# Mars 27hp motor



## major (Apr 4, 2008)

crackerjackz said:


> Has anyone else had this happen often ? This is the 27 hp mars motor from my electric motocross ... The new brush holder is on its way . Had amazing customer support by the company just wondering if its gonna rehappen often :s


Hi crack,

Yep, I've seen a lot of brushed PM motors end up like that on the track. How many hours did you have on it? Running those 4 PC625's still? Got a build or EValbum web page to show us what you're talking about? How's the comm look? How did she run before the motor took a crap?

Sorry for your loss,

major


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## electro wrks (Mar 5, 2012)

crackerjackz said:


> Has anyone else had this happen often ? This is the 27 hp mars motor from my electric motocross ... The new brush holder is on its way . Had amazing customer support by the company just wondering if its gonna rehappen often :s


If you can, show everybody a side by side comparison(front and back) of the old and the new brush plates. It seems to me the old style has some high resistance points. The small, steel brush holder mounting bolts have to carry full motor current and the conductors on the back side of the plate look undersized. Some well placed shunts might help.

At the very least, if possible, use a non-contact thermometer to check component temps. as you're using the motor.

Also, on one motor I was having trouble with, some of the brushes were sticking in the holders (arrows in the picture). Apparently this was a manufacturing error because the brushes in the replacement plate moved freely. A little cleanup work with a file inside the brush holder would also fix the problem. If you're really pushing the motor, it may be necessary to go to the double brush motors ( yours looks to be a single brush?).


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## major (Apr 4, 2008)

electro wrks said:


> If you can, show everybody a side by side comparison(front and back) of the old and the new brush plates.
> 
> ........some of the brushes were sticking in the holders (arrows in the picture).


Good points electro. Notice the difference between the two here. 



















All the brushes in the failed assembly are obviously hung up like the defective ones in your photo. If cracker's motor had 3 stuck brushes like your assembly then all the current (4 times normal) would pass through that one brush and result in the melted brush assembly he shows. With a wave wound armature which I suspect this is, performance would not be noticeably different with a stuck brush or 2 or 3 because you'd get the same torque and nearly the same speed. But non-active brushes would cause that type of failure.

I can't answer the question of whether the stuck brushes are a result of overheating from abuse or the cause of the overheating due to a defect.


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## crackerjackz (Jun 26, 2009)

None of the brushes actually move now lol ... I figurd since everything heated they got stuck or warped ... When i get the new brush holder ill put picks comparing the 2 .

As for the motorcross yes i still have 4 pc625 odyssey batteries in it . I dont use it very often but when i do i tend to abuse it pretty bad lol lots of full throttle and stop and go . Ill have to make a page for it ... I can go about a 110 km with the damn thing  acceleration is descent ... Obviously im limited on range if i beat it a lot i only have power for about 10 min if i half my speed i nearly triple my distance ...

This motocross was a deal with me and my wife to show her what can be done with an ev car but on a reservist and test format ... I love the thing so does she i just hate the batteries and peukerst affect which i only discovered about once it was finished  so i nearly half the time and distance i figured i would have ...


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## RIPPERTON (Jan 26, 2010)

Do brushed motors suck or is it just my perception of things 

I think your problem is the 110km thing. Im assuming you mean 110kmh. Thats just too much work for a little motor.
you simply need more reduction cause you cant do 110kmh on the average MX track.


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## major (Apr 4, 2008)

RIPPERTON said:


> Do brushed motors suck or is it just my perception of things


Your perception  The brushed wound field motors do very well at a lot of things, like drag racing and grocery getters. But the brushed PM motors generally suck at overloads like you're bound to see on the track. I'll bet cracker wouldn't have had this problem using an equally rated series or SepEx motor.


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## crackerjackz (Jun 26, 2009)

By pm im guessing you mean permanent magnet ? If so arent netgains warp 9 and 11 of the same configuration ? Do people have no problem at all with brushes on these motors or it happens just less often ?


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## major (Apr 4, 2008)

crackerjackz said:


> By pm im guessing you mean permanent magnet ? If so arent netgains warp 9 and 11 of the same configuration ? Do people have no problem at all with brushes on these motors or it happens just less often ?


Yes, PM = Permanent Magnet. The Warp9 and such DC motors used by most of the EVcar converters are wound field motors. They use electromagnets (poles and field coils) instead of PM sectors to establish the flux field which enables the armature to convert electric power into mechanical power. These wound field motors are more robust machines and very capable of handling overloads compared to PM motors. Typically the brushes on a Warp9 will outlive the car. I'm not saying they never fail, but it is uncommon and typically linked to severe abuse (drag racing with 2 or 3000A), defects, misapplication or contamination. Whereas the brushed PM motors drop like flies when they smell a race track  

Disclaimer: The brushed PM motors are extremely common and provide a great service to mankind. They are an inexpensive efficient power device used by the millions in toys, appliances, tools, automotive accessories, etc. Most preform well over their intended duty life. But beware when using a brushed PM motor where you'll encounter frequent or sustained overloads.


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## toddshotrods (Feb 10, 2009)

major said:


> Yes, PM = Permanent Magnet. The Warp9 and such DC motors used by most of the EVcar converters are wound field motors. They use electromagnets (poles and field coils) instead of PM sectors to establish the flux field which enables the armature to convert electric power into mechanical power. These wound field motors are more robust machines and very capable of handling overloads compared to PM motors. Typically the brushes on a Warp9 will outlive the car. I'm not saying they never fail, but it is uncommon and typically linked to severe abuse (drag racing with 2 or 3000A), defects, misapplication or contamination. Whereas the brushed PM motors drop like flies when they smell a race track
> 
> Disclaimer: The brushed PM motors are extremely common and provide a great service to mankind. They are an inexpensive efficient power device used by the millions in toys, appliances, tools, automotive accessories, etc. Most preform well over their intended duty life. But beware when using a brushed PM motor where you'll encounter frequent or sustained overloads.


The funny thing about this is I've been beating the crap out of my little ProTech (brushed PM) test motor in my motorcycle, with over four times rated current for many "take-offs", and sprints across the parking lot. It's also a sealed enclosure (no cooling), and it's still going?! It feels as strong as it did the first time I used it?! 

They obviously seriously under rated it (on the label).


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## crackerjackz (Jun 26, 2009)

Ok so heres the update with pics to show how everything went 


























Got the new parts today. there were a few noticeable differences between the old and new brush-holder like the brush springs have changed and the busbars are now covered . But after cleaning my comm and blowing air to clean motor i put everything back together and all is good  now that i see how smooth it is i realize it was obvious something was wrong for a while but it probably degraded slowly . The throttle is much smother and constant ... Ill have to keep an eye once in a while on the brushes i had probably between 15 and 20 hours of riding before it let go so ill try to check it every 5 ?? ...


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## crackerjackz (Jun 26, 2009)

Ps thanks everyone for your input and advice  gotta love this site were always learning on here


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