Thinking about dyno's for brushed motors

[juicedcoupe]

I borrowed juicedcoupe's pinion/spur combo idea. Drilled the center of the spur so the pinion fit tightly into it. Then tightened it onto an 1/8" drill bit and spun the drill full speed to make sure the spur was sitting true on the pinion. Then filled the small voids of the pinion teeth with epoxy.

I came back and glued mine as well. I used medium thickness CA from the back, and let it seep down the teeth.

[coxbros1]

Vid link to the functionality test:

Nice job on that setup....it reads your rpm perfectly and doesnt jump around at all.

[Coelacanth]

Thanks Derek, the hardest part was getting the servo gear & horn modded to bolt onto the motor shaft. I was surprised at how everything worked afterward, and no need to setup a transmitter or receiver.

That said, I've done more research into these cheap tachometers and when some engineers compared the results with more accurate tachs, the cheap ones might over-estimate RPM by a small margin, but it seemed consistently high by about the same amount...maybe 5% or so higher than actual, from what I saw in videos...just off the top of my head. But, all else being equal, after we've limited all the other variables in the test methods, we can use this procedure to compare amongst our own motor sets.

[Coelacanth]

It just occurred to me that a side bonus of this setup is you can set the voltage real low and use it to break in new motor brushes until they're seated properly.

[juicedcoupe]

It just occurred to me that a side bonus of this setup is you can set the voltage real low and use it to break in new motor brushes until they're seated properly.

I will also be able to use the speed control to run my comm lathe from my 12V power supply.

[R6cowboy]

Was able to fab the aluminum mount right quick over lunch break today (since I took an actual lunch break). Motors hold themselves up to the steel mount with no assistance. Have a feeling this will affect performance somewhat.

[coxbros1]

lol...its got too!

[R6cowboy]

Will find out soon enough, or whenever that brushed motor speed control shows up. Which I purchased a week ago last Thursday and tracking number says the item is still awaiting USPS. Estimated delivery was today, gonna assume maybe next Thursday. Ahh well, still need to get a 12V power supply but will use a 3s Lipo until then.

[Dadio]

Got my tachometer today , just designed a motor , esc and servo tester mounting thingy and its printing now

[juicedcoupe]

Ahh well, still need to get a 12V power supply but will use a 3s Lipo until then.

Mine is built from a computer power supply. There are directions all over the web on how to do it.

[R6cowboy]

Mine is built from a computer power supply. There are directions all over the web on how to do it.

Nice. I'd have to source a computer power supply somewhere. Will see if I can come up with one and look into it. I'm guessing there's probably not much cost, if any, if you already have a computer power supply...?

Was looking at getting this one; 6 amp, $45
https://www.amazon.com/Universal-Compact-Bench-Power-Supply/dp/B000A896GG/ref=psdc_10967761_t2_B0002JTD2K

or this one; 2.5 amp, $35
https://www.amazon.com/Universal-Compact-Bench-Power-Supply/dp/B0002JTD2K/ref=psdc_10967761_t4_B000A896GG

[juicedcoupe]

Nice. I'd have to source a computer power supply somewhere. Will see if I can come up with one and look into it. I'm guessing there's probably not much cost, if any, if you already have a computer power supply...?

I've probably got ~$20 in mine. But I chose to add a digital gauge and banana posts to it.

[juicedcoupe]

Got my tachometer today , just designed a motor , esc and servo tester mounting thingy and its printing now

Mine showed up today as well. The silver paint did work in place of the tape.

[Dadio]

Just tested a Trinity Monster Horse power motor at full chat zero timing with a 7.2 NiMH .... Got 32800 rpm

[Coelacanth]

Nice! It's fun to do these tests and share our results! And some of you guys really take your test setups to the next level.