Back from the dead

[BillyShope]

Yeah, I'm still around. Had a bad fall and have been busy with other interests, but, as Mark Twain put it, "News of my death has been greatly exaggerated."

Was away from the dragracing forums and would not have known that the free space I was given on a commercial site was gone...and the site itself...if I hadn't started to receive phone calls. Didn't realize so many of you used those spreadsheets! So, the site URL given below (a new site of my own) includes some of the spreadsheets.

I also answer the question: If you were able to start a new project, which rear suspension would you use? Would it be 4link? Ladder? 3link? My answer might surprise you.

http://www.shopeshop.org

[Dragsinger]

My personal experience building several drag race door cars shows a longer than usual ladder bar to be a very good working, consistent package. For a 100" wheel base car I build a 36" bar. [axle center to front rod end center] For a 108 wheel base I used a 38" center to center bar. Bars mounted 1.5* - 2.0* down, about -2* pinion and double adjustable shocks all four wheels.

[Keith Morganstein]

Thank you for the link to your new website. There is a lot to read and "digest" there.

There does seem to be some pages missing, I was looking for pages 36 & 37 on the "traction dyno"

Have you ever been involved with tractor pulling? I would like to learn more about loading the rear tires and the effect that hitch height has.

[John Wallace]

COOL!

Glad you got your site back up.

[BillyShope]

Thank you for the link to your new website. There is a lot to read and "digest" there.

There does seem to be some pages missing, I was looking for pages 36 & 37 on the "traction dyno"

Have you ever been involved with tractor pulling? I would like to learn more about loading the rear tires and the effect that hitch height has.

That's another Shope in tractor pulling. He's not a close relation. Not very many Shopes, though. I can understand the confusion.

I didn't include everything from the old site. If there's a definite need for something I left out, I'll provide it.

http://www.shopeshop.org

[MadBill]

Hey Billy,
just looking at your roll stiffness article (page 24) and I had a thought: What if you suspended the front end of a pure drag race car with a heavy 'Z' Bar instead of individual springs? This would result in zero front roll resistance and thus automatically ensure no rear weight transfer.

[BillyShope]

While a Z bar does not add roll stiffness, it does nothing to reduce roll stiffness. And, it has nothing to do with weight transfer (other than some small difference in CG height). No, that's not the answer, but keep thinking. It would be nice if there was an easier way than that which I suggested.
http://www.shopeshop.org

[MadBill]

I don't follow. Since the Z bar adds no roll stiffness, and there are no front springs to provide any in this scenario, doesn't that leaves the front end with zero roll stiffness, as if it had a beam axle supported on a central spring-loaded knife edge? As far as weight transfer, wouldn't that depend on the bar's rate and how it was linked to the unsprung components?

[Brian P]

I am not sure what is meant by a "Z bar" but from the description, it sounds like you are proposing something similar to a garden tractor front "suspension" - an axle fixed to the chassis at a single central pivot, no springs. Or something equivalent, so the left and right wheels move up and down oppositely with no roll stiffness.

If you are talking about a drag car with a conventional layout with a live rear axle and actual suspension (not solidly mounted), how do you propose the torque reaction of the drivetrain be absorbed? That torque has to act against something. Normally, it's against the left versus right springs of the car (the balance of front to rear is up for discussion - but one way or another, the bodyshell of the car is rotating to compress the springs on one side relative to those on the other side). If you make the front have zero roll stiffness then this torque reaction has to be absorbed by the rear suspension alone.

Method 1: With BillyShope's asymmetrical rear suspension design, the torque reactions in the rear end are putting asymmetrical forces into the chassis which counteract the torque from the engine, so the left and right sides of the suspension are free to squat equally (because the springs aren't being called upon to absorb that torque reaction). But then, the roll stiffness of the front end is no longer relevant.

Method 2: IRS. The torque reaction from the drivetrain is balanced precisely by the rear end, but since the rear end is fixed to the chassis, none of that torque reaction has to be absorbed by the suspension springs. But again, the roll stiffness of the front end becomes irrelevant.

Method 3 (rather common): Just let the car body shift. Everyone has seen the body of a drag car rotate hard when the car leaves the line. That's the springs being forced to absorb the torque reaction because the design of the suspension linkage is not capable of doing so.

[BillyShope]

Brian, look for a z bar on any formula v (with swing axle). It's used to prevent jacking. I'm mixing terms. That's not the jacking you get with the adjustable spring heights on an oval car. It's the jacking that you try to avoid with a swing axle.

MadBill, you seem to be describing more than a z bar. You evidently have some means in mind to avoid use of the springs. You need to wave your hands more as you talk so I can understand. Wait a minute! I think it's coming through to me. You're considering the "free" state of the z bar to be with both ends down, so the z bar would act as the main suspension springs. Or, rather, the only front suspension springs. Then, with that z bar attached to the frame only at the center, there would be no roll stiffness. That's neat! But, I don't know if you could get enough of a torsion spring in such a short distance. You'd probably have to use 2 coil springs in torsion. Check around. Somebody's probably tried it on a garden tractor or golf cart. Would be an interesting car to drive. As you contact a bump with the LF, it would act as if the RF had also made contact. The more I think about it, the more of a monster it becomes! I'm thinking of dual coils in torsion with an arrangement through the centers of the coils to control lateral motion. Then, you'd have one wheel swinging forward and the other swinging backward. I'm afraid I'm just scratching the surface of possible problems that would be encountered in a long development time. All of this makes my suggestions seem much more straightforward.

http://www.shopeshop.org

[MadBill]

Hi Billy.
Sorry, my notification system seems to be malfunctioning; I didn't see your post until just now.

Yes, I'm speaking of a very beefy Z-bar carrying all the front end weight. As far as getting 'enough spring', a Trans Am Corvette* I work on has a baseball bat-sized front bar (2.5" dia., 0.300" wall, AIR) that provides a wheel rate of over 1,200 lb./in., vs. the suspension spring's 450# *The bar in this pic is smaller but similar. (pay no attention to the distributor location; this is our infamous aluminum 427 SBF "Fordette")

Just to be clear, the bar would pivot on L & R frame rail mounts just like an A-R bar, except for being installed on a diagonal to leave the ends of the links symmetrical with the control arms.(exactly like a Formula V Z bar) As far as bump response, true, a one wheel bump would also raise the opposite corner due to the reaction force transmitted down through the suspension/wheel, but is that necessarily a bad thing?

PS: Brian, the reactions would be no different than for a "wheels up" launch with conventional suspension.