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twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

(OP)
i have learned a few things from here over the years, probably a little out of left field but here it goes. (primary question in bold)

some of you may remember Hurst built several exhibition cars, one of these was the 66/67 twin drivetrain Hurst "Hairy" Olds 442 "4-4-too much"

using two 500+ hp blown 425 olds v8's and the "new" toronado transaxle, it lived up to its name

the obvious suspension alignment/deformation issues led to it wrecking twice and being retired...Toronado stuff hardly being sturdy enough....we do not wish for the same fate

we have been building a 94 cutlass coupe with two 3800 supercharged FWD drivetrains...after 10 years of working with it we are getting ready to unleash two 500+hp powerplants in it and we are redoing the chassis to handle it.

right now we have 4 corner mcpherson (two front suspension work pretty well) but one thing is clear...both drivetrains want to flip this heap onto its back...so we are ending up with a front powerplant thats good at destroying tires and useless off the line.

on the 500fwhp 2000 turbo regal, i have to dial 2* of toe in for us to end up near 0* while under power... so we are going to heim...this car got me thinking about keeping the 442 from killing us...the TR embodies all that is tq steer that'll make you let loose a few drops...and we are looking at two of em in one car...

im looking at an IRS take on the classic IC adjustable drag racing suspension but using 6 links per custom knuckle (plus a sway link so 6.5 lol)

we are dealing with 4,000+lbs and some wide rear rubber...yes we would like to have fun with "on demand" over/understeer around a track. so this thing is going to be sturdy.

while im no slouch im not "schooled" been building racecars for a while...mostly oddball shit (im putting a turbo buick driveline into an 84 cressida WaGN)
i am a hack, there i said it. from what i can figure a std tube chassis with a dropout rear suspension/drivetrain cradle is the primary plan. front is stuck with a coilover converted OEM type McPherson "narrowed" to move the knuckles in a little with the new front LCA/cradle.

the rear im planning on 4 equal length laterals with the drag racing 4 link setup as our radius bar. for drag i can figure equal length lats would be fine...but im guessing anything more is the classic compromise...drag vs handling
yes the layout for the knuckle looks scary...but should give us plenty of adjustment so we can make changes over the years of sorting it out lol

am i missing something with us setting the rear IC to hit so the front is forced down and the rear to lift to directly counter the front drivetrain trying to lift the front and push the rear down....

ive done pretty good with the Tq steer issue...the 4t80e transaxles have equal length female spline shafts so the flex difference is the same.

within the next year we should be up and driving with our current hacked chassis and front suspensions...if the two previous motors are any indication we are going to find this thing is quite a handfull for now we are looking at a coilover sleeve on the rear with some really stiff springs to crutch it along for now...but id love some feedback/idea/reference/reading suggestions.

as you can figure there's not much ive found for twin drivetrain issues... welcome to the headache lol

Regards, James W.

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

The thing that you are missing, is that with any type of suspension in which the differential transmits its forces to the chassis directly and not via an axle guided by links to the chassis, the torque reactions in the suspension linkage are entirely different. Because the differential torque reactions are not transmitted to the chassis through links, the forces involved are not the same so the things needed to achieve anti-squat are not the same.

In your proposed layout, the trailing links will take up only the fore/aft drive forces and not the differential-torque-reaction forces.

Your proposed suspension design is over-constrained. Remove one of the upper lateral links to remove the over-constraint and the resultant binding.

You are probably going to want toe-in on both compression and rebound. To do this, make the front lower lateral link shorter than the rear lower lateral link. "By how much" ... is a darn good question.

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

(OP)
well crap.
the motor/trans are solid mounted via motor plates and i was figuring that the Tq at the hub would be ~1/3rd so i was hoping i could use that tq to counter the front rise.
thing is the Turbo regal does distort the front struts, we kill upper mounts and score the hell out of the front of the strut shafts from contact with the body, id have to figure on me being able to do something usefull with the forces at play to keep the nose down...the LS4 v8 fwd grand prix GXP (same platform) uses custom bilsteins with a 1 3/8ths shaft due to the deflection issues that also kill our upper strut mounts

so the only real option is a V drive/live axle...or some sorta live axle rear subframe...jeez that would be alota added unsprung weight lol

well at least we are moving everything we can down low and the heavier stuff near the middle/front. right now with the fuel cell at the rear we have 49/51 f/r split...thing handles nice...two front suspensions do work well.

best option is then to go with the lower weight of the McPherson eh?
well shoot i guess we could use the bilsteins

still open to any thoughts/suggestions....
oh and a link to the madness. thread has a lot of pics but this post is our last setup with 250hp sc3800/160hp NA 3800
http://www.thechicagogarage.com/forum/midwest3800s...

Regards, James W

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

It's not that the struts aren't transmitting any forces ... it's just that they're not handling the drive torque. There's still plenty of fore/aft thrust force happening.

Since the lower ball joint is below the hub, a component of the drive thrust is going to be applying bending to the knuckle and the strut.

Don't confuse "anti-dive" under braking ... the braking forces and torques are going through the hubs/knuckles, the drive force is going through the hub/knuckle but the drive torque is not!

The only way you're going to get anti-lift up front is if the geometry is arranged to pull the hub forward when the suspension compresses (i.e. the chassis-end pivot line of the lower control arm has to be sloped upwards to the rear). I tend to suspect that this will have all sorts of bad handling ramifications which is why you never see this on OEM applications.

Anti-squat in the rear requires that the hub move backwards on compression ... that you can probably do, but again, the side-effects of doing this to any meaningful extent are probably bad.

The usual course of action is to just use much higher spring rates. Any bad suspension design can be made to work if you don't let it move ...

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

(OP)
so the only real solution to this other than a V drive/live axle is a stiff mcpherson

crud

well i could see laying back the rear LCA/strut with more caster to give us a little bit of a hand...but as you said the side effects on handling might not be worth it for the small gain...

at this point you think an u/l A arm setup would be a better option over the strut?

this is probably the stuff that should be KISS and spend the time/effort on a nice set of traction bars... 12ft behind the car lol

i really do appreciate the insight into my headache.

Regards, James W

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

Well - as one hack to another...
If you're not afraid to add lots of control links, why are you using the McPhersons to begin with?
I know, it seemed like an easy way to go, but it sounds like you're killing yourselves to work around their problems.
Remember all the drag racing stuff like "traction bars" and such do not apply to your setup.
You will have weight transfer due to acceleration regardless of the games you play with suspension - I don't know if you want a soft front suspension to keep the tires on the ground as the noses rises, or stiff ones to keep it from rising as much.
You probably want the link mounting points on the hub as far apart as the wheel setup will permit, so the wheel actually points where you want it. (ref the toe problems you told us of)
But under power, that hub assy is what's pushing the car down the track. So look at how that force is getting transmitted. (re links, angles, load paths)
Got photos?
That Regal is vaguely similar to what's going under the back of my mutant Corvair, fwiw. I intend to dump the struts and go with upper control arms.
Exact configuration tbd.

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

(OP)
well our best option is to keep weight as close to the cg as possible as well as as much of it below the axle/hub centerline as we can.

to this point much like the original car we are looking at the lower tubular chassis as our rear cooling system plumbing.

all of this plus the simplest solution being a set of "traction wheels" as far behind the car as we can manage.

we have been constantly bantering about what we can do... even using the corvette knuckle (same hub bearing pattern as ours so its nearly bolt in as far as the driveline/brakes is concerned) but the control arms are far too long for our powerplant width. so aside from trying to keep the vette arm length ratio's id have no idea what im doing...

still looking at the fab'd knuckle as its the only good option for us to fit wide meats in back regardless of MCpherson or a multilink...

mmm covairs...the newer buick 3800 really is a sweet engine...several stock shortblocks have withstood 800+hp

i love how the Tq curve is...too bad its FWD lol

no recent pics of the 442 really...its been sitting a long time while we build the two new powerplants/collect parts.
with everything ready to bolt in we started questioning our sanity of two 400hp sc v6's with 100-200 shots each in our current chassis.

the only fix for that we've come up with is a drivers seat we can easily remove and wash off...or a new chassis that can fix the major issues...as i said the original car wrecked twice before being retired...and according to "gentleman" Joe Scheubeck...Hairy lives up to its name and then some...

here's a pic of the new rear powerplant, i posted a link to the build thread in my prev post
http://i260.photobucket.com/albums/ii10/JAWSengine...

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

Terminology - I guess what you called traction bars are also called wheelie bars?
Thanks for the build links - I'll look at those closer when I get a chance.

Check out the FAQs and other discussion threads here - lots of good info..
Regards
Jay

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: twin transverse driveline, rear "4 link" to force nose down and counter front driveline re

(OP)
thank you

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