Mid drive DIY BLDC motor

[pmg]

I would like to convert my MTB by using a very simple mid drive system approach like this one here:

I would like to ignore battery and ESC for now.
My main challenge would be the motor mount. Otherwise, I would like to use a spare BLDC 6355 motor. Besides a chain and a sprocket (and the motor mount), which parts/components would I need additionally?

Would this make sense and are there any projects that implemented this approach on the forum? Maybe I could even reuse motor mount? I'm able to design in Fusion 360 and print with PLA.

Coming from DIY esk8 I'm new to the ebike world. I'm sorry if there is already information about this in other posts or if my questions are dumb. I tried to do some research but still a little lost in so much information...

 

[Skaiwerd]

You can’t use pla for Ebike printed parts. I will soften in the sun, the melting point Is too low Use PETG if you can at a higher print temp like 245c vs 220 for the pla.

My recommendation would be to get the cyclone kit from Luna cycle or sick bike parts some lipos from hobby king, two or three 6s type will do. A charger also and forget about your idea. You’ll appreciate the time saved in exchange for that time riding your Ebike. Engineering things takes time and way more than you think. You’ll still need to do some figuring and such with the cyclone but most of it is done for you. Consider the lipos in my link. Figure out series and parallel wiring and the differences. You will want to hook the lipos in series’s where the plus of one battery is connected to the negative of the next, scary to do at first but no worries this adds the voltage but keeps the amps the same as one battery. Parallel would mean the voltage would stay the same but is ideal for amperage increased with each battery. Sooo. You should learn to solder 10guage wire, put shrink wrap on first. Make a special wire harness with three female xt90 plugs for your lipos which will be male xt90plugs. Your power wiring will be in series again and what goes to the controller. The 6s lipo is 22or so volts at storage, 25volts charged and at 20 needing a recharge. Going by %80 of the full charge of 75 volts. So you have 25 times two or three. 50v or 75v it’s a difference of one battery and $200 go for the higher voltage. More rpm less amps for the same amount of output. So you start out at 75v recharge at 60v or less to be on the safe side. Do your research on charging lipos. Hook up your battery voltage to the smaller red wire or the motor won’t turn, need key on also. Make sure the throttle is correct, it’s low voltage in, power ground under 5v. Don’t send 50 or 75v into your throttle. Sure there’s more to it but why make it whey you don’t. Use your 3d printing skills for the battery box and stuff like that.Oh single speed chain for the front, 7-9 for the back works best. Good luck!!

Link to 20ah battery. My estimate going from me using the smaller 16ah battery you should get 15 miles road per battery. So 30mi for 2 or 50v and 45mi for the 75.

https://hobbyking.com/en_us/turnigy-high-capacity-battery-20000mah-6s-12c-drone-lipo-pack-xt90.html?wrh_pdp=3

 

[pmg]

Thanks for the info.

You might be right, this would definitely be the difficult path. I just miss being able to pick the components individually, like motors, motor mounts, sprockets, chains. This kit approach seems a bit boring and kind of a black box to me. I though I might get lucky and there are already some diy components one can choose and make a build with them, similar to esk8.

Regarding batteries, I already build my own from 18650 and 21700 cells using kweld and soldering bullet, xt90 and/or xt150 connectors with 8 or 10 AWG wire. Also like to plug in a charge only BMS for extra safety. LIPOs are also a nice option and I do have the popular IMAX B6 balance charger

Can you recommend a good vendor like Luna Cycle but based in Europe?

 

[W_2B]

https://endless-sphere.com/forums/viewtopic.php?f=28&t=96769&p=1426882#p1426882
This guy has gone for a similar approach with a skateboard motor. However he hasn't used a freewheel crank so the motor turns the cranks and the rear wheel at the same time. Hope this helps.

 

[forcefed]

You can’t use pla for Ebike printed parts.

Sure you can, i used pla for my motor/battery mounts and it survived a 9 hour ride in 95 degree weather(check my signature), but i did get a cyclone kit for my new bike :lol:

pmg: if you already have the motor/battery and know how to design in fusion you're halfway there, there rest is the hours of trial and error of getting everything to work, i was fortunate since all the designs were already on thingiverse.