Cutting a motor commutator & motor tweaks

[Charlie-III]

So after an email to EddieO about the brushes on my Apocalypse 27T type r motor I bought a few years ago he convinced me that I need to cut the comm since I ran through a good 60% of my brushes. I posted here a few years ago about a new Integy super lathe 3 that I bought and was all set to cut my comm when it was needed but a few years went by and I never really used the rig much so the lathe never got used. Of course the idiot in me decided I wouldn't need the lathe so I sold it 3 months ago to a buddy go figure. So here we are at the present and guess what I need a damn lathe again LOL. I hate asking to borrow things so I set off to Ebay and ended up winning a Trinity RC4114 lathe for 21 bucks, is this a good lathe, has me concerned reading binaryterrors post. It is the model that comes with v blocks as well as bearing guides and has maybe made 1 or 2 passes in its life. The seller was awesome and he decided to give me whatever extra arms he had to practice making the cuts before attacking my good brood and Holmes motors. I am a little nervous to try my hand at this and to be honest I never used the Integy because i never had a arm to practice on. I went onto amazon and found some cheap ar4 carbide bits for 1.79 each so I grabbed 5 to practice with, hope they are not crap. I also decided if I am going to be rebuilding i would grab some motor tools, grabbed a hood alignment tool, brush spring nut tool, brush cutter/serrator, extra 10oz laydown springs, extra 766 brushes and a diamond bit for the cuts on my good arms. All this stuff ran me a total of 110 shipped to my door, now I wait impatiently LOL.

So with that here are my few questions that I am not totally sure of. EddieO said to run a stock motor on a 3 cell pack, I have a nip axial 27T motor to use and a computer power supply converted with 3.5v, 5v and 12v for power. I also have a special variable circuit to cut voltage down but it is only rated to 3amps so idk if thats usable but it gives me the option to really dial voltage in if need be. I was thinking that the axial 27T on 3.5v would be good but then was told by other sources that 55T on 12v is the best so what is it. I am also not sure where the best place to start the cut is, do I start at the comm tabs side and work to the end and stop, reset back to the tabs and pass again or do you start at the tabs, work to the end and pass back to the tabs as 1 pass? Also is there an easy way to tell if my bit is square since the lathe is used?

hah revived again 1 year later LOL.

Long but good post on your end.

Bits, since we're cutting copper, the bits last "forever" unless you drop them basically.

Most lathes can do a decent job cutting, making sure the lathe is square (the comm ends up the same diameter from one end to another) is among the biggest things to check.

Cutting speed, there is an RPM on the comm to be cut you want, the voltage required to get that RPM is based on the motor turns driving the lathe. I believe a 27T wants ~3 volts, a higher wind motor wants more voltage to get a higher RPM.
Both should end up at about the same speed at the armature you're cutting. Hope that makes sense.

Cutting, I line the bit up with the comm near the "free end" (away from the windings) and slowly bring the bit in until it contacts the arm in a spot where the brushes DON'T ride.
Move the cutter off the end of the arm, dial it in a couple notches on the feed wheel and start the 1st cut. This goes from the free end towards the windings. It takes ~15 seconds to make one pass, then move the bit back to your starting point taking another ~15 seconds.
Move the bit in a couple of notches on the feed wheel and repeat.
Keep going until you have a clean comm.

 

[EeePee]

Direction in which you cut is based on angle of the bit. The Cobra I've used has the point on the left and I cut to the left (despite what some really early pictures posted in this thread show).

I use a 27 turn motor and 3 cell NiMH battery. Seems about perfect, so use the 3.5 volt output with the Axial motor.

My understanding is that Integy came out with the 55 turn "lathe" motor to be used in conjunction with 12 volts out from a power supply or 12v battery to make it easy for people. Doesn't mean it's right, but it's not wrong either, just different.

I love this thread.

 

[kurtus]

Long but good post on your end.

Bits, since we're cutting copper, the bits last "forever" unless you drop them basically.

Most lathes can do a decent job cutting, making sure the lathe is square (the comm ends up the same diameter from one end to another) is among the biggest things to check.

Cutting speed, there is an RPM on the comm to be cut you want, the voltage required to get that RPM is based on the motor turns driving the lathe. I believe a 27T wants ~3 volts, a higher wind motor wants more voltage to get a higher RPM.
Both should end up at about the same speed at the armature you're cutting. Hope that makes sense.

Cutting, I line the bit up with the comm near the "free end" (away from the windings) and slowly bring the bit in until it contacts the arm in a spot where the brushes DON'T ride.
Move the cutter off the end of the arm, dial it in a couple notches on the feed wheel and start the 1st cut. This goes from the free end towards the windings. It takes ~15 seconds to make one pass, then move the bit back to your starting point taking another ~15 seconds.
Move the bit in a couple of notches on the feed wheel and repeat.
Keep going until you have a clean comm.

Thanks a bunch man"thumbsup". One more question though, what is the best way to measure for squareness and ensuring the bit is at center or a hair above? I have a digital caliper but not sure where to measure. Might come to me when it arrives though what to do there.

 

[EeePee]

I eyeballed the centerline. Paper shims.

Squareness I don't get really. If it's not way out (and how could it be) why would it matter? A fully seated brush is a fully seated brush. Maybe some weird rotational force deflecting the brush up or down, but it's still fully seated.

But to measure for squareness check the left and right side of the comm.

 

[kurtus]

Direction in which you cut is based on angle of the bit. The Cobra I've used has the point on the left and I cut to the left (despite what some really early pictures posted in this thread show).

I use a 27 turn motor and 3 cell NiMH battery. Seems about perfect, so use the 3.5 volt output with the Axial motor.

My understanding is that Integy came out with the 55 turn "lathe" motor to be used in conjunction with 12 volts out from a power supply or 12v battery to make it easy for people. Doesn't mean it's right, but it's not wrong either, just different.

I love this thread.

Mine uses the ar4 bits so I guess its opposite the cobra you have.
These are the bits I bought on amazon to use as practice bits, they are ar4 c2 bits.

Does this get installed so that the flattest unpainted part faces down and the point would be down to the right? Start at the end work my way to the right towards the windings then back to the end again in a 30 second time frame.

Thanks for the confirmation to the axial motor and voltage, Eddie said this is best also so I will listen to the motor gods and do as I'm told;-). Since we are talking motors, I also have a 45t rc4wd motor I am going to use it in the brush cutter I think, any idea what kind of voltage that sucker needs to do a nice brush cuts?

I love this thread u created to, it is just chalked full of valuable information so thanks to you and all its contributors. Now if I can get ahold of the pdf file for jims black book I'll be set but I did find some good info on another site referencing a ton of what was in Jims book. Looking online the paper back version runs $150+, I'm sure there is valuable info ther but damn thats too rich for my blood.

 

[kurtus]

I eyeballed the centerline. Paper shims.

Squareness I don't get really. If it's not way out (and how could it be) why would it matter? A fully seated brush is a fully seated brush. Maybe some weird rotational force deflecting the brush up or down, but it's still fully seated.

But to measure for squareness check the left and right side of the comm.

So if its out I guess its as simple as loosening the bit in the cradle and adjusting a hair to the left or right?

 

[kurtus]

I thought I would post this since I just found it, the motor repair tray he uses in this is bada$$!! I emailed the company to see if they are available but they run 29.99 so no that cheap. Love the idea of keeping everything organized so the springs/brushes dont get mixed up. Also this is the same lathe I just bought so it was helpful for me to see. I think this is a very decent video for an introduction to the world of rebuilding for newbs lol.
<iframe width="560" height="315" src="//www.youtube.com/embed/JPtUucOLH9A" frameborder="0" allowfullscreen></iframe>

 

[EeePee]

I'm not smart enough to answer about the bit direction.

I have a 27 turn in my brush cutter powered by the same 3 cell NiMH pack. I use it to serrate brushes for faster break in.

Here's a Big Jim thread: RC Motor Black Book - HobbyTalk

If it's out and cutting cones it's in the parts that hold the bit and gets cranked, or the part that it rides on. Looks like my Cobra has set screws to adjust both pieces. I don't recall ever adjusting them.

 

[Charlie-III]

So if its out I guess its as simple as loosening the bit in the cradle and adjusting a hair to the left or right?

Adjusting left or right usually is not the issue, it's the up & down relative to the "being cut" armture.

Some lathes have the carbide/diamond on the bottom of the tool, some have it on top, your directions should direct you.

Like EeePee, I eyeballed the up/down setting.

As to having it square, if the comm has a taper, yes, the brush will wear into it (puts a bigger premium on installing the brush the correct direction though....) but can also sideload the brush to the brushhood which may overpower the brush springreducing it's tension against the brush over time.

To check, just do a few cuts on the comm (so you have a good fresh surface at each end of the comm) and measure the diameter at each end. If they are the same diameter, you should be good to go."thumbsup""thumbsup"
If one end is a different size than the other, you may need to loosen mounts on the lathe and slide bits a little so the guides on the tool post are parallel to the armature.

I think mine is at ~0.0003" end to end on the comm diameter.

 

[kurtus]

I'm probably worried about nothing with the alignment seeing how this lathe is basically new, I'll mic the come after my first run......pics to follow cause I know we all like that:mrgreen:.

Maybe I'll just use the 45t on 5v then, think that would be good enough to get the job done on the brushes.

Anyone else know about the bit. looks like there are 2 ways this could be installed, either that large flat surface facing down or on the side so the smaller edge faces down and the large flat would face towards the windings if that makes sense?

Great info guys, keep it coming;-)

 

[TEDROCKZ]

Your bit for that lathe will install like this...


This it on a Twister lathe which is the same motion as the Trinity.

 

[kurtus]

Your bit for that lathe will install like this...
View attachment 262490

This it on a Twister lathe which is the same motion as the Trinity.

My HERO"thumbsup" Thx buddy

 

[kurtus]

I about $hit when I saw this.........




This is a 35t torquemaster pro I sold a buddy a few years ago that he brought into work today to show me. It was ran in his ax10 with stk gearing on 3s, I have never seen one this bad. Sorry John, this sucker is garbage now.....all that hard work

the more I look at this I'm starting to wonder if he reverse wired it and had it at -9 degrees timing, how the hell else could this happen??

 

[SINister]

I've cut worse looking coms. He can always use it as a backup or basher motor if you end up having to take to much off.

 

[EGRESSor]

[/URL]

this sucker is garbage now.....all that hard work

Rebuiding A DC Motor Commutator

great fun ;-)

 

[kurtus]

Rebuiding A DC Motor Commutator

great fun ;-)

Whoa now, thats a great find. I was wondering if there might be a way to do that. Trick here is to find a 10mm od copper piece of pipe to do the same. Looks like a challenge for sure"thumbsup". Clever

 

[Jcplante]

Whoa now, thats a great find. I was wondering if there might be a way to do that. Trick here is to find a 10mm od copper piece of pipe to do the same. Looks like a challenge for sure"thumbsup". Clever

If you draw me a sketch of exactly what you need i could prob make it no prob. If its just a short 10mm od tube i can hook you up for nothing.


Sent from my iPhone using Tapatalk

 

[kurtus]

If you draw me a sketch of exactly what you need i could prob make it no prob. If its just a short 10mm od tube i can hook you up for nothing.


Sent from my iPhone using Tapatalk

Nice, thanks for offering that up for me. I'll grab the arm from my buddy and see if I can get the needed dimensions for it. It would be fairly straight forward but I think the id is actually going to be more important in this case since I can lathe it down. Maybe John or Eddie might know whats needed?? Thanks "thumbsup"

 

[kurtus]

EGRESSor, would I need it to have those segments on the comm or is a solid copper ring ok?

 

[Charlie-III]

EGRESSor, would I need it to have those segments on the comm or is a solid copper ring ok?

When finished, you need it to be segments, each one is connected to a winding/pole. A 3 pole motor has 3 segments, a 5 pole motor has 5 segments.