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AMD FB1-4001 motor failure

18K views 44 replies 16 participants last post by  SandRailEV 
#1 ·
The AMD FB1-4001 motor in our Chevy S-10 conversion has developed a serious problem. Since the installation of the motor in August 2011, the truck has been driven about 300 miles at low and medium speeds. All seemed fine until yesterday it suddenly began to lose power and then stopped entirely. After it was towed in I did some troubleshooting and found that the motor would not turn unloaded with 12v applied.

I pulled the headband off and observed that the outer set of brushes (closest to the end of the motor) were all perched up in their holders with the springs pressing against their sides (holding them up off the commutator). The inner set of brushes were seated normally but all showed signs of discoloration where the braided wires meet the carbon block, and on one of them the wires were burned completely off the carbon block! That brush's spring is also damaged from heat.

I seated the outer brushes down into their holders with the springs on top and now the motor turned with 12v applied, but it made a lot more noise that before. I rotated the shaft by hand while watching the commutator surface - at one point there is a shiny wedge of something thin (insulation sheet) coming out from between two of the metal contact strips - I believe that's what is making the noise as the outer brushes ride over it.

I've posted photos of my project on Flickr. The last few photos show the motor damage.

http://www.flickr.com/photos/32025136@N03/sets/72157627254806189/

As I mentioned, the overheating seems to be concentrated on the rear brushes.

My guess as to the sequence of events would be:

1. While driving the strange thing (marked in the top brushes photo) comes out from between two bars on the commutator.
2. The now-irregular surface makes the front brushes bounce up and get stuck with their springs on their sides.
3. The rear brushes now have to carry all the current and they overheat until all are stressed and one completely fails.

The motor dealer and manufacturer are so far unwilling to accept this sequence of events. They keep coming back to the idea that the motor has been abused or overloaded. They offer to "look at it" - but that involves removing it from the truck and shipping it back to them at my cost (~$150). I asked the dealer for a candid assessment of the chances of getting a warranty repair or replacement and he said it was a crap shoot.



I disagree - what do you think?

This is a very ordinary S10 conversion using components called out in many parts lists. The controller is a Curtis 1231C. The power source is a set of 24 Trojan T-125 6v batteries for 144v total. My simplified schematic is also posted in the Flickr set.

The driving has been on both town and country roads at speeds 25-50 MPH. The day that the motor stranded me I'd been driving 15 minutes at about 30-40 MPH, then stopped at the hardware store for about ten minutes, then headed back to the office at somewhat higher speed (different road max 50 MPH) for about 10 minutes when it died. I've driven the truck on that same errand routine at least 6 six or eight times without any issues.

The tires are the stock P215/75R15 and inflated to the sidewall pressure, so they are 27 inches in diameter. The rear-end is the stock unit with a gear ratio of 3.73. The transmission is the stock manual five-speed "New Venture" NV1500 unit . Gear ratios in the NV1500 are 3.94, 2.37, 1.49, 1.00, and 0.830. An online RPM calculator shows that at the time of the failure the motor would have been turning at 3320 rpm - that seems pretty normal. And the truck was carrying no cargo so there was no load beyond the weight of the converted vehicle.

Thanks guys for any insights you can provide... if I am doing something wrong, I need to learn how to avoid it in the future. And if I am not, then I've learned that the motor manufacturer's warranty is not worth much.


Steve


 
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#2 ·
Did you break in the brushes before driving it? I have the same motor, and its 14 years old and has over 10,000 miles on it and driving fine. I break in the brushed on 12 volts for about 2-3 hours when I first installed it, and I plan on doing the same thing once it goes into my new EV.

Was your timing advanced in the correct direction?
 
#3 ·
Thank you for the response. Break-in? - I ran the motor for two hours on a 12 volt battery and charger combination. Timing advanced? - The specsheet that came with the motor said it was ready for use in either direction with no adjustment. When the dealer asked the manufacturer about this point he was told the motor was to be used as set-up from the factory no matter what the rotational direction.

Steve
 
#5 ·
Thank you for your response. The motor was shipped to me in a crate from the dealer and I installed it on the vehicle. No one else touched it. I never had the headband off before the failure but I looked through the vent holes and saw that all the brushes were in the same position on the commutator. So all eight were originally down and operating.

I disassembled the front of the motor and removed the brushes and holders. I can now see that the front four brushes have wear marks on their leading edges that are the same shape as the protruding piece of insulation. So clearly they were indeed down on the commutator - how else could they get that shape worn into them? I know it sounds surprising but the must have jumped up - they were down under the springs when I installed the motor, and then after it failed I found them up with the springs pressing on their sides.

Steve
 
#6 ·
Let me clarify regarding the motor timing: I did not advance the timing - the motor already came that way.

I have not made any change in the position of the brushes relative to the rest of the motor - it is in the same state as when it arrived and I installed it. I ordered the motor for electric vehicle use at this voltage. The information that came with the motor says it is "designed to operate in CCW rotation for forward vehicle motion." I wired it per the drawing for CCW rotation and that is what I got.

As shipped from the manufacturer the brushes are already in an advanced timing position. They are off the line of the pole piece bolts, shifted in the anti-rotation direction.

Steve
 
#7 ·
I do not have photos of the brushes in the up position because I put them back down right away to test the motor on 12v. I didn't imagine such a basic observation would be disbelieved.

When I installed the motor I saw thru the vents all eight brushes in the down position. After the failure I removed the headband and found the front ones in the up position. That's the facts of the situation.

Steve
 
#8 ·
...When I installed the motor I saw thru the vents all eight brushes in the down position. After the failure I removed the headband and found the front ones in the up position. That's the facts of the situation.

Steve
If thems the facts of the situation then you over-heated the motor and/or over-sped it. A comm bar lifted up and whacked the brushes so hard they were flung up into the servicing position. This isn't an installation failure, it's an operational failure. Do you often drive around in the higher gears so that motor RPM is relatively low?
 
#9 ·
It looks like the over-speed happened first. It isn't difficult to over-speed an unloaded motor.

The burning happened after the over-speed as shown by clean commutator under the lifted brush positions.

If it were mine, I'd see what a new armature and brush plate assembly with brushes would cost.

If you pull the motor and take it apart, you'll likely find that the commutator is no longer round.
Those strange bits you pointed out are mica insulation that lives between the commutator segments.
Did you find a some stuff that looked like "fish scale" in the motor vent area?
That would have been more of the mica that was thrown out from between the commutator segments.

You aren't the first to over-speed an armature...

Some of the newer controllers, such as the Soliton Jr can limit rpm's if mated with a sensor.
 
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#10 ·
No but the first I have ever heard of the 4 front brushes being flung into the service position. Hard to believe that one....
Not so hard to believe... Just the front end of the comm bar could have lifted. Of course I'm just speculating here - not unlike yourself - but in any case why would the OP remark on the brushes being in the service position if he had put them there himself??? That makes no sense.
 
#12 ·
i could see this mode of failure. Something caused that mica stuff to rise up from between the comm bars. Overspeed? perhaps it was like that from the manufacturer?

Once that piece is sticking up, it kicked the front 4 brushes up. The others are now doing twice the work, and eventually overheat.

Your setup doesn't sound unique, a 9" motor in an S-10 with transmission and Curtis 1231 is probably about the most common conversion out there, right? Certainly not a case of poor component choice.

Is there any chance you ever overspeeded the motor? Ever try pulling out of the garage thinking you were in reverse, but were really in neutral? (I've done that a few times...). An unloaded motor spins up REAL quickly.

Isn't it at least 'possible' that whatever is sticking up between the comm bars was there from the beginning, and it's been running on 4 brushes till now?
 
#16 ·
I wonder if the brush holder came apart in your bottom brush position, causing part of its metal frame to contact the connection between the com bars and the arm winding(s). Was it touching when you first looked at it? If this was the case, it would cause all kinds of hell to break loose, arcing and overheating-wise.
 
#17 ·
Interesting thought, "electro-wrks" - I can't say it had touched but it was somewhat deformed.

gottdi wrote:

>With that mica bit protruding you should not just run the motor.
Huh? Who would do that? I trimmed it away with a razor.

>When pushing the brush from beneath, you can't push it out like
>you can pull it out. The spring pressure and position won't allow that.

Thanks for the video demo. The dimensions of the holder, brushes, and springs are different in my motor.
You mentioned the small bit of insulation being too small to kick the brushes up. The insulation is only
protruding a small bit after the failure. I feel confident that it was a big "flap" when it started, and
after the passes of the brushes it was be worn down to the nub we see now.

The worn out areas on the front brushes are larger, but the same shape as the protruding insulation,
further supporting the idea that the protrusion was larger at first.

Steve


Steve
 
#18 ·
I really appreciate everyone's thoughts on this problem. I am not comfortable saying there is "no chance" of one theory or another - in my years I've learned to never say never! Surprise lurks around every corner. But I do play the odds and appreciate your appraisals of the situation.

I cleaned up the commutator and installed the new brush holder, brushes, and springs and rotated the shaft by hand while watching the motion of the brushes. There is a very tiny "wave" to their motion in and out as the shaft goes around, so I think the overall shape of the commutator is not a perfect circle. I hear no clicking as the commutator runs under the brushes, so they seem to be riding smoothly over the bars.

There has been some talk of the need to "seat" the brushes before using them - is there anything special to be done when new brushes are installed?

Thanks...

Steve
 
#20 ·
Very interesting thread. Sort of like "Forensic Files"! I've had to do some similar sleuthing when some of the test sets I've designed or modified have had problems in the field. There are usually several plausible solutions. And sometimes (as Sherlock Ohms has said), if you can eliminate all the usual causes, that which remains, however unlikely, is the culprit.

The only way I can see the brush being pushed out into that position would be if the mica piece had been longer, and flexible enough to initially bend and then extend far enough to push the brush out, and perhaps the leads of the brush could have pressed against the screen to keep the brush from popping out all the way. But then there probably would have been arc marks on the screen, since I assume the brushes have a high potential with respect to the frame.

ISTM, as gottdi asserts, that the motor must have failed previous to purchase because of the mica insulation hitting the brushes, and someone was in the process of servicing it. But then the cover was replaced and maybe the motor was put back in stock. Even if it was basically inspected and bench tested it probably would have seemed OK, and only after an extended period of normal use the remaining brushes were overloaded and eventually failed by overheating. The customer should not be expected to inspect a new motor except to check for obvious shipping damage and such.

I do recommend that the armature should be removed and the commutator with the loose mica insulation should be carefully inspected, perhaps with a new piece of mica forced in place and glued. It may be worthwhile to take it to a motor repair shop to have it done properly. If the commutator segments get loose and short out it could cause a catrastrophic failure.
 
#22 ·
What "BS" are you talking about? I long ago gave up any hope of the manufacturer providing me any help, so there is no economic incentive for me to exaggerate or misrepresent anything!

A guy who sells motors for EVs sent me a picture of a motor that he saw that did the same thing as mine. I really appreciate his willingness to help me understand what happened, and I don't want to say who it is for fear of messing up his business. Simple as that - I urge you to reconsider your accusatory tone.

Steve
 
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#25 ·
Good grief, Pete... Lay off the dude, will you? Why are you so bent out of shape? As far as I can tell the OP is just trying to figure out why his motor failed so I don't really see why you have to go all District Attorney on him...

Your video doesn't prove anything except that in this one particular case you couldn't duplicate his results. Don't confuse a single data point in support of your supposition with absolute proof of it.
 
#24 ·
There does not even seem to be any sign of damage on the commutator where the brush is lifted up. Were there any clues as to what could have caused this? I think it could be possible if a piece of the mica insulation came loose and bent as it encountered the brush, and then extended far enough to push it out as shown. And I think also the travel would need to be limited, perhaps by the brush wires pressing against the cover screen. It would also be helpful to show the condition of the brushes, and a view of the entire commutator to see if there are any open spaces where insulation might have come out. If so, it should be possible to duplicate the phenomenon by inserting a similar piece of material and rotating the shaft by hand.

Problems like this are a good reason to use AC induction motors.
 
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#30 ·
You are entitled to your opinion and I am entitled to mine. Frankly, after reading your responses in this thread, to me you offer no evidence to support your claim.

Firstly, the edge of the brush isn't riding at exactly 90º to the commutator, there is a slight angle there due to the commutator being round. Secondly, the brush edge isn't perfectly squared off, there will always be a radius on it, however small. So, if something on the commutator comes in contact with the brush, it can and will have a lifting effect, particularly at high speed. If the speed is high enough, it is possible to transfer enough energy to lift the brush all the way up until the spring no is no longer on top of the brush. How much speed?? I don't know, but I see it as very possible.

Now, on your theory that a moving object striking another can't move said object in a 90º angle to the direction of travel; If I shoot a gun at a concrete wall, not only will debris come out of the collision at 90º, it will also come out at much smaller angles also, even against the direction of travel. So, your theory is bunk.

Again, I am entitled to my opinion, and this is my opinion. Don't bother to answer this post as I will no longer argue with you.
 
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#34 · (Edited)
Wow, a good example of an ev discussion going awry. I think folks need to be mindful of how it is easy to come off as brusque/jerky/accusatory in print where voice inflection cannot be heard. Politeness goes a long way.

I too am having brush troubles of a different sort (arcing). Yes, these motors have been in forklifts for a long time, but forklifts use VERY low gears, easing the strain on the motor. EV use is COMPLETELY different as people are not using 1st gear. Instead they start out in 3rd putting great strain on the motor. This thread shows one of many failures that are happening with brushed motors of all brands. This is with relatively low numbers in service. Imagine 2 million of these out there. That is a real data set. Industry is gentle compared to the consumer.

The solution has been to use bigger and bigger motors. But that is not a true solution. Just because it can move a forklift at 3mph does not mean it is suitable tech for 500,000 miles of hard use.

Brushed motors, RIP. and just when the controllers are getting good too..


Ok. slaughter me now... :)
 
#35 ·
Wow, a good example of an ev discussion going awry. I think folks need to be mindful of how it is easy to come off as brusque/jerky/accusatory in print where voice inflection cannot be heard. Politeness goes a long way.

I too am having brush troubles of a different sort (arcing). Yes, these motors have been in forklifts for a long time, but forklifts use VERY low gears, easing the strain on the motor. EV use is COMPLETELY different as people are not using 1st gear. Instead they start out in 3rd putting great strain on the motor. This thread shows one of many failures that are happening with brushed motors of all brands. This is will relatively low numbers in service. Imagine 2 million of these out there. That is a real data set.

The solution has been to use bigger and bigger motors. But that is not a true solution. Just because it can move a forklift at 3mph does not mean it is suitable tech for 500,000 miles of hard use. I expect better.

Brushed motors, RIP.

I predict they will quickly become the "budget" option like lead batts. Good for sinkers.

Ok. slaughter me now... :)

No slaughtering here, I have to agree with you...
 
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