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Yes that's how it works , you need an ESC with BEC but that's been standard for a long time , you just turn the knob to the voltage you want and watch the amperage , adjusting the motor timing while its running shows the amperage drawn so you get an idea of the sweet spot between high revs and reasonable amp draw , 1.5 to 2.5 amp being the target .

coxbros1 wrote: ↑Thu Feb 18, 2021 2:00 pm If u have a 12v power supply or 3s battery this item will work perfect to adjust precise voltage to the motor and voltmeter

https://www.ebay.com/itm/12V-24V-48V-2000W-10-50V-40A-DC-Brush-Motor-Speed-Control-PWM-HHO-RC-Controller-/111851538617?_trksid=p2349624.m46890.l49292

Perfect, got 'er ordered up. Much cheaper than buying a spare esc and servo tester.

I'm still collecting stuff but this is what I come up with to attach the reflective tape to. I took a smaller spur gear that I had laying around and opened it up just enough for a pinion to fit snugly.

I haven't glued it together yet, but I spun it up on a 15T modified. It spun true, without any vibration or wobble. I figured that this would give me enough diameter to get a reliable reading without adding much mass.

juicedcoupe wrote: ↑Thu Feb 18, 2021 5:50 pm I'm still collecting stuff but this is what I come up with to attach the reflective tape to. I took a smaller spur gear that I had laying around and opened it up just enough for a pinion to fit snugly.

I haven't glued it together yet, but I spun it up on a 15T modified. It spun true, without any vibration or wobble. I figured that this would give me enough diameter to get a reliable reading without adding much mass.

I was thinking maybe rigging up a small 3 blade propeller. Thoughts...?

Done the full dyno prop deal a few yrs ago testing 21.5 brushless for 12th pan operations...abandoned the setup shortly after making it.
It just didn't yield the results like we wanted. i would just stay with amp/rpm @ 7.2v no load....u will have more fun. plus the prop was dangerous

I made this bracket with some scrap metal. 1" aluminum flat bar bolted to a piece of 1.25" steel bar.

I tried it out but it really needs something more substantial. It will stay upright while running but vibrates around. It will also torque over on a full power start.

I think a small selection 1X lumber and some non-slip feet would do the trick. It would also give me somewhere to secure the tach with a rubber band.

coxbros1 wrote: ↑Thu Feb 18, 2021 8:36 pm Done the full dyno prop deal a few yrs ago testing 21.5 brushless for 12th pan operations...abandoned the setup shortly after making it.
It just didn't yield the results like we wanted. i would just stay with amp/rpm @ 7.2v no load....u will have more fun. plus the prop was dangerous

My worry was those props aren't made to turn 30k rpm.

For mine, I was thinking the same thing juicedcoupe has going, drill a few holes in a piece of L-iron or aluminum for mounting the motor, and bolt that to a small piece of wood. Keep it simple...yet elegant. The whole assembly would still be small and portable/storeable. No need even for rubber feet. Maybe I'll put something together this weekend using a hybrid idea of Dadio's and juicedcoupe's prototypes.

I was thinking of 3d printing a rubbery disk with a hub that just pushes onto the motor shaft to use as an rpm sensor wheel and a mount like the one Juicedcoup did .

I'm thinking with the high RPM's and torque of some motors, you'd really want to secure the wheel, disk or whatever to the motor shaft, ideally with a grub screw. So probably modding a spare pinion gear would work best. A plastic wheel right on the motor shaft might get the center hole rounded out unless it's really secured well onto the shaft.

Coelacanth wrote: ↑Fri Feb 19, 2021 12:25 pm I'm thinking with the high RPM's and torque of some motors, you'd really want to secure the wheel, disk or whatever to the motor shaft, ideally with a grub screw. So probably modding a spare pinion gear would work best. A plastic wheel right on the motor shaft might get the center hole rounded out unless it's really secured well onto the shaft.

Won't take long to find out , just ordered one of the same rpm meter things as everybody else £8.99 delivered

I ordered one of the tach's and speed controls last night. I already have a 12V power supply, DVM, and DC clamp meter.

Dadio wrote: ↑Fri Feb 19, 2021 2:09 pm Won't take long to find out

I like the idea of a lightweight printed disc. You would have more control of the surface that the reflective tape was mounted to.

As suggested above, I would still design it around a pinion gear. I like the idea of a metal hub and secure attachment. Even 540 sized plastic pinions have metal hubs.

Either way, it should be interesting.

I thought this was interesting.

The Revenge of the Monster Pro obviously has the dyno sticker from Trinity, rated at 5V. The Green Machine 3 Pro looks to have dyno results from an outside source.

Given that they are both 27T, 24° Trinity Pro motors from the same generation, I'd expect somewhat similar numbers. The only other alternative is that the Green Machine was tested at higher voltage.

Also, the RoM's literature clearly states that it is a higher rpm motor than the GM3.

I haven't done any research as to whether Trinity tested all motors at 5V or if those may have been intended for 4 cell racing.


You can click on the pics for clarity.

Interesting. That kinda makes me wonder how Kyosho rated the RPMs of their Le Mans motors, as their older motors were all intended for 7.2-volt NiCad batteries, but what about the later cars that were intended to run 8.4V NiCads and 240S-variant motors on those 7-cell packs--like the Turbo Optima and Salute, for example? I wonder if their "official" RPM ratings took this into account, or if they were all measured equally with 7.2 volts of battery power?