Need help finding SLOW motor setup
 

Hi,

I want to start by saying that I know very little about RC in general. I apologize if this is in the wrong section.

I am gutting an RC helicopter for a project. I need to lower the rotor speed significantly, among other things. The stock motor is a 440 size; can diameter of 28mm and height of 35 mm. I'd like any replacement motor to be close to that.

I need to lower the overall rotation speed to 100 RPM's or less. The gearing is around 10:1, so a motor output of 1000 RPM's or less is what I'm looking for. I've heard that a sensored motor/ESC combo can operate that low.

What motor combo should I be looking for? Thank you in advance!

Is it a brushed motor? If so just lower the voltage of the battery.

Even with Brushless, Volts still = RPM. Lower the battery cell count or lower the kV if it's a brushless.

You can also gear down to lower the RPM further.

Edit: Typo on kv, thanks to Dave for pointing that out. Whoops!

Think the answer might be an outrunner motor like used on some airplanes. If I remember correctly they run much slower than the inrunner style used on most surface RCs, and still provide good power.

Brushless motor speed is typically specified by a kv value:

RPM = kv times voltage

One place that might be helpful is the Power Systems forum on RCGroups. Lots of custom power setups are discussed there.

The Captain: I should have been clearer. I need to go brushless for this one.

Others:
I've seen a handful of kv ratings below a thousand, but not too many. I suppose I haven't looked hard enough. Anyway, is there a minimum input voltage on any of the associated electronics? I know that a lot of solid state switches won't operate below 5V for example.

RC Tech does have a Flight forum
http://www.rctech.net/forum/rc-flight-109/
Or a good helichopper site like this might be a good source of info
http://www.helifreak.com/index.php?

if you are after that and your running a esc then there is no problem running any size lipo and use the epa (endpoint adjustment) on the radio to regulate the amount of rpm at the prop of whatever output your running and go from there...

Is there something I am missing and your not running a radio and if thats the case how are you wanting to run a signal to the esc??

More info may be needed :)

cheers
Fordy

I did a little looking around and the lowest kv I ran across was a 750. I suspect the power would be fairly low at the low throttle setting required with a typical RC ESC. Depending on how much power you need it might require additional gear reduction.

Most ESCs like at least 6 volts or so to work, but there are ESCs intended for single lipo cell 1/12 scale racing that work on around 4 volts.

Controlling it without a radio is easy, use a servo tester. Also known as a servo driver or servo controller.

I just wasnt aware he would have been using a servo controller, tester as it wasnt mentioned.
Just have to make sure you have to calibrate the esc to the servo tester yes??

Well actually, me neither. I was just responding to your comment mostly. And yes, if using a tester it would make sense to calibrate the ESC to it, same as a radio.

+1 :sneaky:

I actually have no idea what I'm going to use to control it with. Looks like I have more research to do.