Driveshaft loops: Keep it in the frame or let it out?

Nevermind... I put this in the wrong driveshaft thread.

I'm a dumb***.

-Chris

 

The front loop is pretty serious that's on there right now. It's a triple stack of 3/16" thick flat bar, fully welded. The rear I was thinkinking of redoing with the tubular type and then like Steve's above, add a few length-wise. I would make the bottom removable to drop the driveshaft... I think.

 

Scooter, I have seen only 2 driveshafts cut loose, both on friends cars.

The first (OT 66 GTO) had a bolt in loop per track regulations. The converter came apart, dropped the nose of the ******, ripped out the loop, pretzeled the shaft and continued out the p***engers side.

The second (OT 68 Camero) blew the rear u-joint and shot the shaft THROUGH the gas tank.

Another thing to consider is the Mythbusters did a thing on this. They had a hell of a time to get the car to pole vault. Dug a pit and anything else they could come up with. Took a while but they did get it there. Probably not as common as some people think, I would guess.

Never hurts to be careful.

Len

 

Yea yea whatever!! I've got driveshaft loops!!

Added some panhard bars today!!

 

Loops - shmoops, torque tubes are the future, all the new BMW's have them, worked then, works now.
Seriously, to me, it looks like, what you've done so far, is enough, maybe add another piece, at the bottom, to the rear loop, voila.
Don't overthink things.
Git 'er done.

 

I wondered when someone was going to bring up closed drivelines. HAHA!

Me overthink?? NEVER!

 

hahaha!!! :d

 

Hahah yeah i but welded them together... naaah bro, theres a machined slug pressed in, maybe runs 8" inside of it. They are "U" bends from Art Morrison 1/8 wall

 

If you want to go nuts, I'd add a bottom to the rear loop, size the rear loop down to where it just misses rubbing at full compression, narrow the width on both front and rear to where there is very little room on either side (less room to fling around), add a third loop in the middle, again sized as small as possible, with tubes connecting all three loops. THEN, I'd take some pieces of 1/4" strap and build a ****ter shield around the front u joint. I'd weld a couple pieces of the strap together to make a channel (or bend one wide piece) to contain any shrapnel from an exploding u joint.

That's if I was going to go crazy. Is it all necessary? Probably not, but it can't hurt.

 

What about a 1/4" plate tunnel, top and bottom?

Thanks Steve! I'll check out Art's catalog. They make great stuff and have a ton of great DIY bends and stuff..

 

DO IT!!!!!

Makes me think of e type jags... the drive shaft runs through a fully enclosed tunnel. Top, bottom, and both sides, no removable panels... Have to remove the whole freaking rear suspension to get the damn thing out.

 

What he said....

 

By the way guys, thanks a lot for your feedback! I really appreciate it!

 

I've broken u-joints in the front and the rear on dirt modifieds (~700 HP), and it is not fun.

Our ch***is all had one loop about 6" back from the front joint, and then the back was like yours, except our ch***is tubes made a kinda Mayan temple looking shape, with an open bottom.

Lost a front joint, no big deal, the loop got banged up pretty good, and the shaft was junk, but I survived intact.

You gotta remember that the seat in these cars has your right knee ~3/4" to the left of the front u-joint.

Lost a rear joint a season or two after. Major damage to the shaft, but it stayed in the ch***is. Again, no damage to moi.

However, one year I had a hellatious lick where I almost missed a spinning car. I ducked under him, but he came down the banking and clipped my right rear tire.

This tore the right rear trailing arm completely out of the ch***is mount, and let the rear end housing skew abruptly to the right. This skewing action pulled the slip yoke out of the transmission, AND moved said yoke rearward far enough to clear the front hoop. Obviously, things went poorly from here.

The interior of the car more or less exploded in my face. It all happened very fast, but I distinctly remember thinking, "****!" very loudly. I may have cursed aloud, I can't remember.

When the car stopped spinning, and the driveshaft stopped spinning, I opened my eyes again and found that I was staring at the racetrack . . . . through the center of my car. Yeah, the slip yoke (jammed at 90 degs to the length of the shaft) turned into a whirling wheel of doom and totally dis***embled my interior (no floorpan on the p***enger's side, so once the interior sheet is gone, you can see and touch the ground from the driver's seat).

When I tried to get out of the car, I found that it had also "Splosion Formed" the seat over the top of my right thigh, pinning me in place. Good thing this particular wreck was not also accompanied by a fire.

They dragged me back into the pits, swinging from the hook, and once safety deposited therein, my old man supplied me with a 14" Blue Point Crescent Wrench, which I applied to the seat and won my freedom.

Aside from another destroyed drive shaft, and half a sheet of mangled 0.040" aluminum sheeting, we were no worse for the wear, but it was still a pretty a scary deal.

I'm a fairly "meaty" fellow, so I don't think my leg was in any danger of being broken, but a not-so-padded individual could very well have ended up with a broken femur in the deal, or a broken right arm or something else. I got very lucky that the explosion of driveshaft and interior sheetmetal did not end with a lot of big nasty cuts or broken bones, seeing as I was basically setting right next to the thing, with it tucked under my right armpit.

The solution was to add a second hoop about 24" back from the first one.

I had another nearly identical crash a couple of years later, but this time, it ended with a mangled drive shaft and a mangled rear hoop, and no 'splosion-o-sheetmetal.

Lesson Learned.

I learned it the hard way, but you can reap the rewards for free. Use two hoops, or totally enclose the thing.

Not so much to contain it if the rear joint blows, but to contain the front joint if ever the rear end stops being properly located in the longitudinal sense.

 

Coolhand... thanks for sharing that! Scary stuff FOR SURE! I realize your situation was racing related, but the point sinks in! In the event that "**** happens" be prepared. I like the idea of adding something in the middle as well as a lower rear.

Keeping it from whipping is REALLY what is needed here.

 

No problemo man.

Racing is dangerous, we all accept that, but I find that it behooves me to pay attention when ****-ups occur, so that I can apply what I've learned to prevent a recurrence.

Just as an aside, when the trailing arm tore loose, it immediately dug into the track surface (dirt ya know), and acted as a pogo stick, vaulting the ch***is (and me strapped to it) up about three feet into the air.

The landing ****ed, but the take-off I think is what bent everything. Much carnage to be found in the rear suspension and ***ociated ch***is points. It's not a lot of fun, so I'd suggest against spearing any suspension parts into the road surface.

Thankfully, that doesn't come up much on the highway.

 

Scooter, I know what you're saying about having the drive shaft spinning right next to you. Makes me nervous too. This is what I did two 3/8 x 2 flat plate bent in a u. I'm also going to build my tunnel out of 14 ga. I think after reading this I'm also going to add a shield around the u-joint.

 

Keeping it from whipping is REALLY what is needed here.[/QUOTE]

Exactly!!

 

Here is what I have under my '35 sedan. You can't be too careful, my grandkids ride in this thing.

 

One thing to remember when evaluating a driveshaft safety margin is it's RPM. Most racing incidents are much worse than street cars due to high shaft RPM caused by super low racing gears and super thin floors. In high gear shaft RPM is crank RPM and if you're not regularly floating the car to 7500 RPM in high then you're not really in the same situation as even a low level race car. By a margin of 30% or so. Good luck with the project!

 

Hey Scooter,
****** good work so far mate!
I've had a couple of shafts let go, only on the street, no race experience with this.
Once at freeway speed - glad there was only a front hoop that time - shaft hits the ground and gets dragged out of the car before you know what's happened. Same happened in a limo once too! Only doing about 45, but same thing, shaft out of the car no harm done. I know I'm going against concensus here, but I wouldn't worry about the lower rear hoop.
If you do, make that tunnel bullet proof!
As for over thinking - maybe - a new shaft, properly balanced, in a street car with those rear tires? - I don't think that shaft is going to be over stressed. All my broken shafts were the direct result of my lead lined right boot, or just gave out after years of such abuse.
Cheers
CraigR

 

I think in some cases mine might be overkill but then...I won't turn down a chance to run the old girl down the dragstrip either. The car has run 13.0 seconds, that's quick enough for me to think a broken shaft is possible.