RCCrawler Forums

lksyotas · 09-09-2009, 07:22 PM

Hello everyone. First off - please excuse the long post but I want to give an acurate history of my motor issue.

I recently built a new crawler with Bully axles. I selected two high quality 45T brushed motors to compliment the axles. I built the crawler and have about 3 hours of total run time on the axles and motors. I started to have an issue with the rear axle not turning while trying to use the rear dig. In a straight line it appeared to function fine. But when I tried to engage the rear axle from a stop in a dig it wouldn't move. So I began to trouble shoot. I discovered that the rear motor would not power the axle from a stop but if the front wheels were trying to turn the rear axle the motor would power up. I decided to reverse the motors front and rear thinking something was up with my Punk Dig. When I installed the "rear" motor on the front axle now the problem was the same in the front axle. So I removed both motors from the axles and laid them side by side. When applying throttle with my controller slowly the "bad" motor would not spin unless I helped it by rotating the motor shaft by hand slightly.

Knowing that I have a problem with this particular motor I decided to contact the vendor that I purchased it from. He sugested I do a tear down on the motor and clean the components to look for debris or broken parts or loose washers stuck in the guts. I removed the endbell and removed the armature/ shaft assembly. The internals were dusty but not in to bad of shape. I cleaned all the internals with electric motor cleaning spray. The commutator has normal wear and appears to be in good condition although I think I'll still clean it up a bit on my lathe. The brushes are still in good condition with light/ normal wear from what I can tell - ends of the brushes have a slight blackening rest is like new. The stator and windings appear to be in good order and the magnets in the can are strong as ever. The washers on both ends of the shaft were placed correctly insuring that the armature assembly was centered in its magnetic field and the bearings both still turn free with no grit. Not finding anything out of the norm I reassembled it and made sure the timing was set at zero.

Hooked the connectors of both motors back up and same problem still persists. It takes a bit of forward or reverse movement of the motor shaft to get the motor running under throttle. Once it is running it has a skip here and there in its rpm range up to full throttle. The skip is not consistent and happens at different rpms at different times.

The vendor is sending me new brushes but I'm not sold on that is the issue. If I can't fix it I'm hoping he will offer me a replacement but that between us for now.

So do any of you electrical gurus have any good advise or ideas of what I should try next? I'm pretty much at my limit on knowledge on these motors and need help getting it running properly again! Thanks for any input and sorry again for the long winded post...! :?

lt1zwb96 · 09-09-2009, 07:43 PM

You will need a new arm to repair this.

lksyotas · 09-09-2009, 07:56 PM

Quote:

Originally Posted by lt1zwb96

You will need a new arm to repair this.

Thanks for the response - could you elaborate on the reasoning? I'm trying to learn as much as possible on these motors - I come from a long line of Nitro powered vehicles - Electric is rather new... Thanks!

robbio4422 · 09-09-2009, 08:08 PM

had the EXACT same issue with my brand new motor... pm sent

microgoat · 09-09-2009, 08:15 PM

It's possible that one segment of the arm is burnt out/shorted, or the comm is far enough out of round (Integy's are notorious for this) that the brushes don't make contact. If you have a comm lathe, color the whole comm with a Sharpie and spin it up. Skim off til all the ink is gone.

Got any pics? Preferably clear close-ups.

lksyotas · 09-09-2009, 08:19 PM

Quote:

Originally Posted by robbio4422

had the EXACT same issue with my brand new motor... pm sent

PM responded to. Sorry to hear about your ordeal too. Sucks when we spend the extra $$ to buy a high quality motor only to have it act up.

I know even the best of products have issues now and then so I hope I can get this motor back up and running or at least get a new components or an entire motor to fix it. The other motor runs very smooth and is very powerfull. I'm running them on a 3S lipo and the crawler hauls when at full tilt boogie but has awesome slow speed throttle response...

lt1zwb96 · 09-09-2009, 08:20 PM

It is a comm segment bad and there is no way to repair it with out the tools to build your own arms. If it is new you might get them to replace it, if not just trash it and buy a new one and save the headache of worring about it.

lksyotas · 09-09-2009, 08:40 PM

Quote:

Originally Posted by lt1zwb96

It is a comm segment bad and there is no way to repair it with out the tools to build your own arms. If it is new you might get them to replace it, if not just trash it and buy a new one and save the headache of worring about it.

So if I understand correctly. With a bad comm section, the current cannot flow through that particular comm segment into the armature windings. This would create a dead spot aprox. 120 degrees as there are three segments in the comm assembly. So basically holding the remaining two comms in place because it needs the third to repell the magnetic flux from the field magnets in the can during the energizing phase. Forgive me for incorrect terminology but I'm just trying to get these motors down...

skid plate · 09-10-2009, 06:50 AM

Here is something that happens more often with motors.

Carefully pull on the brush leads and see if one or both of the brushes in the motor are draging in the holder. Even a tiny bit will bind the brush enough to keep it from coming in contact with the comm when the motor gets warm after running for a short time. Sometimes even on a new motor as well.

I have had this happen to me a couple of times. I solved this by lightly removing brush material, (very lightly), from the sides of the brushes the full length and reinserting them. Recheck them for binding.

Hope this helps.

JC

lksyotas · 09-10-2009, 02:04 PM

Quote:

Originally Posted by skid plate

Here is something that happens more often with motors.

Carefully pull on the brush leads and see if one or both of the brushes in the motor are draging in the holder. Even a tiny bit will bind the brush enough to keep it from coming in contact with the comm when the motor gets warm after running for a short time. Sometimes even on a new motor as well.

I have had this happen to me a couple of times. I solved this by lightly removing brush material, (very lightly), from the sides of the brushes the full length and reinserting them. Recheck them for binding.

Hope this helps.

JC

Cool! I'll check it out - thanks for the tip JC!

lksyotas · 09-11-2009, 06:04 AM

Well the brushes move freely in the hood on both sides. No hang ups at all. Is there a way to check the resistance over each segment to determine that it is the Armature assembly that is the culprit? I figured I could check the resistance from one comm to the next and if there is a difference in any of the three then the problem might lie in the stator windings.

Ty-bo · 09-12-2009, 01:29 PM

the easiest way to tell if the arm is good or bad is to just check for continuity between all pads of the comm

lksyotas · 09-12-2009, 01:39 PM

Quote:

Originally Posted by Ty-bo

the easiest way to tell if the arm is good or bad is to just check for continuity between all pads of the comm

Did this and found that between comm 1-2 = 2.5 ohms, 2-3 = 2.5 ohms, and 3-1 = 1.0 ohms. So I believe I have found the problem. Is it strange or normal for an armature assembly to have this happen with light use as I have done?

JohnRobHolmes · 09-12-2009, 05:10 PM

When I have motors with that problem, it is generally a burned and pitted comm that is preventing proper operation.

The root cause is zero timing, and this is why it is so common for crawler motors.

The issues that interact with zero timing-
Magnet placement
hood alignment
brush fitment

The ONLY way to guarantee against this problem is to run your motors with a bit of forward timing and do not slam on the brakes too hard. If any of the interacting factors are off by even a millimeter it can cause arcing and comm pitting. I time all of my motors to zero with an ampmeter to help guard from this problem, but it is a problem that will always plague brushed motors with zero timing and three slot armatures.

You will find this problem with all three slot crawler motors unfortunately, no matter what the quality or brand name. Handwound or machine wound, $20 or $60, the construction factors and zero timing just make it happen.

I suggest you cut the comm down and add a bit of forward timing.

Ty-bo · 09-12-2009, 06:10 PM

I agree with the timing issue. I also agree to cutting the com. I would colour the com with a marker then just cut enough off to get rid of all the marker, then replace the brushes. If still the motor does not function up to par all it has cost you is some of your time to cut the com and $5 for brushes.

lksyotas · 09-12-2009, 07:25 PM

John,
How do I go about setting the timing to a true zero using a multimeter? Thanks,

Also, the vendor I purchased the motor from is sending me new brushes. I'll turn the comm Monday and then set the timing as specified. Thanks for all the help guys. I'll report back when I have results from my medling with this motor...

Quote:

Originally Posted by JohnRobHolmes

When I have motors with that problem, it is generally a burned and pitted comm that is preventing proper operation.

The root cause is zero timing, and this is why it is so common for crawler motors.

The issues that interact with zero timing-
Magnet placement
hood alignment
brush fitment

The ONLY way to guarantee against this problem is to run your motors with a bit of forward timing and do not slam on the brakes too hard. If any of the interacting factors are off by even a millimeter it can cause arcing and comm pitting. I time all of my motors to zero with an ampmeter to help guard from this problem, but it is a problem that will always plague brushed motors with zero timing and three slot armatures.

You will find this problem with all three slot crawler motors unfortunately, no matter what the quality or brand name. Handwound or machine wound, $20 or $60, the construction factors and zero timing just make it happen.

I suggest you cut the comm down and add a bit of forward timing.

JohnRobHolmes · 09-13-2009, 06:56 AM

Loosen the endbell and put low voltage to the motor (3v is easy to work with if you have it), rotate the endbell just a bit back and forth until the amp draw is lowest. Retighten.

If you put the voltage to the motor in the polarity that you will use it, it will be most accurate. I have found that our 540 motors will have different zero timing if you reverse the voltage.

JohnRobHolmes · 09-13-2009, 07:00 AM

more reading Caring for your new Brushed motor

lksyotas · 09-13-2009, 05:30 PM

Thanks for the link John, I've actually read that before but must have skipped the part where you describe using the ampmeter. Anyway, your info you posted in the links were very helpful and I learned most of what I know to date from them. Thanks for all the support!

Quote:

Originally Posted by JohnRobHolmes

more reading Caring for your new Brushed motor

53 willys · 09-13-2009, 06:17 PM

JRH will you PM me PLEASE...I just got 3 batterys on my 40t's and the rear motor is BURNT...it's completly dead..and the 35t I sent you for rebuild was dead on arivail

what the heck am I doing wrong here?????

09-09-2009, 07:22 PM	#1
lksyotas Newbie Join Date: Apr 2007 Location: Southern Tier, NY Posts: 38	Help! Like new brushed motor not working correctly... Hello everyone. First off - please excuse the long post but I want to give an acurate history of my motor issue. I recently built a new crawler with Bully axles. I selected two high quality 45T brushed motors to compliment the axles. I built the crawler and have about 3 hours of total run time on the axles and motors. I started to have an issue with the rear axle not turning while trying to use the rear dig. In a straight line it appeared to function fine. But when I tried to engage the rear axle from a stop in a dig it wouldn't move. So I began to trouble shoot. I discovered that the rear motor would not power the axle from a stop but if the front wheels were trying to turn the rear axle the motor would power up. I decided to reverse the motors front and rear thinking something was up with my Punk Dig. When I installed the "rear" motor on the front axle now the problem was the same in the front axle. So I removed both motors from the axles and laid them side by side. When applying throttle with my controller slowly the "bad" motor would not spin unless I helped it by rotating the motor shaft by hand slightly. Knowing that I have a problem with this particular motor I decided to contact the vendor that I purchased it from. He sugested I do a tear down on the motor and clean the components to look for debris or broken parts or loose washers stuck in the guts. I removed the endbell and removed the armature/ shaft assembly. The internals were dusty but not in to bad of shape. I cleaned all the internals with electric motor cleaning spray. The commutator has normal wear and appears to be in good condition although I think I'll still clean it up a bit on my lathe. The brushes are still in good condition with light/ normal wear from what I can tell - ends of the brushes have a slight blackening rest is like new. The stator and windings appear to be in good order and the magnets in the can are strong as ever. The washers on both ends of the shaft were placed correctly insuring that the armature assembly was centered in its magnetic field and the bearings both still turn free with no grit. Not finding anything out of the norm I reassembled it and made sure the timing was set at zero. Hooked the connectors of both motors back up and same problem still persists. It takes a bit of forward or reverse movement of the motor shaft to get the motor running under throttle. Once it is running it has a skip here and there in its rpm range up to full throttle. The skip is not consistent and happens at different rpms at different times. The vendor is sending me new brushes but I'm not sold on that is the issue. If I can't fix it I'm hoping he will offer me a replacement but that between us for now. So do any of you electrical gurus have any good advise or ideas of what I should try next? I'm pretty much at my limit on knowledge on these motors and need help getting it running properly again! Thanks for any input and sorry again for the long winded post...! :?

09-09-2009, 07:43 PM	#2
lt1zwb96 Rock Stacker Join Date: Jun 2009 Location: Mesquite Posts: 75	You will need a new arm to repair this.

09-09-2009, 08:08 PM	#4
robbio4422 Rock Crawler Join Date: Nov 2008 Location: kansas city Posts: 692	had the EXACT same issue with my brand new motor... pm sent

09-09-2009, 08:15 PM	#5
microgoat I wanna be Dave Join Date: Feb 2005 Location: Cleveland, OH Posts: 8,009	It's possible that one segment of the arm is burnt out/shorted, or the comm is far enough out of round (Integy's are notorious for this) that the brushes don't make contact. If you have a comm lathe, color the whole comm with a Sharpie and spin it up. Skim off til all the ink is gone. Got any pics? Preferably clear close-ups.

09-09-2009, 08:20 PM	#7
lt1zwb96 Rock Stacker Join Date: Jun 2009 Location: Mesquite Posts: 75	It is a comm segment bad and there is no way to repair it with out the tools to build your own arms. If it is new you might get them to replace it, if not just trash it and buy a new one and save the headache of worring about it.

09-10-2009, 06:50 AM	#9
skid plate RCC Addict Join Date: Dec 2007 Location: Chuck Chuck Chuckin Rocks. Posts: 1,224	Here is something that happens more often with motors. Carefully pull on the brush leads and see if one or both of the brushes in the motor are draging in the holder. Even a tiny bit will bind the brush enough to keep it from coming in contact with the comm when the motor gets warm after running for a short time. Sometimes even on a new motor as well. I have had this happen to me a couple of times. I solved this by lightly removing brush material, (very lightly), from the sides of the brushes the full length and reinserting them. Recheck them for binding. Hope this helps. JC

09-11-2009, 06:04 AM	#11
lksyotas Newbie Join Date: Apr 2007 Location: Southern Tier, NY Posts: 38	Well the brushes move freely in the hood on both sides. No hang ups at all. Is there a way to check the resistance over each segment to determine that it is the Armature assembly that is the culprit? I figured I could check the resistance from one comm to the next and if there is a difference in any of the three then the problem might lie in the stator windings.

09-12-2009, 01:29 PM	#12
Ty-bo Newbie Join Date: May 2006 Location: Edmonton, Alberta Canada Posts: 40	the easiest way to tell if the arm is good or bad is to just check for continuity between all pads of the comm

09-12-2009, 05:10 PM	#14
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	When I have motors with that problem, it is generally a burned and pitted comm that is preventing proper operation. The root cause is zero timing, and this is why it is so common for crawler motors. The issues that interact with zero timing- Magnet placement hood alignment brush fitment The ONLY way to guarantee against this problem is to run your motors with a bit of forward timing and do not slam on the brakes too hard. If any of the interacting factors are off by even a millimeter it can cause arcing and comm pitting. I time all of my motors to zero with an ampmeter to help guard from this problem, but it is a problem that will always plague brushed motors with zero timing and three slot armatures. You will find this problem with all three slot crawler motors unfortunately, no matter what the quality or brand name. Handwound or machine wound, $20 or $60, the construction factors and zero timing just make it happen. I suggest you cut the comm down and add a bit of forward timing.

09-12-2009, 06:10 PM	#15
Ty-bo Newbie Join Date: May 2006 Location: Edmonton, Alberta Canada Posts: 40	I agree with the timing issue. I also agree to cutting the com. I would colour the com with a marker then just cut enough off to get rid of all the marker, then replace the brushes. If still the motor does not function up to par all it has cost you is some of your time to cut the com and $5 for brushes.

09-13-2009, 06:56 AM	#17
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	Loosen the endbell and put low voltage to the motor (3v is easy to work with if you have it), rotate the endbell just a bit back and forth until the amp draw is lowest. Retighten. If you put the voltage to the motor in the polarity that you will use it, it will be most accurate. I have found that our 540 motors will have different zero timing if you reverse the voltage.

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09-13-2009, 07:00 AM	#18
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	more reading Caring for your new Brushed motor

09-13-2009, 06:17 PM	#20
53 willys I wanna be Dave Join Date: Jan 2009 Location: laying low Posts: 2,508	JRH will you PM me PLEASE...I just got 3 batterys on my 40t's and the rear motor is BURNT...it's completly dead..and the 35t I sent you for rebuild was dead on arivail what the heck am I doing wrong here?????

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