Simple driveline torque measurement method ? Horsepower also.

[amorrison]

If the torque output of the differential output shafts is always the same - then if one shaft is locked in a simple scale/lever device (to measure the shafts torque at zero rpm) and the other shaft is connected to a load and allowed to rotate - then the torques will be the same.

Also -by measuring the rpm of the rotating shaft the horsepower can be calculated.

Anybody see any problems with this?

This must have been done a hundred years ago!

 

[ivymike]

vibratory effects may make your calculations more difficult, but it ought to (roughly) work.

 

[gearcutter]

I do not believe that the torque will be shared equally between the two shafts.
Usually if you lock up one shaft, the speed of the other shaft will increase.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[MikeHalloran]

Gearcutter is correct; the free shaft will run at double speed. ... and half torque. ... well, less than half torque because of friction within the diff.

Worse, the typical bevel differential gears don't have real bearings or effective cooling, so they'll overheat and fail pretty quickly when used in the way described.

The usual lowbuck (sort of) tactic is to instrument the engine mounts to estimate torque developed.



Mike Halloran
Pembroke Pines, FL, USA

 

[ivymike]

uh, you sure about that? I'm guessing you mean "half of the total input torque" not "half of the torque measured on the other (fixed) shaft?"

 

[pontiacjack]

The basic premise is sound. The aftermarket can provide roller-element bearings of some popular differentials. I've built such 9" Ford differentials, since my pulling tractor needed an efficient/rugged fully "open" differential to allow steering via independent rear brakes. Needle bearing spider gears and needle bearing thrusts for the side gears can be sourced.

 

[GregLocock]

That's basically an inertia dyno and it is fraught with difficulty because of that, and because a diff typically has a lot of friction and hence is not especially accurate at providing each shaft with equal torque.

The oil temp will change rapidly during the test which will alos affect the results.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[pontiacjack]

The original poster talked of applying load, measuring RPM, and calculating power; this implies "brake" dyno operation, not "inertia" type. As for high differential friction, see my 28 March post.