Trouble with prop saver (motor cuts out)

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The speed controller seems to cut power to the motor at high RPMs. This seems to occur when my prop is slightly out of balance. I can get a little more than half throttle, and if I increase it, the motor cuts out completely. I am guessing that putting the prop saver on the shaft makes it even more difficult to get the prop to balance.

What are the solutions to this sort of problem?

Reply to
Peter Olcott
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My guess is that your motor controller is not big enough for the amperage the motor is drawing. Try measuring the amperage of the draw, right before your motor stops.

Be sure to use a meter that will not burn out measuring that kind of amperage, or make a shunt to use on your smaller meter.

Reply to
Morgans

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That is my guess too. It does allow full throttle sometimes, and the speed controller and prop are a combo put together by the manufacturer, so the motor should not be drawing more than the speed controller is able to handle. If the motor is drawing more than the speed controller is able to handle, then this is also too much for the motor. Does a slightly out-of-balance prop tend to draw more power?

Reply to
Peter Olcott

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A slightly out-of-balance anything on the end of a motor will draw more power, if it's attached to something that absorbs vibrational energy (which your airframe will). You can test this with a toy motor and an eccentric weight. Hold it in your hand, turn on the power. If you hold it really loosely or really tight the vibrational energy can't go anywhere, and the motor spins fast. Hold it somewhere in the middle and your hand absorbs a bunch of energy, the motor goes slow.

So balance your prop, and make sure that it's centered on the prop saver before each flight.

If you assume that the manufacturer knows or cares the proper application of the speed controller, you could still be left with one that's a bit marginal; with a bit extra drag due to the off-center prop you could well pop over the controller's maximum current.

I'd measure that current, see what you can see.

Reply to
Tim Wescott

Also check the mechanical side of things: i.e. is the prop free to rotate or is it (or the saver) touching/binding somewhere since you added the prop-saver?

Reply to
Chris Dugan

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That would cost another $65.00 for one of the three brands of meters that can handle that much current. I think that I will upgrade the speed controller to one that is supposed to be able to handle 25 amps, instead of the one that is supposed to handle 18 amps. That will cost less than $20.00 including shipping from China.

Reply to
Peter Olcott

It a tiny little bit out of balance, and I guess that is inherently a tiny little bit out of balance, because the nature of a prop saver seems to be a little less exactingly precise than the conventional connection.

Reply to
Peter Olcott

"Peter Olcott" wrote

Do some searching for amp meter shunts, and you will probably find some do it yourself designs that can handle the higher currents, by using the 10 amps or less feature of most volt/ohm meters.

There was a thread on this subject within the last month or so, in this group.

Reply to
Morgans

Hobby City sold you a combo that should work, and it doesn't. Everyone's first guess (me too!) is that there is a problem with the ESC. While measuring the amperage will tell for sure, you could just try to get Hobby City to replace the ESC..... Randy

Reply to
<rmaheuxr

I tried another ESC, I always buy a spare, same problem. This problem is related to the fact that the esc/prop/motor combo is at the limits of each. I could also try a smaller prop. I just placed a different brand (Turnegy) of 25 amp esc on order.

Reply to
Peter Olcott

Yeah, I started that thread. I concluded that buying an ammeter was the way to go in the long run, yet the long run is not here yet. I don't have time to futz with the home-made solutions, and I don't want to spent the money on a good ammeter just yet. I will probably go with the one on that thread, I still don't know whether I will buy the pro model or the regular one.

Reply to
Peter Olcott

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Sooner or later you want to buy a meter that will measure the current, or build a shunt. You really should measure the current of every new installation as a matter of course. You've mentioned in other posts that you want to design airplanes -- step up to the plate.

I'd build a shunt (in fact, I should take my own advice and build one soon -- I'll soon have a plane that pulls more than 10A, which is the maximum that my meter can handle).

All you have to do is come up with a bit of wire the right length be some convenient resistance, and put connectors on it to measure the voltage across it with a meter that you have. For instance, if you can measure a millivolt accurately, you can make a 1mV/amp shunt. So you find a bit of wire of a convenient gauge to handle your current, and you hook it up like so:

.-------------o to meter | .----o | | o---------------o===o========o===o-----------------. wire | to ESC, motor battery | o--------------------------------------------------'

Adjust the positions of the taps on the wire until you get 1mV/amp, then solder them down. You can do this adjustment by borrowing a second meter and a motor that'll pull less current, or using an ESC at part throttle (most meters these days can measure 10A). Set up to pull near the maximum current that your second meter can handle, and adjust the wire positions until you're reading 1mV/amp. Then solder everything down, check to make sure you didn't mess up the measurement too much, and contemplate putting that butt-ugly shunt into a case of some sort.

Reply to
Tim Wescott

Try a smaller prop and see if still does it.

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Reply to
Jim

Ah, Hobby city. That tells it all.

Reply to
Jim

Could it be it's getting a low voltage from the battery end? mk

Reply to
MJKolodziej

Yes I thought of that too. I am going from 10x4.7 to 9x4.7

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Reply to
Peter Olcott

I will try that again too.

"MJKolodziej" wrote in message news:RPWdndDxR-tVLyDVnZ2dnUVZ snipped-for-privacy@posted.hometowncomputing...

Reply to
Peter Olcott

"MJKolodziej" <

Low voltage should mean lower amps draw.

Reply to
Morgans

It looked like it was just a low battery. I did not count on how much power drops from a fully charged NiMH when it just sits for a couple of days. As soon as I charged it up it worked fine, even with the prop saver.

Reply to
Peter Olcott

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