Converting a hubmotor to a middrivemotor

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
mechhead   1 W

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Re: Converting a hubmotor to a middrivemotor

Post by mechhead » Mar 20 2018 8:11am

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/viewt ... =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."

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crossbreak   100 MW

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Re: Converting a hubmotor to a middrivemotor

Post by crossbreak » Mar 20 2018 6:28pm

mechhead wrote:
Mar 16 2018 8:34pm
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/viewt ... 0#p1316627

The longest runner of this dual freewheel jackshaft setup might be iceman i think

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izeman   10 GW

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Re: Converting a hubmotor to a middrivemotor

Post by izeman » Mar 25 2018 10:45am

crossbreak wrote:
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.

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crossbreak   100 MW

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Re: Converting a hubmotor to a middrivemotor

Post by crossbreak » Mar 26 2018 2:51pm

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.

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izeman   10 GW

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Re: Converting a hubmotor to a middrivemotor

Post by izeman » Mar 27 2018 1:44am

I broke my first shaft on the drilled side.
After that i made a new solid shaft which holds perfectly fine.

fourbanger   100 W

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Re: Converting a hubmotor to a middrivemotor

Post by fourbanger » Jul 20 2018 12:36am

Hey, mechhead, how is the conversion going so far?

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crossbreak   100 MW

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Re: Converting a hubmotor to a middrivemotor

Post by crossbreak » Nov 17 2018 9:42am

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/viewt ... 9#p1404823
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