Converting a hubmotor to a middrivemotor

for the oil cooling you will need to dissassemble and seal the cover plate with automotive oil resistant silicone after solvent cleaning the surfaces to be free of all oils /greases so the super runny ATF does not seep out then ensure the shaft seals are up to the job of running properly against the polished sealing surface of the shaft. some hubs either dont have tight enough seals or use unsprung dust seals not proper oil seals, i would look up the housing andshaft size required and get a good quality machinery oil seal to match, then pick a position while its apart (brake disk mount screw holes may be drilled x2 through for filling and the motor allowed to breathe out the cable. only 20 to 60 mls are needed for most hubs more does not gain any more cooling

read the not snake oil cooling thread
https://endless-sphere.com/forums/viewtopic.php?f=2&t=37972

in which Bigmoose wrote nicely summing it up

"Build the heat flux model of a conventional motor from copper windings > radiate + convect + conduct through air to the covers and the rotor. Then the covers and rotor convect and conduct to the atmosphere.

Now replace air convection (because the radiative component is nil) with immersion oil conduction in the middle step, which is the rate limiting step. See where the gain is now? Why do we immerse an egg in water to hard boil cook it? Just put the egg in the shell on top of the fry pan and compare cooking times. And compare that with a fried egg. Liquid conduction of heat rocks."
 
mechhead said:
As Crossbreak will attest, as he is the pioneer of this conversion and the longest running user , the resultant setup is highly reliable and needs little maintenance other than new chains and sprockets and an occasional teardown clean and regrease of the motor gears.
i didnt run this setup for much more than a year. i headed to other topics like nano piezo motors, cnc machines among other stuff. So i cant really tell if its so reliable. I wrote an unconverted MAC for quite some time and sold my two setups. Bought a BBSHD later as it just works out of the box and i still drive it quite a lot. Sure it's not that powerfull at pedal-able rpm and has other drawbacks- the most important for me is the friction of the freewheel which is much higher than that dual-freewheel setup i built with those ACS freewheels. There is no ideal drive for all apllications.

My next setup will be a simple single reduction middrive using an outrunner and a seperate chain to the wheel, like the ones Arthur builds. ATM this is the most promising setup for me due simplicity and other things. And i didnt built such a thing yet :D No seriously, simpler is better. Most simple is a DD-hub setup, but that has serious supension problems...so the single reduction setup is the most general onethat also performs well offroad. Arthur built some frames for the purpose recently: https://endless-sphere.com/forums/viewtopic.php?f=31&t=61259&start=2050#p1316627

The longest runner of this dual freewheel jackshaft setup might be iceman i think
 
crossbreak said:
The longest runner of this dual freewheel jackshaft setup might be iceman i think
Yes. Not too many km ridden but it's a very reliable setup. Once you managed to make the conversion.
A lot of time went into making adapters and spacers to avoid rubbing and so.
After around 2000km the freewheel failed at 2.6kW peak. Gears are still like new.
 
same with the unconverted MAC. The Bafang clutch did hold up longer but i hda issues with the shaft, so it's good that you want to make a larger dia shaft. i think the changing tension on the shaft kills it. When not converted, the bending tension doenst change its sign, since the shaft doesnt rotate. when converted, that shaft suffers more. I once calced a shaft strenth verification according to DIN for the Bafang shaft and even the not converted calculation was not so promising.
 
Another conversion to mention: ferum converted a Bafang 750W fabike hub to middrive a very professional way, with a heat bridge turned on his lathe and a self made multispline shaft:

You can see many moire pics in his build thread, here are just some about the motor conversion
Link to thread: https://endless-sphere.com/forums/viewtopic.php?f=28&t=95899#p1404823

View attachment 13
4VDW5Bw.jpg
iZxFul1.jpg
FfUME8t.jpg
G1JhuOg.jpg
 

Attachments

  • 5TW1zpC.jpg
    5TW1zpC.jpg
    104.9 KB · Views: 2,054
  • DSC01360.JPG
    DSC01360.JPG
    46.3 KB · Views: 2,054
  • DSC01357.JPG
    DSC01357.JPG
    217.8 KB · Views: 2,054
  • DSC01353.JPG
    DSC01353.JPG
    104.2 KB · Views: 2,054
  • DSC01356.JPG
    DSC01356.JPG
    151.3 KB · Views: 2,054
I'm not entirely sure I agree with that statement about the BBSHD. The best thing about this conversion (as far as I'm concerned) is that it lets you pedal along at high speeds without spinning out whereas most other mid-drive setups--including the Bafang--will not allow for that.

Also, I'm pretty stoked I found a code 8.
 
Hey, thank you for that offer. I'll have to get back to you on that, or you can give it to someone else who really wants it. I'm afraid I have at least one too many projects on the go already (honestly, probably like five too many) including a code 16 that I've re-terminated to delta that I'm still working on coming up with a custom axle.

I have to say, though, even though there are other motors on the market that can achieve the same thing as this conversion does, I really like the ingenuity involved in taking one thing that was built for a specific purpose and re-engineering it to do another.

I think you can pretty much take full credit for that in this case.

What have you been working on lately?
 
Hello, 12 Years after the start of this thread, are there still people doing hub motors to mid drive conversions ? I understand it's quite hassle if you want to build a proper heat bridge and a solid cog mount, but my semi recumbent project happens to be one of the few situations where this solution might comes very handy!
Which hub motors motors would you recommend in the 500-1000W range for a mid drive conversion ? Using a mac sounds like a really expensive option...
 
Perhaps you can use semi- mid-drive, like put the motor somewhere mid way from the cranks to the rear wheel ? :unsure:My attempt at a lightweight EMTB with torque based PAS this you can use an Aikema 128 that is lighweigth and compact, there arę new version named 800W nominal. In addition it is easy to add sprockets to the left or right side of the motor. Of course the heat bridge is difficult to build but maybe not really needed.
 
Last edited:
Perhaps you can use semi- mid-drive, like put the motor somewhere mid way from the cranks to the rear wheel ? :unsure:My attempt at a lightweight EMTB with torque based PAS this you can use an Aikema 128 that is lighweigth and compact, there arę new version named 800W nominal. In addition it is easy to add sprockets to the left or right side of the motor. Of course the heat bridge is difficult to build but maybe not really needed.
Interesting build - thanks for sharing it!
 
Back
Top