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Old Aug 06, 2015, 12:55 PM
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Best brushless motors?

What makes a good or great brushless motor?

And hey, where is Consumer Reports when I need them???

So, I’m looking at brushless motors from various suppliers… some are so low cost, I really have to wonder about them (I spent about $15 each for the motors in my Baywatch boat)… and others are well over $100 each… what’s the difference?

I mean, these things are easy to make, if you have a CNC lathe and mill, and a winding machine… ball bearings are a commodity… there are no brushes to deal with… hardest part is assembling the magnets and balancing the rotor.

So what sets a $200 motor apart from a $20 motor?

And along those lines… if you wanted to put “fine” motors with some wow factor into a boat, what would you choose?

To me, wow factor comes from:
1. Good solid performance—race worthy, even if I’m not racing;
2. Impressive looking construction (like, how an AstroFlight brushed motor looked compared to a steel can Mabuchi…).
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Old Aug 06, 2015, 01:15 PM
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If you want WOW Lehner motors are the best.
http://www.lehner-shop.com/
Neu and castle are very good motors.
TP and Leopard are good motors for the price.
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Old Aug 06, 2015, 02:36 PM
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I may be wrong here, but aren't the really expensive brushless motors like aveox hand built? that could be an excuse/reason for expense
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Old Aug 06, 2015, 02:55 PM
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Quote:
If you want WOW Lehner motors are the best.
Holy ****, Batman! $1,000 for an outrunner?!?!

Who has a budget for that? Salvaging from old electronic devices, appliances and cars sounds like the ticket.
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Old Aug 06, 2015, 03:31 PM
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Anything that you can salvage will not even come close to the power output of a quality motor that costs a grand. Comparing apples and oranges.

Steve
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Old Aug 06, 2015, 03:53 PM
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I won't argue against that. It's just way out of my budget range and I don't anticipate building anything requiring that kind of performance.
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Old Aug 06, 2015, 04:38 PM
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I buy mid grade out runners for my nicer quad copters, helicopters and aerobatic aircraft. I also fly the garbage Parkzone outrunners (plastic can) on the RTF stuff. I have never had a motor or bearing failure on either.
Hobbyking on all boats (4 boats so far) and they have also been flawless.
I see no need to go big on scale boats. Buy a couple spares and be good for years.

DH

So what sets a $200 motor apart from a $20 motor? Quality control and customer service........
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Old Aug 06, 2015, 06:10 PM
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Well... maybe I should say I'm interested in "more betterer" motors, not just the BEST (i.e., most expensive). But frankly, things like "hand wound" don't mean better to me... anything done by hand is just more likely to get done wrong... I'll take machine wound armatures any day!

And the lowest cost hobby brushless motors all seem to be CNC turned & milled from aluminum stock... that's fine. My $20 Exceed motors run just fine and stay cool, no problems... except they're labeled with stickers instead of really cool laser etched markings...

So I'm still not sure...
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Old Aug 06, 2015, 06:37 PM
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I think my favorite motors for quality/cost are
the Leopard motors. I have been running them
in my fast electric boats for 2 years now and
they have held up real well. I don't baby them either.
I'm testing my first TP motor in a hydro now.
so far I'm impressed with it but I only have
3 runs on it.
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Old Aug 06, 2015, 06:59 PM
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Yes, been looking at those.

Another thing to look for-- a wide range of available kV and frame sizes. For typical scale voltages and speeds, 1000 - 1500 kV is pretty useful... don't need no 5000 kV race motors...
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Old Aug 06, 2015, 08:39 PM
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While I'm somewhat new to boats, I have been flying quads for 6 or 7 years. At this time I have six that are flyable, with a couple more under construction on the work bench. While I am not a expert, after buying and using 50-60 motors over the last few years, as well as rewinding and rebearing many motors, I might be able to offer some reasons for the difference in pricing.

Lets start with the 5 main parts of a outrunner, the wire, armature, magnets, bearings, and the bell or housing.

There is a difference in the quality of the wire between the cheap and higher grade motors. The most common wire used that I see, is rated for 155, 180, or 200 degrees C. This rating is the temperature at which the insulation on the magnet wire melts. While this seems high remember that the inside of a motor get a lot hotter than the outside In rewinding motors it seems like some wire is more brittle than others. I'm not sure why, but I suspect that the wire is not made with high grade pure copper. We want the resistance to be a low as can be , so a high grade copper wire is important.

Next up is the armature. The armature is made with thin layers of laminated steel. The steel with the best magnetic properties is high in silicone. Also the thickness of the laminations effect the performance of the armature. While not all manufactures of motors list their specs, those that do will most likely state the armature is made with .2mm thick, high silicone steel. While i'm not sure, I would guess lower cost motors use a lower grade of steel.

The magnets also vary in quality. Heat is a killer of magnets. High heat will cause a permanent loss of strength. The type of magnets used in our motors come with a heat rating. The higher the number the better they can withstand heat. Most good motors seem to use a 40UH rated magnet. While it is often over looked, the quality of the adhesive used to attach the magnets to the bell is very important. In boat use a motor is not going to take the hits and hard landings that one gets with a airplane or quad, but magnets do break loose, and when they do the motor stops. Like now. Again just a quality issue.

I hope that no one thinks that bearing are all about the same. With some of these motors turning 20,000 rpm, low quality bearings are not going to last long. The best bearings seem to be from Japan. Just take a low and high quality motor and fire them up on your bench with no props or load and listen to them. I have gotten new, low cost motors with bearing so bad that I could not use them. While low cost bearings will work and may last a while they just don't compare to a motor with quality bearings.

Last on the list is the bell or housing. The magnets along with the adhesive are mounted on the inside of the bell. Also the shaft on the armature passes though the end of the bell and the forward bearing which is either press fitted or fitted and glued to the inside of the bell. Again the bell may spin at 20,000 rpm and if the bearing is not in the exact center of the bell or if one magnet got a extra drop of adhesive the motor will not run smooth. Loss of balance is a loss of power. Some manufactures do a better job than others of centering the bearing. As a side note, I balance all my motors before using them. Bit of a pain in the a__, but it doesn't do much good to balance the prop and then put it on a unbalanced motor. Sometimes I run into a motor that just can not be balanced, I just return them for a exchange.

As with many things price does not always mean quality, and some lower cost motors are good buys and some high cost motors seem to be getting by on past reputations. Also the quality can vary with the same brand. Most of my motors are in the "medium" price range and serve me well. I balance the motor, oil the bearings, replacing them when needed, and try not to over heat them and get a lot of life out them.

Pat, I Hope this answers some of your questions as to why prices seem to be all over the place. As CaptDH, stated, a mid priced motor should work fine, and if it should fail just buy another and be money ahead over the price of a high end motor.

Mike
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Old Aug 06, 2015, 08:56 PM
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Thanks!

A comment on the brittle wire: I don't know if you're seeing different grades of copper... but copper work hardens... easily. The wire drawing process certainly work hardens it, and the wire may need several anneals between successive draws. It also needs to be annealed after the final draw. Problem is, how that's done... if on a big coil, run through an furnace on a belt, the entire coil might not reach annealing temp... and you get hard/brittle wire. This is sort of thing that goes into QUALITY, whether these details are all understood and attended to.

BTW-- copper washers on brake hose banjo fittings? Same thing- the little buggers are stamped out of sheet, shoveled onto a belt going through a furnace for anneal, and if you're lucky, the whole pile reaches temp. If not, it takes a lot of extra torque to get your brake hose to seal at the caliper...
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Old Aug 06, 2015, 10:00 PM
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Quote:
Originally Posted by patmat2350 View Post
Yes, been looking at those.

Another thing to look for-- a wide range of available kV and frame sizes. For typical scale voltages and speeds, 1000 - 1500 kV is pretty useful... don't need no 5000 kV race motors...
Actually, what i am looking for is more the 300kv to 600kv
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Old Aug 06, 2015, 11:05 PM
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I looked at some big outrunners for turning a 4-inch prop. Nice to have a selection of kV ratings and hopefully lower current draw for the same power output (by a small amount) than a brushed motor.

The biggest sticking point was the controllers... couldn't guarantee that what I'd be getting had fine low-end control and wasn't just an 'all-or-nothing' race machine. The prices on some of them are even more attractive than the motors, but not cheap enough to afford to buy half a dozen and experiment. This is still the sticking point for me: at some point I'd like to upgrade my current tug to twin 500kv outrunners, if I can find some nice precise speed controllers for them.
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Old Aug 06, 2015, 11:31 PM
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Great write up.

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