Cutting a motor commutator & motor tweaks

[EddieO]

Guess I should find all those fussy brush kits I have hidden some where

Break in depends a lot on the brush too. Most of the motors just use the stock Quasar brushes from Sagami, which always took forever to break in....a higher silver content brush breaks in a lot faster...

The Checkpoint Infinity brush is the worst.....20 minutes at 2 volts.....3 volts does nothing quicker as it just gums the comm.....

Later EddieO

 

[whoodie]

Guess I should find all those fussy brush kits I have hidden some where

Break in depends a lot on the brush too. Most of the motors just use the stock Quasar brushes from Sagami, which always took forever to break in....a higher silver content brush breaks in a lot faster...

The Checkpoint Infinity brush is the worst.....20 minutes at 2 volts.....3 volts does nothing quicker as it just gums the comm.....

Later EddieO

Think I could talk you into posting a picture of what you think is a fully broken in brush? I've been breaking mine in for ~5 mins or so from 2.5V to 3V and there is almost a full face of serrations left. I'd like to know from an expert "thumbsup" Thanks.

Oh and if you have an extra brush cutter I'll take it off your hands for you "thumbsup"

 

[EddieO]

Serrations will still be there....thats fine....you are looking for full wear across the entire face of the brush. If you see spots that have yet to make contact or really weird looking wear, then its not fully seated......thats all there is too it.

Later EddieO

 

[whoodie]

Serrations will still be there....thats fine....you are looking for full wear across the entire face of the brush. If you see spots that have yet to make contact or really weird looking wear, then its not fully seated......thats all there is too it.

Later EddieO

Ok, becuse trying to get all of the serrations gone takes forever! Thanks wise one "thumbsup"

 

[EddieO]

Serrations were originally designed to speed up break in with less comm wear, but over time everyone noticed they were simply making the motors make more power.....so pretty much every brush used them in stock or 19t. Not used a lot in mod, but still some....extra power wasn't needed like that, cause you could always increase timing or just drop a wind.

Another thing you guys need to watch out for is not letting the brushes get too short. The shorter they get, the less tension the springs is pushing on the comm, which effects your holding power....I would not less the brush lose more than 1/5th or so before I replaced it.....

Later EddieO

 

[EeePee]

I notice with the big comm motors break in time for the brush is even longer. Seems like most brushes are cut for a 7.5 diameter comm?

Yes Eddie, look for those Fussybrushes already!

 

[EddieO]

Yeah, the big comm stuff will take longer too......brushes are pretty much designed for 7.5mm.....I saw Reedy had some prototypes made for the original KR motor when it first came out with the 9mm comm.....I guess they decided against them because other than breaking in slightly faster, they did nothing else. They were worried customers would buy them and try to use them on a 7.5mm comm.

The 10mm is an accident....when that motor was ordered, Jeff at Fantom told them Large comm, thinking thats what the KR comm was.....turns out the KR 9mm comm is considered the mid size comm....when I first opened my box and pulled apart a motor, I was like uh, wtf is this.....turned out to be a pretty cool mix up.

Later EddieO

 

[rock hard]

4 magnet (technically two pole split magnet) reduces the strength of the magnets. This reduces the torque and saturation point of the motor, but also increases low speed resolution just a touch.

2 magnet has higher torque and lower speed, and a bit better efficiency.


Assuming the flux density of the magnetic material doesn't change, nor any of the other motor components.
__________________

ok here is my question. would this be comparing both magnets from the quad
in this assesmenat.
I understand the idea of the 4 magnet can,the magnets are weaker per magnet.if a single magnet from the quad is put against a single from the dual.
but if you measure strength from both of the north or south pole magnets from the quad. would the strenth still be less than the magnets in the regular can? and if so it cant be by much can it.

I mean you cant take the strength from just one of the north magnets on the quad and compare to the one north on the dual.

 

[JohnRobHolmes]

Let us just compare one can with magnets to the other. The quad mag style is weaker than the dual magnet. There is less volume of magnetic material, and a break in the flux as compared to the solid two mag design. It certainly affects the drag brake, I can tell you that.

 

[rock hard]

I know the rhino was a favorite, it was a kr I believe. the motor from what I have read,heard had no complaints of torque,speed,brake.

now that may be the loss from one[magnets] is replaced by something else.
web,comm,brush.

 

[EddieO]

On a gauss meter, they still measure the same, at least the results Mike Reedy showed me and Big Jim did.......John is correct in his statement its the gap in the flux that causes the loss in drag brake.

The torque loss is kinda weird though.......I think I have a fix for it, but I gotta test it. I am actually almost done with my crawler. I got motor orders tommorrow, then I am playing cards, but Tuesday I am gonna finish it (assuming I find all the parts!).

I have another solution to it anyways, one thats pretty slick.......a trick we used in touring cars. JP tested them for me, along with another driver and had very positive results.

Later EddieO

 

[JohnRobHolmes]

There are three ways I am aware of to combat the flux loss. First is to wind the motor slightly slower, this just increases the torque per amp. Second is to make it a hallbach array, this will direct the flux better and increase the efficiency. Third is to slide a bit of steel in there to direct the flux so that there is no break, a cheap and easy way to get the drag back that I have tried.

 

[scatterbrains]

damn good thread, forgot alot of this stuff LOL

 

[EddieO]

Winding it slower sucks though, as you end up with less overall power....

Hallbach Arrays were tried in racing motors, but they worked terrible.....plus we found out ROAR and IFMAR would not allow them. Would be interesting to try at the slower speeds....

The Steel trick helps, we actually even used that in the racing motors with KR stuff, it helped with efficieny and torque loss, never tested the drag brake back then because we didn't care about it in racing....

There are three other tricks I am working on.....one is with the magnets one is with the arm, the last is with the arm also, which was the trick we used in racing, its done....works, but is doesn't use the 4 mag can anymore.....I have the magnet one almost done, will be testing it shortly....arm one is just a theory and is gonna take a lot to try...

Later EddieO

Later EddieO

 

[JohnRobHolmes]

Cut them arms up Eddie!

 

[EddieO]

Already done on the one I think I posted pics of them a while back in my berg build thread (which is almost done too!).....it's a pain to do right, as the damn laminations split so easy its unreal. Luckily I had tons done up by a machine shop for racing purposes....

The other one is actually machining a new arm itself.....but learning to use the mill and such has been a challenge....mainly because my mentor hasn't been able to devote the time he promised....kinda sucks with the payment on this thing....would love to just make a set of wheels!

Later EddieO

 

[JohnRobHolmes]

Do you have access to an EDM? No worries about delaminating with them.


Machining is a steep curve, but once you learn the materials it becomes a lot easier. The hardest for me was feed and cut rates.

 

[EddieO]

With the right jig its no biggie....I gotta make the jig. The biggest thing too is making it reasonable priced. I remember the first shop I went to wanted $6 an arm to cut.....I was like wow....then of the 100 arms they did, they toasted 20+.....I was like uh yeah....the guy helping me now, actually ended up doing them....he had maybe 1-2 arms toast out of 100....and only charged me $3....some arms are gonna toast no matter what, as the laminations aren't always perfect in the first place....

As for the machine.....well, I am basically starting out at zero. I understand material pretty well, feed rates and such too. Right now its just learning the setup and stuff.....not easy to make sure you don't slam the spindle down....learning the fixtures and stuff too has been a challenge.

Later EddieO

 

[rock hard]

in another thread I asked if you could break a motor in by another source of rotation. so no voltage going through the motor.
eddio brought up a good point,that the motor becomes a generator and makes its own current,which then has no place to go.

I saw this,is this anygood,the way the two are joined does that give the voltage a place to go? or is this still going to be hard on the comm.
http://www.losipartshouse.com/servlet/the-23258/RPM81292-RPM-Motor-Work/Detail

 

[rock hard]

and could you guys touch base on "flat wire winds"