43655
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| posted on 9/8/17 at 12:38 PM |
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Rear Toe
Am going to be fabricating my wishbones in the near future, having a headache with designing in toe adjust.
Would you bother?
If yes, static or dynamic (rear steering)?
Trying to avoid using excess sphericals if possible, just out of longevity.
Front wishbones will be acetal/delrin/peek or something with a big spherical at the outer end.
Would be nice to use solid bushes inboard & outboard in the rears.
Or is this going to be an issue due to flex/compliance, much as I'm trying to design it out?
This is for a mid engine track/road car, ballpark figures: 800-900kg, initial 300hp, target 650rwhp (maybe awhp), 255 front 295/305 rear.
(Linky)
Here's a bit of an out of date screenshot of the basic setup
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nick205
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| posted on 9/8/17 at 01:26 PM |
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Some years ago I built an MK Indy with no toe adjustment on the rear. After having it measured one side was slightly out. At the time I corrected it
by fitting shim washers between the rear (Sierra) hub and rear upright. There was a noticeable handling improvement after it was done.
For this reason I'd say design in some adjustment. I'd also suggest using bushes on the inner end of the wishbones and rod ends on the
outer end of the wishbones. They're not staggeringly expensive and would afford easier adjustment after the car is built (less strip down and
more adjustment).
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britishtrident
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| posted on 9/8/17 at 05:00 PM |
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Under braking and acceleration any compliance at the inner ends has a bigger effect on toe control than at the outer ends
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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43655
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| posted on 10/8/17 at 06:51 AM |
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That makes sense, and my build table isn't particularly good so wouldn't be shocked if my chassis isn't perfect 
I think you're right, I'll just go for a spherical and a rod end on the outboard. At least the pushrod is mounted to the upright in the
rear, not the wishbone as the front.
I shouldn't be getting any measurable deflection, the bushes are hard plastic. If that doesn't work then it will be sphericals, rubber is
garbage
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b14wrc
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| posted on 10/8/17 at 11:12 AM |
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Take a look at my set up, I have gone through several iterations to finally get to this design, I appreciate if I was starting again I would probably
do something slightly different with the hubs, however - I think I have a good strong design now and it looks to provide good dynamic geo.
http://www.locostbuilders.co.uk/viewthread.php?tid=207665
I'm running 255 rear tyres, which I think will be suitable for 300plus.... a 295 will be really phat - what diameter are you looking at?
I'm using 17" x j9. 16" x j7 on front with a 225 tyre.
Rob
20vt powered rear engined locost
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43655
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| posted on 10/8/17 at 12:53 PM |
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Tyres probably are overkill, I've been seduced by the likes of the GT40...
Will probably run a bit less, not really decided on wheels yet.
Yeah that seems a petty standard way to do it.
Just a shame to lose the stiffness with regard to twisting load (braking)
Especially as my upright have a pretty wide base for it already
The spherical bearing-ed arm would just be allowed to move freely.
Am I overthinking it?
Likely
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907
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| posted on 11/8/17 at 05:18 AM |
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I made mine with polybushes at the dif cage end and rod ends to the upright. Seems to work.
Paul G
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