SI units

Well done!

But these days we have an SI system of standard units.
In any country outside the UK and US (? more?) it would look like this:

12.1 Volt x 7.0 Amp = 84.7 Watt

1864 RPM x 0.3048 m/rotation = 568.15 m/min / 60 sec/min = 9.47 m/s

0.700 Kg x 9.8 N/Kg = 6.86 N

6.86 N x 9.47 m/s = 64.96 Nm/s

64.96 Nm/s / 84.7 Watt = 76.7 %

Results are the same (of course) but with slightly less conversions.
A circumference of 60 cm would then be even more convenient because in that case 1864 RPM would mean 18.64 m/s (just divide by 100).

(just a hint to further simplify this)

Ernst.

dynamometer

Thanks Ernst, Peter made it fairly easy to understand.

Thanks for the conversions.

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Here is a vid on a wheel I made for dyno testing. Gives a bit more details on the wheel. Please reference Peter's vid for more info in the first post of this thread.

It is HD so you can choose that option, but youtube messed up the sound.
Dynamometer Wheel - YouTube

Good video!

Very clear and easy to understand, will certainly help those people who are interested in taking measurements of a small motors output power before making any efficiency claims. Any anomaly can then be further investigated by more accurate means.

As an Englishman I prefer to work in thousandth's of an Inch, metric mm second, and fractions thirdly as they are not intuitive and I always have to refer to a conversion chart for non common.

The one area that I feel the open source community would greatly benefit from is a raw formula list. Those who have studied engineering and science at a serious level will know that the first 20 minutes of an exam (you want to pass) is spent writing out your formula cheat sheet from memory.

There are plenty of old timers around here with the knowledge and experience to build a comprehensive list of cross discipline formulas that can be referred to as needed. This would help the credibility of the community in the long run and prevent preventable mistakes.

As an example:

Physics involves a lot of calculations and problem solving. Having on hand the most frequently used physics equations and formulas helps you perform these tasks more efficiently and accurately. This Cheat Sheet also includes a list physics constants that you’ll find useful in a broad range of physics problems. Physics is filled with equations and formulas that deal with angular motion, Carnot engines, fluids, forces, moments of inertia, linear motion, simple harmonic motion, thermodynamics, and work and energy.

Here’s a list of some important physics formulas and equations to keep on hand — arranged by topic — so you don’t have to go searching to find them.

Physics I For Dummies Cheat Sheet - For Dummies

The dummies is not an intended insult, just the title of a page with good examples.

Rob