tajgreidotu
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| posted on 9/3/15 at 10:53 AM |
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Locost Wishbones Design
Hi all,
Once my chassis is completed, its time to start with the wishbones.
Ideally I would like to change the design a bit, 25mm tubes instead of 19mm, and 33.7 for the bush tubes as in the Haynes roadster.
Seamless, ERW or DOM?
I also saw some different designs for different balljoints (transit, Sierra? )
Any advice before I start designing?
Fyi information, the chassis is Locost per the book, planning to use Sierra uprights, and escort mk2 LHD steering rack (unfortunately  , would love
to be able to use the sierra one as escorts are difficult to find on here )
Thanks,
Javi
[Edited on 9/3/15 by tajgreidotu]
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craig1410
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| posted on 9/3/15 at 11:45 AM |
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One piece of advice I would offer is to avoid any bending loads in your design as much as possible. This can be a problem on the lower wishbone if the
lower spring mount is too far from the bottom balljoint. Also try to avoid any sudden steps in stiffness along the length of the lower wishbone which
might develop into a stress point. Those are the main points for me. Have a look at the Caterham design and also have a look at this thread:
http://www.locostbuilders.co.uk/viewthread.php?tid=12587
Consider using oval tubing as it looks better (IMHO) and reduces drag a tiny bit, not that drag is a primary concern on a seven type car. Also, you
might want to make up some simulated coilover units out of a piece of steel box section with holes drilled to simulate minimum length, maximum length
and normal ride height. Those are handy to check out your design when attaching the mountings.
Oh final thing, pay close attention to ensure that your wishbone to chassis mounts are absolutely concentric. You'll need a sturdy jig to
assemble them when welding but even then you might need to do some fettling afterwards to align them properly. If they are not pivoting about the same
axis then you'll get twisting loads which is obviously bad. How accurate you need to be depends on your choice of mounting. If using rod-ends
then you need to be very accurate but less so with more compliant mounts such as PU or rubber.
Good luck!
Craig.
[Edited on 9/3/2015 by craig1410]
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mark chandler
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| posted on 9/3/15 at 12:36 PM |
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Why go heavier gauge?
If you point the shock absorber at the ball joint you remove the majority of the loading on the tubes, you just need longer shocks.
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craig1410
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| posted on 9/3/15 at 12:41 PM |
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That top wishbone looks a bit skinny Mark! 
(I'll get my coat...)
I agree btw, no need for heavier tubes although oval ones would be okay IMO.
[Edited on 9/3/2015 by craig1410]
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tajgreidotu
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| posted on 9/3/15 at 12:49 PM |
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quote:
Originally posted by craig1410
One piece of advice I would offer is to avoid any bending loads in your design as much as possible. This can be a problem on the lower wishbone if the
lower spring mount is too far from the bottom balljoint. Also try to avoid any sudden steps in stiffness along the length of the lower wishbone which
might develop into a stress point. Those are the main points for me. Have a look at the Caterham design and also have a look at this thread:
http://www.locostbuilders.co.uk/viewthread.php?tid=12587
Consider using oval tubing as it looks better (IMHO) and reduces drag a tiny bit, not that drag is a primary concern on a seven type car. Also, you
might want to make up some simulated coilover units out of a piece of steel box section with holes drilled to simulate minimum length, maximum length
and normal ride height. Those are handy to check out your design when attaching the mountings.
Oh final thing, pay close attention to ensure that your wishbone to chassis mounts are absolutely concentric. You'll need a sturdy jig to
assemble them when welding but even then you might need to do some fettling afterwards to align them properly. If they are not pivoting about the same
axis then you'll get twisting loads which is obviously bad. How accurate you need to be depends on your choice of mounting. If using rod-ends
then you need to be very accurate but less so with more compliant mounts such as PU or rubber.
Good luck!
Craig.
[Edited on 9/3/2015 by craig1410]
Got all those advices covered 
-No bendings at all.
-Spring mount as close as possible to the balljoint.
-Oval tubing )almost gave up to search here in Bulgaria).
-Jig for suspension mounts.
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tajgreidotu
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| posted on 9/3/15 at 12:53 PM |
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quote:
Originally posted by mark chandler
Why go heavier gauge?
If you point the shock absorber at the ball joint you remove the majority of the loading on the tubes, you just need longer shocks.
The reason to go heavier gauge is to make them the same size as the Haynes ones, as my chassis has IRS from haynes roadster.
I saw your wishbones, and are exactly what I want to build. Are those transit balljoints?
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mark chandler
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| posted on 9/3/15 at 01:01 PM |
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It's a cortina upright with maxi lower ball joint and landrover series II track rod end at the top.
I scavenged some old landrover panhard rods for the steel at the bottom, the tops when I made them are 3/4" ERW.
Spreading plate is welded in the middle, not popped on top, I may bore some holes in these to lose some weight now I am sprinting the car, the vented
discs also need to go.
Regards Mark
[Edited on 9/3/15 by mark chandler]
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Slimy38
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| posted on 9/3/15 at 01:09 PM |
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I think even the Haynes roadster only uses 25mm for the lowers, the uppers are still 19mm?
The 33.7mm tube works well for bush tubes, I've used it for mine. I've used ERW throughout, making sure that where there is a weld (tube
to plate for example) the tube seam is within the weld.
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tajgreidotu
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| posted on 9/3/15 at 01:27 PM |
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quote:
Originally posted by mark chandler
It's a cortina upright with maxi lower ball joint and landrover series II track rod end at the top.
I scavenged some old landrover panhard rods for the steel at the bottom, the tops when I made them are 3/4" ERW.
Spreading plate is welded in the middle, not popped on top, I may bore some holes in these to lose some weight now I am sprinting the car, the vented
discs also need to go.
Regards Mark
[Edited on 9/3/15 by mark chandler]
If I remember well, landrover panhard rods are made with DOM.
They look great!
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tajgreidotu
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| posted on 9/3/15 at 01:33 PM |
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quote:
Originally posted by Slimy38
I think even the Haynes roadster only uses 25mm for the lowers, the uppers are still 19mm?
The 33.7mm tube works well for bush tubes, I've used it for mine. I've used ERW throughout, making sure that where there is a weld (tube
to plate for example) the tube seam is within the weld.
Yes, uppers are still 19mm so Ill stick with those.
ERW
Thanks mate
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mark chandler
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| posted on 9/3/15 at 03:41 PM |
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Also you do not have to use the bits they specify, if you find an equivilent ball joint or TRE off a common car in your area use that, remember these
cars are very light.
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907
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| posted on 13/3/15 at 06:36 AM |
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Hi
I looked at pipe sizes when I was making mine and my thoughts were:
Mmmm, 19mm ( 3/4" ) bit flimsy.
Oooo, 25mm ( 1" ) looks a bit overkill.
So I made them from 22.2mm ( 7/8" ), working on the principle of, if it looks right it is right.
Cheers
Paul G
[Edited on 13/3/15 by 907]
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