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?

ok i'm being lazy as usual and not figuring it out, but what happens in single wheel bump????

is it the top joint on the blue thing that is rigidly fixed to the chassis? looks like a good system at first glance.

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!!

Joel, yeah, looks like it. The last pic certainly makes it look that way.

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?

The only fixed point has to be the upper most point on the 3-pt pivot.

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...

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

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]

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.

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.

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

quote:

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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?
.........

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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

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.

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!

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.

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?

I'd love to see some pics of your model
video if possible.

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.

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.