aadrew10

Just finished up a project in Experimental Methods. Mounted strain gages on the axles to measure torque, and used an accelerometer to measure wheel RPM. From this, calculated HP. Engine has 98mm Mahle pistons and cylinders, possibly a fancy cam, and a better exhaust. I forget what kind. Horsepower value is of course, HP to the ground.

Hope you enjoy the project.

- Andrew

aadrew10

cc

Amber Gramps

That is kinda cool, but your iphone has an app that only requires you to know the weight of the vehicle. It uses GPS.

User 4221

Very cool. If you could miniaturize and use wireless comm, this could be an option on production vehicles. It could be a feedback mechanism for stability control or torque measurements in vehicles like tractors.

This may have commercial applicability.

Thanks for sharing it was very interesting

Norske

Which AP is it? I know of Dynolicious, & G trac, & Pocket Dyno.

Thanks

irobertson

Cool project.
I know that some semi tractors have torques sensors in the drivetrain.
We had to get a replacement tractor on tour once because one of the rigs had a failed torque sensor in the tranny, and the driver didn't want to pull the trailer over the rockies without it functioning properly.

928drvr86.5

It appears that you have the instrumentation package mounted directly to the half-shaft. Unless I am missing something in the pictures, the centrifugal forces induced on the part by doing that will cause inaccuracies. You should never mount anything extraneous to the test part. I realize you have done this because you did not have a way to commutate the bridge wiring back to the analog to digital input of the instrumentation package. However, there are quite a few slip-ring manufacturers that make products to address that issue, but it wouldn't fit within your in-expensive parameter. There are several wireless torsion transducers available, but again the cost would be prohibitive for a hobbyist.

Additionally, as i look at the pictures, it appears that what you have wired is a full bending bridge or possibly a Tension & Compression bridge. I am not able to discern which it is because i cannot see the gage grids well enough, but what i can tell you is that neither one of these is the optimal application for measuring torsion. Could it be calibrated to do so? Yes, and obviously you have, but a torsioin bridge would be far more sensitive and accurate for measuring torque as the principal strain. Finally, rather than having all 4 gages of the full bridge mounted to one side of the shaft, you should have 2 gages (1/2 the bridge) mounted on one side of the shaft and the other 2 (2nd 1/2 of the bridge) mounted on the opposite side, 180 deg apart.

928drvr86.5

Here is how a torsion bridge is layed/wired. It's recommended to use gages specifically designed with a symetrical torsion grid at 45 deg., but you could use regular gages hand laid at 45 deg. Accuracy in regards gage placement effects the calibration values significantly.

Even when gages manufactured for torsion are used you should expect some difference in calibration for the clockwise and counterclockwise torques.

aadrew10

Thanks for the input Ben. The gages we used are the same gages have pictured at 90 degrees apart and wired how you suggested. It would be wise to put them on opposite sides though. We calibrated the gages with the torque in the same direction the axle sees when accelerating.

Would a slip ring be able to handle the vibration and bouncing movement from the road?

Auto_Werks 3.6

Very interesting engineering project!! I had a brainstorm about doing something similar to this, and by similar, I mean very vaguely similar. I theorized that if you replaced the actual axle with a splined torsion spring, you could get a little more deflection, and use lower resolution instruments. If you had a trigger (magnetic or otherwise) on the transmission output flange, and one on the wheel flange, you could gather enough data to calculate wheelspeed, angular velocity, and looking at the pulse timing you could calculate the twist in the torsion bar (and calculate torque if you know the spring rate of the bar). I have put VERY LITTLE thought into actually implementing it, so I'm sure there are many hangups, or maybe its not possible at all. Perhaps it would only put up with the torque from 4th or 5th gear without risking fracture. It would eliminate having to mount most components to the axle....

PS, depending on the reliabilty of your device, you could use it to provide closed loop feedback to optimize ignition timing, looking for best torque at cruise etc etc. Lots of possibilities. Have any access to computer geeks, and mega squirt? That is an adaptation that would probably give your hippie professors a hard on for fuel economy.

Thanks for sharing!!