Torque measurement

How is torque measured on the inertia dynos ? Is the measurement sensitive and precise ?

http://www.datum-electronics.co.uk/prod ... ransducer/

I notice with John Renwick's dyno, he uses a calibrated paddle device, however I still wonder how the energy is dissipated.

https://www.youtube.com/watch?v=NQIhqazUHg8

Sure, torque is the only thing measured on an inertia dyno [or any dyno] besides rpm. It is read by how long it takes to accelerate the weight. From that and the rpm horsepower is computed.

Of course if you want a steady state power reading then you need some type of brake to control the speed. Jim

Thanks for that, Jim. I thought it must have been something like that. I suppose the sampling rate is important. For my own purposes, I would only be looking at the torque curve shape and position, so the calibration is not so important. As far as I am concerned the horsepower figure is pretty much irrelevant. What does it mean if the bike gets blown backwards in the first breeze ? Two strokes can be a bit like that.

A while back I fitted the 6 speed TTI box to the Seeley and took it to Winton. I tried to ride it around the pits, however it seemed horribly high geared. I had changed sprockets and thought that was the reason. What I didn't realise was the direction of the gear change was reversed. I got a bit frustrated and gave it a good squirt and dropped the clutch. It must have been in 5th gear and it still took off extremely quickly over about 100 feet and I narrowly avoided sticking it through the fence. I would never have thought the bike was capable of doing that. Most other bikes I have ever ridden would stall immediately.

Actually, on an inertial (only) dyno, the only measurement is rpm. With change in rpm from sample time to sample time one an calculate acceleration. The product of acceleration (calculated) against a known rotational mass yields torque. The linear analog of this is Force = mass X acceleration. In the case of an inertial dyno, Torque = rotational mass X rotational acceleration.

In the strictest sense, an inertial dyno is only rapidly measuring (sampling) rotational speed (rpm).

Thanks for that. It makes sense. I couldn't figure out how the load was measured. What does the set of calibrated vanes on John Renwick's dyno do ? (video link in posting above )

acotrel said:

What does the set of calibrated vanes on John Renwick's dyno do ? (video link in posting above )

Click to expand...

I did not see any calibrated vanes in the video nor do I know what type of dyno John Renwick is running in the video.

I suggest you ask John Renwick.