable. Id agree with you though, much easier to use different hubs that
dont need balljoints.
does anyone do ally rear uprights for the sierra based 7s?
[Edited on 18/9/05 by JoelP]
The TRE is probably not suitable for the upper wishbone if you intend mounting the shock to the upper wishbone.
The Transit TRE or DLE is definitely not suitable for use on the lower wishbone.
Fit a propper balljoint (not a TRE or DLE) to the upper wishbone, and don't be tempted to use one that's normally situated on a lower
wishbone (unless you pull one apart and examine its construction), as most balljoints are designed to work either as a lower joint or an upper joint,
but seldom both. There are exceptions.
quote:
Originally posted by Rorty
The TRE is probably not suitable for the upper wishbone if you intend mounting the shock to the upper wishbone.
The Transit TRE or DLE is definitely not suitable for use on the lower wishbone.
OK, if it works it works, but bear in mind you only do a few hundred yards in your car once or twice a month.
I would have thought the Transit TLE would not stand up to the rigours of long road use.
Go to a Kit Car show and look at what all the manufacturers are doing.
The shock should mount straight on to the upright. Thence, no big balljoint probs.
The parts are all commercially available, so why try and reinvent the system?
could you have the shock off centre? If you are worried about twisting forces, have one on either side!
quote:
Originally posted by NS Dev
Why not?
I know what you are saying about compression or tension type balljoints, but the transit one is a steering joint so is neither.
That's probably it, and as Rorty said, mileage is low and maintainance thorough on the grasser.
It's certainly had some biggish hits on the front corners now though (enough to take chunks out of the wheels) and the balljoints are fine.
Interesting to note that folk using a Maxi bottom ball joint are, in theory at least, loading the joint differently to how it was intended as well...