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Old Aug 05, 2006, 11:57 AM
Happy2ndChildhood
Don McGill's Avatar
London Ontario
Joined Aug 2005
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Question
Need some questions about brushless motors answered

1) On a BP21 motor, says Bm2408-21 on the can. I was running this in Gene Bond's Blucub2 and having heat problems with motor and battery, never checked esc. Was using a Phoenix 25 esc. It also momentarily cut out the odd time when running high throttle. I see that the stator has a painted on insulator, not plastic like gobrushless. I also noticed today that one hammer head has insulation chipped off right to the bare stator. Can this cause a short and being a 25amp esc it not cut out till you put lots of throttle to it?

2) Should I be using a smaller esc with a motor like this and why, or is bigger esc fine?

3) When winding a stator, if I press accidentally on top of wire when positioning a wind with finger nail, and can see a dent in that strand under magnifying glass should I consider this a short and start over?

4) If one screws up say second tooth of a phase and is short one turn by the end of the tooth is it ok to run wire out to the end of the tooth to do one last turn then down and to the third tooth of that phase, or is it better to rip that whole phase out and start it again?
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Last edited by Lakota; Aug 05, 2006 at 12:12 PM.
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Old Aug 05, 2006, 01:00 PM
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Niagara Falls/Toronto area
Joined Dec 2003
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Quote:
Originally Posted by Lakota
1) On a BP21 motor, says Bm2408-21 on the can. I was running this in Gene Bond's Blucub2 and having heat problems with motor and battery, never checked esc. Was using a Phoenix 25 esc. It also momentarily cut out the odd time when running high throttle. I see that the stator has a painted on insulator, not plastic like gobrushless. I also noticed today that one hammer head has insulation chipped off right to the bare stator. Can this cause a short and being a 25amp esc it not cut out till you put lots of throttle to it?
Unlikely - especially if there is no wire near it. Shorts between stator laminations are not good, but not as bad as shorts between the wire and the stator.
Quote:
Originally Posted by Lakota
2) Should I be using a smaller esc with a motor like this and why, or is bigger esc fine?
The bigger one is fine. I'm wondering if you should be using a smaller prop though - this motor sucks amps. I'm not a big fan of this wind - but then again I'm not in the "go like stink" crowd This motor pulls 13-14 amps on a GWS 8040 DD prop - kinda high in my books.
Quote:
Originally Posted by Lakota
3) When winding a stator, if I press accidentally on top of wire when positioning a wind with finger nail, and can see a dent in that strand under magnifying glass should I consider this a short and start over?
It's not a short, just a dent. A short is when metal touches metal without the benefit of insulation. The easiest way to check this is with an ohmmeter - it should read infinite between the wire and the stator (check against both sides of the stator) Some guys actually put their wound stator in between 2 pcs of wood, and then into a vise to compress things down so the bell doesn't hit the winds
Quote:
Originally Posted by Lakota
4) If one screws up say second tooth of a phase and is short one turn by the end of the tooth is it ok to run wire out to the end of the tooth to do one last turn then down and to the third tooth of that phase, or is it better to rip that whole phase out and start it again?
I'm trying to read between the lines on this one, Don. I'm assuming that you can't get one more wind in by the center, so your putting it on further out? If this is the case, then your answer is yes. A wind is a wind is a wind - it doesn't matter where on the tooth you put it, as long as it's there. It doesn't even have to be nice and neat - some of the motors coming from China look like winding-wise, but they work perfectly fine.
If you're asking about missing a wind on the 2nd tooth then winding the third tooth, and then going back to the second tooth to add one, I dunno. My gut says it should be okay, but the anal part of me would tear it down and start over.

Brad
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Old Aug 05, 2006, 06:15 PM
Happy2ndChildhood
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London Ontario
Joined Aug 2005
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Thanks Brad, yes, last question was all about the same tooth, eyes got buggy and missed ninth turn on bottom layer, did not realize till I finished the last turn on top and because the turns were perfectly neat it was obvious I was missing one at the hammer head of tooth. Yes all my purchased outrunners look like a rats nest, due partly to all the teeth being wound with three wires. With this I think I will finally get a motor finished tonight. Have wound this same stator a few times now and ripped it apart, not being happy with the appearance of the wind. Seems I can now wind with finger nails and skewer and get it looking perfect. Not sure I am finding motor winding fun. Maybe that will change when I get one airbourne.
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Old Aug 05, 2006, 06:26 PM
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Niagara Falls/Toronto area
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Quote:
Originally Posted by Lakota
Have wound this same stator a few times now and ripped it apart, not being happy with the appearance of the wind.
Why? Neatness makes absolutely no difference electric/mechanic/magnetic-wise. Must be anal like me Guess I'm the opposite - I found them more fun at first.

B
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Old Aug 05, 2006, 08:39 PM
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East Anglia, UK
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Quote:
Originally Posted by arx_n_sparx
Why? Neatness makes absolutely no difference electric/mechanic/magnetic-wise. Must be anal like me Guess I'm the opposite - I found them more fun at first.

B
A pile wind is longer and has more resistance than a neat wind.
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Old Aug 05, 2006, 10:00 PM
Happy2ndChildhood
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London Ontario
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Quote:
Originally Posted by vintage1
A pile wind is longer and has more resistance than a neat wind.
Less resistance is good right? I'm a "go with the flow" kind of guy. Actually I don't understand the theory behind it, but I am assuming that means I will either lower or raise the amp draw? Hopefully neater is lower.

Oddly enough Brad, it does not bother me to see a rats nest in my bought outrunners, and I am happy with their price/performance, but if I took the time to wind it and it does not look visually appealing to me.....would feel like a waste of time no matter how well it flew.
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Old Aug 06, 2006, 06:43 AM
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That's splitting hairs, Vinnie. What do you figure it will add? Are we talking micro, nano, or pico-ohms?

Let's call it no discernable difference - other than the mess

Quote:
Originally Posted by Lakota
Less resistance is good right?
Yes, less resistance is what we're after. That's why we use different wire gauges to wind different # of turn motors - the idea is to pack in as much copper as you can fit onto the stator. A handy thing to remember is that doubling up the wires (using 2 in parallel) = 3 AWG sizes down - a pair of #26 = #23 Sometimes it's easier to use twinned or tripled wire instead of one thick one - these are the times whre the stator ends up looking like a rats nest.

Brad

Brad
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Old Aug 08, 2006, 04:59 PM
Make 'n Break!!
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Walled 'tucky, MI. USA
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Don't know if this helps but I just got the same motor and the bell was rubbing on the gold mount. I cut the gold mount off just in front of the set screws and epoxied it back on. Amps and heat dropped dramatically.
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Old Aug 08, 2006, 08:45 PM
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I just got to ask whats with the prop
nice fix btw
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Old Aug 08, 2006, 09:09 PM
Make 'n Break!!
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Walled 'tucky, MI. USA
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Quote:
Originally Posted by olmod
I just got to ask whats with the prop
nice fix btw
That's my variable pitch prop. hahaha! Actually that's what happens when you don't use a prop saver, I guess.

I tried an 8x4.3 slofly prop on my wing with some big honkin 8 cells. It didn't work. Dropped like the brick it was.

I chopped an 8x4HD down to 6x4 though on 3s and it kicked but. Low amps too.
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