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adoman
06-04-2007, 07:34 AM
Hey guys,
I just ordered a do it yourself kit from gobrushless.com. I ordered the GBX outrunner double http://www.gobrushless.com/store/cgi-bin/cp-app.cgi?usr=51H3169615&rnd=2020702&rrc=N&affl=&cip=63.227.58.141&act=&aff=&pg=prod&ref=GBxM2&cat=diy+brushless+kits&catstr=HOME:diy+brushless+kits

So far it's been difficult as this is my first brushless build. The biggest problem i'm having is gluing the magnets to the can. They just don't seem to want to stay. Second, no matter what I do i still get rubbing between the magnets and the stator. Any suggestions? Has anyone else here gotten a motor from these guys? Thanks!

--Alex

DBacon
06-04-2007, 05:39 PM
adoman,

I built the single stator unit, and it is great.
I bought the plastic spacer tool that holds the magnets in place, then put a dab of thin CA on each magnet to hold it.
There was no interference when I was done, and it went together smoothly.

Hank47
06-04-2007, 05:40 PM
Hi Adoman,
My advice to you would be go to WWW.unitedhobbies.com (http://www.unitedhobbies.com) and purchase a good motor for less then one half what you paid for the kit. No headaches, no messing around.

Hank47

SGecko
06-04-2007, 05:47 PM
Hi Adoman,
My advice to you would be go to WWW.unitedhobbies.com (http://www.unitedhobbies.com) and purchase a good motor for less then one half what you paid for the kit. No headaches, no messing around.

Hank47

I'm not sure this is the best answer for someone who already spent the money on the kit but it might be good advice for next time.

Happy|Harry
06-04-2007, 08:03 PM
Hi Adoman,
My advice to you would be go to WWW.unitedhobbies.com (http://www.unitedhobbies.com) and purchase a good motor for less then one half what you paid for the kit. No headaches, no messing around.

Hank47

trust me when i say that when you get a GBx2 built properly you'll have a much better and more efficient motor than you could buy for less or equal money ;)

phil

bz1mcr
06-04-2007, 08:33 PM
Hey guys,
I just ordered a do it yourself kit from gobrushless.com. I ordered the GBX outrunner double http://www.gobrushless.com/store/cgi-bin/cp-app.cgi?usr=51H3169615&rnd=2020702&rrc=N&affl=&cip=63.227.58.141&act=&aff=&pg=prod&ref=GBxM2&cat=diy+brushless+kits&catstr=HOME:diy+brushless+kits

So far it's been difficult as this is my first brushless build. The biggest problem i'm having is gluing the magnets to the can. They just don't seem to want to stay. Second, no matter what I do i still get rubbing between the magnets and the stator. Any suggestions? Has anyone else here gotten a motor from these guys? Thanks!

--Alex

As others have said the GBx double should go together easily and with no rubbing. It sounds like you had trouble glueing magnets and may have a build up of glue between the magnets and flux ring. I suggest you take the magnets out. Clean them and the flux ring with acetone until all traces of glue are gone. Acetone will disolve CA over night, if that is what you have been using. If you have been using epoxy it may be easier to just get a new can and magnets.
Then use a magnet spacer from www.strongrcmotors.com (http://www.strongrcmotors.com) and follow the instructions for glueing magnets in the "motor Building Instructions" posted in the Strong RC Motors "instruction documents.
Have Fun!
Don

adoman
06-05-2007, 02:39 AM
Thanks for the replies guys! I'll try removing the magnets and starting over with that. This if my first motor build so I kinda figured I would have some problems...but oh well, it's a learning experience! I did buy a park 400 outrunner to use while i'm trying to get the building done.

What kind of performance have you seen out of the motors and what kind of planes are you using them in?

Thanks again guys!

--Alex

chainlink
06-06-2007, 03:17 PM
The spacing tool, a tweezer and a toothpick are all use full tools for magnet spacing.

I have several GBx (single) kits and love them. FWIW I also have some other pre-mades, and while they work fine - they do not give me near the satisfaction that winding my own does. I use the low end pre mades when I want to save time or money (and top performance is not an issue). Likewise I suspect that high end pre mades might even be better than the GBx, but I am way to cheep to spend $$$ on motors.

Doc Pete
06-06-2007, 05:36 PM
I'm not sure this is the best answer for someone who already spent the money on the kit but it might be good advice for next time.

Err................. there are times when you just need to bit the bullet and dump the problem.......
How do you argue with $13 bp12's/etc. that run well????
http://stores.ebay.com/Heads-Up-RC

adoman
06-07-2007, 04:08 AM
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?

adoman
06-07-2007, 04:43 AM
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

bz1mcr
06-07-2007, 03:23 PM
Building Motors Vs buying factory built motors: I agree building your own motors does not save a lot of money these days, but it can get you a motor that fits your application and flying style better than available factory builts. Winding motors brings many builders great satisfaction. Knowing they have something special and confident they can adjust performance as desired without buying a whole new motor. Also, when the unthinkable happens they know they can get parts and make repairs as needed. It's another dimension of the Hobby. Some like to build planes, some like ARF or even RTF's. Some like to build motors, some want factory builts, and some just want to FLY. To me it's all fun! The more I put into the hobby the more I enjoy it.

UH is is a good supplier and offers some nice values:
I have had good service and feel the products from UH are well described, and generally good value. However, I have seen several posts about problems when orders included an out of stock item. The entire order is held up, sometimes well over a month. I'm not sure I'd call that "No headaches, no messing around." But it is a good deal if you avoid out of stock items or don't mind the wait.

The UH 9 g servos are a terrific deal. Coreless motors, fast response, good centering, and less than $4. The blue 24 g motor has had lot of good reports.

DBacon
06-07-2007, 05:24 PM
bz1mcr,

I agree that building your own motor is very rewarding. I started in e-flight this way, and I learned a lot more than I would have with a stock built unit.

I learned, with help from a few great people on this forum, that the motor windings can make all the difference. It is simple to change the windings, which I did many times, and rewarding when you get it just the way you want it.

Plus it is very economical to try your hand at it.

Doc Pete
06-07-2007, 05:26 PM
I checked out the motors at www.unitedhobbies.com (http://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 hate to tell ya, but it's just one of those good things in life. You will be happy...........
Pete

clive45
06-08-2007, 03:37 AM
I have GBx from Gobrushless and a couple of other DIY makes. Great fun building and you can tailor to suit your needs. Best is when I had one burn out (well overloaded) for the price of a stator plate and some wire from the local motor rewinding shop. I was back in business. You can make several different winds and just swap the bell housing etc over and use the motor in a different situation.
Gives you great flexiblilit for very little money compared to haveing several motors around doing nothing.:ws:

rca
06-09-2007, 05:51 AM
I have GBv and GBx single and double kits that I have built. I can say without a doubt that the motor spacer Don at strongrcmotors.com (http://www.strongrcmotors.com/Magnet%20Spacers.htm) sells is well worth it for the price. It makes putting the magnets in super easy and removes a lot of the frustration. I love my GBx double too, great motor.

I also have motors from UH, but I still like winding my own too.

Ron

ron_van_sommeren
06-25-2007, 09:33 PM
Excellent motorbuilding articles by Brian Mulder,they cover the all the basics, a must read:
http://www.southernsoaringclub.org.za/
-> Articles by SouthEasterners.
-> Electric Motors - part 1-5

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:
http://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

Two instructive motor winding/assembly videos, 14 & 10Mbyte respectively (cd-rom and lrk have different winding diagrams!)
http://www.youtube.com/watch?v=iHYlWKICkqc&e
http://www.youtube.com/watch?v=Ybb0Ysh0FRE


Vriendelijke groeten ;) Ron van Sommeren
• int. electric fly-in (http://home.hetnet.nl/%7Eronvans/), Nijmegen, the Netherlands
• brushless motor building tips & tricks (http://www.rcgroups.com/forums/showthread.php?t=240993)
• diy brushless motor (http://www.yahoogroups.com/group/lrk-torquemax) discussion group
• Drive Calculator (http://www.yahoogroups.com/group/D-calc/) download & discussion group

juneaujim
02-06-2008, 02:51 AM
Having built my own motors, I now know how to buy them. But I still frequently build them anyway. I get exactly what I want-usually.

shotgunsmitty
02-06-2008, 03:34 AM
Very interesting. I think I'd like to try my hand at this.

juneaujim
02-06-2008, 04:11 AM
Be, Be careful, one thing leads to another and then suddenly you know alot more about more stuff that you never knew you wanted to know and are still trying to learn more so you can make more stuff that leads to more questions.
I lived in Sitka for five years back in the eighties.

shotgunsmitty
02-06-2008, 04:48 AM
Well, the waiting may be the hardest part, but I've got time. You know how it is up here. I'll have more opportunities to build than fly. And I've been known to know my way around a voltmeter, which is just dangerous in and of itself.
I pulled a motor out of a cdrom last week and successfully powered it with an apc prop on it...but I think I can get more out that motor.....:)

DBacon
02-06-2008, 07:52 AM
shotgunsmitty,
Make sure you use an electric style prop. APC props are my very favorite for fuel, but did not work well for my electric, and delayed my progress trying to get the 16 oz thrust I was sure I was supposed to get.
I rewound the motor several times, just wouldn't do it. Changed to a thin GWS prop, made all the difference in the world.

shotgunsmitty
02-06-2008, 11:27 AM
I'll keep an eye on that. You know what, I have one gws prop that a fellow flyer gave me. Sounds like I need to grab a handful more. I wonder what sizes? Or, better yet, I should do an amp check with different props with my watt meter that isn't here yet either and find out what it's pulling with the 9" and 10" props that I have.

Oh, and on the topic of UH, I've had an order in with them for several weeks, now. They show it shipped on the 24th of last month, it's been 13 days and still no show, maybe I'm just being impatient. But it was the best deal in town.

ron_van_sommeren
02-06-2008, 11:48 AM
A list of outrunner manufacturers. Kit/parts suppliers are marked with a '*':
http://www.rclineforum.de/forum/thread.php?threadid=43664


Unfortunately, I cannot edit the first post anymore (too old?), I cannot add the Motrolfly kits (http://www.gobrushless.com/shop/index.php?app=ccp0&ns=catshow&ref=MOTROLFLY+MTR+KITS), nor the Scorpion kits (http://www.innov8tivedesigns.com) (very high temperature magnets :)), nor the MicroDan 2505 (http://www.gobrushless.com/shop/index.php?app=ccp0&ns=prodshow&ref=MD2505-KIT) and 2510 (http://www.gobrushless.com/shop/index.php?app=ccp0&ns=prodshow&ref=MC2510-KIT) kits .

Two of the many MicroDan threads (there are more):
http://www.rcgroups.com/forums/showthread.php?t=770832 (excellent tutorial by Dave North)
http://www.rcgroups.com/forums/showthread.php?t=774862

The Scorpion motors use thin laminations (0.2mm). Very good.

@Don
I did not forget your www.strongrcmotors.com (http://www.strongrcmotors.com) kits but you are already in the kit manufacturers compilation thread :)

Vriendelijke groeten ;) Ron van Sommeren
• int. electric fly-in (http://home.hetnet.nl/%7Eronvans/), Nijmegen, the Netherlands
• brushless motor building tips & tricks (http://www.rcgroups.com/forums/showthread.php?t=240993)
• diy brushless motor (http://www.yahoogroups.com/group/lrk-torquemax) discussion group
• Drive Calculator (http://www.yahoogroups.com/group/D-calc/) download & discussion group

shotgunsmitty
02-06-2008, 12:03 PM
Thanks.
Now about those props...for my foamies I should be going with gws props?
Currently I have a small stock of APC slow-fly props.

DBacon
02-06-2008, 01:57 PM
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...

shotgunsmitty
02-06-2008, 02:03 PM
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.

Gohmer
02-06-2008, 03:38 PM
I checked out the motors at www.unitedhobbies.com (http://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.

DBacon
02-06-2008, 03:56 PM
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.

shotgunsmitty
02-06-2008, 05:27 PM
So where do you find additional windings wire? What gauge do you use?

I've got a bit to learn here, I can tell... :)

DBacon
02-06-2008, 05:42 PM
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.

ron_van_sommeren
02-06-2008, 06:02 PM
... 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 :D 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 (http://home.hetnet.nl/%7Eronvans/), Nijmegen, the Netherlands
• brushless motor building tips & tricks (http://www.rcgroups.com/forums/showthread.php?t=240993)
• diy brushless motor (http://www.yahoogroups.com/group/lrk-torquemax) discussion group
• Drive Calculator (http://www.yahoogroups.com/group/D-calc/) download & discussion group

ron_van_sommeren
02-06-2008, 06:08 PM
... 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

DBacon
02-06-2008, 06:15 PM
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...

ron_van_sommeren
02-06-2008, 06:21 PM
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

http://static.rcgroups.com/forums/attachments/1/2/2/8/8/0/a1698240-87-wirbelstrom.gif

DBacon
02-06-2008, 06:36 PM
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.

shotgunsmitty
02-06-2008, 08:08 PM
So bigger is better?

DBacon
02-06-2008, 08:31 PM
Anybody that tells you different probably did not go big...

shotgunsmitty
02-06-2008, 08:36 PM
[response tactfully self-edited]

DBacon
02-06-2008, 08:44 PM
Chicken ha ha

ron_van_sommeren
02-07-2008, 03:00 PM
...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 :D

Vriendelijke groeten ;) Ron

ron_van_sommeren
02-07-2008, 03:05 PM
... 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

oct2633
04-29-2008, 10:18 PM
I took a look at www.unitedhobbies.com (http://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!

bz1mcr
04-29-2008, 11:21 PM
I have purchased many motors from www.UnitedHobbies.com (http://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.

kyleservicetech
05-14-2008, 02:29 AM
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.

DBacon
05-07-2013, 05:54 PM
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!

kyleservicetech
05-07-2013, 06:37 PM
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.

DBacon
05-08-2013, 12:39 AM
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.

kyleservicetech
05-08-2013, 03:27 AM
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.

Ohm
06-06-2014, 06:36 PM
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.

ron_van_sommeren
06-06-2014, 06:49 PM
... But who really needs efficiency? ...Efficiency governs power/weight ratio.
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.
A rather extreme example, just for calculation's sake/fun: going from 80% to 90% efficiency would increase the input power the motor can handle by a factor two (a.k.a. 2).

DBacon
06-06-2014, 07:11 PM
Excellent explanation of the value of bigger windings. One of the characteristics of rewinding with fewer turns of larger wire is that the RPM per Volt (kV) goes up, which is not always desired for scale planes and noise.

So a smaller prop, with less pitch may be required to allow this higher RPM.

I like small props as they transmit less torque to the plane's body.

kyleservicetech
06-07-2014, 04:40 AM
Efficiency governs power/weight ratio.
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.
A rather extreme example, just for calculation's sake/fun: going from 80% to 90% efficiency would increase the input power the motor can handle by a factor two (a.k.a. 2).

Precisely!

Some of those name brand motors only fill 50-60% of the available winding space for the magnet wire. Even though they have the same exact KV rating, nearly the same total weight, the the motors that completely fill the available winding space can have 1/2 of the winding resistance.

Since maximum power capability is inversely proportional to the winding resistance, cutting the winding resistance in half results in a similar increase in maximum power capability.

Take the E-Flite Power 32 motor vs the Hacker A40-12S motor. Both are the same physical size, both have the same KV rating, but the Hacker motor has about half of the winding resistance. The E-Flite measures 0.023 Ohms, the Hacker is 0.012 Ohms. So, for the same current, the Hacker windings get half of the heat of the E-Flite Power 32.

Yup, those E-Flite motors do work well, and a lot of them are in use. The Power 32 is rated by the mfg to 800 Watts, the Hacker A40-12S is rated to 1000 Watts. Running the numbers through www.motocalc.com, the Power 32 will be pulling about 900 Watts on a 4S LiPo with a 12X8 Prop. It will be pulling 65 Amps, and gets about 73% efficiency. Prop is predicted to be 8050 RPM. Motocalc suggests this will fry the motor. Yup, this is above the Power 32 rating.

Putting the same 12X8 prop on the Hacker A40-12S, Motocalc indicates this motor will be pulling about 1100 watts on a 4S LiPo, while pulling 79 Amps, getting 88% efficiency. Prop is predicted to be 9100 RPM.Yup, this is also above the Hacker current rating. But Motocalc indicates no problems with the Hacker.

Check out the photo of the Tera Hobby motor. It's windings measure 0.046 Ohms, four times that of the Hacker. Interesting, the rotor and stator of the Tera Hobby motor and the Power 32 motor directly interchange with each other.

kyleservicetech
06-07-2014, 05:14 AM
Excellent explanation of the value of bigger windings. One of the characteristics of rewinding with fewer turns of larger wire is that the RPM per Volt (kV) goes up, which is not always desired for scale planes and noise.

So a smaller prop, with less pitch may be required to allow this higher RPM.

I like small props as they transmit less torque to the plane's body.

Or, if the mfg completely fills the winding area of the motor winding slots with copper wire, a heavier gauge wire with the same exact number of turns (and same KV) can be used. Completely filling the winding area with copper wire is a lot more work.

Yeah, I've rewound a bunch of brush and brushless motors over the years. It was nice to have access to the shop winding area with their big spools of wire. The "End of the spool" magnet wire could easily provide enough copper wire to wind a dozen small brushless motors. The coil department had every size wire from #34 or so, to heavy flat copper strips two inches wide. Some of those spools were hundreds of pounds.

Ohm
06-07-2014, 05:10 PM
The united hobby link goes to Hobby King? go figure.
Having wound many motor kits and OEM rewinds I find it cheaper more satisfactory to buy low cost motors and upgrade the winding, the bearings and sometimes magnets . IMHO the cost of motor kits is atrocious considering they did not do the hard work. They did not build the stator, they did not make the bearings or shaft. It doesn't take much to push the button on a CNC machine and load the stock. It takes little skill to draw a picture of a motor frame considering all the standards are in place. So I suppose the huge mark up in price is due to someone putting them in a box and marketing them. No complaint just observation, anything to make a buck. Buying high priced motor kits is no guarantee that your getting top quality parts. I have bought several high priced kits that the bell was not made correctly so it needed balancing after assembly or other problems from sloppy machining. It's a PITA step. In contrast I have bought HK motor kits that have been the cats meow. All that being said a technique to low cost, high performance motors has come to finding reasonable quality motors on sale and then upgrading the weak points. I have found .2mm laminate stators in dirt cheap motors, usually accompanied with crapy bearings (only because they are full of dirt) and a sloppy wind and mediocre magnets. Key there is the motor has a top notch stator. It's the parts the kit manufacture doesn't make (although they do source them, I suppose that's worth 300% markup) that are the key to a good motor. IMHO

ron_van_sommeren
06-07-2014, 08:47 PM
... Even though they have the same exact KV rating ...Denny, keep in mind, and spread the word ...
The Kv constant (motors have just one Kv, not 180Kv), is not a rating, not a figure of merit. More windings will give lower Kv, less windings will give higher Kv, that's all there is to it, no big deal, anyone can do that (http://www.rcgroups.com/forums/showthread.php?t=240993).
Also
A motors Kv constant says nothing about a motors max.power, max.current and rpm (http://www.rcgroups.com/forums/showthread.php?t=2131492).
Maar we weten wel dat motorstroom wil stijgen met kwadraat van spanning en derde macht van Kv.

ron_van_sommeren
06-07-2014, 09:59 PM
Efficiency governs power/weight ratio.
... ...
An example ...Say the motor has an efficiency of 70% ....On the other hand, it can be advantageous to keep some open space for cooling air to pass through, because better cooling is also good for power/weigth ratio. So there can be a trade off.

E.g. several rewinds by Bert Dekker, notably the rewinds for helicopters
translate...www.modelbouwforum.nl/forums/model-elektronica/126944-scorpion-hk3026-hk4225-hk4020-hk4025-hk4035-buitenloper-wikkelen-35.html (https://translate.googleusercontent.com/translate_c?depth=1&hl=nl&ie=UTF8&prev=_t&rurl=translate.google.nl&sl=nl&tl=en&u=http://www.modelbouwforum.nl/forums/model-elektronica/126944-scorpion-hk3026-hk4225-hk4020-hk4025-hk4035-buitenloper-wikkelen-35.html)

Kontronik Pyro 850 5+5YY 1.6mm, Kv = 470rpm/V
http://i284.photobucket.com/albums/ll6/_Dekker/6.jpg (http://www.modelbouwforum.nl/forums/model-elektronica/126944-scorpion-hk3026-hk4225-hk4020-hk4025-hk4035-buitenloper-wikkelen-post2764434.html#post2764434)

kyleservicetech
06-08-2014, 02:00 AM
The united hobby link goes to Hobby King? go figure.
Having wound many motor kits and OEM rewinds I find it cheaper more satisfactory to buy low cost motors and upgrade the winding, the bearings and sometimes magnets . IMHO the cost of motor kits is atrocious considering they did not do the hard work. They did not build the stator, they did not make the bearings or shaft. It doesn't take much to push the button on a CNC machine and load the stock. It takes little skill to draw a picture of a motor frame considering all the standards are in place. So I suppose the huge mark up in price is due to someone putting them in a box and marketing them. No complaint just observation, anything to make a buck. Buying high priced motor kits is no guarantee that your getting top quality parts. I have bought several high priced kits that the bell was not made correctly so it needed balancing after assembly or other problems from sloppy machining. It's a PITA step. In contrast I have bought HK motor kits that have been the cats meow. All that being said a technique to low cost, high performance motors has come to finding reasonable quality motors on sale and then upgrading the weak points. I have found .2mm laminate stators in dirt cheap motors, usually accompanied with crapy bearings (only because they are full of dirt) and a sloppy wind and mediocre magnets. Key there is the motor has a top notch stator. It's the parts the kit manufacture doesn't make (although they do source them, I suppose that's worth 300% markup) that are the key to a good motor. IMHO

If you ever wondered how some of these motors are wound:
https://www.youtube.com/watch?v=2JsRYUTK5Pw

I'd guess those motors whose windings completely fill all available winding space are wound by hand.

DBacon
06-08-2014, 11:07 AM
Good info here, should be required reading. Yes Kv is not a figure of merit, just a characteristic. But is it "Kv", "KV", "kV", or "kv"?
In my business (resistance welding) we use "kVA" for power handling ability of a transformer, and we capitalize the Volts and Amps out of respect for Count Alessandro Giuseppe Antonio Anastasio Volta and André-Marie Ampère. (http://en.wikipedia.org/wiki/Andr%C3%A9-Marie_Amp%C3%A8re)

That winding machine is amazing! Thanks

ron_van_sommeren
06-08-2014, 01:23 PM
... But is it "Kv", "KV", "kV", or "kv"? ...Kv, in rpm per volt, and Kt, in newton per ampère, voltage respectively torque Konstant.
Kt = 1 / Kv, in units for grown-ups, i.e.SI units, not imperial units.

See also Joachim Bergmeyer's excellent article about brushed motors. Since brushless motors are just brushed motors with electronic commutation (ESC) instead of mechanical commutation (brushes), all if it applies to brushless motors, mutatis mutandis:
www.rcgroups.com/forums/showthread.php?t=185271

DBacon
06-08-2014, 04:43 PM
Hmm...

Ohm
06-08-2014, 09:35 PM
If you ever wondered how some of these motors are wound:
https://www.youtube.com/watch?v=2JsRYUTK5Pw

I'd guess those motors whose windings completely fill all available winding space are wound by hand.

The E-max motors of late are machine wound and they squeak by when tested against the advertised spec, consistently! But there is gobs of room for more wire. I think the big advantage to the OEM motor market is providing a consistent product. Which can be more valuable to the consumer instead of getting some good ones and bad ones that the hand wind market offers. The big advantage to folks who like to max-out their motors is that it provides a reliable base to work from.

kyleservicetech
06-09-2014, 01:09 AM
:oops: Since brushless motors are just brushed motors with electronic commutation (ESC) instead of mechanical commutation (brushes), all if it applies to brushless motors,

Yup
FYI, these brushless motors are actually three phase AC motors with a variable frequency three phase AC driver, namely the ESC itself.

I've taken several of those high quality brushless motors, such as the Hacker A60 line, and connected them to a low voltage three phase AC power supply. (12 VAC Three Phase) You guessed it. Those motors immediately started spinning, locked into an RPM determined by the frequency of the AC power supply. In fact, spinning up a brushless motor with a battery operated drill, you can display a three phase AC voltage across its windings with a four channel oscilloscope. (Also done that)

And, last but not least, I've taken a Hacker A60-5S motor, directly connected it to a Hacker A40-10L motor, using brass adapters. (Jumpers don't work, to much resistance) Spinning up the A60 motor results in the A40 turning over exactly double the RPM of the A60, due to the different number of poles in the two motors. Trying that with some of the bottom of the line motors is not as successful, due to the higher winding resistance of the motors windings, and who knows what else.

Interesting but somewhat useless information :mad: :oops::eek:

ron_van_sommeren
06-10-2014, 02:30 PM
BK3VGX87X_Y
More SLS videos
www.sinusleistungssteller.de/projekte.html

... FYI, these brushless motors are actually three phase AC motors with a variable frequency three phase AC driver, namely the ESC itself. ...Although RC Permanent Magnet Brushless motors (PM BLDC) can be driven by AC and VFD's, RC ESC's are not variable frequency drives Denny (ignoring the SLS controllers (http://www.sinusleistungssteller.de)). In a brushless ESC the PWM pulse width (https://en.wikipedia.org/wiki/Pulse-width_modulation) is controlled by the throttle stick. But it's the that motor 'tells' the controller when to switch/commutate, using zero-crossing detection. Motor and ESC are an iso-synchronous system.


www.aerodesign.de/peter/2001/LRK350/index_eng.html (http://www.aerodesign.de/peter/2001/LRK350/index_eng.html)
-> SPEEDY-BL self made brushless controller
BLDC controller design (http://www.rcgroups.com/forums/showthread.php?t=200567&highlight=takao) (excellent and active thread)
several diy brushless ESC designs (http://www.rcgroups.com/forums/showthread.php?t=140454&highlight=takao)
DIY Brushless Speed Control (http://www.rcgroups.com/forums/showthread.php?t=181247&highlight=takao)

kyleservicetech
06-10-2014, 05:14 PM
Although RC Permanent Magnet Brushless motors (PM BLDC) can be driven by AC and VFD's, RC ESC's are not variable frequency drives Denny

Hi Ron
You're right, should have been more precise on what an ESC consists of. Early on, our brushless motors had extra lead wires that sent information to the ESC that synced the ESC to the motor as it rotated. Modern electronics allowed those wires to be eliminated, using the three motor wires them selves for sending that required information to the ESC. And, as you indicate, these ESC's vary power input to the motor by "Chopping" the three phase waveshape to the motor. This is easily observed by anyone that has access to an oscilloscope. (I've got three Tektronixs scopes)

One company, www.microchip.com has a lot of information on just how this is accomplished. Reading through this is a lesson on why it's not a good idea to try building one your self :oops:

As for me, I've designed and built a whole variety of brush type ESC's that were controlled by one of those Microchip PicChips. The last one made was capable of handling an Astroflight 90 motor, pulling 35 Amps at 50 Volts DC. The software for that ESC was some 20 pages of machine code.

The software in these brushless ESC's are several orders of magnitude more complex than what I had in my Brush type ESC's. Attached is a photo of one that I'd made back in the mid 1990's. Those brushless motors made all of this stuff relegated to the "Old stuff in the drawer".

Also attached is three Microchip files on what's involved in designing your own brushless ESC using the Microchip "PicChip" line.

Now, you can buy a little tiny brushless motor driver for those computer fans. Take a look:
http://ww1.microchip.com/downloads/en/DeviceDoc/22263B.pdf

You can buy one for $1.30 each, quantity of one.
http://www.digikey.com/product-detail/en/MTD6501G-HC1/MTD6501G-HC1-ND/3131735

kyleservicetech
06-17-2014, 04:50 AM
I had occasion to bust off the motor shaft of my Hacker A60-16M motor last Saturday. That after some 400 flights on the motor. Problem was caused by a high speed pass over the field, and getting hit by a downdraft, 5 feet off the ground. Winds were 15 - 20 MPH. Stupid. One blade of the 19X12 APC-E wide blade unit has sod stains on it that shows that the blade cut into the sod 3 1/2 inches during the hard bounce and go. That bounce and go bent the landing gear.

Hacker has replacement shafts in stock, I'll be getting them later this week.

That gives an opportunity to take a photo of one of the windings in this motor with my USB microscope. Note how the windings occupy 100% of the available winding space. Sign of a quality motor.

Ohm
06-17-2014, 03:20 PM
The next step for a higher quality motor is with a single strand wind that fills up the stator. SSW has better air to flow thru the coils. SSW also provides more copper in the provided space.

kyleservicetech
06-17-2014, 06:08 PM
The next step for a higher quality motor is with a single strand wind that fills up the stator. SSW has better air to flow thru the coils. SSW also provides more copper in the provided space.

Agreed:
Problem is, that will usually involve non-standard wire sizes which might be a problem.

What I ran into though, is when using larger single strand wire, the sharp turns required resulted in the varnish type of insulation cracking. That might have been the result of using $$$$ wire from work though.

ron_van_sommeren
06-17-2014, 08:15 PM
Chamfer (bevel? what's the difference?) the edges with a file a bit before winding.

kyleservicetech
06-19-2014, 04:52 PM
The next step for a higher quality motor is with a single strand wind that fills up the stator. SSW has better air to flow thru the coils. SSW also provides more copper in the provided space.

Yup
Doesn't take much work with a compass and a piece of paper to show that. Just draw a big circle for a single strand wire, then drawing perhaps 6 smaller circles inside the big circle to show six smaller strands of wire inside the big circle. You wind up with lots of air space.

On the other hand, if you've got a half filled winding area, that does provide more air cooling. But, at a cost of higher winding resistance for the same size motor.

Cases in point:
The Hacker A60-7S has ratings of 215KV, 90 Amp, 2400 Watts, 1.2 Amps no load current, 0.026 ohms winding resistance. It weighs 595 grams.
http://www.espritmodel.com/hacker-a60-s-28pole-series-motor-v2.aspx

The E-Flite Power 180 has ratings of 195KV, 65 Amp, 3000 Watts, 1.5 Amps no load current, 0.042 Ohms winding resistance. It weighs 642 Grams.
http://www.e-fliterc.com/Products/Default.aspx?ProdID=EFLM4180A

I've got the Hacker A60-5S motor, a real power house. Its windings completely fill all available area. You can actually run it at its rated power level of 2400 Watts.

I've also had a Power 180 in my hands, its windings filled perhaps 60% of available winding space. That shows up in the 0.042/0.026 or 60% higher winding resistance. That will show up in higher temperatures at the same ampere loading.

So, which motor is better? Per www.motocalc.com, actually running the Power 180 motor at 3KW will fry its windings. I've run my Hacker at 80 Amps with no problems what so ever. And, the Hacker is cheaper.

kyleservicetech
06-19-2014, 04:57 PM
Chamfer (bevel? what's the difference?) the edges with a file a bit before winding.

I was using wire from work, a type called heavy duty formvar wire. That formvar insulation might be a bit more susceptible to cracking. On the other hand, its made for transformers, and is high quality stuff.

Ohm
06-19-2014, 05:24 PM
The solution to damaged stator coating
can also be used for custom coloring.
http://http://www.harborfreight.com/16-oz-powder-coat-paint-matte-black-93306.html

I cook them in my toaster oven after piling up the powder where I want it on the stator. The sand castle building skill developed at the beach now has a real world use.:rolleyes:

Ohm
06-19-2014, 05:29 PM
http://http://www.techfixx.com/
I find the amber wire top notch stuff,very supple. The red and green insulation not as tuff, but good for making light weight servo extensions. Their service has been A-1 to date.