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Old 01-30-2003, 08:53 PM   #1
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Default How many cuts can I get out of a motor?

Approx how many cuts can I expect out of a typical mod motor. I usually have to cut 3 notches deep on my hudy lathe if that helps.

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Martin.
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Old 01-30-2003, 09:09 PM   #2
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i don't quite know what you mean by three nothches but a mod motor can vary in life it depends if every time you skim the com you take off only what you need to come off no more no less use harder compund brushes they can last for a fairly long whyle and agin it can vary depending on wind of the motor and some othor minor factors. i don't know for sure but as a guess a mod motor last's about half the time a stock does but a good plus is that you can reuse the cans a couple of times which can help to save money

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Old 01-30-2003, 09:15 PM   #3
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Thanks for the reply. by 3 notches I mean when I usually coat the comm with marker on the lathe I need to turn in 3 notches to get a clean cut. The notches on the dial arm.

Anyway, is there like an approximate range for the amount of cuts I should be getting out of a motor. 5?10?20? 30? 50? 100?
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Old 01-30-2003, 09:15 PM   #4
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Well I really can't say....that all depends on how much you take off when you cut it.
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Old 01-30-2003, 09:19 PM   #5
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Can you guys just tell me like 10 cuts if I take off a lot and 20 if I take a little off? Just a range not an exact number.
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Old 01-30-2003, 09:22 PM   #6
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man ur putin us under alot of pressure you really can't say because it all depends on the conditions but i can tell you that when the com get's down to about .705-.700 then it's time to buy a new motor

ps i'm talking in centimeters

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Old 01-30-2003, 09:28 PM   #7
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I think the generally accepted minimum diameter is about 0.025 - 0.030 smaller than where it started.

I don't know how much a 'tick' is on the hudy, but just use calipers to measure the diameter (at a place where the brushes WON'T be riding, of course).

I think standard diameter comms are around .295 - .3" or so.
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Old 01-30-2003, 09:34 PM   #8
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Ok, thanks for the help. I guess I will see how much my comm diameter changes afer each cut and figure it out. Its kinda hard without digital calipers so I wanted to ask you guys.
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Old 01-30-2003, 09:44 PM   #9
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The lowest you can go, well, safely, is around .270 or so on the comm. I've seen comms go down to 260ish, so lower, but because each comm is different (and cutting bits are EXPENSIVE!!!!), you might not want to 'race' a motor that is smaller than .270. Now, I'm not saying you CAN'T cut it smaller, but a 'safe' limit is .270.
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Old 01-30-2003, 10:02 PM   #10
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Quote:
Originally posted by rcpilot
Can you guys just tell me like 10 cuts if I take off a lot and 20 if I take a little off? Just a range not an exact number.
Each tick on the hudy is .0003" radius or .0006" on the diameter. So going from .290 to .270 is like 33 cuts. I've verified this with trial cuts. I usually skim it every 2-3 runs. On my MS the other day I went 5-7 runs and it needed 3 skims to get it clear of grooves, and it went from .289 to .288" and this motor already had several cuts on it before, so this arm will last awhile(which is great because its a good one)

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Old 01-30-2003, 10:22 PM   #11
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Default Com Lathe markings

Most Lathes are marked in either .000" or .00mm's. and depending on the lathe, turning the dial one mark will cut twice that amount. So one marking .001" actually cuts .002" from the
Com.
With an average cut being .002" that means about10 cuts from a brand new armature more or less. If you run your motors into the ground, you will have to take more off each time and may only get 3 or 4 cuts.
The proper care and maintenance of a motor is key to getting maximum life and performance.
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Old 01-30-2003, 11:01 PM   #12
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it also depends on how much wear is on the comm. last time i ran on carpet, an 8dbl comm went from .274 to .268 in 2 runs. I think it was .2745 before i trued it on my hudy before its last 2 runs.
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Old 02-01-2003, 06:26 PM   #13
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Thanks for the replies. Much Appreciated.
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Old 02-04-2003, 08:50 PM   #14
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Thumbs up .270 limit

Hi All, nice forums!!

What happens when you start to get down to the .270 limit is the com segments are starting to get very thin and that makes it harder for the electric current to flow through the armature. It is easy to burn right through the com segment. Especially in a hot mod motor.

Also if you try to go much smaller you risk peeling up a com segment and possibly ruining your bit. It will ruin a diamond bit if this happens. Not to mention the copper bits flying off at high speed. Ouch!!!!

See ya,
Rod
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