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Nov 24, 2015, 01:46 PM
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Help...why am I frying motors? Axial Yeti 1/10


I have been away from RC for about 7-8 years and just getting back in. I have just completed assembling a 1/10 Axial Yeti from a kit and I have ruined 3 motors in the first 2 packs, I'm running a 4000mHa 3 cell lipo. Someone gave me a brushed system from a HPI road car, the ESC is a SC-3s WP2 from HPI and the motor is a 15T Firebolt. I was told the motor may not be good, it lasted about 2 minutes, fair enough it was a worn out freeby! The next motor I tried was the only one I had, it was an old Trinity ROAR 91 motor from about 15 years ago, it lasted about 20 minutes and it started smoking, fair enough it was probably not rated for a 3 cell lipo. The 3rd motor I tried was a brand new Traxxas 12T and it lasted about 5 minutes. I was surprised it started smoking also since I'm sure people run these motors all the time on 3 cells. I'm running the vehicle with a 12 tooth pinion gear and that is well within the recommended gear range (but maybe for a brushless?) The drive train seems to be free and not in any kind of bind and nothing is rubbing. I wanted to use a brushed motor because I don't need all the speed where I drive it. Is the ESC causing this problem or is there something else I need to look at? Thanks for your time.

David
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Nov 24, 2015, 02:44 PM
Bash the planet!!
Please go brush less and let that yeti rip like it's supposed too. That like buying a Corvette and putting a 4 banger in it. I will gladly trade you my t-maxx for the yeti. It's converted to a brushed motor and is nice and slow.
Nov 24, 2015, 04:39 PM
Buggy in style
The 3s and bushes motor is just asking for trouble. Why did you do that for?

Also, motors fry because they over spin and burn. You might want to gear it up more with a larger pinon.

Either way, you really should look at going brushless..
Nov 24, 2015, 04:50 PM
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Brake Weight's Avatar
I'd go with a ridiculous low turn motor or brushless. As for why the motors are dropping? I do t know.
Nov 24, 2015, 05:19 PM
Suspended Account
Get 2 cell lipos thats your only problem.. a 3 cell will kill the motors you listed unless geared Lower
Nov 24, 2015, 08:45 PM
Traxxas.... !!!CONFORM!!!
Something like a yeti should be brushless, hell I feel bad just having a brushed setup these days in my rc10.
Nov 24, 2015, 11:55 PM
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I just like the more scale like speeds and longer run time of the brushed motors. I have a Castle Sidewinder in another car I will try.
Nov 25, 2015, 08:12 AM
Traxxas.... !!!CONFORM!!!
You can try it, however if its the 4600kv sidewinder its not going the help keep the temps in check. The axial vehicles are heavy, and need a lower kv motor, probably around 3800kv. Maybe less and gear for temps. You'll need the torque of the lower kv. As for run times, you could expect the same or better with brushless and a lipo. I'd try to keep it a 2s, unless you fit an 1\8 scale electronics package.
Nov 25, 2015, 08:49 AM
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Any suggestions for a motor? What about the 3800 kv Slash motor? I guess the factory Vanguard motor would work fine with my Sidewinder ESC?
Last edited by green river rc; Nov 25, 2015 at 08:55 AM.
Nov 25, 2015, 09:05 AM
Did I make the A Main?
bill_delong's Avatar
gearing is key regardless of brushed vs brushless motors, I've got brushed motors that are several years old and still going strong, more info here:
http://www.ultimaterc.com/forums/sho...d.php?t=158567
Nov 25, 2015, 02:08 PM
Heli's rule!
dacaur's Avatar
My first guess if the motors all ended up smoking, they were geared too high and/or too low turn count. All three of the motors you burned are pretty low turn, which is equivilant to putting a high kv brushless motor in. Sorta like putting an 8000kv motor in where a 4000kv should be. Then running it on 3 cell jus makes it worse. If you want to stay brushed, look for a 35-55t motor....
Nov 25, 2015, 08:20 PM
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RustyUs's Avatar
Quote:
Originally Posted by kcolraw
You can try it, however if its the 4600kv sidewinder its not going the help keep the temps in check. The axial vehicles are heavy, and need a lower kv motor, probably around 3800kv. Maybe less and gear for temps. You'll need the torque of the lower kv. As for run times, you could expect the same or better with brushless and a lipo. I'd try to keep it a 2s, unless you fit an 1\8 scale electronics package.
+1 ...Well said.

There is a reason why Axial recommends a 550 sized motor for the Yeti.
Nov 25, 2015, 09:01 PM
Traxxas.... !!!CONFORM!!!
Dacuar , that puts it to rock crawler territory . I don't think it was mentioned what yeti model it is. Not to mention the loss of top speed regardless of what scale speed is wanted.

Bill, It's not just or only a matter of gearing with a brushless that will determine the longevity. If you take a 4600kv motor and put it into a vehicle that should use a lower kv motor (let's say a 3200kv motor) and just run a smaller pinion then stock to try and compensate for rpm, it can still smoke said 4600kv motor. It's not a matter of rpm or compensating for a higher revving motor by regearing , but the load and motor operating range.
Nov 25, 2015, 09:51 PM
Bash the planet!!
Oh no. Here we go again. Lol.
Nov 25, 2015, 10:10 PM
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RustyUs's Avatar
The maximum dimensions of a motor to be put in a 1/10 Yeti is somewhere around 42mm x 68mm. I just recently acquired a new motor for an eBuggy, and I had to try and mount it in the Yeti. 'Cause if it fit well, I was gonna order another one. Well, the 68mm length of the motor is pushing the limits. Any longer and I would have had to trim the battery tray.

Long story short...Another motor ordered


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