Ralphy wrote:

Day that's frikin funny!

whats funny?? did I miss something??

IRS vs. solid axle housing. With a solid housing when accelerating you get a wraping force trying to twist the rear upward in front.  So the lower forward link has a lot of force induced. This aids in anti-squat. With an IRS because the hubs are free and the carrier is bolted in place, you loose this torque effect. So anti-squat/anti-dive is less.

Anyhow any angle is better than none. But you also have to watch your wheel base change, you don't want the wheels moving to far back.

I've seen others add a forward shock above the half shaft to gain some strength.

Last edited by Ralphy (8/26/2011 5:06 am)

A Jag set up with only a LCA flat has no anti-squat. If you do have the anti-squat it can be tuned to add or remove as needed. Some Corvette racers move the trailing links to reduce anti-squat. Some rearward body roll helps coming out of a turn.

Stock C4
http://media.photobucket.com/image/c4%20anti%20squat/SuperL98new/BRK2.jpg

Here is a pic showing the bracket to alter a C4's anti-squat
http://www.corvettefever.com/techarticles/corp_1001_c4_suspension_rebuild/photo_06.html

Last edited by Ralphy (8/26/2011 7:38 am)

Don't get me wrong guys. I'm not trying to tell anyone how to do their cars. I was just trying to point out what I think I have learned reading boards and articles. Your car has it's own quirks. I mentioned to Daze once I was going to build a suspension model. I think that would be the only way a guy at home could measure data at home. I have no software to run 3D modeling that can give data through motion.

So neither of you have any thoughts on what I said earlier???

Daze wrote:

Here is another thought what if the rear steer was more about controlling suspension movement???  Think about it this way the rear tires are going to try to stay in line with the fronts so if the fronts are cornering the back tires will attempt to corner as well and that force that is turning the rear tire should be translated in to the suspension moving toward the position that would induce the same tire positioning.  same would be true when going strait the tires will try and remain in a forward position and will try and get back to that forward position after going over something that caused suspension travel which should in theory improve suspension reaction times and be some what self correcting.  thoughts???

Ralphy wrote:

Day I agree about the cornering, I would think it would take less HP. Or a better way of saying it, there would be less rolling resistance.

I am not talking about rolling resistance, although I agree it should be less.  I am talking about chassis positioning.  think of it kind of like a sway bar (I know totally different than what were talking about but illustrates my point)  If you have a wimpy sway bar and you hit a tight corner the inside wheel suspension will compress and the outside wheel suspension will extend so the car goes around the corner leaning.  In contrast however a thicker sway bar puts more downward force on the outside wheel than it gets with out it and this causes the whole front suspension to compress and creates less leaning as you corner.  Why could the same not be true of the rear steer???  if suspension compression causes the tire to toe, than the same should be true in reverse .  A tight corner should cause the tire to to which should compress the suspension.  See where I am going with this???

I guess I am not explaining this right because you are totally missing my point.  Let me try again

Forget about the rear end for a minute. if you turn the steering wheel the motion goes through all the steering components and the wheels turn not spin but turn, BUT if you get out of the car and grab a tire and turn them the same happens in reverse, the spindle steering arm moves the steering linkage which turns the steering wheel.

now go back to the rear suspension.  if compressing the suspension causes the tire to turn slightly, than the same should be true in reverse.  if the forces applied to the tire by cornering turn the tire it should compress the suspension. 

The rear tires are always going to try to follow the fronts so as you go in to a corner the suspension should react to the pressures from the weight of the car AND the pressures on the tire should also effect suspension height.  As you come out of the corner the suspension should level out because of the car no longer cornering AND because of the wheel trying to get back to the pointing forward position.  SOOOO rear steer should create faster and more consistent suspension response times.

Make sense???

Last edited by Daze (8/28/2011 8:28 am)

no I am referring to the car doing both cornering and going straight.  More than anything the transition from one to the other.  Because the rear tires will want to follow the fronts, steering when cornering and be facing forward when not cornering it should work backwards and help position the suspension.

"every action has an equal and opposite reaction"

nope, lets try agin and I will try to make it even less involved (I tend to over state things)

If suspension movement causes rear steer, than shouldn't the opposite be true that rear steer should cause suspension movement??    I am saying that the rear steer could also be a product of following the front tires and the movement  of the rear tires to the steer position should cause the suspension position to change.  I believe you are thinking the only way the rear tires can steer is if the suspension moves, but I am saying that because the rear tires are designed to move that following the front tires  will cause them to move (some) and the force should be translated BACKWARDS through the suspension causing the suspension position to change.  The two forces should push and pull against each other and make the suspension reaction times quicker.

if that makes sense now go back and look at what I said before and see if it now makes sense.

Day said: "Here is another thought what if the rear steer was more about controlling suspension movement???  Think about it this way the rear tires are going to try to stay in line with the fronts so if the fronts are cornering the back tires will attempt to corner as well and that force that is turning the rear tire should be translated in to the suspension moving toward the position that would induce the same tire positioning.  same would be true when going strait the tires will try and remain in a forward position and will try and get back to that forward position after going over something that caused suspension travel which should in theory improve suspension reaction times and be some what self correcting.  thoughts???"

Day your getting kinda deep for me. If you pushed this car by hand on a level surface at 1mph, if true. You would see body roll. I don't think you will. Because the only way the rears would be able to try and follow the the fronts would require body roll.

I read once of a guy who could not figure out why the rear of his IRS car would sit at different heights. He transplanted a Corvette IRS int a little British or Japanese car. I later figured it out, to much toe. That little light weight thing had wide tires and no weight. The combination allowed the rear tires to walk inward, jacking the rear upward as it moved forward.  LOL

A side note the front tires on most cars, 99.9999999999999999 % have caster. The caster is what makes a chassis go straight. Put zero caster up front and you will have to steer your car non stop. Some racers have played with zero caster. Less caster also makes a car easier to turn. Same as a shopping cart wheel, trailing it's fixed point.

Another watts link pic.
http://www.clubcobra.com/photopost/showphoto.php?photo=55580

Last edited by Ralphy (8/28/2011 6:53 pm)

My thinking is that gravity and G forces dictate response. A car has an axis point and as you drive that axis point moves left, right, forward and back. How you control it is only by design. To design a fluid system is the builders ultimate goal. It's no different than a runner, golfer, swimmer or a baseball pitcher searching for that ultimate body mechanics.


Jim Blackwood said, "Uh, not to throw a wrench in the works, but if you substitute separate links for the Jag LCA what is going to control torque?"

JB

With this setup Jim you would have a trailing link. Such as Klaus Arning used. Or ? Also it seems to me if you wnt to build the ultimate design. The only way for a backyard guy to do it, is by first building a model.

Last edited by Ralphy (8/29/2011 5:51 am)

This is a design a guy from Holland was, is trying to build for a C3 Corvette. It's modeled after Klaus Arnings AC Cobra design.

http://www.google.com/imgres?q=5+link+irs&um=1&hl=en&safe=off&sa=N&biw=1024&bih=613&tbm=isch&tbnid=lhIvY539N6QSKM:&imgrefurl=http://www.digitalcorvettes.com/forums/showthread.php%3Ft%3D83379&docid=ZLfUeTMCHkuchM&w=1017&h=809&ei=64hbTuOxK9CCtgfj0-CcDA&zoom=1&iact=hc&vpx=187&vpy=237&dur=338&hovh=162&hovw=245&tx=175&ty=125&page=3&tbnh=138&tbnw=241&start=25&ndsp=12&ved=1t:429,r:4,s:25

Last edited by Ralphy (8/29/2011 6:00 am)

I apologize for going off on a tangent that involved different designs. I had thought about that myself and was apologizing sort of back a bit. The original post I asked was how to build anti-squat into a Jag LCA, also toe/steer. The pic I recently posted a link to with the Viper clearly has anti-squat built into it. So trying to show maybe the Jag can be modified the same. Then as I originally asked can the toe/steer be added? I'm trying to relate, to get toe/steer the front bearing carrier mount has to be higher then the rear. That is how Klaus Arning's design works. With his camber rod you have two pivot points/ arcs. The front hub mount is higher in it's arc then the rear hub mount. If you called the three motions of direction of the suspension XYZ and X  was the distance out from center. Again the front hub mount will travel X less then the rear hub mount. Because it is further horizontal. This in turn causes the hub to rotate in regard to jounce. Then the reverse under rebound, the rear hub rotates in causing the hub to rotate out. So when the chassis leans right the wheels turn left and the reverse, TOE/STEER! OK so it's the hub mounting points that create the toe/steer. Can the be incorporated into a LCA by twisting the hub mounting points at the hub on a Jag IRS? AND ALSO mount the LCA leaned backward at the carrier? 

Ralphy said, Think this over you Jag guys. I f you were to make your own lower arm. Then modifying the hub bearing carrier with an angled hole upward to the front. You will achieve toe/steering. You just need to find the right angle!

You may and probably would need to make a new bearing carrier from scratch. The two ends would need to be equal distance from the original position.

So if this works, let's try a step further. Raise the front inner mount of the control arm and lower the rear mount at the carrier. This should do two things.  First under jounce the rear wheel will move back elongating the wheel base. Then also it would create anti-squat/anti-dive? What do you think?

_____________________________________________________________________________________________


Jim said; You've got to admit that it is an elegant design feature, if somewhat clunky and heavy.

I do not agree, it's neutral. It's better than my C3 Corvette design.
However neither incorporate ant-squat/dive, understeer, or an elogation of wheelbase.

Last edited by Ralphy (8/29/2011 12:01 pm)

When you incorporate anti- squat you automatically get anti- dive. When you go into a turn you brake, and turn. In this process weight/axis moves toward the outside front corner/tire. The ant-dive reduces body roll front to rear and dive, holding the rear and especially the rear inside down. Does a Jag IRS do this?

Then I think you can run softer springs improving ride. Go even softer on the springs and add more anti dive, hmmm....... Better ride more control, it's a balancing act?
Think of it as a front to rear sway bar! Would you say I don't need a swaybar?

Jim said: "I'm still not so sure about the toe-steer."

HI

Thanks for the feedback.  Yes, everything in suspension design IS a compromise.  The only proof is in the driving.  Porsche & Mercedes paid Ford a license to use the anti-squat / steering feature for years.  They finally figured out how to add a 5th bar to get around the patent.  It all really works, as Gurney said about the GT-40 at LeMans, "It's really easy to go fast in this thing."

Duane

http://irsforum.boardhost.com/viewtopic.php?id=88

Last edited by Ralphy (8/29/2011 2:16 pm)

I do not know. There is much yet to be discovered, at least on my part. However what does seem clear is that fundamental differences exist between the types and those differences can be exploited. The end goal of course should dictate the design to be used, along with mechanical constraints, but the built in anti-dive/anti-squat characteristics brought about by the axle being mounted on a lever arm is pretty unique. I'm not real sure how you could fine tune it. As far as the toe steer, it seems that could be accomplished.

On the whole the design seems far better suited to twisty roads than to straight line power.

JB