Bafang/BPM geared-hub specs, teardown, and pics

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spinningmagnets
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Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Jun 25, 2013 10:19 am

Page 2, Bafang web-catalog http://szbaf.com/product.asp?page=2&pid ... &keywords=
Green Bike Kit http://www.greenbikekit.com/index.php/e ... w-36v.html
E Life Bike http://www.elifebike.com/peng/pic.asp?M ... ID=S220062
BMS-Battery http://www.bmsbattery.com/90-bafang-motor
EV-Assemble http://www.evassemble.com/index.php?mai ... ktb9j7dle7
Bafang 500W-BPM also available from ES member Keywin / ecrazyman@gmail.com
http://bruceteakle.blogspot.com/p/blog-page_8.html

Crossbreak and Miles have calculated that the Bafangs "might" run well up to 2,000-RPMs at the motor (5:1 reduction to the output shell, so 2,000 motor-RPMs = 400 wheel-RPMs), and any RPMs above that: efficiencies and waste-heat both slowly curve to the bad side...
https://endless-sphere.com/forums/viewto ... 00#p608467

Here is a breakdown of the BPM-II, showing the minor differences.
https://endless-sphere.com/forums/viewto ... 00#p768925

A short video of "fullthrottle" opening up his BPM to clean, re-grease, and replace the freewheel...
https://endless-sphere.com/forums/viewto ... 25#p590956
Firstly, the two BPM models [from BMS-Battery] and the new CST cassette-hub model are all rated at 36V. The coding applies to a 36V input and all the values I will be giving you are in unloaded conditions. Let's begin with a code-16 motor and work our way to the code-8 motor.

Code_____RPM
16_______192
15_______205
14_______215
13_______230
12_______250
11_______280
10_______300
_9_______335
_8_______378. mind you, all of these specifications are directly from the engineers of Bafang.
Jeremy Harris' and Wurlys' acquired data on Bafang code#/turn-counts
https://endless-sphere.com/forums/viewto ... =2&t=43106
https://endless-sphere.com/forums/viewto ... 23#p515152

This drawing is reported to be a BPM
https://endless-sphere.com/forums/viewto ... 15#p207898
Image

Specs per ES member full-throttle: https://endless-sphere.com/forums/viewto ... 50#p703912
BPM 500W Code-9
Phase impedance 70mOhm
Phase inductance 275uH
9 turns x 10 strands of d0.56mm (23-AWG)
34 lams 0.50mm
18 teeth: 17mm wide x 10mm deep x 14mm high
Stator diameter 130mm
Air gap 0.50mm
Magnets 8 pairs 18mm wide/deep x 26mm long (along the rim) 2.5mm thick
Flux ring 6mm thick
The motor pictured below was purchased from Green Bike Kit in April of 2013, and may vary slightly from older Bafang-BPM versions. Here is a link with pics of a BPM from 2012 which show some of the internal differences: https://endless-sphere.com/forums/viewto ... 04#p513278
Bafang 002.JPG
Edge view
Bafang 002.JPG (145.18 KiB) Viewed 22909 times
Bafang 007.JPG
Flat side up (freewheel)
Bafang 007.JPG (182.48 KiB) Viewed 22909 times
Bafang 008.JPG
Planet gear side, disc brake mount, facing up
Bafang 008.JPG (195.89 KiB) Viewed 22909 times
Wooden stand central hole is 80mm diameter, the cord slot is 18mm wide
The distance between square sides when the stand is flipped over is 5-1/4 inch / 133mm
Bafang4 014.JPG
Starter kit. An empty clear jar with a large opening to put parts in, plus smaller pill-bottles for small screws. An impact-driver to remove Phillips-head screws without damaging them (which might require drilling them out to remove the damaged screw-head). A plastic mallet (a steel hammer would work, but it would also leave visible dings on the aluminum).
Bafang4 014.JPG (123.17 KiB) Viewed 22811 times
Bafang 005.JPG
Mark the case and sideplate by drilling shallow dimples for re-assembly, to ensure it goes back together exactly as it came apart.
Bafang 005.JPG (101.24 KiB) Viewed 22909 times
Bafang 006.JPG
Use the impact driver to prevent damage to Phillips-head screws. A normal screwdriver might strip the slots and make it very difficult to remove. Threads are common M4.
Bafang 006.JPG (128.72 KiB) Viewed 22909 times
Bafang 010.JPG
Remove retainer nut on the other side with an 18mm wrench
Bafang 010.JPG (152.18 KiB) Viewed 22909 times
Bafang 009.JPG
Pull with your thumb while tapping the side-plate edge with plastic mallet.
Bafang 009.JPG (160.6 KiB) Viewed 22909 times
Bafang 011.JPG
Lift off the planet-gear sideplate and outer case shell. EDIT! the silicone washer and metal washer have their positions reversed by accident. The metal washer should be on the bottom, silicone on top.
Bafang 011.JPG (130.67 KiB) Viewed 22909 times
Bafang 012.JPG
Remove silicone washer and thin metal washer. EDIT! when I set up this pic, I got it backwards, the metal washer is supposed to be on the bottom and silicone washer on top!
Bafang 012.JPG (105.56 KiB) Viewed 22909 times
Bafang 013.JPG
The planet-gear carrier, stator, and flat sideplate separate easily, there are no retaining clips.
Bafang 013.JPG (124.25 KiB) Viewed 22909 times
Bafang 015.JPG
Steel magnet-bowl / planet-gear side of the stator.
Bafang 015.JPG (213.37 KiB) Viewed 22909 times
Bafang 014.JPG
Flat side of the stator.
Bafang 014.JPG (196.78 KiB) Viewed 22909 times
Last edited by spinningmagnets on Sep 23, 2013 9:10 am, edited 31 times in total.

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Re: Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Jun 25, 2013 10:20 am

Shaft bearing on the flat sideplate is 15mm ID / 32mm OD / 8mm thick? part number is 6002RS
Shaft bearing on planet-gear side / disc brake side is 20mm / 37mm / 9mm, part number is 6904RS

Large central bearing 25mm ID / 37mm OD / 7mm thick, part number is 6805RS, there are TWO of them side by side.
The three planet-gears each have a bearing, a 6001RS, 12mm X 28mm X 8mm

Steel sun gear, 16mm wide, 21T
Plastic planet gears (three of them), 42T / 14mm thick,
Steel ring gear, 105T, 16mm wide

Stator tooth width 16.80mm~17.20mm
Stator diameter (air gap) 5-1/8-inch / 130mm

Axle-threads are 12mm X 1.25
Last edited by spinningmagnets on Jun 28, 2013 5:14 pm, edited 4 times in total.

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Re: Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Jun 25, 2013 10:20 am

Bafang3 001.JPG
Foam under stator, impact driver on 3 screws holding sun gear. The screw thread is common M4
Bafang3 001.JPG (145.1 KiB) Viewed 23071 times
If you look closely, you can see three extra holes on the sun-gear flange that are threaded. I see no purpose for these on the Bafang-BPM, so I assume this sun gear is used for several different models. Once you remove the sun gear and the circlip that is then exposed, you can re-attach the sun-gear, and then make a puller out of three M4 bolts that are longer (to separate the magnet-ring from the stator if you don't have a 3-arm pulley-puller). It's possible these threaded holes are for jacking bolts to help separate the sun gear if it is difficult to remove.
Bafang3 002.JPG
Sun gear pops off easily, and exposes the circlip.
Bafang3 002.JPG (190.44 KiB) Viewed 23071 times
Bafang3 003.JPG
Remove circlip, place it immediately in the jar.
Bafang3 003.JPG (144.29 KiB) Viewed 23071 times
Bafang3 004.JPG
Tape coins under each jaw to ensure the three puller arms are not hitting the edge of the stator. Put the axle nut on the end of the shaft to keep the puller central push-rod from slipping off the end of the axle, and tape the three arms together to keep them from slipping off the magnet bowl.
Bafang3 004.JPG (97.76 KiB) Viewed 23071 times
If I were doing this often, I would make an aluminum sleeve that was 17mm ID, 25mm OD, and 42mm+ long. If you slide such a sleeve over the 3-arm puller side of the axle and tighten a nut onto it, this sleeve will slide along the central bearing ID and force the stator and axle to slide out (and slide in on re-assembly) following a straight line, rather than pulling back and forth to the sides.
Bafang3 005.JPG
The stator will try to pull to one side, and then to the other. If I was doing this often, I would make a jig to hold both pieces in-line while they were being separated.
Bafang3 005.JPG (103.18 KiB) Viewed 23071 times
Bafang3 006.JPG
On the Bafang-BPM, the axle-nut does not need to be removed to separate the magnet bowl from the stator/axle assembly since the side-plate bearing has a large ID.
Bafang3 006.JPG (98.1 KiB) Viewed 23071 times
Bafang3 007.JPG
Here's a closer look at the magnet bowl. Notice it uses two thin shaft bearings, instead of one wide bearing.
Bafang3 007.JPG (105.13 KiB) Viewed 23071 times
Bafang3 008.JPG
The stator tooth width varied from 16.80mm to 17.20mm.
Bafang3 008.JPG (117.3 KiB) Viewed 23071 times
Bafang3 009.JPG
The planet-gear side of the stator. Hall sensors located at 10:00, 12:00, and 2:00 O'Clock, The phase wires are green @ 8:00, Blue @ 6:00, and yellow @ 4:00 O'Clock.
Bafang3 009.JPG (230.75 KiB) Viewed 23071 times
Bafang3 010.JPG
The stator facing the flat side of the motor.
Bafang3 010.JPG (172.13 KiB) Viewed 23071 times
Until someone asked me to check, I assumed the entire magnet bowl was steel. Upon closer inspection, I tested the different parts, and the outer ring is steel (of course), while the bowl face with the six wide spokes is aluminum. This pic is framed to show the color difference at the steel/aluminum joint. The round dimples on the steel ring perimeter have no apparent purpose. Since there are four of them that are evenly spaced out, I suspect they held this part onto a lathe jig.
008.JPG
Steel ring, aluminum face.
008.JPG (92.52 KiB) Viewed 22261 times
Last edited by spinningmagnets on Jul 23, 2013 6:46 pm, edited 9 times in total.

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Re: Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Jun 25, 2013 10:20 am

Oil cooling the Bafang-BPM:

This is an experiment, based on the experience of others. I hope to report back after a while with any additions/deletions/or changes necessary to improve this operation. Here is the oil-cooling experiments thread: https://endless-sphere.com/forums/viewto ... =2&t=37972

I am drilling and tapping threads all the way through on two opposing bolt-holes from the disc brake mount, to allow for future oil-cooling by filling 1/3rd of the motors internal volume with Automatic-Transmission-Fluid (ATF). When the motor is not spinning, the oil level should be just below the axle bearing, since the axle bearing would leak no matter how well the rest of the motor-case is sealed.

The sealant I used here is a small tube of "Permatex High-Temp red RTV Silicone Gasket Maker", which should be cheaply and readily available at most automotive parts supply stores. It is formulated to be resistant to all common automotive fluids, including motor-oil, engine coolant, and automatic transmission fluid (ATF).

The threads are M5/5mm X 0.80 (removed with a 4mm hex-wrench), so I used a tape-wrapped 1/8-inch bit (3.2mm) to drill through-holes from the threaded side. I flipped it over, and the aluminum was so thin at that spot, I hand-turned the drill bit with a screwdriver handle (my small bits have a hex-shaft). I used an 11/64-inch bit (0.172, 4.3mm), which is actually a perfect bit for this. Then, I started tapping the new threads from the threaded side.

First, cover the bearing hole with tape, and remove the two bolts in the holes you wish to drill and tap threads. Holes were originally 8.5mm deep, now open all the way through, and now 11mm deep before screw end will protrude. When using 3mm thick brake disc with no washers or lockwashers, you can now use screws with 14mm of thread.
Bafang6 033.JPG
Remove the screws from the holes you want to thread all the way through.
Bafang6 033.JPG (90.5 KiB) Viewed 23012 times
Bafang6 037.JPG
Wrap tape around a 1/8-inch drill bit to protect the existing threads and also to center the bit, then drill all the way through from the outside. Notice I drilled a shallow dimple next to each hole that will be threaded all the way through, for future identification.
Bafang6 037.JPG (94.93 KiB) Viewed 23012 times
Bafang6 030.JPG
Flip the case over. Very slowly and gently...open up the hole down to the existing threads with an 11/64-inch bit (4.3mm diameter). Do not drill all the way through, as it may damage the existing threads.
Bafang6 030.JPG (97.17 KiB) Viewed 23012 times
Bafang6 040.JPG
Spray some lube into the hole and onto the tap. Flip the case back over and tap new threads all the way through with the M5 tap (5mm X 0.80). Stop each complete turn, and reverse direction for a quarter turn to clear out chips.
Bafang6 040.JPG (99.48 KiB) Viewed 23012 times
Bafang6 027.JPG
Clean out all the chips, and this is the finished product.
Bafang6 027.JPG (96.91 KiB) Viewed 23012 times
BPMoilCool1 002.JPG
Red high-temp silicone sealant in the hollow axle, magnet-bowl side.
BPMoilCool1 002.JPG (94.71 KiB) Viewed 22076 times
BPMoilCool1 003.JPG
Flipped over, more sealant where the phase wires go into the axle.
BPMoilCool1 003.JPG (102.17 KiB) Viewed 22076 times
BPMoilCool1 009.JPG
Apply a thin bead of sealant around the motor case edge, if you use too much, the excess will squeeze out inside the motor. Set the side plate in place with the witness location dimples lined up. Apply one drop of threadlocker fluid to the threads of the six side plate screws and set them in place. I'm sorry for the fuzzy pic, but I could only do this part once, and I could not re-take the pic without disassembling the motor.
BPMoilCool1 009.JPG (98.89 KiB) Viewed 22076 times
BPMoilCool1 012.JPG
Gently lower the side plate until you can insert the six screws a couple threads, this will ensure exact alignment, so no rotation of the side-plate will be needed after the plate is completely assembled. Tap the side-plate gently down, and then finish tightening the six screws. The amount of excess sealant shown is approximately how much will ALSO be squeezed out on the INSIDE. Use just enough to seal the close-tolerance fit, but not so much that you have a significant excess protruding into the motors interior. If you do not want the external excess sealant showing, wait for it to thoroughly dry, and then cut it off with a razor.
BPMoilCool1 012.JPG (103.31 KiB) Viewed 22076 times
Last edited by spinningmagnets on Oct 26, 2013 8:57 am, edited 19 times in total.

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Re: Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Jun 25, 2013 10:21 am

This post is about how to double the phase wires copper to allow more amps to be used on this motor.

On the stator with phase wire terminations facing up, going clockwise with the halls at the bottom, the phases wires from left to right are Yellow, Blue (center), Green. The three screws holding the shaft onto the stator core are common M5 thread. Each phase wire is 19 strands.

Hollow shaft ID: 0.300" / 7.6mm

BPM axle flats width: 10mm

Two 0.060" copper-diameter 16Ga wires that have been stripped of insulation and then twisted together equal a roughly 0.090" diameter of copper, which is approximately equal to Hobby King 12Ga.

The stock wire insulation is thin, but is actually quite good. I tried stripping a few inches of the stock insulation on the paired wires, and re-insulating the two of them with a single sleeve of heat-shrink, but the result was slightly bulkier than just the paired wires with the stock insulation still intact. I then tried taking the six phase wires (with the stock insulation intact) and covering that 6-stock-wire bundle with a sleeve of 6mm heat-shrink. This worked well, and even passed through the axle fairly easily with a small amount of lube on the outside of the 6mm heat-shrink sleeve.

The six-wire bundle inserted so easily, that I wondered if I could do that again with three of the original hall wires added to the bundle to be used to connect to a temp-probe. It worked! There was enough air-space between the fatter wires that three of them easily worked. The original sheath over the wire bundle is quite thick, and the 16-Ga wires are easily adequate for 500W, which allows a diameter of bundle that still easily and quickly inserts through the hollow axle on an assembly line with no lube. By using lube, removing the thick-walled sheath, and removing two of the hall wires...the phase wires can easily be doubled.

In this phase-wire upgrade, the stock cable length was cut in half to result in two equal-length sections. This also results in ten shorter hall wires, instead of the stock 5. It might be possible to double the phase wires, retain 5 hall wires for sensored operation, and also add three of the extra hall wires for the temp probe operation, since the hall wires are very thin.
Bafang6 001.JPG
Fold the cable in half and cut, so you have two equal-length sections.
Bafang6 001.JPG (88.12 KiB) Viewed 23171 times
Bafang6 002.JPG
Put foam under the stator, and use the impact-driver to loosen the 3 screws that are holding the shaft onto the aluminum stator core.
Bafang6 002.JPG (125.55 KiB) Viewed 23171 times
Bafang6 003.JPG
Cut off the heat-shrink sleeve that holds the cable anti-kinking metal coil in place, and then remove the coil.
Bafang6 003.JPG (120.7 KiB) Viewed 23171 times
Bafang6 004.JPG
Spray a small amount of lube-oil down into the cable, and let it flow downwards for a few minutes.
Bafang6 004.JPG (119.66 KiB) Viewed 23171 times
Bafang6 005.JPG
Flip the stator over and put the 12mm axle-nut on the tip of the axle to protect the threads. Then, tap the end of the axle-nut until it comes loose from the stator.
Bafang6 005.JPG (116.54 KiB) Viewed 23169 times
Bafang6 006.JPG
Untwist and remove the three twist-ties that hold the phase wires onto the stator spokes.
Bafang6 006.JPG (76.41 KiB) Viewed 23169 times
Bafang6 009.JPG
The cable is held in place by an "Omega" shaped steel clip (a "U" with the ends bent outwards). Push the ends towards the center and downwards to release it.
Bafang6 009.JPG (131.39 KiB) Viewed 23169 times
Bafang6 007.JPG
Flip the stator over, and cut off the 5 hall sensor wires. I suggest cutting them where they attach to the ends of the green half-circle circuit-board, and leave a short stub with some of the colored insulation. That way, hall wires can be easily identified and re-attached in the future if desired.
Bafang6 007.JPG (85.65 KiB) Viewed 23169 times
Bafang6 010.JPG
After the hall wires are cut, the axle can be lifted out of the stator. Take a black felt marker and mark the aluminum stator with a Y, B, G...for yellow, blue, green. Place the marks next to the corresponding phase wire to make ID fast and easy. Note that the yellow phase wire shown has black insulation near its top, and the yellow can only be seen near its root.

After cutting off the section of heat-shrink that covers the soldered joint between the phase-wires and the axle-wires, cut the phase-wires while leaving a short stub that still has some of the colored insulation, so identifying each phase will be easier (note the yellow phase wire being handled has a short section of black heat-shrink over it's tip). That way they will go back together exactly as they came apart, and identification will be fast and easy. Note the Omega clip at the top right of this picture, place it in the parts jar immediately, since it can be easily lost.
Bafang6 010.JPG (122.01 KiB) Viewed 23169 times
Bafang6 013.JPG
Three phase wires and 5 hall wires cut.
Bafang6 013.JPG (118.02 KiB) Viewed 23169 times
Bafang6 014.JPG
The wire-bundle is easier to pull out in this direction.
Bafang6 014.JPG (77.89 KiB) Viewed 23169 times
Bafang6 017.JPG
There was a dried glob of silicone goop, remove it to make re-insertion easier.
Bafang6 017.JPG (89.63 KiB) Viewed 23169 times
Bafang6 020.JPG
Two stock 16-Ga phase wires have the same copper cross-section as one 12-Ga wire from Hobby-King (measured with a caliper)
Bafang6 020.JPG (81.91 KiB) Viewed 23169 times
Bafang6 024.JPG
After several experiments, this is the recommended configuration for max amps and high-heat survival. No halls due to sensorless operation, three stock hall-wires to operate an internal temperature probe, and the stock phase wires have been doubled. The new bundle is covered by a single 6mm heat-shrink sleeve. A small black section of heat-shrink was put over the wire tips to smooth insertion and pass through the axle before the wires begin insertion.
Bafang6 024.JPG (115.26 KiB) Viewed 23169 times
Bafang6 026.JPG
Re-attach the axle in preparation to re-solder the axle-wires to the phase-wires.
Bafang6 026.JPG (111.31 KiB) Viewed 23169 times
Last edited by spinningmagnets on Feb 26, 2014 8:19 am, edited 7 times in total.

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Re: Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Jul 14, 2013 10:50 am

BPMwires1 003.JPG
Here, I am using a long blue wire to hold down the phase-wire bundle into a stator-recess that was designed to nest it. Once the bundle is held in place, re-insert the steel "Omega" clip into its original position. Note the green stub still attached to the white phase wire at the top right of this pic, used to ease identification.
BPMwires1 003.JPG (98.33 KiB) Viewed 22319 times
BPMwires2 003.JPG
Press the wires down into the recess that was designed for them, and then align the two leads. Trim the excess insulation (yellow in this pic), and trim the axle-wire tip so they are equal. Note the "Y" and the "B" for yellow and blue (green not shown here).
BPMwires2 003.JPG (100.59 KiB) Viewed 22320 times
BPMwires2 006.JPG
Take some multi-strand copper wire, strip several inches of insulation. Then separate out 3 or 4 strands, and twist them together. Form a loop that can be used to "choke" the phase wire and the axle-wire together. Amberwolf recommended the strand-wrapping technique, and it has made my soldering much easier and faster.
BPMwires2 006.JPG (62.75 KiB) Viewed 22320 times
BPMwires2 010.JPG
After choking the two leads together with the thin wire loop, wrap them with the rest of the strand length, then trim off the excess strands in preparation for soldering. The white card was set under them only to make the visual image clearer.
BPMwires2 010.JPG (92.48 KiB) Viewed 22320 times
AmberwolfMethod.JPG
A visual recap of the Amberwolf butt-splice method.
AmberwolfMethod.JPG (110.83 KiB) Viewed 21834 times
BPMwires7 002.JPG
When you are finished soldering the joints, let them cool and then feel for sharp points that might cut the heat-shrink insulation. Use needle-nose pliers to flatten any sharp points. Slide a section of 6mm heat-shrink over the joint and heat it up. After the insulation is shrunk on, feel it for sharp points that may have been missed. Use a second 6mm sleeve to be extra certain if any irregularities are found. A shorted phase may damage the motor, and at a minimum it would require dis-assembly to find and repair.
BPMwires7 002.JPG (120.81 KiB) Viewed 21834 times
BPMwires8 002.JPG
Replace the wire twist-ties that hold down the phase-wire joint ends.
BPMwires8 002.JPG (120.72 KiB) Viewed 21685 times
If you want to attempt to re-insert the anti-kinking spring around the phase-wire bundle in the location where the wires exit the axle-tip, now is the time to try it.
BPMwires3 004.JPG
Cut the paired phase wire ends to staggered lengths so the three joints are not at the same place. Join the two phase wire ends to the 12-Ga wire with the "Amberwolf" method. You untwist the strands so they are straight, and then gently insert the opposing ends into each other so the strands from both sides will intermingle. Wrap the joint with thin strands of copper wire that were taken from a piece of scrap, then solder the joint. The 5mm red heat shrink section is shown as a reminder, but slide it farther away when soldering, so it will not shrink onto the wrong spot if it is as close as it is shown here.
BPMwires3 004.JPG (91.07 KiB) Viewed 22254 times
BPMwires5 004.JPG
Because the Hobby King silicone insulation is thicker, I have to use 10mm heat shrink (black, on the right) over the three 12-Ga phase wires instead of the 6mm heat shrink previously used (red, on the left) over the six stock 16-Ga wires, which have thin insulation.
BPMwires5 004.JPG (56.18 KiB) Viewed 22216 times
Last edited by spinningmagnets on Aug 06, 2013 4:55 pm, edited 16 times in total.

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Re: Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Jul 14, 2013 10:50 am

Installing an LM35 temp probe.
TempSensor1 003.JPG
I chose to mount the sensor here so that if there is ever a problem with the sensor in the future, you can access it without separating the magnet ring from the stator. You would only need to open up the motor case.

Flip the stator, prepare 2mm heat-shrink insulation sleeves. The length of the sleeves should be longer than necessary, because the tip near the soldering might start to shrink down onto the wrong place. This would require you to trim off a short section, and you need the remaining sleeve length to be long enough.
TempSensor1 003.JPG (150.23 KiB) Viewed 22008 times
TempSensor1 004.JPG
Tie back two of the axle-wire leads so they are out of the way, and also bend two of the sensor leads slightly, so once you start soldering, you will not mix up which color of wire goes to which sensor-leg. Slide on one of the heat-shrink sleeves, and solder one of the wires to one of the sensor leads. This first join is poor, but it will hold the sensor in place (like a third hand). Once I solder the other two leads, I will re-solder the first one better. The wire leads should be fairly long, because a short lead will get hot during the soldering, and the heat-shrink will clamp down in the wrong place.
TempSensor1 004.JPG (110.05 KiB) Viewed 22008 times
Temp sensor2 002.JPG
A single strand of fine copper wire formed into a choking loop to hold the two leads together during the soldering operation.
Temp sensor2 002.JPG (57.14 KiB) Viewed 22006 times
Temp sensor2 003.JPG
Three leads soldered, not easy because my vision is weak and my gorilla-fingers are fat. Try to solder the connection quickly so the heat-shrink doesn't clamp down in the wrong place. Notice here that I will need to trim a short tip of the heat shrink on the red and yellow wires with a razor, the blue was soldered quickly enough that the heat-shrink was barely affected.
Temp sensor2 003.JPG (122.33 KiB) Viewed 22006 times
The pic below is a standard size servo socket, the micro servo connectors are half of this size:
http://www.hobbyking.com/hobbyking/stor ... _bag_.html
LM35b 001.JPG
RC servo female 3-wire socket, 26-Ga wire, very similar to BPM hall wires. I would trim the sensor legs as short as possible, pre-tin them with solder, and after insertion I would touch the short exposed section of the leg to re-melt the solder inside the socket. I might then coat the joint with insulating goo. I will post results whenever I get the opportunity to try this. The socket shown and the red/black/white color code is a Futaba standard (JR and Hitec are similar but orange/red/brown).
LM35b 001.JPG (52.67 KiB) Viewed 21975 times
LM35pinID.jpg
These LM35 temp sensors can also be used to shut down a charger if the battery is getting hot during the charging operation.
LM35pinID.jpg (13.85 KiB) Viewed 21972 times
LM35pinID2.jpg
The "+" power input can be anything between 4V up to 20V, and 5V is pretty common for throttles and other electronics, so a 5V power supply has many cheap and available options.
LM35pinID2.jpg (8.81 KiB) Viewed 21972 times
BPMwires9 001.JPG
LM35 epoxied to aluminum stator core. I cut a section of white packing foam and shoved it into one of the holes of the stator to press against the sensor until the epoxy dries. Then I put a tiny gray dab of JB-Weld epoxy on the flat face of the sensor and pushed the sensor in-between the foam and stator on the outer ring side, just under the coils (where the heat is generated).
BPMwires9 001.JPG (161.49 KiB) Viewed 21863 times
BPMwires8 001.JPG
Wire ties hold down the phase wires, motor case side. The excess length of heat shrink on the blue/yellow phase wire ends have been trimmed so they do not extend past the rim. The ends will be filled with high-temp silicone sealant in preparation for oil-cooling the motor.
BPMwires8 001.JPG (131.88 KiB) Viewed 21856 times
BPMwires8 002.JPG
Wire ties hold down the phase wires, magnet ring/central bearing side. The central axle hole and all wire ends will be filled with high-temp silicone sealant in preparation for oil-cooling.
BPMwires8 002.JPG (120.72 KiB) Viewed 21856 times
Last edited by spinningmagnets on Sep 23, 2013 9:27 am, edited 1 time in total.

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spinningmagnets
100 GW
100 GW
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Joined: Dec 21, 2007 10:27 pm
Location: Ft Riley, NE Kansas

Re: Bafang/BPM geared-hub specs, teardown, and pics

Post by spinningmagnets » Aug 30, 2013 10:34 am

"Motor Temperature Monitoring via Axle"
https://endless-sphere.com/forums/viewto ... 6&p=795143

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