NoPhart

One thing I have noticed with my eBike conversion is the amount of drag on the crank when the battery is turned off (or when you run out of juice). The only mid-drives I am aware of that have zero drag are the ones that have 2 chains; one from the motor to the crank and the other from the crank to the cassette (normal bike setup). I guess the motor sprocket on the crank has some type of free-wheel setup that only connects in one direction.

Are there any mid-drive conversion kits that have zero drag resistance when pedeling with the battery off or after it runs out of juice?

Arcanum

The problem you're seeing is that pedaling when the motor isn't running essentially means you're running the motor in reverse, as a generator. Instead of electric current in the motor windings generating a magnetic field that moves magnets attached to a crankshaft that ultimately spins the chainring, you're spinning the chainring that rotates the crankshaft that moves the magnets that generate an electric field that create an electric current in the motor windings. Generating that electric current uses energy that could otherwise be used for moving the bicycle.

So, fundamentally, you're unlikely to get away from that resistance entirely without some clever (and probably less reliable) engineering.

350htrr

Exactly, tho there are some systems out there that you can, pedal just like a regular bike with the system off... As there is some (clever engineering) around, Just costs more...

Robert C

As you noted, the models with two chains all have freewheels. Further, the mid drives are nearly all made with geared motors; they will also freewheel.

I am left wondering, what model of mid-drive do you have that doesn't freewheel?

The only one I can think of is the old "stroke-monkey" design. I would never recommend one, like that, that has a non-geared motor directly coupled to the bottom bracket. It has been off the market for some time, I saw it as being unsafe.

Now, if you mean an honest "zero" drag; it cant't exist. Even magnetic bearings, that cannot function anywhere but the most controlled environments, have some drag.

Arcanum

Maybe I'm wrong, but I believe he's talking about additional resistance while pedaling with the motor off, not additional resistance while coasting.

BruceMetras

I'm running two road bikes with BBS02 kits and I pedal both frequently without assistance (mainly to ride with friends @15mph) .. other than the extra 18lbs of added motor/battery weight, neither seem to slow me much due to extra pedal drag .. on a bike stand, I can spin the cranks with one finger and feel some drag, but on the road pedaling, not much.. one of the reasons I like the BBS02 mid drive so much..

Robert C

I get that; but most of the geared motors freewheel when you ride them without the motor on. That is the reason I went with a geared hub instead of a direct drive (other then weight). When I pedal it, with the motor off, there is, effectively, no motor resistance.

I am really trying to think of which mid-drive he has experienced, other than the possibility of a stroke-monkey design. I haven't actually seen an old style Cyclone, did they allow for the motor to release when pedaling?

I agree with the above post, a BBS02 will probably give you what you want (again, if you want true-zero drag, it can't happen).

Arcanum

I'll check it again to make sure when I get a chance, but I noted when installing my BBSHD that there was significant resistance when rotating the crank with the motor off.

NoPhart

As stated to the left, my ride is a BBS02 BaFang 350W mid-drive. I am referring to the resistance while pedaling with the power off or when out of juice. In my opinion there is substantial resistance. My guess is that it relates to the magnets in the electric motor. I understand that even bearings have resistance.

You can ride/cruise the BBS02 without power, but the resistance is VERY noticable, and seems to limit the speed you can ride the bike when compared to a normal bicycle.

With the dual chain mid-drives, the electric motor doesn't turn when you are riding without power, thus you have no electric motor resistance, but obivously still have bearings and whatever resistance there is similar to back pedaling on the chain ring that the electric motor attaches to.

Arcanum

I checked mine and there seems to be more resistance than I would expect from a normal bottom bracket. Whether it's due to running the motor in reverse or an inefficient freewheel system or what, I couldn't say for sure.

first trip

hi i tried aelectric bike motor form yamaha 250wsee pict
and there was a lot of drag when pedaling with motor off. THe bike had only one ring at front so the number of speed available was the number of ring in the back. what do you mean by 2 chains ? there has to be a second chain for all somehow no?

I'm looking at Cyclone 3000W lunacycle.com/cyclone-mid-drive-3000-watt-planetary-kit/
planetary from luna cycle, it is not so expensive atm. Did anyone try it ? Does this setup allow us to use the bike without drag when pedalling without the motor help? i mean with his system, when you dont use the battery power, does your bike acts like a regular bike (no drag from motor)

txh!

Robert C

You are responding to a old post. Ebike technology changes rapidly. Here is an example of a system using two chains:

from here

As you can see, there is a chain being used to reduce the motor speed to a normal crank speed. Really, if you just want something usable I recommend the Ba-Fang mid drives form the site you referenced.

NoPhart