violentblue
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| posted on 8/1/04 at 04:57 AM |
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DAX suspension
Anyone know much about this suspension setup? looks like it'd be great for handling but geomery would have to be near perfect for it to work.
plus more to go wrong.
but if it was possible to make it work on a middy, I'd be all over it.
anyone familiar with this system?
anyone have measurements from a working version?
a few pics of my other projects
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MikeR
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| posted on 8/1/04 at 05:37 PM |
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ok i'm being lazy as usual and not figuring it out, but what happens in single wheel bump????
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JoelP
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| posted on 8/1/04 at 05:51 PM |
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is it the top joint on the blue thing that is rigidly fixed to the chassis? looks like a good system at first glance.
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GO
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| posted on 8/1/04 at 06:02 PM |
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I dunno! Its giving me brain ache trying to figure it out!
Tempted to make a model and see how it behaves. Certainly interesting though.
But... if it is that great, why haven't other makes taken it on - could be patented I guess.
It looks... and I'm probably wrong... like the wheel in bump will try to push out the top wishbone on the other side but I'm not sure what
effect the fact the bump wheel is rising will have on the rocker for that side.
Bet that really cleared it for you didnt it!!
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GO
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| posted on 8/1/04 at 06:03 PM |
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Joel, yeah, looks like it. The last pic certainly makes it look that way.
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violentblue
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| posted on 8/1/04 at 06:46 PM |
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one wheel bump looks like it'd act the same as body roll. in which case it'd throw the camber off fot that split second.
looks like it'd be a definate advantage for autox
apply this concept to the rear suspension and I wonder if it'd foul up on the axles?
a few pics of my other projects
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kb58
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| posted on 8/1/04 at 07:38 PM |
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The only fixed point has to be the upper most point on the 3-pt pivot.
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kb58
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| posted on 8/1/04 at 10:54 PM |
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After staring at this for a while I see how it works. It's *almost* perfect. In the fourth case of leaning in a corner, you'd want
negative camber on the outside tire. You could set it statically but then it hurts you during braking. By moving link points it may be possible to
increase the mechanical gain in the system to get the camber during cornering, but I suspect it will then add negative camber during braking... and
you're right back to a "typical" IRS. It may be very inlightening to model this in Excel...
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rontyler
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| posted on 8/1/04 at 11:34 PM |
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It looks to me that a lateral force on one tire produces lift on the other, much like a sway bar would. And since I'm not a proponent of
swaybars on the driven end of a car I am a bit skeptical.
How do you calculate the amount of jacking a supension like that might produce? Where is (are) the RC's?
rt
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kb58
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| posted on 8/1/04 at 11:43 PM |
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Agreed on the sway bars.
Like you said, jacking can be found by knowing roll-center height, CG height, track, and cornering force. I wondered what would happen if the chassis
shown had it's roll-center were higher or lower, or does it always cancel out evenly...
Oh, and with the geometry moving around as it is, I'd think finding where the roll-centers are at any one time could be, um, challanging. A
computer may be the only way to simulate it without going nuts.
[Edited on 8/1/04 by kb58]
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scuzzer
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| posted on 9/1/04 at 10:12 PM |
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There would be a lot more tire scrub (sideways movement of the tire) and the track would be changing all the time. I will try to build a small model
from the picture and see how it works.
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violentblue
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| posted on 9/1/04 at 10:53 PM |
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the movement would have to be identical on both sides or else it'd screw your stearing up
I'd have to see it in action.
a few pics of my other projects
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pbura
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| posted on 10/1/04 at 03:07 PM |
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I'm having trouble understanding how the push/pull linkage would work without one of the rods being contained in a sliding joint.
Wouldn't the rods just flop around otherwise? Agreed that a hands-on model would help a bunch.
Working out the geometry for one of these wouldn't be too bad. A time-honored method for solving mechanical linkages is the 3-position
analysis, in which you first plot your desired results for three stages of movement, then determine what linkage will work by drawing a series of
lines and arcs to locate the pivot points.
As an example, I did a three-position analysis of a Locost suspension on my website and it worked a treat, as you Brits would say:
3-position analysis
There are two linkages to solve for this proposed suspension, with the first being for the upper wishbone pivot, and the second being the push/pull
linkage. Unlike the model I did, wheel verticality would be a given, though tire scrub should still be taken into account (it will be forced by the
displacement of the lower wishbone).
My two big questions, aside from whether the push/pull linkages need to be restrained somehow:
1. In a standard Locost, camber change is restricted to a range of a couple of degrees over a normal range of chassis movement. In other words,
it's very well controlled. Would absolute perfection make that much of a difference?
2. How the hell would you build one of these things? 
Pete
Pete
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Alan B
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| posted on 10/1/04 at 03:34 PM |
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quote:
Originally posted by pbura
.......1. In a standard Locost, camber change is restricted to a range of a couple of degrees over a normal range of chassis movement. In other
words, it's very well controlled. Would absolute perfection make that much of a difference?
.........
Probably would on an absolutely perfect road surface (which never exists), but even then not much.....so IMO it begs the question...why bother?
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MazdaJim
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| posted on 10/1/04 at 05:23 PM |
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Here's a page that shows it in real life on what I guess is a DAX locost-type car.
http://locost7.info/mirror/dax.php
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pbura
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| posted on 10/1/04 at 06:03 PM |
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So the upper link is fixed; that explains a lot!
Very interesting system, indeed, especially for a racer or off-roader, eh Rorty? Can't see any reason not to use it with IRS as well, space
limitations aside.
Pete
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JoelP
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| posted on 10/1/04 at 06:23 PM |
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personally i think its a clever idea, and if a computer says it works i will trust it! as you would expect its too complex to analyse in your head.
should work if all the lengths and gaps are right.
But can it be right for every situation?
i think this system is best left to a perfect car, ie precisely straight, square, light and strong, as chassis flex will soon ruin the system!
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Rorty
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| posted on 11/1/04 at 04:56 AM |
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Phew! Just made it.
Groan...I took a quick glance at the images and imediately spotted the intensional omission of an example of one-wheel-bump, which then made me
curious. It would be a potential abomination in this scenario. I couldn't be bothered to look at it any closer. It really is a case of trying to
reinvent the wheel.
It may have possible implications in F1 etc. where the total travel is commonly somewhere in the region of 20-40mm. In the real world on real roads, I
think you can guess why it's not in mass production.
In an off-road racing situation, apart from huge grip loss, it would blow the CVs apart upon hitting the first decent sized bump.
Looks trick though.
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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MikeR
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| posted on 11/1/04 at 07:30 PM |
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If anyone is interested I should have a working model which i can take pictures off in a few hours - I knew their was a good reason to keep that lego
from when i was a kid!
Any pictures people esp want?
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violentblue
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| posted on 12/1/04 at 02:43 AM |
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I'd love to see some pics of your model
video if possible.
a few pics of my other projects
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MikeR
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| posted on 12/1/04 at 10:33 AM |
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Hmmm, turns out the lenghts of those are not just important, they are critical.
I was expecting some strange behavour due to using lego but at the moment i can't get it to work. Also the stresses involved seem quite high.
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violentblue
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| posted on 20/1/04 at 08:50 PM |
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seems as though it was a lovely idea, but not terribly practical, at least the average builder.
looked as though it might have been trouble in real world driving conditions, maybe on the track it would be benificial.
a few pics of my other projects
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