924Board.org

[Pete Gossett]

I've been working on an oddball 924/VW-based Locost(Lotus-7 clone)project for about 3-months now & just finished shortening the torque tube to fit into the custom-built tube chassis. I know there's probably not much need for anyone here to shorten their tube but I thought it might be a good place to document it for anyone else who does.

Here's the thread for my project & post detailing the job: http://www.locostusa.com/forums/viewtopic.php?p=5422&sid=56e9612762a01dbb0705e178b872f6f1#5422
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W. Pete Gossett
Rossville, IL 60963

[Peter_in_AU]

That`s a really interesting read. Using a hose clamp to get a cut-line is such a great idea, so simple.
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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[sequential]

Hello Pete,

My question regarding the mods done on the torque tube, do you believe you will have to balance the shaft ? It is interesting , as i had thought of making a rear drive golf, but with the engine in the back mated directly to the transaxle....
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928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2

[Pete Gossett]

I think I'll be OK w/o balancing the shaft.

As I was grinding down the welds on the sleeve tube I tilted the grinder to get the shaft spinning up to speed - not sure how fast, but it's about a 4:1 ratio between my 3" grinding wheel and the ~3/4" shaft, so if the grinder was running about 3krpm the shaft would have been spinning around 12k! I know it wasn't that fast, since there was slippage between the disk & shaft, but I'm sure it was spinning around 6-7krpm. So I should be OK at operating speeds.

Besides, the engine/tube/trans are all going to be mounted solid to the chassis, so I'll be getting a good massage whenever I drive it.

I don't think I'll have to worry about shaft failure either. The original design of the shaft is somewhat poor(You really should have the splined ends larger than the rest of the shaft, w/a gently curved taper from the splines down to the smaller shaft. This will prevent cracking where the splines end.), but since I haven't read about many shaft failures I'd say it was sufficiently over-engineered. When I ground down the final welds, I did taper the shaft between the splines and sleeve, and again after the sleeve, which should remove any stress-risers. And since the torsion of a shaft or tube increases with the 4th power of diameter, the joint *should* be stronger than the rest of the shaft. Coupled w/the fact that it's going to be used in a ~1300lb car, even increasing HP to 140-150 shouldn't present any problems....I hope!
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W. Pete Gossett
Rossville, IL 60963

[Peter_in_AU]

"torsion of a shaft or tube increases with the 4th power of diameter" makes you think really; the 931/944 driveshaft has 2.44 times the torsional strength of the 924 shaft so it can handle 344 ft-lb of torque without breaking a sweat. Given that the Euro 924 is rated at 141 ft-lb and the Euro 931 is rated at 180 ft-lb there's plenty of head-room.
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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[PORSCHEV]

I shortened my TT by 10 mm but had it done on a lathe...then had a chev input shaft welded to a flange. Then a flange on the porsche shaft. They bolt together.
Your job looks good!
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1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.