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GoBrushless.com Motor Question

Old 02-06-2008, 01:57 PM
  #26  
DBacon
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shotgunsmitty,
My experience is limited to my first two planes, a Miss Hangar One, and a stripped down second generation of it.
It was 13 oz originally and I wound my own motor from GoBrushless.com, it is a GBxT Custom Outrunner Kit. I settled on 12 turns. The prop is a GWS EP7035 and the battery is a Kokam 910mAh, 3-cell.
I get plenty of performance, especially now that ver 2 is down to 10.5 oz. It is a little much for me, so my Son flies it while I try to but usually crash...
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Old 02-06-2008, 02:03 PM
  #27  
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Okay. I'll definitely keep that in mind. I certainly have more time to build and test than I do to fly right now.

I plan on doing lots of tests with the few motors I have to find which prop tweaks the best performance.
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Old 02-06-2008, 03:38 PM
  #28  
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Smile Go cheap, get cheap

Originally Posted by adoman View Post
I checked out the motors at www.unitedhobbies.com and from the ebay link Doc Pete gave me, and I just don't understand how they can sell those motors for so cheap. It just seems too good to be true. And from my experience things that seem too good to be true, are too good to be true. Anyone agree?
I agree with you. I have a couple in my junk bin, nothing but trouble. One of the pilots drove to the indoor site with his friends to fly yesterday. He paid his fee and got in one short flight with a landing nose over. Bent the prop shaft on his cheap chinese motor and had to watch from then on. The rest of us got in another five hours flying time.

If you just like to tinker then they might be OK. If you like to fly then you need to bring several cheap chinese motors and a airplane that you can change them quick on.
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Old 02-06-2008, 03:56 PM
  #29  
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Never thought about the prop shaft...hmmm
It is true that my Go Brushless has survived a lot of crashes with no bent prop shaft. My Chinese motors are in a boat right now, so may be OK. Good point.
BTW the Go Brushless was not expensive, you just have to build it yourself, but it is easy.
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Old 02-06-2008, 05:27 PM
  #30  
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So where do you find additional windings wire? What gauge do you use?

I've got a bit to learn here, I can tell...
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Old 02-06-2008, 05:42 PM
  #31  
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When you get the kits at GoBrushless, it includes lots of wire, even in three different colors, which is thoughtful, but not necessary, you can only wind one (of three) phase at a time...
Or Magnet wire, I got mine from Radio Shack years ago.
A great experimenter's electronic outlet is Mouser. They have all the industrial parts, but no minimum order. For some things that shipping is more than the order, you may wish to quantity buy and share with your club buddies.
For wire size, cram the biggest you can in. Experimenting sometimes wastes some wire, but the lower the resistance for the same number of turns, the higher the effeciency and lower the heating. Although that is not the main source of the heat...
I think I used 18 ga, but I am not sure now... If you really need the answer, I will go "mike" it, but the motors are different, and how you wind it is different, so you have to experiment.
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Old 02-06-2008, 06:02 PM
  #32  
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Originally Posted by DBacon View Post
... For wire size, cram the biggest you can in ...
... but first you have to figure out the number of winds of course. The thicker the wire, the higher the motor efficiency. Higher efficiency does not only mean that the motor makes better use of the batteries' power, it also means the motor is able to handle a higher power input before hitting its maximum temperature mark i.e. a the power/weight ratio will be higher.
An example:
Say the motor has an efficiency of 70% and it can handle 50Watt input. That means it can get rid off 30%*50=15Watt excess heat. Now, by cramming in thicker wire (and/or using better stator-iron, segmented magnets), efficiency increases to say 75% (I'm a bit optimistic here). The motor's ability to loose those 15Watts has not changed (by radiation, convection and conduction). This means the motor now can handle 60Watt before it hits the 15Watt (25%*60Watt) losses mark. An efficiency increase of 5% gives an increase in the power to weight ratio of 20% (from 50Watt to 60Watt). That's why efficiency plays such an important role, in any motor design: efficiency governs maximum power. The motors weight may have increased a bit due to more copper.

Go to your local friendly motor/transformer rewinder/refurbisher or repair shop. Excellent quality, all gauges, penny stuff, you'll probably get it for free if you bring your motor along. They love it when they can handle a motor without a crane And maybe let them have a spin with your plane once you finished your motor? You know, in case you need wire again for your next motor

And last, but not least, do have a look at the links I gave in post #17, i.e. if you haven't already done so. Lots of tips and tricks.
Vriendelijke groeten Ron van Sommeren
int. electric fly-in, Nijmegen, the Netherlands
brushless motor building tips & tricks
diy brushless motor discussion group
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Old 02-06-2008, 06:08 PM
  #33  
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Originally Posted by DBacon View Post
... but the lower the resistance for the same number of turns, the higher the effeciency and lower the heating. Although that is not the main source of the heat...
Copperlosses (wire resistance) are together with iron-losses (hysteris and eddy current losses in magnets, flux ring and stator) the main source of losses/heat.

Vriendelijke groeten Ron
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Old 02-06-2008, 06:15 PM
  #34  
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Thank you, ron van sommeren.

You really put the value of fat wire in perspective. Since the motor can get rid of only so much heat, make sure the portion of power that is converted to heat is small.

And the portion that is converted to heat depends (mostly) on resistance, and (partially) on eddy current losses, which is really a resistance loss.

So that efficiency number is important, I see. I used the fattest wire I could get, and I am running about 11 amps on a 3-cell, and the motor never gets warm. (Of course, most flight is less than full throttle.)

I just checked out your links, thanks, these are great. I am now 1 year behind in my reading...
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Old 02-06-2008, 06:21 PM
  #35  
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Contrary to copper losses, in the case of eddy currents, the higher the (specific) resistance of the material, the better. See this 'lamination thickness versus edddy currents' thread:
http://www.rcgroups.com/forums/showthread.php?t=813618

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Old 02-06-2008, 06:36 PM
  #36  
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Yes, that makes sense. I know with welding transformers, the "Hypersil" units are equipped with high silicon steel, and the core is wound with this steel in sections so thin you can hardly see them when you cut one in half. These transformers are optimized for 1200 Hz, rather than the 60 Hz line frequency we use, so hysterisis losses are important. They handle 30KVA to 90KVA and produce 10-20kAmps on the secondary.
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Old 02-06-2008, 08:08 PM
  #37  
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So bigger is better?
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Old 02-06-2008, 08:31 PM
  #38  
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Anybody that tells you different probably did not go big...
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Old 02-06-2008, 08:36 PM
  #39  
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[response tactfully self-edited]
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Old 02-06-2008, 08:44 PM
  #40  
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Chicken ha ha
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Old 02-07-2008, 03:00 PM
  #41  
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Originally Posted by DBacon View Post
...I just checked out your links, thanks, these are great. I am now 1 year behind in my reading...
Always glad to be of service

Vriendelijke groeten Ron
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Old 02-07-2008, 03:05 PM
  #42  
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Originally Posted by DBacon View Post
... And the portion that is converted to heat depends (mostly) on resistance, and (partially) on eddy current losses, which is really a resistance loss ....
In a good design, they are roughly the same.

Vriendelijke groeten Ron
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Old 04-29-2008, 10:18 PM
  #43  
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Default United Hobbies motors

Originally Posted by adoman View Post
I took a look at www.unitedhobbies.com and at the ebay link Doc Pete posted. I just don't get how they can offer motors of comparable performance to ones that cost $50-$60 at 1/4 of the price. It seems too good to be true and from my experience, things that seem too good to be true are too good to be true. What kind of performance/value have you seen out of the motors at unitedhobbies.com?

--Alex
These motors are sold out of Hong Kong with 3-5 weeks delivery times, firstly. Secondly, "you gets what you pay for". My experience with them has been OK, but nothing special. Screws are missing, wrong size screws are included, etc. You takes your chances!
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Old 04-29-2008, 11:21 PM
  #44  
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I have purchased many motors from www.UnitedHobbies.com . About 90% have performed as well as motors costing much more. In the 10% of others I have had a few bad motors (noisy bearings, bent shaft etc.), and some have not matched the website description, and a few just have less than the expected performance. If you search the net you will find many posts from those who have enjoyed the bargians. You will also find some have had problems with slow customer support, slow delivery if the order contained an out of stock item, and a few other problems.

If you want the best and a minimum of problems go elsewhere. If you like bargians and a little adventure give them a try.

Don

PS- normal delivery is more like 7-14 days. I have never had an order take anything like 5 weeks.
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Old 05-14-2008, 02:29 AM
  #45  
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Default Gobrushless motor magnets

This thread is near a year old, but I've built up several of these motors, using magnet wire from work.

Best way I found to install magnets, is to first place the magnets with thin CA. Then, hold the magnet structure horizontal, and fill in the space between the two bottom magnets with baking soda (From the grocery store!). Make absolutely certain the baking soda does not exceed the hight of the magnets!! Its near impossible to remove after its CA'd!

Then, place a drop of thin CA on the baking soda. Instant Concrete! Then fill in all magnets around the circumference, and you are done.

By the way, this baking soda/CA is a very old trick, and it is a permanent mounting of the magnets.
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Old 05-07-2013, 05:54 PM
  #46  
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Your baking soda is an excellent tip. I find I can use CA without the "kicker" if I use baking soda, or just a spritz of water mist for a joint that doesn't need the filler and strength. With the kicker, I can't breath for about a week, very scary.

So people should do like you say, use baking soda, and stay healthier!
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Old 05-07-2013, 06:37 PM
  #47  
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Originally Posted by DBacon View Post
Your baking soda is an excellent tip. I find I can use CA without the "kicker" if I use baking soda, or just a spritz of water mist for a joint that doesn't need the filler and strength. With the kicker, I can't breath for about a week, very scary.

So people should do like you say, use baking soda, and stay healthier!
Yeah, I bought a bottle of kicker some time back, used it once. And never again. Those fumes can't be good for anyone.

Probably 90% of my gluing is done with Titebond or yellow carpenter glue, and for where even more strength is needed, epoxy. CA is reserved for a quick glue job where IMHO strength of the glue joint is not to important.

I've had plywood landing gear plates come off that were CA'd.

Last Sunday, a club member had his gasser engine quit, resulting in landing the model in a plowed field. That was an expensive model with a twin cylinder gasser up front. He was lucky, only damage was to the landing gear structure , plus busting the $50 propeller. Even worse, two minutes before, he had that giant scale in a hover, with the tail less than 3 feet from the ground. An engine failure while pulling out of a hover is going to be danged expensive in a giant scale model.

Didn't take long to find out what happened. The plywood servo tray for the engine servo was CA'd in place. And the throttle servo plywood tray fell out, taking the servo with it. You'd better believe he is going to epoxy that plate back in place, and really go over the rest of the model's glue joints with a fine tooth comb.
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Old 05-08-2013, 12:39 AM
  #48  
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Yes CA is tricky, often brittle, but there are many places where it is great, like all the ribs in a wing. With CA and kicker, you can build a 1/5th scale plane in just a few hours.

I think that is how I got allergic to it, building planes so fast. I migrated to a plastic cover and furnace fan to draw air from my covered work bench, but it would still get to me, had to give up CA altogether. But now I find this CA in the local WalMart from LocTite, which is foam friendly, and if I don't use kicker, I'm OK.
LocTite has a similar glue called "Go Glue" looks like CA, but it says it is more flexible. I have yet to break open that bottle, but I am optimistic that it will be even better.
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Old 05-08-2013, 03:27 AM
  #49  
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Originally Posted by DBacon View Post
I think that is how I got allergic to it, building planes so fast. .
Yeah, after working with a soldering iron for near 50 years, I got allergic to the flux from soldering fumes. Picked up a very high powered squirrel cage type exhaust fan that they threw out at work, hooked it up to some 4 inch diameter dryer vent hose, and blow it outside.

Works very nicely, and those fumes are moved completely out of the house.
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Old 06-06-2014, 06:36 PM
  #50  
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Custom winding motor provides a superior motor to any of it's particular contemporary's. A top quality set of parts can only be utilized to the fullest extent with a proper hand wind. Can't buy that off a shelf. But who really needs efficiency?, batteries don't cost that much and even with a rig getting 30% efficiency the pilot does not know that it's a "gas hog" as there is no reference, like MPG has to cars.
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