The Mid Drive Hub as a Non Hub Group

[markz]

What are the best motors to build a D.I.Y. mid-drive setup, for climbing stairs and steep hills?
I was personally thinking the MXUS 3000W is too powerful, too big and too heavy.
9C seems to be popular.
What about the Leaf 1500W?
Or is it better to go with a Geared Motor?

 

[fourbanger]

Stupid question, but is there a reason no one applies the crossbreak method to a DD? Or will this become apparent as soon as I crack one open?..

 

[amberwolf]

Would take a bit different approach than with a geared hub, because a geared hub has the rotor (magnet ring) on a bell inside the motor housing, so there's no particular reason the housing *has* to rotate when the motor spins, vs the axle. But a DD has it as part of the motor housing, which means if hte motor spns the housing spins.

So you'd need to use double bearings on the wire-side side cover and fix that ring of that side cover to the stator, so the wires have somewhere to exit and you can bolt the stator to the bike on one side.

Then disconnect axle from stator and put bearings in the stator for it to ride on (it is usually welded or pressed into it), and let it rotate on the new inner bearing on that side cover, and the whole housing and magnet ring / spoke flange would rotate on the outer bearing on that side cover..

Then you'd take out the axle bearing on the other side cover, and fix the side cover to the axle there, and it would then drive the axle while rotating.

So, it doens't do exactly what he did with a geared hub, but it could still be done, allowing you to mount the motor by something other tahn it's axle, and using it's axle as a shaft to drive something with, even though it *also* still rotates most of the outer housing of the motor as well (rather like an RC motor outrunner with a spinning shaft).

 

[fourbanger]

That sounds pretty involved, but thanks for walking me through it. I think I'm starting to get the picture now.

Can't wait for someone *else* to try it

 

[markz]

Its best, I would think, to let the motor rotate normally, have the axle bolted down to the frame, then have the motor spin with its freewheel on it, chain to BB or rear wheel. I think making the hub itself stationary is too complicated. I have my BMC V1 open right now, putting it back together slowly with upgraded teflon wires however I used Cat 5e or cat 6 wires which are solid, kind of a dumb mistake on my part I think because stranded wire in a very large guage (small diameter) would be best, maybe I will do that from axle to controller.

I can see why others have bolted the housing down, because the axle itself sticks out lots, 130-150mm which would get in the way of the crank pedal movement.

I still cant picture how it is done that way, I will have to reread it several more times.

I am contimplating doing a mid drive, would be so much nicer I think beause its such a low power unit 36V, but I did upgrade the gears, I think the clutch is still a 2 peice, but I will buy a 1 peice clutch and cover from em3ev. My cover plate is horribly mangled.

 

[spinningmagnets]

Its complex to take a geared hub and adapt it to have a stationary shell and a spinning axle. On a DD hub, you can't do that. On a geared hub, the magnets on the rotor are attached to a separate piece, on a DD hub, the magnets are attached to the outer shell. The wires have to be attached to the phases on the stator, and if the shell is stationary, then the stator is the piece that would spin. It would require adding brushes to allow stationary phase wires to power a spinning stator.

Fix the axle as stationary, just like when its in the rear drop-outs. Drive the shell, just like stock. If you want to make a shield over the spinning shell, its easy and cheap to create.

 

[amberwolf]

On a DD hub, you can't do that.

You can, but it's a PITA. See my post above for the thought experiment.

 

[izeman]

On a DD hub, you can't do that.

You can, but it's a PITA. See my post above for the thought experiment.

tbh i have NO IDEA what you tried to explain
maybe post a picture? i'd be interested to see how this could work in real life ...

 

[999zip999]

Experiment that how those get done. Good luck. Show and tell.

 

[spinningmagnets]

https://endless-sphere.com/forums/viewtopic.php?f=3&t=84160
https://endless-sphere.com/forums/viewtopic.php?f=28&t=44997

 

[Santa'sLittleHelper]

Miles - Is that a "geared" front hub motor? What kind of drag/friction do you feel when riding with the motor turned off? Thx.

http://www.endless-sphere.com/forums/viewtopic.php?p=290115#p290115

 

[Santa'sLittleHelper]

Can anyone report on what it feels like to pedal a ride with a "geared" front hub motor setup like this? Considering something similar, but don't want the ease of pedaling my FS MTB to become a horendous pig to pedal when not under power. Is dragging that a "geared freewheel" front hub motor when turned off a real chore? Thx.

A Bafang BB-drive from d8veh...
http://endless-sphere.com/forums/viewtopic.php?f=3&t=37999&p=612221#p611970

 

[fourbanger]

Also, what kind of pants do you people wear? These setups look dangerous.

 

[Warren]

I don't notice any extra drag from my geared hub setup. What is noticeable is the extra weight of a motor/controller/battery, when pedaling unassisted uphill, and when flying downhill. Nothing like an extra 40 pounds on descents.

 

[markz]

Nothing like an extra 40 pounds on descents.

makes you go faaaaaaster huh :wink: oh wait what what did Newton say

 

[Warren]

markz,

Do you ride your bike in a vacuum? You know why they set a fixed gross weight for soapbox derby cars? In a fluid, for two identical objects, the one with greater mass has a higher terminal velocity.

 

[markz]

I skipped that class decades ago. It is all Mr. Google's class nowadays.
I thought it did not matter what the weight of an object was, both would fall at the same speed.
So us "heavier" dudes actually have an advantage.

Darnit
https://en.wikipedia.org/wiki/Gravitational_acceleration

 

[Warren]

Starting at the top of a hill, side by side, both bikes will accelerate at the same rate, but the lighter bike will reach its terminal velocity as the heavier bike keeps accelerating. So long suckers!

 

[sn0wchyld]

Starting at the top of a hill, side by side, both bikes will accelerate at the same rate, but the lighter bike will reach its terminal velocity as the heavier bike keeps accelerating. So long suckers!

Just sounds like a good excuse to drink more beer.

 

[APL]

Last post April/2017? All I see is empty beer bottles and spider webs in here, must have been a hell of a bender... :wink:

Anyway, thought I'd back some rides up into the line up, and put the kickstand down. Yea, she's a flat footer, but a mid drive
just the same. Not quite as nimble as the off roaders I see here, but she feels real good cruise'n the hood.

And the potential for putting some serious power down on the pavement should be obvious. Slide a Crown motor in there,
and some kind of monster pack, and I'm pretty sure you'll be looking for a new drive system on the rear hub.

But all that's a little illegal, he, he.

More on this build here; https://endless-sphere.com/forums/viewtopic.php?f=6&t=95745

And a righteous article by spinningmagnets here; https://www.electricbike.com/appel-cruiser/


View attachment 1

 

[fourbanger]

That's pretty wicked. I've been thinking of something along the same lines for some time.. I like how you didn't have to drill all the way through the side plate to get everything locked in place. Looks like you've got enough axle left that you could fit one of those dinky 12t freewheels so you could still pedal along if you ever wanted to up the voltage.

Well done!

 

[APL]

Thanks fourbanger, the front gearing thats on there now is 16T + 40T? Thereabouts, and I will sometimes pedal on the big
hills to help with battery range, if it's a long ride. Fairly fast spin..but I can do it. I could put a bigger chainring on there though.

Or, like you say, a higher gear in back. (or are you talking 12T in front?) In one of the high rear gears, pedaling is doable,
although the pee wee cranks don't help matters. With a slight design change, you could use longer crank arms.

The sit down position doesn't lend itself well to any serious pedaling, as compared to a road bike, but is still good for some
continous assistance.

Another thought I had , was to use a multi cog freewheel and der on the motor, instead of a single freewheel. But I think the
chain line may be too short. It would need to be experimented with. Perhaps a front der, jockey der, and double chain rings?

Another nice feature of this set up is the fact that you can pedal while coasting and it will turn the motor, if you hook up the
regen mode, there may be some beneficial charging. Or if you prop the wheel up, or disconnect the chain, it could make a
people powered generator.

 

[amberwolf]

Another thought I had , was to use a multi cog freewheel and der on the motor, instead of a single freewheel. But I think the
chain line may be too short. It would need to be experimented with. Perhaps a front der, jockey der, and double chain rings?

The distance between your motor and the rear axle looks about the same as a typical bike's BB-rear-axle distance, so it's probably long enough to use multi speeds on the output of the motor to the rear wheel.

But the distance between motor and cranks may be too short for more than a couple of sprockets.

On my SB Cruiser trike, I had planned to put a multispeed cluster on the input of my 3speed IGH and be able to shift gears on both of those, and/or have a shiftable triple on the front, but the frame-mounted IGH is too close to the cranks, and the chainline is short enough that it causes the chain to pull off the top of the rear sprocket, or the bottom of the front sprocket, wenever I am backing up. :/

So I ended up lining up the granny gear on the frotn triple with the single sprocket on the IGH input, to get the lowest possible pedaling gear I could, since for me my pedals are more a backup in case of complete electric drive failure. I pedal all the time while riding but it's not really contributing anything past the first couple MPH in that gear. I just don't have the strength and can't handle the joint pain to do it all the time, so it's just geared as low as I can get it, with the IGH to let me gear it down more if I have to pedal without motor.

If I ever get to redo it I'll probably just put two IGHs in series, so the chainline always stay the same but can still shift more gears.

 

[John in CR]

Properly geared adequately powered ebikes have no need for multi-speed setups unless you have drastically different riding uses, eg normal riding as well as low speed mountain climbing or otherwise hauling big loads. My solution has always been more power on tap, but some day I'll build a retro-direct 2 speed ebike so I can have billy goat climbing to go with modest power.

 

[APL]

Depends on your riding needs for sure, but it doesn't hurt to speculate on drive variations. Personally I don't see a need
for change, because I don't pedal all that much. I get my exercise from my road bike. But I can see where others would
want more pedaling involvement. Fourbangers point was if the battery voltage increases to say, 60v or more, then the
pedal system would possibly be to slow to be useful.

And I agree, it would be nice to have a front gearing option, although a large chainring might do the trick.
As amberwolf stated, the chain line may only be good for a few gears.
But perhaps that might be enough.

With the drive cog mounted right next to the motor face, there may be enough room to place a 5spd(?) freewheel.
And if the drive side 'dropout/motor mount' were to be a larger version with a der hanger, that connects the three
frame tubes, it would make things easier. Although a pedal extension may be needed to clear the der.
Dual chainring guards may keep the chain on the front ring.

Excuse the quick sketch.



A lot of if's and maybes, easiest thing to do is just keep the voltage low.