Ralphy -
You've touched part of the problem I think.  The binding. 
Another problem is  Geometry Change - 2nd order effects - from those  IRS components/elements  & the binding you reference. 
The Corvette C3 single rear trailing arm - or any dual trailing arm is going to be in the similar outermosts position on the axle.  As they move through their range of motion - the forces on the hub will certainly change the camber, caster, and resulting contact patch.  If it binds erratic discontinious motion jerking may be experienced - resulting in a vehicle that may be "twitchy."  Compound those changes with a track surface  ruts, bumps, other vehicles - and the ride may be "off course."
Using a pushrod to a torsion bar may transfer some of the forces and motion inboard, and reduce the binding at the hub, but the bars influence on the IRS set up also reduced - calling for larger/stiffer = heavier,  to get the same chassis rigidity.  That additional weight is nearly wholely sprung - a good thing.  The pushrod unsprung  - light by comparison.

Sounds like you are looking for a double wishbone - adjustable link set up? 
I know my engineering and execution will require much adjustment - so am oplanning those bits in.  It all adds up and like Listers List - for now the cost factor in the bottom half: (His list in order - My edits are the numbers in brackets)

    Installation stiffness, [4 - again added after the geometry is fixed and minimize its effects on the higher priority items]
    Car packaging (aerodynamics, chassis structure and regulation requirements) [5 Stiffen chassis, add aero improvements]
    Cg height [3 - I can influnce marginally with a modificaton to my 'vette - small amounts - but useful]
    Unsprung weight [10 - wheels and tires are killer]
    Cooling (brakes and bearings). [9 - actually I'll include in the Aero]

Other, secondary, priorities include – in no particular order:

    Cost [6   NOTE;  I add Time to this and would call it RESOURCES - maybe include the Design resources here too]
    Ergonomics [7 - Hey its a racecar!]
    Design resources [8]
    Motion ratio [2 - this  is driven by the geometry]
    Geometry [1  My main focus  - once its settled al that is left is adjustments]

The sooner I can exit the DESIGN SPIRAL - the sooner I can cut metal and get on with it!

Cheers - Jim

All is true. However you have to first decide how the car is to be used. For street application or drag racing maybe, the anti squat is a usable feature. But for say road racing or just pure street performance cornering ,anti squat creates a varied effect on suspension load rates at each wheel. Depending on just how much acceleration or braking is used in each (turn) individual situation. In order to tune a suspension for high speed cornering, consistency from a neutral design, creates a more easily tuned chassis. With the more modern designed dual wishbone you can add anti squat, however the force is transferred from the wheel to the chassis from the inboard point of the control arms. Closer to the center line of the chassis. This allows for a more consistent spring rate at any wheel corner.

Ralphy

I would love to see some pics. Can you post some shots here?

Phantomjock I'm sure has read on Vettemod of the guy removing almost all his anti dive on the front f his Corvette. He reports better control.

http://www.vettemod.com/forum/showthread.php?t=7815

Last edited by Ralphy (1/07/2012 12:17 pm)

tyrellracing wrote:

...  Up til then I was gentle with my acceleration so I down shifted at 45-50 mph to third and cracked open the secondary's.  This would normally have made the car take off like a rocket.  This time the rear of the car rose up 3-4 inches and the rear wheels hopped so bad I was sure I had broke something. This was not a standing start nor did I drop the clutch violently.  I simply down shifted a gear and gave it 3/4 throttle.   The type of anti squat designed into the Jag rear is IMO, very torque sensitive.  My first solution was to make new LCA  mounting brackets with a greatly reduced angle and subsequent anti squat.  The problem was reduced but remained.   I purchased new AFCO shocks and changed the valving for max dampening on rebound    I had a pair of heavier rate springs so I installed them.  Each change helped to reduce hop and  improved the cornering grip  but none of them solved the wheel hop entirely.  The Arning type hub carrier and linkage finally did that.

That is an interesting story - and surprisinmgly enough - I spent my lunch hour talking with Mark Savitske.  He was mentioning a similar situation with another vehicle.  With this one, again revalving/reshock was so go.  They could just crack the throttle then at 65 and 'smoke-em' Mind you 850BHP ath te wheels - but such an interesting coincidence.  This was a former Drag Car they were bring up to all-around Pro-Touring and amazingly - their 60ft times were better too. 

Got Lotto Numbers to pick?!

But, its making me think - for my IRS - and outboard brakes - for starters - I'll set zero anti-squat. 

Cheers - Jim

The beauty of this layout - is it is trying to get favorable toe steer - and that will be useful.

Unfavorable Toe steer is what the C3 Corvette single trailing arm set up has - though small - and why I am moving off the "Jim's Giovanni" to a double wishbone, etc set up.
Cheers - Jim

I've been away for awhile but we began driving the big block MGB a couple months ago and I thought you'd like to hear how the suspension is working out. It's very well behaved. Wheel hop has never been an issue so far, although we have not wound it up and dropped the hammer because we don't want to break the T5 tranny. Still, it has enough power that a sudden power roll on can break the tires loose in second.  I haven't noticed any squat or hop so far but maybe I'm just not paying close enough attention. Regardless it hooks up quite well.

JB

The link going forward as it travels moves in a different arc of the LCA. The arc is app 45 degrees to the LCA. In either direction the arc goes forward, this in turn pulls the LCA forward. This forward motion toes the wheel/tire in, ever so slightly. In turn you get a bit of understeer at the rear axle. As best I have found, the total typical toe steer is only app. 1/3 degree at max travel. Hope this helps.


The silver colored lower link in this picture is the link that induces the roll steer. Note, the suspension in this pic is not at ride height, it's hanging. Picture is looking to the rear of the chassis.

JEM wrote:

Ralphy wrote:

The lower forward link adds some roll steer.

I don't see anything from the picture that would indicate that.

Last edited by Ralphy (1/17/2012 9:40 am)

Ralphy
From what I have read, the 45 degree angle plays little role in roll steer. I always had the understanding that link was how the rear toe was set and it has no other function.
       If you can find a copy,   buy  Engineered to win.  This has to be one of the best suspension books I have ever found.   The author has a whole series of Engineered to.... books for the construction of race cars  and all of them are outstanding!    The paper back copy  (about the size as a phone book) I got cost me 80 bucks on E-bay but was worth every cent.    Seriously,  Its light years ahead of  Chassis Engineering by Herb Adams

Last edited by tyrellracing (1/18/2012 7:08 pm)

For my link positioning.  I copied the Klaus Arning design as closely as I could.  The design was one of the first to have been proof tested on Fords new suspension computer program.  This is the program that refined the GT40  as well as the 427 cobra's then new suspension.
      I found a blue print on line of the Klaus Arning hub carrier but the dimensions were undecipherable.   I had one Ace in the hole,  I knew the bearing size  and armed with that,   I enlarged the image at work with their print copier, printed it at as close to full size as I could then scaled the rest of the dimensions with relative ease. 
    The hub carrier was the key to making this design work!  From what I read the original design used the Vette stub axle and bearing.   Kind of strange for a ford!   I used the Jag stub axle and bearing dimension as well as the Jaguar carrier bearing separation.   That  way the hubs could be assembled the same proven way as the Jag with the  parts I already had. 
    The front link attachment point was the front spring eye mount . I used 1/2 heims with aluminum spacers to fill the void and allow the bolt to pinch the ball firmly.  The original carrier used a tie rod to connect the front link to the bottom of the carrier so it had a tapered hole.  I changed this to two ears with 1/2 in. holes to support the heim in double shear at the same location.
     The rear attachment used the threaded holes in the mustang frame rails that originally held brackets for tying down the vehicle during shipping.   Klaus used these same holes for his rear pivot mounting brackets. The original rear links used tie rod ends on both ends.  I made double ear type clevis mounts on the carrier and as pert of the frame mount in an effort to utilize 1/2 in. heims.
    The LCA inner pivots were removed from the differential.  I made new ones that had the same general foot print so the connecting plate could still be bolted on and used to jack up the car.  The new brackets placed the pivot in the same axis as previous but I placed the clevis mount two inches forward of the center line of the disk brake.  The opening for the 3/4 heim is 1/2 inch wider than the ball so I can shim the toe setting for alignment. I placed the inner pivot forward two inches to reduce the amount of goose neck in the lower arm required to clear the larger than stock vented disk.
    I fell into a deal for another XJ6 rear for 50 bucks. (I mentioned it in a previous post) I took the LCA's to work and band sawed off the outer pivots at the weld then machined off all excess steel to make a simple "u" then welded two segments of 1.25x .125 wall round tube with off set  bends to the "u" in a manor that from above looked like a 2 inch off set front  control arm.  Viewed from the front the goose neck at the inner mount as clearly visible.  I took a 1.25x3 round solid bar stock.  Tap drilled for 3/4 unf threads and tapped it the same then welded it to the union of the two tubes.  The coil over mounts were then moved outward 1 inch and lowered to the bottom of the tubes because my AFCO shocks are a little longer than the stock units and this helped to compensate.
      Well that sums up how I altered my IRS to eliminate wheel hop.   I didnt take any pictures when I built the parts but I will as soon as I have paint on the car and can tear off all the masking paper.     
    PS     You are absolutely right   The 289 Cobra won the majority of the races .  Ironic how every one loved the 427.  The men who raced the 427 cobra said it was a tank to drive compared to the nimble 289.   The 427 took much more effort to man handle it around a course and was totally unforgiving to driver error.  The nose heavy 427 could be off set by its over abundance of torque that was used to throttle steer and rotate the car around the tight turns.  In the right hands they were ballistic on most road corses,  The unskilled were often made dead from the learning curve.  This one car is what started the manufacturers to give fake low hp ratings for insurance purposes.  It got tough to sell cars that could kill an average driver with in a month of buying it when you cannot insure it.

OK, I think I see the key! I do best when I look at something in an extreme form. The key is the distance between the inner pivot of the LCA and the forward link inner pivot. That is, the variation of the two. Notice the LCA is further to center on the 427SC. The shorter the length of the forward link, widening the gap from it to the inner LCA pivot. The more forward motion created, the greater the roll steer. If both were at the same point, it would be neutral, no fore or aft motion. Then if the forward link were inside the LCA, the LCA would move backward. Sorry I included the inner center pivot on the LCA, it should be removed.



In this chassis walk around, you will see the LCA is approximately 2" inside the forward link. Typical Cobra 427SC main tubes were 4" dia. I believe. The 15 second mark gives a great rear view.
http://www.youtube.com/watch?v=YmtrvPkWfAg&feature=related

Last edited by Ralphy (1/19/2012 4:57 pm)

Thats a good one too!
If - as you do machine work - you want one for the "shop"a great one he wrote is; Carrol Smith's NUTS,BOLTS, FASTENERS, and PLUMBING.
Focuses only on the components and bits.
CHeers - Jim

JIM...
   BTW yes I have a copy of that one too!

TR,
Do you really want anti squat? Or do you really want those tires to just drive into the asphalt as hard as possible and stay? What I'm saying is the further back the trailing links mount to the chassis the less weight they have to raise. Giving a higher chance of jacking the rear up under hard throttle. A C4 Corvette is an example of this. Your setup has your lower link much further forward. I can see several advantages with this. This for one creates less jacking. And also when cornering on and off throttle would cause less, would it be roll or yaw?  I can see a C4 Vette maybe getting a little twitch breaking traction in a turn. phantomjock may know. For street and drag racing this may be good. But for performance cornering seems not. That's where I think the double wisbone excels, moving the fore and aft forces more to the center of the chassis even with anti squat.

Some squat is good. And as my drag race buddy said, "the weight can only be in one place when the front wheels are off the ground."

If I went your route, I have room for a 21" long lower trailing link. The Cobra guys running the C4 IRS, are using trailing links about 8" long. You can see it here. The back end of the link is in front of the H/S as you probably know. They keep the same geometry on the links as factory. The four inch square tube in front of the tire, on the frame. Is where I would go with the T5 design, if I go that way.

Last edited by Ralphy (1/19/2012 11:03 pm)

WOW! Let's back up.
First you mentioned in a previous post the 427SC was un-drivable. That was because it originally had the 289 suspension like this below.


That was the inferior suspension that caused the uncontrollable 427. So Arning steps in with his new at the time roll steer design below.


This was 1965 never seen or used. Since that time racers have found roll steer a bit quirky. So for racing, it was scraped for a more conventional design. The kit car guys are building this design, trying to create as close to an exact replica 427SC.
Then you just now you said people who have roll steer must hate it. But you have it, with your T5 copy! Not sure where your going., that's roll under steer not over steer. All Arning's designs created under steer. For racing you never want over steer. That's one of my C3's flaws. Maybe drifters want it or dirt racers. Not on asphalt.

Last edited by Ralphy (1/25/2012 8:38 pm)

I have no problem with wheel hop what so ever now.  The description you gave applies more to a live axle with under ride traction bars.  My linkage applies near equal force to both leading and trailing arms and as such does not produce as much lifting force to the body.   The forward force is divided into the two links.   The portion of thrust pushing the car forward through a angled leading link , when broken into force vectors will give some lift.  No where near what the Live axle did with under ride traction bars. When axle rotation was applied to a lever arm,  it would physically lift the car under hard acceleration.  I had the old Nine in. dialed in very well for the standing start.   If a line were drawn through the link it would start 6 inches below the axle housing and go through the centroid of vehicle mass so when the car launched the link would literally lift the whole car and plant all that weight on the rear tires.  This is very near 100% anti squat.  This amount of A.S. cannot be achieved on an IRS.   The only examples I have seen gain that good of traction with a IRS did it through an ultra stiff springs and racing slicks.  not A.S.
    The K.A. set up has yet to show any down side other than it cannot initiate the grip required to produce weight transfer under full throttle acceleration.  Non judicious throttle application will get you sideways quick. The main reason I switched to the IRS was for lateral G's.  The roads around here are often nothing more than a series of filled pot holes with a little asphalt in between.  The un-sprung weight of the nine in. rear got real spooky when pushing it around corners on Oregon's typical rural roads.  Snap over steer was my most dreaded problem.