Testing 17.5 motors
 

I am from the old school. Went to the track with my turbo dyno, com lathe, box of brushes and springs. Would spend hours filing brushes to try and find a few hundred RPM on the dyno.

How do we do that with 17.5 motors? I know the dyno is like almost impossible. I hear people say they measure resistance --- but how? With what device?

I have seen those motor checkers - but what do they really measure?

Thanks for any help guys.

They measure kv/rpm and amp draw. Some may do resistance as well (but that can be done with just a regular multimeter).

The other item is a gauss meter to test the rotor.

A few other tips, check and play with shimming the rotor (forward and backward) and test where the sweet spot is for timing. Past a certain point on all motors you hit diminishing returns.

What are you racing? On road, off road, oval?

Dynos are still being used for setting up motors. Different rotors, makes, timing, stators, esc's, etc.


( I remember, but don't miss those things, lol)

If you still have that old turbodyno, check this out:

http://www.hobbytalk.com/bbs1/showth...ght=Turbo+Dyno

Calvin - thanks - long since got rid of the turbo dyno, got lucky when brushed was going out, found some folks down south who didn't want to change and were buying up brushed stuff. That was a long time ago.

Curious how the measurements were being done with a multimeter? Read you needed a special unit that would read really low resistance.

Anyone else find it weird that even if you try to search all the information about how to test and find information on the motors is from 2007-2009, nothing recent. Guess that is why I am asked.


TOM- Touring car and off road buggy

This thread may be of interest: http://www.rctech.net/forum/electric...highlight=dyno

Some measurement tools and info for the windings and rotor:

Racer's Measurement Systems

Fantom Brushless Motor Tools

Besides the rotor shimming mkiiina mentioned, the sensor board can be shimmed to get the quickest triggering of the phases. Maximizes timing advance for blinky class. Can't remember the recommended gaps I've seen mentioned.

Some guys measure the free run amps in the car to adjust endbell timing to track and help get somewhat consistent settings from motor to motor. Can't remember what threads have info.

A special meter is needed to measure resistance. They can be expensive. Here's a cheaper way to do it with a "normal" DVM and a handful of parts:

http://www.rctech.net/forum/radio-el...esistance.html

The gauss meter is a great tool. If a rotor is too strong, it will bog down the motor, as if its stuck in the mud. Too little and it will have no torque to get the car/truck up to speed. Its great tool for measuring for different stators. As others have mentioned, shimming is vital as well.

Curious if anyone has tried to build a DIY gauss meter for this purpose

Yes, many years ago, using an analog-output Hall effect sensor. I'm sure it's still buried somewhere here. It wasn't difficult, but the Hall sensor had a lot of offset drift with temperature. The technology has probably progressed quite a bit in the intervening years.

It could also be done with a field mill, but that sounds like a Rube Goldberg design.

Search the web. Search homemade gauss meter. I mad one for about $5. Will measure to about 1600 gauss.