3.5" aluminum driveshaft 54" in length, who runs one?

[Dragsinger]

This topic is under discussion on my Super 10 build thread but I want more to see the question so posted here.

I am curious if some of you have an aluminum driveshaft, 3.5" OD, .125 wall, 54" in length, in race service.

The Super 10 will have a 32 x 14 bias tire, 6.0 gear, and for purposes of math use 5% converter slip. Since it has never run the finish line RPM is unknown.

The expect ET is 10.40 - 10.30 range.

One poster explains that finish RPM will exceed the safe limits for a 3.5" shaft 54" in length.

Another poster ask, "in the olden days how did the old modified and comp cars turn 9,000 + RPM with most using some from of factory driveshaft?"

Just for conversation I suspect the on-line critical speed charts we find have a large window of cushion.

I look forward to comments.

[Dragsinger]

PS, I have the above explained driveshaft in house. I do plan to test 1/8 mile with that shaft.

[GL PERF]

I was told by a driveshaft mfg that my small block (327) Powerglide equipped 1971 Nova needed a 4' aluminum driveshaft if I were going to run it to 7500 rpm. My thoughts were that this was not needed. I have been running a 3' MS shaft with 1350 u joints (If my memory is correct it is 55' long) and have not had any issues. It is what I have used in numerous cars over the years without issue.

[Jim Kaekel]

Mark Williams has a chart/formula that they use for driveshaft recommendations. It may be even on their web site.

[buzzinhalfdozen]

Though it's not quite 54inches long (52) I've run a 3.5 inch Mark williams aluminum shaft since 08 6.20 gear 138 MPH 9900 RPM you can do that math, then look at their chart. I BELIEVE they leave alot of room for safety. Just my opinion.

[Dragsinger]

Joe, I agree about the safety factor. I think you can find many situations like you describe with your combo.