MOTOR MAX VOLTAGE ?

[VOODOO]

I have the motor I salvaged from an FMS PT17 and wonder what is the max voltage that can be safely used with this motor. I've noticed esc's are usually labeled with the range of cells they can carry, but the motor numbers seem to relate to size but not max voltage.

[WintrSol]

Some are rated for max Voltage, but not all. Do you know what the KV rating is? In general, Voltage doesn't matter a whole lot, except if it is high enough to raise the rpm to the point that the bearings will burn out; many motor specs give a maximum, but can safely be run at a higher Voltage, as long as current and power aren't exceeded. For example, motors with a KV rating of 800 or less can be run on 6S, even if the specs say 4S.

[OV10]

Hello VOODOO,
I happen to have tech spec sheets on 8 of the most common FMS motors because I do a lot of balsa ARF conversions to electric and am familiar with the FMS products and like them for their reliability and dollar value. For the FMS PT-17 the motor being used is a 3536-850kV. Below are the listed electrical specs.
3S rated with Max voltage of 16V
Max current is 34A
Power is 350W
It was also used on the 1100mm HS123 and Waco as well as the 1400 Skytrainer 182 as reference for ideas on what type of props it can handle.
A month ago I recommended it to Grossman56(one of our Squawk moderators) as a power upgrade for his Freewing Pandora. He is real happy with this increase in performance he realized by going from an 800kV motor to this 850kV using the stock prop.
I also want to point out one thing to be cautious about regarding WintrSol's advice about using higher 'S' rated power over the motor spec and that is as he said " as long as current and power aren't exceeded". Too many folks that don't have the electrical theory knowledge for system changes go off and do some rather ludicrous mods to their power systems without as much as even putting a power meter on it and then wonder why their power system let out the magic smoke. If you are going to be involved in the electric arena of RC flying to any degree, do yourself a huge favor and invest in this valuable tool. It is great for troubleshooting or mods and can save a lot of frustration and unneeded expense.
Here's a link: http://www.motionrc.com/gt-power-130...ower-analyzer/
Hope the info I've provide has been helpful.
Best regards,

[VOODOO]

Thanks for the info

[WintrSol]

Well, I did say, "as long as current and power aren't exceeded". The only way to make sure of that is with a good Watt meter. At 850KV, that motor, run on 6S, would try to turn 21,420 rpm; call it about 17,000 rpm in use. You have to choose a pretty small diameter prop for that, but if you plan to use it in a small racer, it will be pretty fast; a prop with a pitch of 6" will pull it at ~90mph, but it would take a few laps to get there. Not so good for a trainer or general sport aircraft, where you want a larger diameter prop with plenty of pull, and not so much speed, in which case a 3S or 4S battery would be preferred.

As Charlie warns, if you're going to experiment with electrics, you really need to do some homework. Don't forget to check the maximum rpm of your props, too; having one come apart in flight is too exciting for me.