2 stage LH drive on single speed road bike

[Squilt]

2.7kw with a custom made 350Wh battery. Made a 2 stage reduction. 3:1 first stage, 5.4:1 second stage. I made the small sprocket removeable so I can swap between 9, 11, and 14 teeth on the fly. Current gearing gives it a 31mph max speed. Done in just over a week.

 

[TrotterBob]

Hmmm... Direct drive to the rear hub. Interesting. That setup looks like it would easily lend itself to regen braking. Just out of curiosity, how close is that belt clearance next to the seatstay mount?

Edit: oops. Where are my manners? Awesome build. :thumb:

 

[Squilt]

Hmmm... Direct drive to the rear hub. Interesting. That setup looks like it would easily lend itself to regen braking. Just out of curiosity, how close is that belt clearance next to the seatstay mount?

Yep, regen is working well. When I made the aluminum part of the mount I got the spacing wrong for the belt I had on hand so I had to 3d print a bigger pulley. The grey part of the mount is 3d printed too, I cut a bit off to make it just clear the belt. Once I get a smaller belt I'll make a smaller pulley and replace the plastic part with aluminum.

 

[spinningmagnets]

Nicely done!

 

[nicobie]

x2

 

[amberwolf]

If it helps, it's often called a "left side drive", if you want to see other examples of this general type of drive (which have used many different types of motors, including hubmotors mounted in the frame or on the swingarm).

This is one possible search for posts containing the term, but it doesn't show all the drives (many don't show one at all), as a start for those interested:
https://endless-sphere.com/forums/search.php?keywords=%22left+side+drive%22&terms=all&author=&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=-1&t=0&submit=Search

 

[BalorNG]

2.7kw with a custom made 350Wh battery. Made a 2 stage reduction. 3:1 first stage, 5.4:1 second stage. I made the small sprocket removeable so I can swap between 9, 11, and 14 teeth on the fly. Current gearing gives it a 31mph max speed. Done in just over a week.

Belt/chain reduction with eboard/RC motor, great!
Been running a very similar setup myself just lately, but for ~5 and ~5 reduction ratios, so 25 overall from 13s.
Torque is truly huge for something that weights like half of a typical geared hub motor.

 

[CONSIDERABLE SHOUTING]

That's super cool! I take it you're running an ESC?
I've always wondered why those small RC motors can be so powerful. My best guess is they can just spin faster and have just denser windings.

 

[BalorNG]

That's super cool! I take it you're running an ESC?
I've always wondered why those small RC motors can be so powerful. My best guess is they can just spin faster and have just denser windings.

If you take a typical e-bike direct drive hub motor, rewind it for a much faster wind, use high voltage AND high current AND considerable gearing reduction, you'll easily be able to harness absolutely huge power, but it would be 'unpedalable' due to cogging (iron) losses + reduction losses when off.

Also, a small motor can be made to higher spec, have thinner laminations and more powerful magnets and still be relatively cheap.
The main problem is tiny bearings that you want to isolate from radial forces.

 

[nicobie]

12 years ago Thud and PaulD were building RC powered bikes. Thud's had a nice 2 speed gearbox on his when we were at the "Death race in NM. At the time he said having the 2 speed transmission didn't do him any good.


Check out Thud's RC Controller blowing up during the race;

https://youtu.be/YMBySXnIFsI

 

[nicobie]

12 years ago Thud and PaulD were building RC powered bikes. Thud's had a nice 2 speed gearbox on his when we were at the "Death race" in NM. At the time he said having the 2 speed transmission didn't do him any good.
2022-09-28 13_19_44-Thuds death race weapon..Video added 5_20_11 - Endless Sphere.png2022-09-28 13_20_43-Thuds death race weapon..Video added 5_20_11 - Endless Sphere.png2022-09-28 13_35_23-Tucson Death Race 2011 roll call. Results on page 1 - Page 17 - Endless Sphere.png

Check out Thud's RC Controller blowing up during the race;

https://youtu.be/YMBySXnIFsI

 

[PaPaSteve]

Nice build :thumb:


Here's a 1996 example of a motor and chain drive on the left side of the wheel.
During the trial stages of development letting off the throttle would cause the re-generation energy to blow the caps in the controller.
To stop this problem a BMX freewheel was added to the left side chain.
Brushed DC motor came from a 24V cabin heater in a semi truck.
Prototype controller was designed by Nusun.
Sealed lead acid batteries.
Crude stuff by today's standards.

 

[SlowCo]

2.7kw with a custom made 350Wh battery. Made a 2 stage reduction. 3:1 first stage, 5.4:1 second stage. I made the small sprocket removeable so I can swap between 9, 11, and 14 teeth on the fly. Current gearing gives it a 31mph max speed. Done in just over a week.

Very well done :thumb:
Maybe next best step is to move the battery and other thing from the rear rack inside the frame triangle. To center the weight better and improve handling a lot.

 

[Squilt]

The 3d printed pulley kept wearing out/melting. I machined one out of aluminum, but I must have had a bad drawing because it started chewing up belts. Instead of trying to fix it, I just replaced it with another chain drive. Expected more issues than I've been having. Especially because the drive sprocket has only 9 teeth and it's spinning around at over 6.5k rpm. It sure is noisy, but I'd be lying if I called that a downside  . While I was at it, I replaced the bearing with one that should handle the moment load better and replaced the shaft with a stainless steel one that closer fits the I.D. of the bearing. Used some large gap loctite between the two to prevent wobble, and it's still rigid after about 75 miles now. Only issue I've had is the drive sprocket getting loose because I was jamming a set screw into a key slot on the shaft. 2 minutes with a dremel turned it into a flat and it's staying tight. As per many suggestions I did away with the seat post rack which has given me some peace of mind going over bumps. It lets the battery be lower too so it's not so unwieldy.



I limited it to 30A while I was dealing with shredded belts and haven't changed it back. 1,350w feels adequate and I don't want to set it back up to 60A just for my new drive train to explode.



Next step might be replacing the 3d printed bits clamping the motor mount to the seat stay with aluminum parts. It shimmys down over time. Loosening the chain until I readjust it, which isn't frequent enough to annoy me into fixing it just yet.

 

[Squilt]

I made a new mount for the motor and jackshaft. I was thinking about giving up on this idea and trying to figure out how to support the jackshaft from both sides. I decided to throw more bearings at it. It's got three bearings now instead of the one, and the shaft is now a dowel pin instead of a shoulder bolt. So now the shaft press fits into the bearings instead of being a slip fit so it can't wobble and vibrate. The boss at the shop I work at told me that having bearings up against each other like this could cause premature failure but I don't mind replacing them a few times a year if I have to.



Just on the ride home from the shop I noticed that it was much quieter and I could go faster with less throttle. I added the cooling fins just because I could. I doubted they would do anything but the motor now runs a bit cooler.



I hope to not post another update. Since it's just a commuter, working on it feels more like a chore than a project. I just want it to work reliably so I can start working on my other projects. If this drivetrain gives me any more grief I'll consider just getting a hub motor. The only significant changes I might make are moving the battery to the inner triangle and maybe some attempt at water proofing.

 

[Squilt]

Chinesium strikes.

After over 100 cycles, the battery started having issues. It would cut out while charging. Sometimes for hours at a time, sometimes rapidly on and off. If I left it on the charger it would still charge eventually so I let it be. But it kept getting worse and worse. I worried that I had made a bad connection somewhere. But after a lot of fiddling, I can say with certainty that the Daly BMS is to blame.

I noticed that shoving a bit of plastic between the BMS and the battery would let it start charging again. I still thought this could be due to a bad solder joint, but when I got the bms separated from the battery I discovered that bending/squeezing the BMS a certain way would allow charging. There's got to be a bad connection inside the bms. I tried opening it up but everything is sealed in resin.

Seems the only option is replacement. You get what you pay for I guess. I suppose 130 cycles isn't too bad for what I paid.

 

[FarthingPenny]

What motor did you use?

 

[Squilt]

What motor did you use?

Turnigy SK8 6374-149KV
I don't recommend, it overheats easily.