Setting up dual drivetrain ebike

C

Chromotoast

1 mW
Joined
May 12, 2020
Messages
17
Hey friends. Like many of you stuck in quarantine I’ve been thinking of ways to pass the time. I have a bunch of old motors, sprockets, chains etc and I figured I’d convert one of my old bikes into an ebike. I would also like to pedal it, otherwise I’d just strap a brushless motor onto the existing drivetrain and be done with it.

I’ve been thinking of the best way to do this, and ultimately seems like the best way is just to have a dual drivetrain system, one for the pedals and one for the motor that are independent of each other. My bike has a flip flop hub already so I’m sure that makes it much easier to execute what I have in mind. Ideally I’d have the motor drivetrain connected to the freewheel side of the hub and leave the fixed gear side to peddle, but since it’s fixed gear that would just mean the pedals would still turn with the motor engaged which I don’t want, so removing the fixie gear and putting in a second freewheel seems likely what I’d have to do. Anyone have any suggestions that I can pull inspiration from or just general advice?
Thanks!
 
Chromotoast said:
Anyone have any suggestions that I can pull inspiration from or just general advice?
Click to expand...

There's lots of variations on the middrive setups in the Non-Hub Motor section of the forum. Start with the Sticky Index, then various build threads.

https://endless-sphere.com/forums/viewforum.php?f=28
 
I'm not really understanding the dual drive-train part. Could you explain more of the benefits you'd like out of the dual drive-train? What part of a standard set-up won't suit your needs, or needs to be different? Unless this is just for the sake of fun, which I totally get. I'm just not sure how it would be functionally beneficial. Maybe I'm overlooking something.
 
amberwolf said:
Chromotoast said:
Anyone have any suggestions that I can pull inspiration from or just general advice?
Click to expand...

There's lots of variations on the middrive setups in the Non-Hub Motor section of the forum. Start with the Sticky Index, then various build threads.

https://endless-sphere.com/forums/viewforum.php?f=28
Click to expand...
Cool thank you thank you!
 
Electric Earth said:
I'm not really understanding the dual drive-train part. Could you explain more of the benefits you'd like out of the dual drive-train? What part of a standard set-up won't suit your needs, or needs to be different? Unless this is just for the sake of fun, which I totally get. I'm just not sure how it would be functionally beneficial. Maybe I'm overlooking something.
Click to expand...

Yeah mainly just for kicks but I also just want to pedal and have a mid drive instead of using a hub motor so a dual drive train seems to be the only/best way to accomplish that. I’m not really into pedal assist bikes, much prefer independent drives for pedaling and the motor.
 
Chromotoast said:
Yeah mainly just for kicks but I also just want to pedal and have a mid drive instead of using a hub motor so a dual drive train seems to be the only/best way to accomplish that. I’m not really into pedal assist bikes, much prefer independent drives for pedaling and the motor.
Click to expand...
You can use the same drivetrain for both just fine. Depends on your design, gearing, etc.

The primary benefit of a separate drivetrain for each (preferably on separate wheels, but at least on different sides of the same wheel, so that there is no single-point failure that could disable both) is redundancy in case of failure.

But there's no compelling reason *not* to have separate drivetrains other than that it adds the complication of separate chainlines, tensioners, freewheels, etc., so if you don't mind those things, it's just a design choice.

Most likely every possible variation of either one has already been built or used somewhere on this forum at one point or another. ;)
 
amberwolf said:
Chromotoast said:
Yeah mainly just for kicks but I also just want to pedal and have a mid drive instead of using a hub motor so a dual drive train seems to be the only/best way to accomplish that. I’m not really into pedal assist bikes, much prefer independent drives for pedaling and the motor.
Click to expand...
You can use the same drivetrain for both just fine. Depends on your design, gearing, etc.

The primary benefit of a separate drivetrain for each (preferably on separate wheels, but at least on different sides of the same wheel, so that there is no single-point failure that could disable both) is redundancy in case of failure.

But there's no compelling reason *not* to have separate drivetrains other than that it adds the complication of separate chainlines, tensioners, freewheels, etc., so if you don't mind those things, it's just a design choice.

Most likely every possible variation of either one has already been built or used somewhere on this forum at one point or another. ;)
Click to expand...
Thanks for the reply! I’ve been looking through the forum and most of the builds for mid drive motors seem to use a freewheel chainring/crankset to facilitate independent motor and pedaling. And it seems like dual chain drive systems on a flip flop hub are very rare because flip flop hubs are threaded RH on both sides. I’m probably going to weld a sprocket onto a motor shaft, but then I’m not sure how to connect the wheel sprocket for the motor drive train. If I buy a freewheel and attach it to the left side of the wheel, and then weld the sprocket to that, wouldn’t it just screw itself out anyway? Lmao. Apologies for the incredibly novice questions.
 
Chromotoast said:
And it seems like dual chain drive systems on a flip flop hub are very rare because flip flop hubs are threaded RH on both sides. I’m probably going to weld a sprocket onto a motor shaft, but then I’m not sure how to connect the wheel sprocket for the motor drive train. If I buy a freewheel and attach it to the left side of the wheel, and then weld the sprocket to that, wouldn’t it just screw itself out anyway?
Click to expand...
There are solutions to those in some of the LHD threads, but one of them is to file a keyway into the threads of hub and sprocket and use a "woodruff key".

Others are to replace the hub with a disc-brake capable hub and just use the rotor mount for the sprocket (there are already sprockets available to directly bolt there, and/or adapters for existing sprockets of other types).

More solutions in the various threads. Sorry I don't have any direct links, there's just too many of them. ;)
 
amberwolf said:
Chromotoast said:
And it seems like dual chain drive systems on a flip flop hub are very rare because flip flop hubs are threaded RH on both sides. I’m probably going to weld a sprocket onto a motor shaft, but then I’m not sure how to connect the wheel sprocket for the motor drive train. If I buy a freewheel and attach it to the left side of the wheel, and then weld the sprocket to that, wouldn’t it just screw itself out anyway?
Click to expand...
There are solutions to those in some of the LHD threads, but one of them is to file a keyway into the threads of hub and sprocket and use a "woodruff key".

Others are to replace the hub with a disc-brake capable hub and just use the rotor mount for the sprocket (there are already sprockets available to directly bolt there, and/or adapters for existing sprockets of other types).

More solutions in the various threads. Sorry I don't have any direct links, there's just too many of them. ;)
Click to expand...

Dope dope I’ll just search the forum for LHD drives, thanks again!
 
You should install a front hub motor, a rear hub motor and install on a bicycle, then if you are feeling ambitious enough, throw on a mid drive to that bicycle just for giggles.

edit (after chromotoast replied)
A fat 5kw mxus front and a fat 5kw mxus rear, and a Cyclone 18kw........ for gigglessss$$$$$$$$
 
markz said:
You should install a front hub motor, a rear hub motor and install on a bicycle, then if you are feeling ambitious enough, throw on a mid drive to that bicycle just for giggles.
Click to expand...

I would if I could brother.
 
What about normal pedal drive-train on the right side as normal, motor on the left side. Freewheel on the normal drive side. Weld a 9t BMX freewheel to the motor shaft on the motor driven side. So it'll still be fixed in the rear, with the freewheeling on the motor shaft itself. That seems most simple to me.

Edit: Just found this. https://www.planetbmx.com/shop/acs-southpaw-lhd-16t-freewheel.html I wonder what makes it "only" work with certain LHD hubs. Something to look into. Are there other LHD freewheels out there?

Edit again: This one says it works for flip-flop hubs. https://www.planetbmx.com/shop/acs-southpaw-lhd-16t-freewheel.html

Problem solved?
 
Electric Earth said:
What about normal pedal drive-train on the right side as normal, motor on the left side. Freewheel on the normal drive side. Weld a 9t BMX freewheel to the motor shaft on the motor driven side. So it'll still be fixed in the rear, with the freewheeling on the motor shaft itself. That seems most simple to me.

Edit: Just found this. https://www.planetbmx.com/shop/acs-southpaw-lhd-16t-freewheel.html I wonder what makes it "only" work with certain LHD hubs. Something to look into. Are there other LHD freewheels out there?

Edit again: This one says it works for flip-flop hubs. https://www.planetbmx.com/shop/acs-southpaw-lhd-16t-freewheel.html

Problem solved?
Click to expand...

Yeah this is how I wanted to do it in theory, nice to see my idea validated haha.

Hey so what exactly is the benefit of using a freewheel on the motor shaft instead of just a regular sprocket?

Also sadly I don’t think that freewheel would work on my hub cuz I’m pretty sure my flip flop hub is right hand threaded on both ends. I’m leaning towards doing what was suggested above and replace the hub with a disc brake hub and mount the sprocket to where the rotor Holes would be.
 
The benefit would be so that you can freewheel rather than being fixed gear all the time. It just seemed like it would be easier to weld a freewheel onto the motor shaft than to mess around with adapting the rear hub.

Also, I just noticed I posted the same link twice. This is the one that says it works with flip-flop hubs.
https://www.planetbmx.com/shop/acs-paws-4-1-cr-mo-replaces-crossfire-model-freewheel-all-sizes.html

What kind of hub do you have? I've only looked over a couple of flip-flops. They had key-ways to keep them from coming lose. Not saying yours does. I'm just curious how it's designed.
 
For me I'd like to get powerful regen from the motor, requires a fixed drivetrain

while also freewheeling on the pedal power.

Also the motor generates more torque than an IGH can abide.
 
Electric Earth said:
The benefit would be so that you can freewheel rather than being fixed gear all the time. It just seemed like it would be easier to weld a freewheel onto the motor shaft than to mess around with adapting the rear hub.

Also, I just noticed I posted the same link twice. This is the one that says it works with flip-flop hubs.
https://www.planetbmx.com/shop/acs-paws-4-1-cr-mo-replaces-crossfire-model-freewheel-all-sizes.html

What kind of hub do you have? I've only looked over a couple of flip-flops. They had key-ways to keep them from coming lose. Not saying yours does. I'm just curious how it's designed.
Click to expand...

Ahhh I see. I read in another forum post about how a freewheel attached onto its own drive train is unnecessary because the freewheel on the other side of the hub would allow it to coast, but I’m guessing that’s incorrect.

I don’t believe I have a keyway I think it’s just threaded on and locked down with a bolt but I’m gonna check tomorrow and see how I’m going to do this build.
 
Did some more research and found this video of a guy who built a mid drive. He just takes off the fixed gear, leaves the freewheel on the other side attached to the pedals, and attaches a belt and pulley system to the other side to be powered by the motor. The motor doesn't spin the pedals even though there's no free wheel on the motor shaft or the pulley that he put on. So maybe I don't in fact need a freewheel on the motor chain drive part and can just keep it on the pedal drive?

https://youtu.be/TiAlt6_cNCQ?t=532
 
Sounds like you found what I was going to suggest. Follow the gassers typical easiest method. Belt drive made by adding a large pulley to the left side of the rear wheel, one way or another. More reliable or at least quieter than chain, and the only real technical difficulty is actually attaching the pulley to the spokes of the wheel. This is done with some sort of ring on the inside of the spokes, lots of rubber spacer, and bolts on the pulley itself, possibly another metal ring on the outside too.

to clutch it, a simple tensioner on the belt.

You see this type of rig often, when gassers take an old weed whacker, and make it into a bike motor. Will work fine also for electric motors you may have laying around.

For even more fun, spend a hundred or so on a cheap wire feed welder, and start modifying bike frames. Simply for the fun of it.
 
dogman dan said:
Sounds like you found what I was going to suggest. Follow the gassers typical easiest method. Belt drive made by adding a large pulley to the left side of the rear wheel, one way or another. More reliable or at least quieter than chain, and the only real technical difficulty is actually attaching the pulley to the spokes of the wheel. This is done with some sort of ring on the inside of the spokes, lots of rubber spacer, and bolts on the pulley itself, possibly another metal ring on the outside too.

to clutch it, a simple tensioner on the belt.

You see this type of rig often, when gassers take an old weed whacker, and make it into a bike motor. Will work fine also for electric motors you may have laying around.

For even more fun, spend a hundred or so on a cheap wire feed welder, and start modifying bike frames. Simply for the fun of it.
Click to expand...

Yeah for sure man thanks. Now I just need to figure out a good gear ratio. I’m a motorcycle guy so I’m used to not super extreme gearing ratios but this dude has like a 16/128 gearing or something absurd like that. Do you really need those kinds of gear ratios for acceleration and torque on electric bikes?
 
Gearing must be according to motor RPM. Electric motors can be very fast. Bigger, slower motors don’t require much reduction. They are more silent too.
 
Chromotoast said:
Did some more research and found this video of a guy who built a mid drive. He just takes off the fixed gear, leaves the freewheel on the other side attached to the pedals, and attaches a belt and pulley system to the other side to be powered by the motor. The motor doesn't spin the pedals even though there's no free wheel on the motor shaft or the pulley that he put on. So maybe I don't in fact need a freewheel on the motor chain drive part and can just keep it on the pedal drive?
Click to expand...
Ah. I thought you were trying to give it a freewheel to avoid motor drag anytime you're peddling the bike normally. My misunderstanding. If you don't mind the drag then you have no problems. Just throw on a motor and go.

Yours will be easier since you have the fixed gear hub and can just utilize that gear rather than his belt system. That should be a fun project.
 
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