sgraber
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| posted on 23/12/04 at 05:21 PM |
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Well I just confirmed my suspicions. I am totally stupid and not worthy to participate in this conversation! LOL  (really!) I had your design turned
sideways with the single triangulated link being the lateral and the dual links facing forwards. And I couldn't figure out why you wanted so
much anti-squat!!!!  
As soon as you mentioned Locost front, it all came into focus...
I'll get my coat. 
Graber
PS- It's not THAT different than what you already have built...
[Edited on 12/23/04 by sgraber]
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Alan B
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| posted on 23/12/04 at 06:09 PM |
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quote:
Originally posted by sgraber
PS- It's not THAT different than what you already have built...
Exactly, so it won't need much in the way of frame mods....but it will allow me to get rid of the Toyota hub and fabricate a hub/trailing arm in
one piece...using the one piece hub assemblies that are just a bolt on job....and save a bunch of links and rod ends.
I just measured the toe change...from level to around 3" bump its about 0.015"...less than 0.5mm
It will need engineering for the optimum geometry, but I think it's a go.
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tadltd
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| posted on 23/12/04 at 06:21 PM |
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Alan,
Which way does the toe 'change' in bump?
From what I can picture (and I may be as wrong as Mr. Graber here - but then I would be in good company!) this set-up will give toe-out in
acceleration, and toe-in during braking, which I believe is what you want...
...to a certain degree.
Also, are you running without ARB's? Is this why you have so much camber control?
Best Regards,
Steve.
www.turnerautosport.com
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Alan B
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| posted on 23/12/04 at 06:28 PM |
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Steve, as drawn so far the it toes in by around 0.06 degrees.....
The positions of the links and chassis pick ups are a pure guess as shown so far....the goemetry is probably miles out as is now.
I have given no though to ARBs at this stage.
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Aloupol
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| posted on 23/12/04 at 06:32 PM |
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quote:
Originally posted by sgraber
I had your design turned sideways with the single triangulated link being the lateral and the dual links facing forwards.
I did exactly the same confusion, so there's more than one stupid.
Now put in the right side I understand, it seems OK..
There is still a lot of anti squat since the motor (or braking) torque tends to turn the trailing arm and to extend (or compress) the spring when
accelerating (or braking) but it's not a problem, a lot of cars have good behaviour with simple trailing arms.
Another issue could be the bending of the trailing arm under cornering force. The Lotus member seems huge, probably for that reason...
[Edited on 23/12/04 by Aloupol]
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kb58
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| posted on 23/12/04 at 10:07 PM |
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quote:
Originally posted by tadltd
... this set-up will give toe-out in acceleration, and toe-in during braking, which I believe is what you want...
...to a certain degree.
I though the holy grail was slight toe-in whenever the suspension moves away from its rest position. AFAIK you never want toe out. Toe-out under
braking would make the rear end squirrely (sp?) OTOH I agree it's all by degree, that a "little" toe is okay, whatever that
means... I'll sit down now.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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kb58
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| posted on 23/12/04 at 10:10 PM |
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quote:
Originally posted by Aloupol
Another issue could be the bending of the trailing arm under cornering force. The Lotus member seems huge, probably for that reason...
[Edited on 23/12/04 by Aloupol]
I don't think it's possible to bend the trailing links. There's a pivot at one end, and the other end is free to move up and down
(the axle) The only way it can bend is if one end tries to move and the other end is fixed.... neither are.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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Aloupol
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| posted on 23/12/04 at 10:23 PM |
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... Or if there's an important torque or load (there are both actually) between the supported nodes.
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tadltd
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| posted on 24/12/04 at 02:00 AM |
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Usually, when cars with unequal length wishbones are set-up, there is slight toe-in on the rear which is compensated for during acceleration, when the
wheels want to toe-out (i.e. they'll tend towards being parallel to each other rather than have an obvious toe-out condition).
On the front it's usually the opposite (slight toe-out) for the opposite situation, i.e. it tends towards toe-in under braking for stability.
Which is a good thing on the rear, too!
But then this is for a conventional unequal length double wishbone arrangement, which is not what Alan has... :s But it seems like that arrangement
will give the correct suspension 'behaviour' for stability.
Anyway, that's enough for this side of Christmas - have a good one, everyone! Hope Santa's good to you!!
Best Regards,
Steve.
www.turnerautosport.com
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locost_bryan
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| posted on 24/12/04 at 03:27 AM |
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Alan,
I keep thinking of the "traditional" arrangment single-seaters had in the seventies - upper and lower lateral links (like yours) and twin
semi-trailing radius arms, effectively giving 2 very wide-based wishbones.
I presume you space limitations would prohibit that design (and it's requirement for 8 joints per side!
Your design seems similar to the Nissan 300Z IIRC
Bryan Miller
Auckland NZ
Bruce McLaren - "Where's my F1 car?"
John Cooper - "In that rack of tubes, son"
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Ratman
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| posted on 24/12/04 at 07:50 PM |
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Hi Bryan.. I think it is classically 9 or 10 joints per side. You need at least one more to stop it steering. It certainly is a lot of joints. Brian
(in Wellywood)
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JoelP
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| posted on 24/12/04 at 08:39 PM |
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hey guys. this set up is very similar to a set up posted recently - IIRC, it was in an archive down a link i had followed from a new builder. The only
difference was that the lower bone had two joints at the hub end, to prevent steering. This is much like the underneath view photo posted further up
the thread.
in the scheme proposed by alan, i think that it would be hard to keep the wheel facing forward - what actually would stop it steering?
when i saw the photo before (maybe 3 weeks ago, before i got cut off... ) i was impressed and remembered it. I also posted in the thread a few
comments about it. I will try to dig it out, if my memory serves well!
[Edited on 24/12/04 by JoelP]
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JoelP
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| posted on 24/12/04 at 08:43 PM |
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here we go...
this is from 7/12/04, on the locost gt40 thread. ross is the chaps name, you can work out his website from the link above!
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JoelP
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| posted on 24/12/04 at 08:45 PM |
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note that the bit that goes forward (technical term) is split in two, to avoid the hub pivoting forward (maybe the cause of the earlier comments about
the setup locking up?)
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Alan B
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| posted on 24/12/04 at 09:48 PM |
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quote:
Originally posted by JoelP
- what actually would stop it steering?
The fact that the trailing arm and hub carrier are one solid piece....
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JoelP
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| posted on 24/12/04 at 10:47 PM |
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there is that, i suppose...
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cymtriks
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| posted on 16/1/05 at 09:14 PM |
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toe out is supposed to be a no-no on a rear middy suspension. BMW get around this by having a squashy front bush and hard lateral link bushes so that
twhen a side load is present the front of the trailing arm toes in thus undoing the links natural geometry. Lotus get around the problem by having
very long trailing links which minimise the problem.
How about sneeking a look under the Elise? The Elise has double wishbones of a conventional layout and they manage to get them round a transverse
engine.
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JC
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| posted on 23/1/05 at 10:29 AM |
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How about this? (Lotus Elise rear suspension).
Thought: The 'classic' Mini front suspension strongly resembles Alans design, except with a tie bar instead of trailing link and I remember
few complaints about the Mini's handling!
[Edited on 23/1/05 by JC]
 
Rescued attachment rearsuspension.jpg
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bpaar
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| posted on 27/11/05 at 03:01 AM |
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Toe In?
Can someone explain to me how there is toe in in this design?
From what I see, there is toe out with both rebound and compression (assumming the bottom control arm is level at rest). Any movement will shorten
the bottom control link giving toe out, the top link will twist the assembly and control camber. The amount of change is neglible with long arms, I am
just trying to understand the motion. What am I missing?
Bill
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Stephant
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| posted on 30/11/05 at 06:53 PM |
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toe
Hi
I guess in rear view the wishbone and the
balljoints are at one hight,so no toe changes at moving.The effect may be,that the toe link is stiff (balljoints ) and the wishbone has rubber
bushes.At cornering the wishbone get's "shortened" through the bushes and the toe link doesn't.Toe in is the result,depending
on loads.
Best regards,Stephan
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u401768
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| posted on 1/12/05 at 12:03 PM |
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OK - to throw a bit more in to the pot - Why not use two wide based trailing links, and ditch the lateral link - ie GTM Libra method - is easy to
package, puts the loads in to the tub, and means you can get the spring/coil over damper to lead straigh in to the tub too.
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Alan B
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| posted on 1/12/05 at 02:12 PM |
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quote:
Originally posted by u401768
OK - to throw a bit more in to the pot - Why not use two wide based trailing links, and ditch the lateral link - ie GTM Libra method - is easy to
package, puts the loads in to the tub, and means you can get the spring/coil over damper to lead straigh in to the tub too.
How does that handle camber?...Surely there is no camber change with that set up?
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iank
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| posted on 1/12/05 at 02:38 PM |
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quote:
Originally posted by Alan B
How does that handle camber?...Surely there is no camber change with that set up?
No there isn't, though camber can be set statically.
Works well on the mini and GTM , and the onyx firefox/clubsport use them and are reputed to handle well.
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u401768
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| posted on 1/12/05 at 04:14 PM |
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Plus has excelent load transfer cherecteristics too - but the down sid is there is no camber change, but this should'nt be too much off an
issue.
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Stephant
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| posted on 1/12/05 at 05:34 PM |
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Hi
low wight transfer means low roll centre too.With tailing arm suspension it is exactly at the ground,which is ok with a 7 type car.A full bodied car
with screens etc. should have it slightly higher.For getting Camber changes ,the swing axle of the upper upper tailing arm could have a different
angle.
Stephan
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