DIY Motor Dyno/load?

[geemy]

to be clear I'm not intending to use the alternator as an alternator. I would convert it to a motor that would then oppose the motor under test. I can make the alternator apply braking force via magnetism.

Basically adding resistive electrical loads to the alternator would just approach the same thing as shorting the alternator phase wires to each other. This does cause mechanical resistance but not enough I'm afraid.

a motor that opposes rotation IS a generator. shorting an alternator would make it a 0% efficient alternator, that would convert 100% of mechanical power into heat. considering electric motors under nominal load is probably around 90%+ efficient, running it with 0% efficiency means heat x10 so you would only be able to sustain a load that is 10% of the rating of the motor. also you would have zero control on the current generated (and the resisting torque associated) so anything stronger will rev very quickly and anything weaker won't be able to rev at all. basically zero advantage vs simple inertia Dyno. when you make a Dyno you want it to have the widest range possible

 

[hbozyq]

Is there a simple and inexpensive way to measure mechanical power? It could be useful if it's possible to measuere electrical to mechanical power conversion efficiency while comparing motors.

 

[amberwolf]

You're looking tor a dyno (dynamometer). There are a number of DIY versions of various types and complexities, including some threads here on ES.

 

[DogDipstick]

Is there a simple and inexpensive way to measure mechanical power? It could be useful if it's possible to measuere electrical to mechanical power conversion efficiency while comparing motors.

Yes.

It is called a " piece orf rope, spring scale, and a known weight".

....one of the most inexpensive and simplest ways known to man. To measure mechanical hp. KNown as a " Rope dynamometer"

If you know how, and what you are doing, it is very simple and inexpensive.

 

[hbozyq]

Yes.

It is called a " piece orf rope, spring scale, and a known weight".

....one of the most inexpensive and simplest ways known to man. To measure mechanical hp. KNown as a " Rope dynamometer"

If you know how, and what you are doing, it is very simple and inexpensive.

Thanks for the information.
Definitely need some cooling! I can see the rope will wear out fast.

 

[DogDipstick]

Thanks for the information.
Definitely need some cooling! I can see the rope will wear out fast.

that is why you use water and latent heat of phase change.

To make a pound of water go from 32-212 takes 180 BTU with it. Heating the ( cooling ) water.

However, takes another 970 just to go from 212 to ... vapor ( steam).. give or take a few, based on wet dry saturation and temperature of the atmos... .

vaporize a few pounds of water. Not a problem. Just getting it hot who cares.. but when you actually flash it to steam it takes 100x more heat with it so ... its not a problem. the steam rises naturally.

Rope will never reach 213* ever ever if it is wet. Never more under 100kPa standard temp and pressure. 59*. Water flashes at 212 if under atmospheric pressure.. if you rais the pressure you can get it hotter ( superheated water" ) but under natural temp and pressure, it flashes at 212. Never reaches 213,214,215.. and so on.

Rope burns at 450*+. You will have alot of room for error ( rope wont burn).


I work for ( my dad ) a steam engineering co as a technician... fabricator.. doer and go getter... I help him make shit for his contracts. .... a steam engtineering company btw. i know alot bout steam. Lol. yes water will cool a rope easy with a stream and the latent heat of phase change.