Alan B
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| posted on 22/12/04 at 07:19 PM |
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Rear suspension idea
Comments?
I'm trying to develop something simple and easy to fabricate.
It's basically a trailing arm/upright and two lateral links.
[Edited on 22/12/04 by Alan B]
Sorry guys the pics aren't working....look in my archive under R Susp or similar
[Edited on 22/12/04 by Alan B]
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sgraber
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| posted on 22/12/04 at 08:01 PM |
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Sorry Alan, I searched your entire site and could not find a section named archive nor any photos of a new rear suspension design!
Can you point me there with a link?
Graber
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Cita
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| posted on 22/12/04 at 08:22 PM |
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I think Alan means the photo archive on here Steve.
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sgraber
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| posted on 22/12/04 at 08:34 PM |
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quote:
Originally posted by Cita
I think Alan means the photo archive on here Steve.
Argh. I misread to say Look at my website.... Will pay closer attention!
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Alan B
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| posted on 22/12/04 at 08:45 PM |
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quote:
Originally posted by Cita
I think Alan means the photo archive on here Steve.
Spot on...
I'm sure I inserted the image correctly...I have done lots of them....but it did not work...
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Peteff
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| posted on 22/12/04 at 08:48 PM |
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It looks like it will lock up as it stands there Alan or swing in an inwards arc. Any way of animating it?
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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sgraber
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| posted on 22/12/04 at 08:54 PM |
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Yeh, I see it now.
To me it seems quite similar to the old VW swing arm suspension. From looking at it I think that you will experience a large amount of negative camber
under bump and positive camber in droop. Also this design may be susceptible to jacking the same as the Vdub suspension does.... Or am I missing
something here?
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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JonBowden
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| posted on 22/12/04 at 08:58 PM |
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reminds me of what I believe is a lotus experimental version of the seven - I think it was refered to as the type 37
 
Rescued attachment l737ag9.jpg
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Alan B
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| posted on 22/12/04 at 09:00 PM |
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quote:
Originally posted by Peteff
It looks like it will lock up as it stands there Alan or swing in an inwards arc. Any way of animating it?
I'll look at animating it..I have already moved it within solidworks.......no it doesn't lock up...the main arm is rose-jointed as are the
two links...
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JonBowden
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| posted on 22/12/04 at 09:00 PM |
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another view
 
Rescued attachment l737ag4.jpg
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Alan B
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| posted on 22/12/04 at 09:01 PM |
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quote:
Originally posted by sgraber
Yeh, I see it now.
To me it seems quite similar to the old VW swing arm suspension. From looking at it I think that you will experience a large amount of negative camber
under bump and positive camber in droop. Also this design may be susceptible to jacking the same as the Vdub suspension does.... Or am I missing
something here?
Steve, it's unlike the VW stuff in that you have good comber control.....picture the two rear links acting like front wishbones.....
I'm going to work on the animation...
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Aloupol
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| posted on 22/12/04 at 10:21 PM |
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IMHO while it's quite different it gives nearly the same result as the BMW system, with angled rotation axis which give camber gain and anti
squat.
I don't understand how is the camber gain controlable, for me it's at a high value, and difficult to change.
 
Rescued attachment 2RSusp2.jpg
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Matthew_1
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| posted on 22/12/04 at 10:22 PM |
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With that design the suspension will pivot laterally on the front joint as it goes through bump and droop. It will effectively toe in and out quite
heavily - it would be interesting to see how much toe change there is in the model.
Having looked at the picture above you're going to get toe out on bump, which means on a bend the outside, heavily loaded wheel will go into toe
out, causing oversteer.
[Edited on 22/12/04 by Matthew_1]
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Alan B
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| posted on 22/12/04 at 10:28 PM |
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I mean camber is controllable by design as in a regular unequal length non-parallel two wishbone front system...(ala Locost).......or am I missing
something...?
Don't forget I'm looking for reasonable handling not neccessarily F-1 standards....
Yes there will be castor change (to give antisquat?)...and some small toe change...but I feel the camber should be fairly well controlled.....
Thanks for the input so far guys..
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Ratman
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| posted on 22/12/04 at 10:32 PM |
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I like this simplicity. I once sketched all sorts of rear suspension alternatives and comparing them on the basis of the number of rose-joints
involved, and what you have is about the simplest. The problems are:
1. The wheel does steer a bit with suspension movement. This need not be a bad thing if well controlled.
2. The links going forward have to accept quite a bit of bending load, so they have to be substantial (= heavy). The longer they are the better, and
this adds even more weight.
3. Brake anti-dive. If the brakes are on the hubs (other then inboard on the dif) then when the brakes are on, the suspension "retracts"
so you loose grip on the road. The wheel skips. This is the reason why bikes have an additional "parallel" link for the rear brakes.
Again, this effect is reduced if the link is a long one.
All in all, it is probably better to put a reversed wishbone in for one of the inward links, and have two trailing arms. Like the Lotus example above.
The upright is more complcated, but the chassis pick-up points are much the same.
Cheers, Brian
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violentblue
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| posted on 23/12/04 at 04:11 AM |
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RSUSP
a few pics of my other projects
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Rorty
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| posted on 23/12/04 at 05:58 AM |
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Alan, may I ask what your train of thought was/is for this design. As per usual, I arrive late and most of the points I can think of have been
mentioned. I don't think it's a complicated design, but it seems to present more problems than it solves. It would also be fiddely to set
up and with 5 rose joints it would be fairly expensive. Obviously, solid bushes are out of the question.
Would a semi trailing arm with a wishbone-like top link not be easier and cheaper? Maybe something already fills the rear corner hence the peripheral
design?
[Edited on 24/12/04 by Rorty]
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Alan B
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| posted on 23/12/04 at 12:44 PM |
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Rorty...you have hit the nail on the head spotting my other motive...space.
From working on my current design using transverse FWD style power trains you find that locatations for conventional wishbones are very limited or you
are forced into very short wishbones.
I feel the current rear suspension I have on the Meerkat, while workable is quite complex....I'm just really throwing ideas out there for
feedback....
Steve, do you agree on the lack of space for wishbones comment?
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Alan B
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| posted on 23/12/04 at 01:22 PM |
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Well.....I'm feeling a bit happier....my idea is basically the same as the Lotus Esprit......never known for terrible handling if I
recall....
It has a long trailing arm with hub built in and two lateral links (the driveshaft is one of the links)
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Alan B
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| posted on 23/12/04 at 01:28 PM |
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quote:
Originally posted by Rorty
........ Obviously, bushes are out of the question........
Not neccessarily....if I can keep my links farly long, my suspension travel farily short and my bushes fairly soft it could be doable....
My model shows minimal side movements when travel is minimised and links maximised.
Sorry guys if it sounds like I'm arguing back at everything...I'm just trying to respond to everyone's comments and
observations.
Again, thanks and keep it coming...
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sgraber
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| posted on 23/12/04 at 03:49 PM |
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I completely agree about the lack of space. A fact that drove me somewhat towards the use of deDion for my first build.
I still think that there will be lots of camber change over your range of travel. I mean, the lateral link pivots on a single point and the hub is
perpendicular to this lateral link. When the link pivots, the wheel will camber in and out. Just like the old VW suspension. Ever seen a lowered VW?
The rear wheels have incredible camber! Because of the single pivot.
The trailing arms transfer the driven load back into the chassis and control the castor. They flex in camber, so camber is directly correlated to the
length of the lateral link and the amount of travel.
Please smack me if I'm being thick, but I have animated this in my mind and can't see it any other way...
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 04:06 PM |
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Steve, try to imagine the two lateral links being equal and parallel...then there would be zero camber change....the camber control is purely a
function of their length and parallelism...(just like a locost front end)....the trailing arm just follows the path the links lead it......dont forget
the big joint at the end of the trailing arm is compliant and not acting like a regular bearing.
Or am I missing something....?
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Alan B
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| posted on 23/12/04 at 04:22 PM |
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Ok...these are three rear views....
Someone tell me why camber control here is different to a locost front.....I'm not talking about specific geometry...just the principle..
 
droop
 
level
 
bump
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kb58
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| posted on 23/12/04 at 04:50 PM |
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It is the same... The front link will just cause toe in/out during travel.
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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Alan B
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| posted on 23/12/04 at 05:01 PM |
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quote:
Originally posted by kb58
It is the same... The front link will just cause toe in/out during travel.
Agreed....but it is not much with a long link and short travel.
How much toe change constitutes a significant problem?
Any opinions?
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