FRporscheman

I like the titanium idea.

944er-teile.de

any idea about the cost for titanium?

944Phil

I am a mechanical engineer at Bell Helicopter. I work in the materials and composites group. Everyday we see metal bonded to composite, it is the weakest link in the assembly. If someone were to build a composite torque tube, it would be best to build it in one piece.

We have a lot of difficulty certifying critical bonded assemblies when they are not also riveted (usually called chicken rivets because we are scared of failure).

The exhaust also passes close to the torque tube (ever feel your shift boot after driving for a while) epoxy softens and loses it's properties as temperature rises. You'd need some high service temp epoxy. Other resin systems may not be toughened enough for the job, but can handle higher strength. Also you'll probably need to cure it in an oven.

I'm not sure how hot the torque tube gets but even temps above 230F can start changing the phases in the al. albeit slowly. Someone mentioned al. fatigue, it is true that al does not have infinite fatigue life at any stress level. There are special design criteria for materials that do not have infinite fatigue life and we use them to build many, many part of the helicopter that are cyclically loaded.

Someone said carbon and al. don't go well together, this is very true. But ti. and carbon do go well together as do stainless and carbon. Steel is not so good either.

Titanium would be an awesome torque tube... you'd just have to sell your car to make one.

If someone wants to take on the task of building a carbon torque tube i would be willing to help them out with the project.

V2Rocket

phil,

i think the big issue aside from the epoxy choice for heat resistance is the torque applied to the tube while driving.

i think it would be necessary to somehow measure the amount of torsional force the torque tube is subjected to while driving at various engine loads and speeds. i imagine it would be a function of the engine output torque, but that is speculation.

once that data is determined, a carbon tube could be made by selecting a particular weave (any suggestions?) and increasing tube wall thickness until the torsion load value is met or exceeded.

i think the transmission bellhousing could be made to bolt on to a metal ring bonded to the carbon tube. you say titanium or stainless would bond well to carbon, so maybe those could be the material for the ring.

alternatively, you could put a thin-wall titanium or stainless tube bonded inside a carbon tube to achieve the needed torsional strength and still have metal for the bearing cages to ride on and for the bellhousing to attach. it would still be very lightweight although slightly heavier than a pure carbon tube.

attached is an incredibly detailed, highly-precise engineering-spec drawing. dark grey is titanium, light grey is aluminum, and the black spatter is carbon. on the top tube picture the dark grey bands are 4 bearing cage holders and the ring at the back for bolting on the trans bh

Bri Bro

Got me thinking, what does the Corvette use for its TT? A quick goggle found these pictures. Looks like the TT and the drvieshaft are Aluminum with steel input and output shaft. The second picture shows what is inside a TT.

Looks like way to much money and time for the return and you don't know what it will do until you crash one...something GM does and most people try not to do. Lots of good ideas to think about, sounds like it would be a fun project.

Scott H

There also exist after market carbon fiber drive shafts to replace the factory C5 one.

Bri Bro

Did a google and got this. For $2000 you can save four pounds but their testing showed it was stronger then the stock drive shaft. The stock drive shaft is in the second picture in the above post.
http://www.pfadtracing.com/catalog/p...roducts_id/172
"The stock drive shaft and rubber guibo ends weigh 8.85 pounds. The Pfadt Carbon Fiber drive shaft assembly weighs only 4.28 pounds!! "

schwank

I was thinking about this just yesterday... if you made sure some holes were at the bottom for drainage I would think you could lighten it a bit without sacrificing too much strength.

Then again I am a computer engineer and not a structural guy.

CarbonRevo

How did I know there would be a MS Paint photo in this thread?

Techno Duck

Might only be a 4lb savings but its also less rotational mass in the drivetrain.

Next time i am playing GT5 i will put a carbon driveshaft in a C6 and compare it with laptimes on a stock C6 on the Top Gear test track.. .

V2Rocket

944Phil

V2Rocket, i love the photo.

I would determine the amount of torque the steel TT could take, and them make a composite or al. one based on that value. That way you are keeping the same factor of safety that Porsche originally built into the TT.

as for a particular weave, you'd need a braid, which is like a sock you'd put over the mold. Another way is like the picture Brian posted which is automated/robotic ... big bucks.

BTW has anyone even broken a torque tube? not in an accident but because of regular use and fatigue?

95ONE

Check this out..

Did Constantine write a post on here and delete it? I thought he directed us to something like this, but now I can't find his post.. once again.. I'm going senile.

Click here for the .... "OH.. we're not the first."

I've made a decision, whatever the case.. I just bought Some T6 6061 3" Sch40 Pipe. (Better/Stronger than the original tube I mentioned in an earlier post) - which is 3.5" OD and 3.06 ID. Same as the Torque tube. It will save me a well calculated 20lbs. I've already got the Steel out of the Aluminum trans Housing. Seems like I'm half way there anyway.. The Tubing shipped to my door wasn't bad. To go with Carbon Fiber seems like more of a "fun" and expensive alternative that really doesn't net me much more for the cost. Its about 8lbs less weight total, but the extra $900 and all the "laboratory" fitment to aluminum just isn't worth it really. I even found Titanium rod to substitute the Drive shaft. That rod is an additional $800 plus machining and ... (case hardening?) It could be totally baller. Weigh about 35lbs less.. or for a total weight of 25lbs. And really give me some bragging rights. So, for about $2200 and a ton of my time, I could make a 25lb Torque tube, as strong as original, light as hell.. Would anyone buy it? MAYBE 2 people. Does the extra 15lbs of weight loss (from the Aluminum option) Justify the Cost.. HELL NO.. not right now.. I have too many things to do to get up and running.. So..... I doubt something like this will EVER come to fruition. If someone does..awesome.

V2Rocket

How much was shipping? I would like to see what you come up with because I have alot of pipe companies near me and a spare torque tube and plenty of time to waste...

I would imagine that with sufficient torque, the steel tube would twist around inside the aluminum housing at the back. Or the aluminum would crack, or the nose flange weld would crack, or the bolts holding the tube to the motor would shear off first.

potent951turbo

I haven't read this thread fully, but my brother works for a driveline company that builds custom drive shafts for anything and everything. Seeing carbon fiber and aluminum shafts in the shop is a normal thing and I am sure they would be interested in doing this project for someone who was serious.