mrG
Rock Crawler
So what exactly shorts with a heat short and what exactly stalls with a stalled armature?
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Cutting a motor commutator & motor tweaks
- Thread starter EeePee
- Start date
EddieO
I wanna be Dave
Heat shorts are just that....a short that happens with heat. Typically its the insulation of the wire gets hot enough in a spot where the wires can then touch....short happens. Arm cools down, insulation hardens stopping the short. Run it again, and it repeats. They are nearly impossible to find when you rip the armature apart as it often pulls the wire apart and you can't tell if it was epoxy or the shorted area...sometimes depending where the short is, the motor will still run, just badly and really hot....which often leads to a full meltdown.
A stalled arm is something that I coined a while back as we got into crawling, we never really saw these in racing. It for all intents is a shorted armature as well, but there is no direct thing to point a finger at let alone knowing 100% what causes it, my guess excessive amp draw, but not all stalled arms were exposed to excessive amp draw.
Basically, its when the arm needs to a push to go, and works fine until you stop typically. Then needs a push to go. It kinda mimicks a hung brush, which makes it a pain in the ass to spot sometimes, as a hung brush often just needs a quick comm cut and brushes, problem solved. A stalled armature there is no fix, just need a new arm. Problem is, a rebuild often shows NO problems on the bench, even the dyno shows no issues....but as soon as its back in the truck the ugly problem rears its head again.
Its to the point, when a motor comes in for a rebuild....if in any way I suspect a stalled arm from the symptoms, I run a whole extra set of tests. Lately my meters have been pretty good at picking them up, but not always...the big issue still is customers not telling me known problems, so I don't always catch them during a rebuild....then I end up the asshole when I send it back thinking its fixed.
Later EddieO
A stalled arm is something that I coined a while back as we got into crawling, we never really saw these in racing. It for all intents is a shorted armature as well, but there is no direct thing to point a finger at let alone knowing 100% what causes it, my guess excessive amp draw, but not all stalled arms were exposed to excessive amp draw.
Basically, its when the arm needs to a push to go, and works fine until you stop typically. Then needs a push to go. It kinda mimicks a hung brush, which makes it a pain in the ass to spot sometimes, as a hung brush often just needs a quick comm cut and brushes, problem solved. A stalled armature there is no fix, just need a new arm. Problem is, a rebuild often shows NO problems on the bench, even the dyno shows no issues....but as soon as its back in the truck the ugly problem rears its head again.
Its to the point, when a motor comes in for a rebuild....if in any way I suspect a stalled arm from the symptoms, I run a whole extra set of tests. Lately my meters have been pretty good at picking them up, but not always...the big issue still is customers not telling me known problems, so I don't always catch them during a rebuild....then I end up the asshole when I send it back thinking its fixed.
Later EddieO
Like you're not used to that by now?
mrG
Rock Crawler
So I advance the timing on my 2 motor in my xr. To get the rpm the same the amps are different by about .25 amps. Whats the deal? When I drive I can tell that the front motor (it's the one that has the lower amp draw) has less torque than the rear. I'm going to adjust the timing so the amp draw is the same.
I recently rebuilt my first motor with the motivation from Eddie. It was a Chaos R 35t. The brushes I had were a bit soft and ended up gumming up my comm after long trail runs. We typically run 3-4 hours with a mix of trail and rock crawling. Pace is a fast walk when we're on the trail.
I cut the comm and then installed new harder brushes that I got from Eddie. Then I broke the motor in at low voltage for several minutes and cleaned it good. Anyway, the motor ran excellent and I'm very happy. The brushes are definitely harder and I installed firmer springs. I'm pretty sure the comm will wear out much faster, but I'm willing to deal with that and buy another motor from Eddie when that time comes.
So, thanks to Eddie for great service and support on his products.
I cut the comm and then installed new harder brushes that I got from Eddie. Then I broke the motor in at low voltage for several minutes and cleaned it good. Anyway, the motor ran excellent and I'm very happy. The brushes are definitely harder and I installed firmer springs. I'm pretty sure the comm will wear out much faster, but I'm willing to deal with that and buy another motor from Eddie when that time comes.
So, thanks to Eddie for great service and support on his products.
cherokee95
Quarry Creeper
Can't let this thread die!
Bought the Cobra a couple years ago when I first read this thread, it came with the brush cutter. Picked up the Hudy from a local racer for $30 about a week ago.
I have a fussy brush set coming from John and just placed an order with Eddie last night for brushes, springs, bearings and some tools. Going to town today to get some small wire to rewire the switch on the Hudy.
Should be throwing copper in a few hours, pics of carnage to come I'm sure :lmao:.
Bought the Cobra a couple years ago when I first read this thread, it came with the brush cutter. Picked up the Hudy from a local racer for $30 about a week ago.
I have a fussy brush set coming from John and just placed an order with Eddie last night for brushes, springs, bearings and some tools. Going to town today to get some small wire to rewire the switch on the Hudy.
Should be throwing copper in a few hours, pics of carnage to come I'm sure :lmao:.
TEDROCKZ
I wanna be Dave
You still got the borrowed one? Or did you think one would get lonely in the RC closet(along with all the other untouched in a long while RCs)?
step child
Pebble Pounder
Wanting to try my hand on a lathe but not sure which one I should look for, I run both 540 and 550 size motors. Are all lathes able to fit both? Did some looking and this is the one I could find Xipp Perfect Lathe 2 for 130-550 Size Armatures w/ Drive Motor & Carbide V-Block for R/C or RC - Team Integy. From what I have read it is an ok brand that need a little set-up. With the price of the Hudy I would be looking for a used one.
Thanks John
Thanks John
cherokee95
Quarry Creeper
Hudy will take a 550. Just look for a used one and put the extra money towards motor parts or a good motor from Brood or Holmes.
EddieO
I wanna be Dave
If you plan on cutting 550 arms, that integy is one of the few choices. Many of of the other lathes are not adjustable for a 550....or are a pain in the ass to adjust a 550
Later EddieO
Later EddieO
step child
Pebble Pounder
I'll look around for a Hudy and think on the Integy, and you know what 550 I'm going to be working on Eddie ;-).....
cherokee95
Quarry Creeper
Ancient Integy 55t that has seen better days.
After so many passes to get it round I lost count lol. Not really sure on the finish, this is the first arm I've ever cut. Running at 4.8 volts, thinking maybe slow it down a little to 2.5-3v. I'm running off my Icharger so it's 100% variable.
suggestions or criticism strongly advised.
After so many passes to get it round I lost count lol. Not really sure on the finish, this is the first arm I've ever cut. Running at 4.8 volts, thinking maybe slow it down a little to 2.5-3v. I'm running off my Icharger so it's 100% variable.
suggestions or criticism strongly advised.
cherokee95
Quarry Creeper
Any recommendations for a bearing puller?
killswitch
RCC Addict
Looks like maybe a not so sharp carbide bit and a deep cut. I tend to not get chips or curly q's either, but a dusting like EeePee. Only time I've ever seen curly q's come off a comm lathe was watching a hack at a carpet race take a quarter of the comm in one pass LOL. As for your voltage question, it really depends on what your lathe motor is... A hotter motor is going to require less voltage than say a 55t.
killswitch
RCC Addict
All I can think of now is the Goonies... "Copper pubes." ... "That's what I said, curly q's"
