question on drive coupling

[gccutler]

I'm building a lakester this year to replace the lightning pickup AA/MP I ran the last two years. Some out there may know this car (I'ts only money #116), last raced in '97' with a small block chevy and muncie 4-speed. I'ts a 280", no suspension , rear engine layout.
My question is this... the car did have a short drive, about 4" center to center, my engine/trans combo is now a 638" Boss 429 with a full comp c-6, can I use a single u-joint from trans slip yoke to rearend yoke?
The engine crank centerline is dead on to rear axle, same plane, no angle. Used a machined bar with bushing through engine mains, trans case and quick change rear.
Any problems with this or is a coupler a better design?
Thanks, Cole Cutler

[Stainless1]

Take a look at the couplers the dragsters use.  The one on the MSA blown alcohol dragster seemed to work well.

[gccutler]

Thanks Stainless 1. I do know about the dragster type coupler and if need be I'll do that, but it would be many many times easier to use a slip yoke, u-joint and diff yoke (did I mention cheaper). I would just like to hear that someone else has done it that way (one u-joint only).
Cole

[interested bystander]

I realize you're 450 miles away, but two really good driveline services down here in So Cal, Lee Watson's Inland Empire Driveline in Guasti and Ed Moore Drivelines (the ex- Fuel Altered pilot) in San Bernardino are understanding abour racecar stuff and Ed has made me close coupled U-joints in the past (mid seven second drag cars) and has built many El Mirage and Bonneville record holding conventional shafts. Today, couplers from Strange or MW MIGHT be cheaper, the quick change might be a problem, spline-wise, tho, with the drag race parts.

[Don Brent]

I have used the set-up you are considering in my rear engined roadster.  A Muncie four speed connected to a 8 3/4 Chrysler with a single u-joint.  Alignment is critical but it sounds like you have that covered.  I think a coupler would be the best but the u-joint set-up works.  I have had no problems but need to qualify that by letting you know this set-up is behind a flathead so there is nowhere near the kind of power you have.  I think that Jack Kelly uses a u-joint connection in his tank also.  We talked about it and he mentioned that he had some heat from the joint but never a failure.  Another thing, Tech required a shield like a driveline retaining loop even though there is no shaft.  This is in case the joint comes apart.  Good luck with your new ride.

[SPARKY]

I sure have liked my Mark Williams coupler!!!!!!!!!!Sure makes things simple!!!!!!!!!

[edweldon]

Cole --
Your chassis is probably pretty stiff in the back; so it probably wouldn't flex much. But it might be useful for you to know just how much.  Too much flex will make it rough on the rear tranny bushing unless there is enough side to side movement in the u-joint or coupling to accommodate it.  The way to check it is to load the car to as near your soaking wet weight as you can and then jack it at each corner near the wheel centerline as you can get.  Take the coupling out first and put a dial indicator between the tranny and the rear end u-joint much the way you'd check alignment between the engine and tranny to make sure they are aligned right at the bell housing. 

Do the measurement both horizontally and vertically and if the two come out about the same do it again 45 degrees away. Now take the highest reading and multiply it by 2 to allow engine torque loading and for shock loading from hitting sharp bumps.  The springiness of the chassis/tires/and other parts can soften that some.  That's your worst misalignment.

That's the amount that any coupling will have to absorb while it's under torque load to keep from loading the machinery structure and bearings on either side.  I suspect the guys who would sell you a special coupling will be interested in that.  In the world of application of high hp industrial machinery couplings that is the area of greatest concern to the engineering types.  After they ask you about HP and RPM's the next question is "how much misalignment are you going to have under your worst operating conditions?"

Any of you guys that have a better rule of thumb number than my "2" please chime in here. 

In the engineering world the theoretical worst case multiplier for load amplification under shock is 2 for perfectly stiff structures and 1 for perfectly soft structures. In most real world engineering situations we use factors between 1.25 and 1.5 to calculate stress and deflection because there is always a certain amount of springiness and dampening in most real world structures to provide some isolation from shocks. But that does not account for internal loads such as come from engine torque within the structure.  So I figured 2.0 in this case to stay on the conservative side.
Ed Weldon

[Rex Schimmer]

Cole,
I would highly recommened going with the dragster style gear coupling. Even if it is not the "easy fix" any missalignment on a single U joint will cause a vibration and if you have any flex between the engine and the diff that would add to the missalignment it will get much worse, quickly. Nothing is worse than loading a killer car on the trailer to go home because you took the easy way out.

Rex

[gccutler]

Ed, Rex, thanks so much for the ideas! Rex, I did decide to go with the dragster coupler. Found the parts from Mark Williams as suggested earlier.
Ed, the chassis is strong and well braced but there will be 400 lbs just in front of the rear axle as well as wet weight added so some sag is possible not to mention torque twist. I have considered building a brace from the pinion support on the quick change forward to the c-6 trans mount instead of a mount to the rails, kind of like a torque arm. This may help to retain alignment at the coupler. Your advice on alignment measurement will be followed.
The mid mount block plate just came off the mill for trial fit. It will be bolted to the bottom rails and clamp on upper mounts. This should allow some alignment shift in that plane and the QC can be ajusted side to side as well as pinion angle.
Thanks again, Cole

[salt27]

Cole,
I remember seeing your 34 and 50 in the mag's, very nice rides. How about some build pictures on your lakester?
Thanks,Don

[RoosterBooster]

Ed, Rex, thanks so much for the ideas! Rex, I did decide to go with the dragster coupler. Found the parts from Mark Williams as suggested earlier.
Ed, the chassis is strong and well braced but there will be 400 lbs just in front of the rear axle as well as wet weight added so some sag is possible not to mention torque twist. I have considered building a brace from the pinion support on the quick change forward to the c-6 trans mount instead of a mount to the rails, kind of like a torque arm. This may help to retain alignment at the coupler. Your advice on alignment measurement will be followed.
The mid mount block plate just came off the mill for trial fit. It will be bolted to the bottom rails and clamp on upper mounts. This should allow some alignment shift in that plane and the QC can be ajusted side to side as well as pinion angle.
Thanks again, Cole

Cole
IMHO using a solid connection and a spline coupler works a lot better then a single U-joint.

its a different application (high powered mid engine dune buggy) but i know about a car builder (Buckshot) that did try the U-joint setup; the chassis flex (even when well X-braced) is destroying the input shaft bearing and/or the QC/trans housing fairly quickly.


btw
i use a short drive shaft on my QC`s (front/midship engine car) but i know that the B&J Quickchange (located in Kingman AZ) that i use was originally designed to run inverted and flange direct to a trans (with spline coupler) ....notice the extra bolt surface/flanges for the adapter housing:




maybe this QC would also work for LSR ?? (it works very well for me; the QC housing is extremely strong and all the internals are made of 300M.)

[Sumner]

........




maybe this QC would also work for LSR ?? (it works very well for me; the QC housing is extremely strong and all the internals are made of 300M.)

That is some nice work.  What is the ring/pinion ratio??  Most of the circle track ones have a 4.11 or lower and even if you can gear the gearing back that you want through the quick change gears that pinion gear can really be flying.

Good luck with your buggy venture on the salt,

Sum

[gccutler]

Here's some photos of the chassis and the rear QC with engine block plate and block. The alum plates mounting the rear end are for setup only. We decided to buy a laser bore sight to confirm all three components, block, trans, rear end. Yea, that's really a prostreet 72 LTD
Cole

[gccutler]

more pics!

[salt27]

Cole,
Thanks for the pictures, keep us updated.
Don