My Comm is black after cutting! RCCA People!!!

[mavrick0611]

ok this is a continuance from my last thread.

OK i went to cut my comm for the second time. i marked it all black with a sharpie set it up and junk and cut it after cutting this is what the comm looked like:
http://albums.photopoint.com/j/View?u=1199481&a=8843154&p=50325873&Sequence=0&res=high
http://albums.photopoint.com/j/View?u=1199481&a=8843154&p=50325872&Sequence=0&res=high

That one black line on top i think i missed. But if you look at the comm the top of it kind like bends outward. Is there a reason it like bends outward?

Any idea why it is cutting the center but missing the center around the slits of the comm?

thanks!
aj

[Grizzbob]

Well, the reason why you still see black on the comm is because it isn't completely trued yet. You'll have to make a few more passes to make it even(just repeat the process for additional cuts, cover the whole comm surface with marker again, & make another pass a bit deeper than the last one, until all the ink is gone). Sometimes it takes a number of passes before the comm is true, it just depends on how many runs you've done with that motor before rebuilding it..... :)

[mavrick0611]

ok kinda understand now, i made like 10 passes with out moving it in or out, should i move it in when i go to re-cut it again?

if it is suppose to be perfectly cyclander shapped why would i have to move it in or out to completly cut it?
Starting to understand electric but cant quit grasp all the little small things
aj

[cck]

The reasons I can think of about your comm being bent outward are:
1. You located the cutting bit too deep before your first cut. Or when you were making your first cut, you pointed the cutting bit to the middle of your comm.(Middle of the comm is always worn out the most) You should rotate the adjustment wheel backward little bit before you make the cut, also you should cut the comm all the way to the end until the bit touches nothing.
2. The drive belt's tension wasn't tight enough.
And one more thing: By looking at your pictures, I think you should adjust your Stop Screw little bit, turn the screw out little bit, I think you did not cut the comm low enough.

[mavrick0611]

ok, when i first desassembled the comm (and before i had a lathe) it was bent out like that, so it may be from use or the factory. i should have mentioned that.

Im going to recut the middle later tonight.
thanks
aj

[Grizzbob]

Yeah, the extra wear in the middle is what brushes do to it, & they can do that within 10 runs. Today's brushes are pretty hard on the comm, that's why the recommendation to true it every 4-8 runs(in other words, about every race day, & change the brushes too).... :)

[WhoKnowsWho]

See, that sharpie trick worked! You can easily see that it isn't trued correctly! :)

[jeepinator]

Be sure you START your cuts on the part of the comm with the largest diameter and then make COMPLETE passes. Make sure the bit traverses the entire width of the comm.
Make many small cuts and be sure to keep lubrication on the comm surface.
Keep making passes until all the ink is gone.
http://colo.theshreves.com/pics/commcut.bmp

[Leet TC3]

Check out the following for tips (and a video!) on comm cutting:
http://www.rcvehicles.about.com/hobbies/rcvehicles/library/rc101/blrc101_cutcomma.htm

[mavrick0611]

ok, cool! i re-cut it last night and it looks great. Maybe a few more cuts and i want need to post a thread :)

Thanks for all the help!
aj

[mavrick0611]

man, i got around to reassebling the motor and it squilled again!!!! and black dust came out from the cooling vents... it was a very clean cut, any one have any explanations or any thing????
aj

[jeepinator]

squilled ?
Heheh, is that some new term I have not heard of ? :D
Do you mean squeal ?

[mavrick0611]

it skreeches and junk,,, well tommarw morning ill take a sound bit and try to post it. Does any one know where and how to post a sound bit?
aj

[mavrick0611]

well i just tried running the motor again, for some reason it sounds normal now, but it has a lower screech. i got a sound clip but were can i post it?
aj

[mavrick0611]

ok i got it on my site, go here: http://rcconceptcreations.homestead.com/commsound.html
and you can here what the motor is doing now. Before i did that, it was REALLY LOUD not even getting up to speed. Now if it acts that way, theres no way i can cut it at the track becuase i cant have my radio on to like "get it fixed" at the track...
aj

[Grizzbob]

I'm not sure about the noise, but I wonder, did you break in the brushes? Also, there's something else you should do when you cut the comm, that seems to help.....right after you finished the cut, take an Exacto blade & scrape out the gunk from those slots between the segments of the comm(there are 3 of them), & then take a ball-point pen & run it along the slots carefully, it helps remove any burrs that can develop & it camphers the slots. Then you can spray the arm with motor cleaner. After that, you're ready to reassemble the motor, install brushes & break them in(for about a minute on 5 volts or less). After all that, see if the noise is still there.... :)

[mavrick0611]

those are new brushes. use about 4 times. i did use the trick with the ball point pin. this is weird... let me look over it tonight. i tried running it again to see how it sounds, every time i go to run it it sound better and better.... wierd huh?
aj

[TC3Racer]

well it takes a couple runs for your brushes to break in. So thats probably why the motor sounds better and better every time you run it.

[mavrick0611]

ok, im in the proccess og cutting the motor like jeepinator said, taking a long time and gradly cutting it to a perfect cylander (or as aclose as possible) i got the lip of that cucker off of it (pictures above) im almost dont cutting as soon as i am ill post a pic and if there is any wierd noises ill post that too.
aj

[mavrick0611]

ok, i got it re-cut but dont know where to post a picture becuase photopoint locked up my account, but go here to see how it looks:
http://y42.photos.yahoo.com/bc/rc_racer_007/vwp?.dir=/car&.src=ph&.dnm=comm.jpg&.view=t&.done=http%3a//y42.photos.yahoo.com/bc/rc_racer_007/lst%3f%26.dir=/car%26.src=ph%26.view=t

does it look right?
aj

[ 06-15-2001: Message edited by: mavrick0611 ]

[ 06-15-2001: Message edited by: mavrick0611 ]

[jeepinator]

Much better at least !
That sound really sounds like a bad bearing to me.
Actually, now that I think about it, it sounds like the bearing is rotating inside the bearing well. Meaning the OUTSIDE of the bearing is spinning. OR it is the arm shaft is turning inside the bearing without the bearing spinning at all.
I am assuming you have lubed the bearings, or they stil have the factory lube in them ...
Take the arm out and put the end without the comm inside each bearing from the outside and the spin it. Inspect closely to be sure the inside race of the bearing is rotating. The wiggle it back and forth to be sure the bearing is seated VERY tightly in the bearing well.

For sure the noise is not because of the comm.

Another important note:
I cannot even tell you how long I played with my bit height before the comms started cutting clean and precise. The Height of the bit is VERY important. More important than anything else. Your comm did not come out very mirror like. Neither do mine, at least not a perfect mirror. But your is really pretty rough. This can be because you have a carbide bit, or because the bit height is off.

I hope this helps !

[Obi112]

Ouch... reminds me of the dentists (except it would probably be a new dentist with really old tools). If the cut was clean, you probably reassembled it wrong. Take it apart and try again, making sure everything is seated properly. Also, make sure you put all the shims back on (check the table where you took it apart to make sure none fell out).

[Leet TC3]

Curious - how high to you set your bit?

I have a Cobra, and they recommend setting the bit height just above the center of the comm. It is better to err on the high side, but never on the low side.

For my setup, I have the bit shimmed all the way to its highest point.

[ 06-16-2001: Message edited by: Leet TC3 ]

[mavrick0611]

jeep, my reedy pulse r motor has buchings and not bearings. Could they be loose or something?

Leet TC3, the lathe im using is a cobra pro 2000. i placed two peices of think paper underneth of the bit. it is slightly above the center but those directions should have pictures with it. it would make things alot eaiser to understand.


also a wierd thing happened last night too with my motor, (what else could happen your thinking). after i cut it i took it outside sprayed the amiture, can, and end bell down with electric motor cleaner. i dred it and rubbed it clean with a towel a few minutes later. after i reassembled the motor the amiture was kinda hard to turn. but i went ahead and hooked it up the the esc and plugged in a 1800 pirrahna pack. i hit the throtle and the motor hardly moved for about 3 seconds then took off acting like normal but when it hardly moved smoke came from the pirahna battery pack.

i took the wrapping off of it and at the bottom of the battery the side of one cell is burnt. Can i still use this pack? or discard it? i really dont want to becuase it was using it to tace with.
aj

[mavrick0611]

the cobra is pretty simple to use. the incstructions **** tho. theyre black and white and stapled together with one staple at the top like a orignal was put through a copier at krogers.

the bit last a good while. if you look at the first pictures at the top of the thread and that new picture i gave a link to, you can see i cut the "lip" off from the top of the comm. Took like a hour to get it fully cut. and the bit is still pretty sharp. iv heard of people sharpening carbon bits.

can any one answer my question about my battery pack? i really want to know if i can still use it.

well im out to run my car after im done tear it back apart and cut the comm again. now its a chore. :(
aj

[Leet TC3]

If you want to spend the long distance money, call Cobra (number is in the instructions) and talk to Chris. He designed their lathes, and he is VERY helpful with any info regarding comm truing and lathing.

Question for you - are you SURE your armature is spinning in the correct direction? When facing it on the comm end, it should spin CLOCKWISE. In order to do this on a Cobra, you will have to reverse wire your slave motor.

That is the only thing I don't like about the Cobra, having to reverse wire the slave motor. You may have trouble using a stock motor (with its advanced timing) as a slave. I ended up having to use an old ONYX 12T, and lowering the voltage to 2v to lessen the RPM.

Chris at Cobra told me a good way to find a good motor to use as a slave - lay it on a hard surface, turn it on using the power supply you will use for the lathe, and see if it vibrates around on the suface. This is how I determined 2 volts was the best voltage for my ONYX slave motor.

[mavrick0611]

man,,, i thought i had just got a good grasp of cutting my comm. i cut it today. reassembled it and it wont move when throttled, only hum really loud and smoke. i dropped in a stock amiture and it turned so there is something up with the amiture. any one have any clues? this is getting ridiculaus
ak

[tc3guy]

Mavrick,
Is the cobra lathe easy to use, because I'm planning on getting one sometime soon. Does anyone know how long does a carbide bit last.