Tony is describing the torque reaction resulting from the gearbox twisting the wheels (car is trying to wheelie), so the proposed bracing needs to restrain the gearbox in a vertical plane, not horizontal.

 

Dave, hope this does not seem like I am arguing, I am not, just confused. Both Patrick and I asked if it was rotating fore and aft, pivot point being the horizontal centerline of the transaxle thus near where the two stub axles bolt on and Tony said No. So if it is not rotating fore to aft or horizontally from the rear in a CW or CCW manor, I am totally confused as to what other possibility there is. Of course the horizontal issue could be solved by the mock up post Chris posted, but that would not be very effective for the fore and aft movement. I would think torque tube bracing spaced out along the length of the TT would be very effective in conjunction with a single vertical stabilizer on the rear most point of the transaxle. Might send some serious vibrations throughout the chassis though.

 

Sorry.... maybe I responded incorrectly when you asked the question about the direction of rotation being fore/aft.

Just to clarify, the transaxle is rotating backwards, which is the opposite direction of the wheel travel. And BTW, the very reason the torque tube is called the torque tube. The torque tube is what stops the transaxle from rotating. It's that with so much torque, the tube is actually flexing under load, which is what's allowing the transaxle to rotate (albeit very slightly).

And for the record, the dyno pulls are done in 4th gear.

TonyG

 

Understood, thanks! Curious to see the Vision "Fix".

 

I think the description of wheelie is a good one. If you saw it in 4th, imagine how much more moment is going through it in 1st. Is there anything to anchor to on the chassis at the back or front of the transmission?

 

If you want to reduce the vertical flex you could put a 'snubber' above the torque tube mid way between the engine and transaxle. Its a simple device - just a piece of stiff rubber mounted just above the torque tube. When the tube flexes it will hit the rubber and stop any more flexing.
BTW - if you are getting a really noticeable amount of flex then the torque tube bearings will not be very happy about it.
BTW2 - I did interpret the original comment as a in line twisting of the torque tube - and I wouldn't be surprised if some of that were going on as well.

 

wow, great discussion! does this thread ever disappoint?

solidifies the v8/944T cars can only benefit with having Constantine's bearings in there.

and with decent shafts anywhere near Eric Hill being about nil,

I called Constantine to get a tube w/ virgin shaft and bearings – and lucky, he's got a batch coming in.

 

is the torque tube flex something to be concerned about, or could it perhaps be taking up slack that might otherwise damage another part of the drivetrain?

if one were to build a beefier torque tube, would that increase the likelihood of a broken axle/diff since there's less slack for the counter-torque?

 

I would say that the risk is higher of damage being done by bending the drive shaft. I'm no mechanical engineer, but putting that kind of rotational speed and torque into a shaft and then bending along an orthogonal axis seems like a really bad idea. The force will still be there, but it will more try to lift the engine off the motor mounts and the front end of the car instead of bending in the middle. That's why Chris was suggesting putting a stopper on top of the tube so it lifts the body.

 

The drive shaft is designed to flex. It twists by design. Even on low HP cars, it flexes and twists. It's far from rigid.

What surprised me was that the torque tube itself flexed in an amount that was clearly visible with the eye. Not much, but a very slight flex could be observed.

Dwain at Vision said it's common and not to worry about it.

So, for now, that's the end of that.

But I will tell you it's an eye opener to sit there and watch under a car, at full load on a dyno, with essentially zero protection.

So... scratch from my bucket list.... "Being under a a 600+Hp car on a dyno at full load to inspect for oil leaks.".

Yeah....

Won't be doing that again anytime soon... :-)

TonyG

 

On behalf of everyone following along here - please don't do that again. We would like to continue to get updates as this project progresses...

 

Told about this thread by Odurandina and about the torque tube flexing in TonyG's car. Whoa!

Can't really imagine the forces needed to do that type of flexing.

I will go along with Chris White about placing a snubber/bracing of some sort to control this movement as much as possible or eliminate it all together. I would think this type of movement places a lot of strain on other parts like the bolts holding the torque tube in place, not too mention the aluminum bell housing. Unless this has all been completely changed.

Also when something flexes it changes its length making it shorter. This shoves the drive shaft into its front and rear placements.

Just some thoughts and not meaning to derail this thread.

Awesome build by the way. Just wow...

 

That was my thought as well. The shortening of the shaft under flex.

 

Still in development mode.

Got the brakes working pretty good. Balance, ABS, and pad selection.

Still fighting an engine oil leak. It doesn't show up on the dyno, but it shows up on the track. Very strange. It's back at the engine builder today to try to figure it out.

Installed some new tall Katech valve covers as well.

TonyG


...

 

Which pad did you go with?