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Brushless Motor Stutter

Old 04-08-2007, 06:10 PM
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Default Brushless Motor Stutter

Sal,

I'm putting together a 75" sport/sail plane with a 3650B (540S) made by XYH, 2300KV and rated at 400W. Recommended speed control is a 45A. I have and E-Flight 40A (EFLA312B) and a 3S 2150ma 20C Li-Po. On bench-testing the motor: rocks back and forth and doesn't start smoothly. Is this an ESC timing incompatibility with motor? Is this a 2 pole motor? (The motor stops at 180 degree intervals.) Once turning, it sounds good and pulls hard. But the speed controller gets hot. Do you think a hi-model 60A professional series would work? If not, can you recommend a speed controller? What kind of timing and/or switching rate is optimum for my motor? About what should I be drawing on a bench test, prop installed? Which wires do I contact for the draw test?

Thanks for your help,
Jerry
Old 04-10-2007, 12:04 PM
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Default RE: Brushless Motor Stutter

I am not familiar with your motor, but I am sure you can get the specifications from the vendor you bought it from.

I can answer the question about the "stutter". Unfortunately that can be one of tweo things. Either the motor or the ESC!!. I would look at the motor first as this is more likely. Sometimes when the windings or shaft are a little out of true the motor will not start and that will cause the ESC to heat up. Do not allow this "stuttering" to go on for more than a few seconds as it can damge the ESC. The ESC that you have should work on most major motors including both inrunners and outrunners. I think it is a good idea to consult with your vendor to see if the motor has any special requirements. In the meantime, try your esc with another motor. If that works, I would guess the motor is the problem.
Old 04-14-2007, 09:23 PM
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Default RE: Brushless Motor Stutter

Hi Sal,

Thanks for your response. Called vendor, no tech assistance, but will refund. Can you recommend a motor/speed controller for my OMEI 2k in the 400W range? It should be about 46oz. and 29DM squared area. I've (heavily?) reinforced it and plan dives/mild acrobatics. I have to use my new battery and would like to use my speed controller if I can for now, but eventually shouldn't I get a 10-20% higher one than needed? My original plan was a little higher rpm/smaller prop setup than the out-runner motors I've seen, but I realize I don't have the budget to experiment. One motor that seemed to be a good match for less money was the Atlas 2921/08. It's 1180 kv, 3-LiPo max, 45A speed controller recommended. Couldn't find any more info on it. I try to find out as much as I can but there is a lot out there. I realize without all the info about this motor you can't give me exact numbers on draw and prop, etc. but a suggestion on motor will get me started.

Thanks, Jerry
Old 04-19-2007, 01:21 PM
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Default RE: Brushless Motor Stutter

Sure!

The best buy for really good performance on a budget would be the Multiplex B480L-4g. This is a 480 sized brushless motor modeled after the Plettenberg design and has a planetary geardrive.

On you battery assuming it really is 20C. you would get:

Prop 13 x 7
amps 37.5
thrust 65 oz.
prop speed 45 mph.
This should climb really well and give you a fair amount of climbs.

I don't have the specs on the Omei so I would have to go with something similar, but my best guess is that you could assume over 10 climbs to 500 feet using 75% of battery capacity.
Assumptions:
Omei has reasonable performance
Battery is true to spec
you climb efficiently as how steady you climb will effect to performance drastically. The more powerful the system the easier it is to maintain a good climb.
Using an Omega 2ME as an example and suing this system, I should get 2675 ft/min climb at 43 oz and at a climb angle of 70 degrees. My 90 degree climb would be 2600 ft/min max.

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