Autoflock Motorsport
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| posted on 21/4/15 at 07:35 AM |
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re welding my rear wishbone mounts help please
Right peeps need some urgent help, I need to sort my wishbone locations out in the next efw days, at the moment as you can see from the pics their
angle is totally wrong, I would like them to be slightly pointing downwards, what is the best plan of action for me to sort this asap? the plan so
far is to gring the wishbone to chassis mounts off and lift them so the bottom one is horizontal and the top one is slightly pointing down, ive done
no calculations due to lack of time but i would imagine once ive got next weeks trackday out of the way a fll setup will be worked out. My main
concern is the amount the wheel will be forced outwards.
Also ive been running the car at 50mm off the floor, is this too low as ive noticed some of the rgb racers running a lot higher than that?
Any comments would be most appreciated
Kind regards
Raj
http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=183445
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40inches
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| posted on 21/4/15 at 07:40 AM |
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If you lift the car until the bottom wishbone is parallel with the ground, what ground clearance do you have?
If the drive shaft is connected, it is at one hell of an angle. It looks to me that the chassis was designed for a lot more ground clearance than you
have.
[Edited on 21-4-15 by 40inches]
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CosKev3
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| posted on 21/4/15 at 08:01 AM |
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Inner joint on shaft is unbolted 
I wouldn't be cutting anything off as a first job, surely raising the suspension will straighten your wishbones as you want?
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JimSpencer
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| posted on 21/4/15 at 08:03 AM |
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Hi
OK - first question Why do you want to change it - it looks wrong? or it handles wrong?
Take another picture with the driveshaft tacked into place?
Re the ride height - as a very rough rule of thumb:-
the lowest you can go, if playing by the rules, is 40mm and most folks would run some rake in it - lets say around 15 - 20mm as a rough figure.
So
if you've got 50mm all round (with you in it don't forget..) drop the front a bit, raise the rear to around 60mm and with the drive shaft
in place - is the shaft more or less horizontal?
And lastly has it got the right size tyres on it?
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40inches
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| posted on 21/4/15 at 08:05 AM |
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quote:
Originally posted by CosKev3
Inner joint on shaft is unbolted
DOH!
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liam.mccaffrey
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| posted on 21/4/15 at 08:52 AM |
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I think you're running the car too low for your wishbone geometry. Raise the ride height until the bottom wishbone is parallel with the ground
and it will at least "look" more correct
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daniel mason
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| posted on 21/4/15 at 12:08 PM |
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I'd roughly raise the rear until the wishbones are more parallel thus raising the rear ride height then allow around 20-25mm sake as jim said to
he front!
40mm is minimum on the hills and sprints but most circuit racers run much more and are working to different regs!
Where are you measuring your ride heights from?
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daniel mason
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| posted on 21/4/15 at 12:13 PM |
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One over point is I'd leave it alone until after next Friday on track. Bring a tent. Stay at the circuit and look at some of he sprint cars
taking part. This will give you a good idea on ride heights and geometry!
Also if you raise the ride enough to make your wishbones parallel then your cambers will be miles out. And depending on manufacturer they will vary in
the ammount of negative camber they need. But some are so excessive that running positive camber will make the car much worse than it currently is!
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bozla
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| posted on 21/4/15 at 05:09 PM |
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The RGBs run higher as the minimum ride height is 75mm with driver seated.
From regs:
Ground Clearance
: Under no circumstance can any part of the
bodywork, or of the suspended part of the car with the exception of
the exhaust system, be below a horizontal plane passing 75mm
(50mm for exhaust systems) above the ground, the car being in
normal racing trim with the driver aboard. A gauge of 75mm or
50mm may be used by Scrutineers be
fore or after races or practice
to check the ground clearance. There is no minus tolerance to these
measurements
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motorcycle_mayhem
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| posted on 21/4/15 at 05:47 PM |
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Geometry (by eye) looks good to go if you raise the ride height, problem eliminated. Any other action will require a few beers and some thought.
Other action:
Ascertain what you want to use the car for, look at the regulations, obtain the ride height requirement.
Dial this in.
Look at the result, if the bottom wishbone looks sort of parallel enough to the ground (or ideally slightly lower at the upright end) then
you're good to go. If things aren't looking good, then adjust the wheel/tyre diameter until (with commensurate dialling on the spring
height) you get that lower wishbone looking good for the ride height you need. This will introduce a gearing issue, usually manageable. When
it's all looking good, check for droop, etc., if still good. You're done.
*Adjust ride height with wheel diameter*, not by compromising the geometry.
If none of the variables give what you need, dial in your ride height, pick a close enough wheel diameter that is near to getting the geometry in the
ballpark, and then re-weld the bottom chassis pickup so the lower wishbone looks OK. Check you get a reasonable negative incline on the top wishbone,
a bit of camber on droop (and ) if so, you're done. If not, play about with the top pickup a bit.
Everything is a compromise.
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