real-time engine torque measurement 1

[ivymike]

anyone have a slick method for measuring real-time engine output torque in a running/installed engine? In my case, the engine and driven equipment each have multiple mounting locations, and the engine block is "rigidly" connected to the driven equipment. Could conceivably do strain gages on the crankshaft tail with a slip ring, but I was hoping for something a bit more robust (want 30k hours life).

 

[Lou Scannon]

Howabout high resolution crank angle velocity with a model to convert acceleration to torque based on inertia?

 

[MikeHalloran]

S. Himmelstein probably has what you want.

Bring your wallet.



Mike Halloran
Pembroke Pines, FL, USA

 

[ivymike]

hemi, yours sounds like it'd work for the unloaded condition, but I'm not sure how I'd get to the steady component of torque by that method.

Mike, yes, it looks like they've got what I'm after (especially the red disc one). I can see just from looking what you mean about the wallet.

 

[j79guy]

Some turboprop engines have a two piece driveshaft, (Inner, main shaft transmits the torque, the outer is a floating reference sleeve, locked to the inner shaft at the input end.) and use phase shift between the two shafts as measured via gear type pickups at the output end. So long as you know the modulus of elasticity of the inner shaft, the phase shift is a rock solid method of torque measurement. Allison uses this system on their T56/501 engine line, to give the pilot a torque reading for each engine. (C130/L100 aircraft.)

Not sure if this can be adapted to your particular application, but if you have a single output shaft transmitting the torque, it may be suitable. (And parts are readliy available, cheap.) We've used this system with optical pickups as well to measure the phase shift, which promised to be simpler, however any dirt or oil covering the optical strips caused grief.

Robin Sipe.

 

[GregLocock]

Might be possible to find a likely spot near the mounting points and mount a strain gauge(s), then apply a known torque and see if you can get a calibration. We do this for other things.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SomptingGuy]

If you are looking to measure torque variation through the cycle, where do you measure it? Before the flywheel, after the flywheel, gearbox output shaft, etc. The amplitude of the in-cycle variations will depend on how much inertia you include in the "engine".

- Steve

 

[ivymike]

actually just looking for steady torque.

Measuring at the mounts sounds like a good idea (one of the first I considered), but many such engines are packaged by third parties with unknown (to me) driven equipment, which might impact the results.

the concentric shafts idea sounds interesting. I'd been thinking about a 2-piece flyswheel for a similar setup. I wonder whether the system could be made robust enough for production use in an industrial piston engine application (~40L-70L total displacement). That's the end game, and might change the feasibility of some ideas.

 

[thruthefence]

I've seen torque meters that use the thrust loads between two helical gears. One gear, driven by the engine, meshes with another, that moves an piston, which ports, or unports a oil passage. As the gears try to move away from each other, the piston moves, and pressure rises or falls in the port. (there's a fixed bleed in the port also.) The pressure rise or fall is either read directly on a bourdon tube gage (calibrated to horsepower, torque,percent of power, etc or more commonly,a transducer.

I have checked the torque calibration on certain turboprop engines with a test instrument called a "Lebow", that mounts bettween the propeller and engine drive flange. It contains strain gages ( as mentioned ) and a slip ring affair for the telementry.

 

[malbeare]

ivymike ,
some tractors I have worked on with hydrolic gearbox have in place of a clutch a twopiece flywheel . the first half ridgidly connected to the engine the other half spring loaded to the first half and connected to the hydrolic pump . It has a magnet stuck on it with a pickup to read it position relative to the first half input, thus a torque value.

 

[tbuelna]

ivymike,

There are lots of ways to measure real time torque in a running engine. The easiest would seem to be using load cells at each engine mounting point. That is where the engine torque moment is ultimately reacted.

Turboshaft engines use a concentric drive and reference shaft arrangement, with hall effect sensors on each, for measuring torque. This shaft device is called a "torquemeter". But this would require you to engineer and build a fairly expensive piece of hardware.

The radial aircraft piston engines of the 40's and 50's used a floating ring gear in the reduction gearbox that had a helical spline on its OD. The thrust reaction forced the ring gear against a set of hydraulic pistons that pressurized a hydrostatic fluid circuit. The resulting circuit pressure was converted to a BMEP rate by a dial gage. This method would only be practical if you were designing and building your own gearbox.

If you want to do something super-high-tech (but expensive), check out this "magnetomechanical" gizmatron:

http://www.magcanica.com/products.html

Regards,
Terry

 

[Lou Scannon]

ivymike, you threw me off when you said real-time torque. That can be modeled based on fuel flow (rack position?), BSFC & rpm.

 

[ivymike]

tb - I don't think there's much steady-state torque reacted at the mounts when the driven equipment (housing) is rigidly coupled to the engine and there's no torque output from the driven equipment. Take a compressor or pump, for example. As I mentioned above, some of the design of the attached equipment is not known a priori... which could perhaps be corrected for later, in some instances. There is not always a gearbox involved... but I suppose that gives a new "twist" on the two-piece flywheel concept. Perhaps I could "float" the flywheel (or a portion of it) in such a way as to cause minor axial deflection in response to output torque, and then measure the axial deflection.

PB-II shown here

http://www.magcanica.com/torque.html

sounds very interesting - I wonder how long the magnetization lasts?

hemi - you'd have to assume that combustion is happening properly, which is one of the things I need to verify w/ the measurement.

 

[MikeHalloran]

Put a simple spacer between the flywheel housing and the load.

Put a tubular spacer between the bellhousing flange and the load's flange. Put strain gages on that to measure the reaction torque.



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

ivymike,

If you can access the flywheel or flexplate OD, a Hall effect sensor with a high sample rate should be able to measure the variations in angular velocities (at, say, the starter ring gear teeth) produced during any given crank rotation. The starter ring gear is a large diameter with lots of teeth, so it should give fairly good resolution.

Of course, you would need to do some mapping of the engine torsional characteristics beforehand, in order to make sense of the results you will get in operation.

Good luck.
Terry

 

[BobM3]

Maybe a custom gaged/slip ringed output pulley hub that is universal enough to mount to any of your engines and has the ability to have various pulley rims bolted to it?

 

[larrylcoyle]

I remember reading in the September 2008 issue of one of the Automobile Magazines about a young man in the Memphis area who developed just such a thing that should fit this application perfectly. He is initially calling this thing a U-Joint Dyno and it does work. He has now patented it and has some pretty sharp people that are showing interest. The very first prototype built went on his highly modified Mustang and the results were verified and the decision made to develop this for production.

If anyone is interested in this and please no tire kickers as he does not have the time for that, please respond to this thread and I will find his email address and post it. First though, I want to get his permission to do so.

Larry