well guys, i am a little bored at work today, and the ol' mind is wandering . . .

so i was wondering, i thinking abotu building a torque arm for myself. my question is. we all know how the length of the torque arm effects wieght transfer, and the instant center, ect.

but how do you figure the optimal length for the toque arm, for diffrent applications. (math equations are VERY welcome here ) what i am strugling with , is do you base the length on wheel base and weight distrobution? if so, how do you figure it. and is there anyway to accuritly predict the outcome of differing lenghts.



hope this will spice up the suspension board hopefully the veterans will enjoy this more than answering a question about relocation brackets and lowering

 

i was just thinking that same thing yesterday when i was going over a th400/or350 swap for my car. i am very interested in this one.

 

ok, i found this diagram . . .



my question is, how do you determane where you want the instant center. i know that the further up and back you move the IC, the better it is for anti-squat, but if you go too high, you ger rear wheel hop on braking. does anyone know where the optimal place for the iC is?

 

how do you understand all the napkin drawing science. i am stumped and a little brain dead just from looking at it.

 

This looks like a job for!!...rigid body dynamics. All the equations you want can be derived from the basics. But we're all too lazy to do that. And my textbook is at home.

I'm sure someone has already figured it out and can just give us the equations.

 

i guess my real question is, can you figure out the desirable lenght of a tq arm, by knowing the weight bias front to rear? figuring the IC is easy enough, but how do you know where the IC should be locatated, based on the weight of the car.

 

I can tell you it works out to about halfway between the tranny and rear..but it's been way too long since I've seen the actual equations to remember. If I were you I'd look at the MAC Tq arm design and copy it...I personlly believe that it the best commercially availble design.

 

wow , i haven't heard from you in forever Jester.

so you really actualy want it more like the MAC, or BMR location? is that for road race, or drag racing? i would think if you get too far back, braking is going to get dicey.

 

It's those damn ewoks...long story. Anyway.

I think the BMR is a good piece construction wise, but it's the same length as stock.....wayyy too long from a geometry standpoint, not to mention being double the wieght. I've never heard of any complants about braking with a shorter style arm either. Maybe if you made it way way too short it might.

 

i wasn't talking about the standard BMR unit, but either the trak pack, or the extreme TA's are supposedly shorter than stock.

 

Oh yeah..I forgot about that one. I don't really have any practical knowledge with it, but in theory I still don't like it as much. The MAC mount is both shorter and higher in the chassis, which I like but isn't the problem with the bmr. I like that the mac is a pushing member directly on the body whereas the BMR trak pak one pulls on a looong crossmember between SFC's. I think that crossmember is too long, and has to be too thin because of ground clearance to be stiff enough. I think it will induce wheel hop by acting much like a bow. Plus, if you have a cage, like I do, the cross braces under the main hoop can directly support the mounting point the MAC uses.

 

thats great info jester, i am still wondering if there is a way to figure out exactly where you want the IC to be, for best performance, hopefully someone will pop in with that (agood, hunter, stevespohn )

 

IC length depends on the center of gravity for each individual car. However, as a car wheelstands the CG changes making the application of the IC to CG theory, just that.....a theory. Other factors include horsepower and weight. The shorter and higher an IC length the more rearend lift you will encouter. The will "hit" the tires hard on lauch but not maintain the load at the tires. There are several Chassis books at the library that can explain this much better than I can. I just created a completely new rear set up for our cars that I am in the process of applying for a patten for. For all intents and purposes it will have an adjustment for IC and pinion angle. I have it on my car and have tested it at the track with very impressive results. I'm getting a headache now because I crammed a ton of Chassis theory into my brain in the last 2 months. Have fun

 

I thought he average for our cars is either 27 or 37 inches from mount to tip or torque arm.