sietze
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| posted on 21/8/04 at 07:24 PM |
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Anybody thought of using Audi A4 front hubs and uprights?
Hello,
The latest Audi A4 (last 4 years at least) has a very funny front suspension. The cars are front wheel or four wheel drive. They use 4 seperate arms
to connect to one front-upright (plus steering arm). The connecting arms are positioned in such a way that the tire maintains very good grond contact
in turning (as opposed to some mercs). It is a sort of double wishbone set-up with flexible wishbones.
What do you guys think of this design? What do you think of using the upright in a Locost front suspension (especially if you consider building a 4x4
Locost)??
greetings
Sietze
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giel
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| posted on 21/8/04 at 10:15 PM |
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I'm not sure what the lower arms look like, but I know the upper one is made of two rods. The centre lines meet in a virtual point that lies
'inside' the tire. They're also quite high, might not be so useful for an open wheeled car.
I've been looking at them myself for my project, but my wheels will be inside the body (not a 7-style car).
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Mark Allanson
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| posted on 22/8/04 at 08:27 AM |
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The uprights are about 2' tall!, the upper and lower arms are ally with metallastic bushes on the car end and non tapering balljoints on the
other. They are also very heavy, except for the S4 which has ally ones.
If I remember, I will post a picture tonight (I've got a few at work)
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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crbrlfrost
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| posted on 22/8/04 at 11:09 PM |
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Anyone know of any good technical articles regarding the Audi four link? Checked SAE.org last night and was coming up somewhat dry. But regarding the
applicability to the locost, seems like overkill to a problem that isn't significant. Not to mention the fun engineering problems of adapting a
four link to an entirely different vehicle. But don't let that stop someone who wants to give it a try! Cheers!
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Mark Allanson
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| posted on 23/8/04 at 06:48 PM |
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I think they are a non starter, just too tall and complicated, the lower arms are too long......
Just look at this photo I took today at work
 
Rescued attachment A4Susp.jpg
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Mark Allanson
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| posted on 23/8/04 at 06:49 PM |
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The steering rack would have to be above the bonnet line
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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sietze
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| posted on 23/8/04 at 08:50 PM |
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quote:
Originally posted by Mark Allanson
I think they are a non starter, just too tall and complicated, the lower arms are too long......
Just look at this photo I took today at work
OK, I am convinced
But I find the principle operation of the two excentric arms intrigueing (spelling??). You could make something like that out of the lower part of the
sierra macpherson strut. Cut the bottom 10 cm off, weld two plates (with matching holes) around this, brace it with a third vertical plate and you
have got the facilities to fit trackrod ends between them. Of course, lengths, angles, etc. will be a pain to figure out, but still the result could
be worth it!
Sietze
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Noodle
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| posted on 24/8/04 at 09:21 AM |
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quote:
Originally posted by sietze
quote:
Originally posted by Mark Allanson
I think they are a non starter, just too tall and complicated, the lower arms are too long......
Just look at this photo I took today at work
OK, I am convinced
But I find the principle operation of the two excentric arms intrigueing (spelling??). You could make something like that out of the lower part of the
sierra macpherson strut. Cut the bottom 10 cm off, weld two plates (with matching holes) around this, brace it with a third vertical plate and you
have got the facilities to fit trackrod ends between them. Of course, lengths, angles, etc. will be a pain to figure out, but still the result could
be worth it!
Sietze
I should try not to be too intrigued. I suspect all that elaboration in the front suspension is to try and quell the idiosyncracies of attempting to
drive the front wheels. It's just plain unnatural 
Cheers,
Neil.
Your sort make me sick
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giel
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| posted on 24/8/04 at 05:56 PM |
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quote:
I should try not to be too intrigued. I suspect all that elaboration in the front suspension is to try and quell the idiosyncracies of attempting to
drive the front wheels. It's just plain unnatural
Cheers,
Neil.
The 'elaboration' does actually serve a purpose: a small kpi without the disadvantage of either
- the upper balljoint inside the rim with a resulting small distance from upper to lower BJ
- the upper BJ above the tyre, wich requires a taller upright and pushes the fenders up too
This could well be a plus for every suspension, driven or not.
BR
Giel
[Edited on 24/8/04 by giel]
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crbrlfrost
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| posted on 27/8/04 at 05:50 PM |
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Not to mention with a little ingenuity it could be tuned to give turn in caster gain, or put another way, added negative camber on a turning wheel
while being able to leave the wheel upright in the straight ahead condition. However, with these advantages come disadvantages, like the really tall
upright. In order to control caster, the angle gain has to relatively small. The longer the upright the smaller the angle change per unit of
longitudinal travel of the upper pivot point. Not to mention that the change doesn't have to be symetrical (ie inside and outside wheel the
same), so that adds another layer of complexity, as most likely you won't want them to be identical. Add some steering concerns and you can see
it would be quite an undertaking, but doable if scientifically and mechanically inclined. However, due to the light weight of these cars and the
usually moderate aspect ratios of the tires, I wouldn't, in this case, think of it as a large gain worthy of the effort. Cheers!
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Peteff
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| posted on 27/8/04 at 07:25 PM |
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The steering rack would have to be above the bonnet line
Which would solve the problem of getting the column round the alternator. It's all good news so far then, go for it Sietze.
[Edited on 27/8/04 by Peteff]
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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Mark Allanson
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| posted on 27/8/04 at 09:38 PM |
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If you are thinking about using something similar, make sure you get the trackrod end with no tapered attachments, as this height adjustment is used
to alter the 'S' curve of the castor/camber
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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robinbastd
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| posted on 27/8/04 at 09:58 PM |
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If you use the shims from the octavia range (less complicated setup), you can alter the castor, the KPI and the camber at the same time, and if you
invert the shims, you will increase the castor as lock increases thus getting more self centering as you turn the wheel.
Alternatively you can use something that is tried and tested and build a locost.
sietze: Ik hoop je neemt het me niet kwaadlyk.
[Edited on 27/8/04 by robinbastd]
Only a dead fish swims with the tide.
http://smuttygifts.com/
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sietze
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| posted on 31/8/04 at 06:41 PM |
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quote:
Originally posted by robinbastd
If you use the shims from the octavia range (less complicated setup), you can alter the castor, the KPI and the camber at the same time, and if you
invert the shims, you will increase the castor as lock increases thus getting more self centering as you turn the wheel.
Alternatively you can use something that is tried and tested and build a locost.
sietze: Ik hoop je neemt het me niet kwaadlyk.
[Edited on 27/8/04 by robinbastd]
Almost right: 'Ik hoop, je neemt het mij niet kwalijk' or better ' Ik hoop dat je het mij niet kwalijk neemt'
BTW, the idea is to take a locost as starting point but craft 4 wheel drive onto it. And as a locost is for twisty and turny roads you want to be able
to apply power in corners, especially at the front wheels as this provides the main advantage of 4 wheel drive. So you need a good contact patch.
Which means, due to the low weight of the car, keeping the tire flat to the surface. Hence my interest.
Sietze
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