Need Help: BMC Gear Hub Rebuild Questions?

geosped · May 15, 2018

I recently burned out the hall sensors on my BMC Gear Hub and would like to rebuild it but have run into some snags and have not found a good DIY.

1) Can anyone identify what version this is? As you can see they have the white gears.
2) I can take the can off but unable to figure out how to disassemble this further so that I can get to the hall sensors. Anyone have a clue? If I had to guess I'd have to drill out what looks like rivets?
3) From what I understand there are steel gears I can purchase for better durability. Would these be recommended for off road use?
4)Who offers rebuild services? And how much would I expect to pay? I will reach out to Leyn and @ Ebike CA anyone else?

For those that are wondering. I use this for off road. I run 10Ah 48v pack pushing around 1300-1700w for short burst of about 10-15 seconds during climbs while riding. I'm 250 and I'd say it's a bit more that this setup can handle lol. This is the setup I want to run and it's been pretty durable. I just want to rebuild this and keep going.

Help is greatly appreciated!
Regards
-G

teklektik · May 15, 2018

geosped said:
1) Can anyone identify what version this is? As you can see they have the white gears.

By the gear color and old two-piece clutch, it looks like an old V1.

geosped said:
2) I can take the can off but unable to figure out how to disassemble this further so that I can get to the hall sensors. Anyone have a clue? If I had to guess I'd have to drill out what looks like rivets?

Just slide the side cover off the shaft and there they are - no additional disassembly required. Optionally heat the retaining epoxy then pick/chip it away with a sharp probe/awl, unsolder the leads from the PCB, and pull out the old hall. Easy-peasy.

geosped said:
3) From what I understand there are steel gears I can purchase for better durability. Would these be recommended for off road use?

If your gears actually need replacement the new composite gears are very much stronger than your originals. Don't mess with steel gears. If that was a smart idea, the motor would come with them.

geosped said:
4)Who offers rebuild services? And how much would I expect to pay? I will reach out to Leyn and @ Ebike CA anyone else?

Nobody I know offhand, but any BMC dealer should be able to do the job. The problem is that there are very very few BMC dealers anymore owing to the lousy manufacturer support for dealers and the astronomical parts cost. A BMC gear cluster runs in the hundreds. A MAC cluster will work fine and costs less than $60. This is a simple job - see my Yuba build thread for some rebuild tips with links to other resources. Search ES for other teardown/rebuild info and DIY.

geosped · May 15, 2018

Thanks Much!

motomech · May 15, 2018

Well, I just explained how to repair/replace the Halls
https://endless-sphere.com/forums/viewtopic.php?f=3&t=94260&p=1380315#p1380315
As I suspected, nothing is cooked and if you have a "burned Hall" as you described(have you actually tested them?), it's probably a cold-solder joint @ the PCB. It may be possible to resolder it, but like I just explained in great detail, I have found it easier just to start over w/ 3 new Halls and the V2 board, but at least the BMC PCB isn't smeared w/ epoxy like my Ezee's were.
Frankly, Im wondering if anything is even wrong w/ this motor since you dianosed it as "on it's way out" and it looks brand new! You really don't need to dianose your motor as having every problem you have read about and present them to us as fact. Folks here try and be helpful and will spend their time explaining a course of repair and it's time better spent on someone who actually has a verified problem.

Good luck.

geosped · May 16, 2018

I can't get the top off it simply does not slide off as suggested. Looks like the shaft is pressed in.

geosped · May 16, 2018

motomech said:
Well, I just explained how to repair/replace the Halls
https://endless-sphere.com/forums/viewtopic.php?f=3&t=94260&p=1380315#p1380315
As I suspected, nothing is cooked and if you have a "burned Hall" as you described(have you actually tested them?), it's probably a cold-solder joint @ the PCB. It may be possible to resolder it, but like I just explained in great detail, I have found it easier just to start over w/ 3 new Halls and the V2 board, but at least the BMC PCB isn't smeared w/ epoxy like my Ezee's were.
Frankly, Im wondering if anything is even wrong w/ this motor since you dianosed it as "on it's way out" and it looks brand new! You really don't need to dianose your motor as having every problem you have read about and present them to us as fact. Folks here try and be helpful and will spend their time explaining a course of repair and it's time better spent on someone who actually has a verified problem.

Good luck.

Thanks the reason I think the hall sensor it's going out is I've gradually noticed that the motor stops spinning under load. It does get hot. I try to be very careful with short burst. Lately even just going on pavement where I hold the throttle longer it seems to give out muck quicker than it used too. Not sure that this is an indication of the hall sensor going out or not. But seems that besides broken gears and melted wires this is the only other thing that gives out on this motor. The gears are in good shape although I would like to replace them with the composites but unless I can figure out how to dismantle this I'm pretty much stuck.

The batteries are still in good shape. I use them on my RC planes and hold load fine. When I had my watt meter attached and the wheel would stop spinning. I checked the batteries they were between 3.91-and 4.02 per cell so they still had plenty of juice.

Is this the correct site http://www.ebikes.ca/about-us/contact-grin.html unfortunately there out of Canada. I'm going to send my 40lb wheel oversees. I need to find someone in the US.

teklektik · May 16, 2018

geosped said:
I can't get the top off it simply does not slide off as suggested. Looks like the shaft is pressed in.

In the post above I indicated where you could get hints on how to do this in my Yuba build thread. You need to dress any burrs on shaft shoulders and get a puller.

Here's an exact link. Again, you can search and find others...
https://endless-sphere.com/forums/viewtopic.php?f=6&t=36959&p=589121#p589121

geosped · May 16, 2018

Thanks reviewing the info now.

geosped · May 17, 2018

Finally making some progress. I got it all apart. Now need to see if the hall sensors are bad or if the wiring on the PCB board has a cold solder joint. Do the pictures suggest anything or anything look out of wack? Also what kind of greese should I use?

For good measure I'm going to order the composite gears with a new hall sensor from Leyn. Great person to work with always very responsive.

geosped · May 17, 2018

So I ordered some parts what kind of Grease do I need?

amberwolf · May 18, 2018

You can look here
https://endless-sphere.com/forums/viewtopic.php?f=2&t=80951&p=1378153&hilit=ezee+hall#p1377788
for my sensor issue wiht an ezee motor (very similar to bmc, nearly identical to yours). was just solder/wires on mine.

geosped · May 20, 2018

Thank you I read your thread very cool trike. I was planning on replacing my hall sensors. I ordered three of them and the compoiste gears. the gears look like there just held in with some snap rings so that should be easy to swap out. However the hall sensors seem to be JB welded in? How do I replace the hall sensors with out damaging anything?

I went shopping at haror freight and bought a heatgun and some epoxy. I was going to try and heat the epoxy on the controller board and see if I can peal off the epoxy and desolder the controller board but not sure what to do about the existing hall sensors.

amberwolf · May 20, 2018

which part of the test did the sensors fail?

geosped · May 22, 2018

Making good progress. Got the gears swapped. But have no idea how to get to the hall sensors. The heat gun isnt really working on the gray stuff. Did good on the epoxy but it looks like heat doesnt do a whole lot to the JB Weld stuff any ideas or thoughts how to get that controller board off?

amberwolf · May 22, 2018

before you waste time replacing hall sensors that might be good, and potentially breaking the motor trying, which part of the hall sensor tests failed?

We've asked a few times about the hall tests, so we can help you find and fix the problem--if the halls test ok then there's no point wasting time and risking breaking other things replacing them, if the problem is going to still exist when you're done.

geosped · May 22, 2018

Ok sorry I must have missed the link where you describe how to test the hall sensors. Let me do that first. If I can find the link.

Got it will probably do this tomorrow. Looks like I'm going to have to re-assemble the wheel at this point.

http://www.ebikes.ca/documents/HallSensorTestingFinal.pdf

I wish I had this info from the start. Good stuff here.
http://www.ebikes.ca/learn/troubleshooting.html

geosped · May 23, 2018

This is the grease I got MOBIL 28 Synthetic Grease. 2oz should more than cover it correct?

amberwolf · May 23, 2018

You don't need to reassemble the motor; you can hand spin the magnet shell around the stator core to pass the magnets over the halls as you test them. But you do need to connect the motor hall connector to the controller hall connector and turn the power on (no throttle needed), so the halls get power and are connected to their pullup resistors.

if you haven't already, you should also continuity test the wiring itself for breaks or shorts, and the connectors to be sure there is a complete path from controller to motor, or else the halls could test as bad, but actually be perfectly fine. Replacing them wouldn't change the problem if it's the wires.

geosped · May 23, 2018

Ok so I did the hall sensor test. I did a continuity test on the yellow, blue and green wires. On yellow I was getting 4.85 on green I was getting 4.95 and on Blue it stayed on 4.95 it did not fluctuate when I turned the wheel. Indicating an issue with the hall sensor that goes to the blue side.

I then reheated and applied to solder to the blue wire ontop but this did nothing. Did I do this correctly? If so and I need to replace the hall sensor do I just replace the one or all three? Also with all that JB weld in there I'm really afraid of doing permanent damage. Any ideas on how I'm going to get the controller board off? I was thinking of using a dremel with a thin blade and cut through the JB Weld stuff?

motomech · May 23, 2018

geosped said:
Ok so I did the hall sensor test. I did a continuity test on the yellow, blue and green wires. On yellow I was getting 4.85 on green I was getting 4.95 and on Blue it stayed on 4.95 it did not fluctuate when I turned the wheel. Indicating an issue with the hall sensor that goes to the blue side.

I then reheated and applied to solder to the blue wire ontop but this did nothing. Did I do this correctly? If so and I need to replace the hall sensor do I just replace the one or all three? Also with all that JB weld in there I'm really afraid of doing permanent damage. Any ideas on how I'm going to get the controller board off? I was thinking of using a dremel with a thin blade and cut through the JB Weld stuff?

.
I explained the procedure (twice) which addressed those exact questions.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=94260&p=1380315#p1380315
Even though you ignored them, I will answer your last question in the hopes you might believe me this time.
To remove the old PCB, simply use one or two sm. screwdrivers and pry it off, taking care not to damage the copper coil wire. Mine popped right off, it's not stuck on there that solid. If it doesn't, heat it up w/ a heat gun.
As I explained before, you will need a new V2 PCB and all 3 new halls to finish it up.
Use new "Vaseline" type grease on the gears and you don't need much.
Seal the cover w/ a sm. bead of "automotive" RTV.

teklektik · May 24, 2018

If this was previously repaired with JB Weld, then you may have a tougher time softening the epoxy - JB Weld is good to around 500degF - better than the original stuff.

Strictly speaking, it's not necessary to remove/replace the PCB - although that gives the tidiest solution if you are replacing all the halls. Above all else, you don't want to pursue a strategy that causes more damage to repair. You should be able to pick out the epoxy using a strong dental pick - at least enough the free the hall body from the laminations. At that point you have at least two choices:

Rebuild as the factory did:
Pick out additional epoxy under the PCB then unsolder it and pull it out with the PCB in situ. This is not really very difficult if you have electronic-sized tools and are not trying to do this with giant electrician's tools. Use a solder-sucker to clean the PCB holes, then slip in the new hall, solder, glue, done.

Cheat to reroute hall leads
It's also not strictly necessary to replicate the fabrication technique that was originally used to simplify assembly in the factory. With the hall body exposed, sever the 3 hall leads but leave them glued in place and soldered to the PCB. Free and remove the hall body. use a Dremel or small triangular file to file three small notches in the edge of the PCB. insert the hall and route the leads up over the top of the PCB using the three notches to hold the leads. Solder the leads to the pads on top of the PCB. You may need to extend the hall leads with some tiny bare wires to reach the PCB solder pads - just put a glue blob over them.

You need to look at your available tools and skills to decide how to proceed.

geosped · May 24, 2018

teklektik said:
If this was previously repaired with JB Weld, then you may have a tougher time softening the epoxy - JB Weld is good to around 500degF - better than the original stuff.

Strictly speaking, it's not necessary to remove/replace the PCB - although that gives the tidiest solution if you are replacing all the halls. Above all else, you don't want to pursue a strategy that causes more damage to repair. You should be able to pick out the epoxy using a strong dental pick - at least enough the free the hall body from the laminations. At that point you have at least two choices:

Rebuild as the factory did:
Pick out additional epoxy under the PCB then unsolder it and pull it out with the PCB in situ. This is not really very difficult if you have electronic-sized tools and are not trying to do this with giant electrician's tools. Use a solder-sucker to clean the PCB holes, then slip in the new hall, solder, glue, done.

Cheat to reroute hall leads
It's also not strictly necessary to replicate the fabrication technique that was originally used to simplify assembly in the factory. With the hall body exposed, sever the 3 hall leads but leave them glued in place and soldered to the PCB. Free and remove the hall body. use a Dremel or small triangular file to file three small notches in the edge of the PCB. insert the hall and route the leads up over the top of the PCB using the three notches to hold the leads. Solder the leads to the pads on top of the PCB. You may need to extend the hall leads with some tiny bare wires to reach the PCB solder pads - just put a glue blob over them.

You need to look at your available tools and skills to decide how to proceed.

Looking at the pictures I posted. I was able to easily remove the yellowish looking epoxy from the top of the PCB board by heating it up with a heat gun and picking at it with a small flat blade screw driver.

However looking at where the hall sensors are located they used gray what appears to be JB Weld to hold the PCB and hall sensors in place. This is much much harder than the epoxy they used on top of the PCB board. Using a small dental pick isnt doing a whole lot as it like steel. Applying heat didnt really soften it up either. Exposing the hall body seems like it's going to be a challenge. I was thinking of using a dremel tool and cutting the leads to the hall sensors / JB Weled
from underneath but not sure if the cutting wheel will get deep enough to get through all of the JB Weld. Dam not really liking my options.

Alan B · May 24, 2018

Can hall sensors be installed elsewhere in this motor or is there something special about the existing locations?

geosped · May 24, 2018

Here is the progress I've made so far. I was able to use a dremel and cut away at the JB Weld. Unfortunately I dont think there is a way to remove the JB Weld that's covering the holes on the underside of the PCB Board. I've attached three pics. I was able to remove the JB Weld on the far right side exposing the holes. However I can NOT for the live of me get the wires to stick to the PCB board. I tried flux I tried tinning the wires they just seem loose. Any suggestions guys. Once I'm able to secure that hall sensor I will do a continuity test and make sure I read 4-5v on each wire (Y,B,G)

I was able to chip away at the JB weld with a small pick and flat screwdriver. The plan is to JB Weld back in place the BCB board once everything is verified. Just cant get the one hall sensor to stick to the soldering pads.

teklektik · May 24, 2018

Hard to tell what the issue is but it does look like the hall leads are not actually in contact with the pads on the PCB = you seem to be making the connection by bridging an air gap which is not the best plan on a couple of fronts - most difficult is that you need to heat both the wire and the pad at once and that doesn't work out so well with the wire airborne.

I would try to either clamp the wires down with an alligator clip or put a bit of something heavy on the long ends to hold them in place on the pads. Make sure your iron tip is tinned and wipe it on a damp sponge briefly to clean it shiny just before you make a connection - dull, dark, dirty tips radiate heat like crazy and solder pretty poorly - particularly if you're using lead-free solder. Similarly, if the tip won't wet with solder, you will have a terrible time trying to wet the joint because you can't transfer heat through the solder puddle. If you've cleaned the pad so it's bright and tinned it, the leads should solder down literally in a second with very little additional solder.

If you've been struggling heating these suckers for awhile, I'd recommend a full hall test before you button up the motor instead of a simple continuity test - just to be sure you don't have a heat casualty...

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