We (in amateur robotics roles) wanted to characterise surplus/UNK
motors, and came up with the following scheme which we brought
to the 'duct-tape'-' whatever else works' stage.

We mounted two identical (not necessary but convenient) motors
nose to nose with a coupler. They rested between two adjustable
rails (for a range of motor sizes). The motor-under-test ( "M.U.T."?)
was clamped to the rails (radiator hose clamps) the 'load' motor
could turn (more or less) freely but was attached to a bar which
extended radially to the side, from which we could hang weights.
There was a 'hard' limit on the bar at near horizontal, to prevent
propelering. In use we loaded the load motor with a resistive
load (big pot., light bulbs as appropriate) hung a weight on the bar
straight down and ran this; measuring R.P.M., input current/voltage
and measured the angle of the load bar (for torque). This was
simple, cheap, "exciting" at times, and had the advantage of
measuring torque independent of load-motor electrical properties.

The simple measurements we could make with this crude equipment
'made sense'. I don't think I would want to get 'this' (jury-)rig up to
what seems to be your speed/power range. But 1/8 H.P. dosn't require
a blockhouse either. But don;t forget the bar rotation stop, with
maybe an integral 'kill' switch.

Horsepower = (some const.) X  Torque  X  R.P.M. ;dep. on units

Ourr next steps were to make a better mechanical system and
less junk box instrumentation. One thing was to measure the
torque ( proportional to sin (angle from vertical)) with a calibrated
pot. and servo the electrical load to control the angle using something
like a LM350 (with power xsister) based variable power (sink) supply..
We wanted to use a fish-scale to measure the torque but didn't
have an 'honest' one <G.>.

But we went on to other things. It would be interesting to hear
your solution. We wanted: cheap, and adaptable to a large range of
DC motors,  size, power, speed.


jeff wrote:

> Hello all.
>
> I have been asked by a co-worker if this would be difficult to build.
>
> What we are looking to do is make a d.c. motor test machine. It needs to
> do just a few things.
>
> 1. Test the rpm. No less than 10,500 RPM
> 2. Test the Amperes being drawn at that speed No More than 6.2 Amps.
> 3. Torque it can handle.
> 4. Horse Power of motor. no more than 1/8 H.P.
>
> That's really about it.
>
> As far as RPM goes  I thought about using a small magnet and a hall
> sensor. Let it sample for say 5 sec. the calculate it out. As for the
> amps. A simple amp meter would work. Is there a way to read the amps and
> then print it out or display a report ?
>
> Measure Torque ??
>
> H.P. can be done with the amount of watts that it draws. 1H.P. = 745
> watts (I think)
>
> Any suggestions on which pic to use? Or anything else I might need to
> look at?
>
> Please remember I'm just a hobbyist. Have only made a few simple things.
> But I would like to figure something out. If noting more than just to
> have a challenging project.
>
> Thanks..
>
> Jeff