1 horsepower = 746 watts. You can calculate watts by multiplying voltage
times amps and factoring in efficiency. You can't really get horsepower
just from the voltage of a motor.
Here's a page to get you started -- search on Yahoo etc to get more.
You could make a small dynamometer using another dc motor as
generator with a variable resistor load. You would need to be
able to measure the rpm and the torque being produced by the
motor being tested (possibly using a torque arm on it and a cheap
Thank You. This is a great page. I should have stated it better in
that I meant, not "other than it being 12v", but knowing it is 12v
and using other "common" hobby tools, like multimeters, to calculate
the horsepower. This page you referred me to is going to be very
helpful. I will have to take a guess at efficiency, but it is going
to be a lot closer than I could have done without your help.
Thank you as well. I think my biggest problem with this
method, although probably more accurate, would be a simple way of
measuring speed with common hobbyist equipment.
If you have a multimeter that has a frequency meter built into
it, then you probably could use that to measure the rpm. There
may be other ways to measure the rpm. Below are ways from the old
days to measure the rpm of phono turntables using a fluorescent
light as a strobe source. To measure the running motor torque,
the torque arm on the running motor could be a thin bamboo skewer
with a weight on the end, with the torque being calculated by the
amount of distance the skewer is rotated from a bottom verticle
position in the side/upward direction.
a very simple way is to put a load on your motor with or without any
One way to do it is built anything with a kit like your Meccano.
Power (in Watts) is simply Voltage mutlitplied by Current.
Then, take two multimeters and any tranformer (10x1).
Make sure that you have one multimeter with high amp capacity.
You mount an electrical circuit with the power source, motor and
Be careful to put the one side of the transfo in your circuit
and the 10 side will where you will connect the ampmeter set on the
The Amperes that you read have to be mutliplied by 10 in order to get
your motor current.
Here you go.
Hey LHR, thanks! That I can do with the palytry collection
of eletronic equipment I have available. Thank you again!
This is very helpful, and I might add difficult to ferret
out of the internet as I have tried. This is a good group
to get help from on these kinds of problems.
Yes, I am naive about electrical calculations, that's why
I asked for help. And no, I am not selling anything. This is
for my own curiousity and understanding. The phrase
"for demonstrations" was meant to keep this short and
simple. It is for me and some fellow robotics hobbyists.
I can't afford to create a full scale model. I have some
numbers as to how much horsepower is used on full size
equipment which uses gasoline engines and are rated in
horsepower, which is a unit of work (mass, distance, time).
I realize that there are transitional differences in
going from scale to scale, and torque, horsepower,
power ranges, engine speed, etc. I know what I am
getting into on this level.
I am not an expert, but I need to start somewhere. If the
initial requirements by calculation prove to be too much,
then I will save myself a lot of time and expense. My
hobby is robotics, but I still don't want to waste my time on
something totally impractical.
I don't want to get everyone involved in a discussion about
all the scale transitional differences. But as an example, if I
wanted to create a scale boat, plane, car powered by small electric
motors, and the scale model was exact (I know!), and the
real boat, plane, car is powered by xxx horsepower motors, etc. (not
necessary to point out the differences), I want to determine
if any popular cheap small electric motors could emulate the same
performance. To do that without building the model, I would like
to calculate out the project first on "paper". Therefore, to be able
to calculate a *rough* scale of horsepower supplied by these motors.
Trying to keep it simple at this stage.
I find use of the word "horsepower" somewhat suspicious in any
engineering discussion. In a strictly mathematical sense, as Gordon
points out, one horsepower is indeed about 0.746 kilowatts. In common
usage, however, a kilowatt is a unit of measure used by engineers to
calculate things whereas a horsepower is a unit of measure used by
salesmen to sell things. That you seem to believe that simply by
using the correct quantity of horsepower you can accurately
demonstrate something with a scale model strikes me as naive. The
physics of most systems scale in nonlinear ways. What exactly is this
project and what are the parameters you hope to estimate?
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