Regen/no freewheeling/e-clutch?

[dannym]

I have a particular design "situation" where I need a cheap hub motor capable of regen. It's not a normal bike.
I'm quite skilled and can build such a controller myself. I also have machining capabilities.

Yes I'm aware of the issues involved in regen, but it remains necessary to the design for my case. I've got A123 cells in the design that can take high charging currents. I read 10W-20W (0.5-1 N-m) drag at 15mph for an unpowered but not freewheeling hub motor- is that basically right? But to be able to regen, I can't have it freewheeling.

I'm looking at the Cute motors, which seem to fit my budget nicely, or maybe Bafang motors. The drag does concern me, they will be unpowered a lot of the time. This has made me wonder about an electronic clutch modification.
Does the "no freewheeling" option actually mean the motor doesn't freewheel, or is that only about the freewheeling capability for a sprocket for a rear wheel?

Is it possible to disable the clutch? I saw where one fellow here did exactly that, on his Bafang, permanently, with a load of JB Weld :? This looks like a "sure thing" option, but is the drag as high as they say? Are there some motors which would have lower drag? I fear nobody else has been trying to figure out how draggy they may or may not be with the freewheel disabled

What seems to be necessary is an ability to engage/disengage the clutch electronically. Has anyone ever done work in this area? Doesn't the Cute freewheel at the sun gear? That seems like it could be more of a problem to e-clutch like this, although I've not figured out how the Bafang type could be e-clutched either.

 

[amberwolf]

Is the regen so that you can recover power, or so that you can use it for braking?

If it's to recover power, it's possible that an electromagnetic clutch strong enough to hold the unit against braking forces might take as much power as you get out of the braking. Or enough so as to make it not worth doing.

If it's just for braking, it would be worth it power-wise, but may be an issue mechanically.

Another way to do this is with a dog-clutch, so that it is mechanically shifted in and out of the drivetrain only when needed. This is what I want to do with CrazyBike2 or it's descendant designs eventually. It would have a two-speed Thud-style dog-clutch transmission, with a neutral in between. Unless I am braking or accelerating using the motor, it would always be in that neutral. When power or braking is needed, it would shift into one of the two "gears", as needed.

Actual control of that I havent' worked out yet, but it should be easy to do with a linear actuator of some type, or a servo, etc. I figured on a simple comparator-type control circuit, so it'd just follow some very basic logic on when to engage, plus a manual override from the handlebar controls for any of the three positions.


Regarding using already-freewheeling motors for this, you'd just need to disable the freewheel, or replace the planetary gear unit with one that doesn't freewheel.

 

[dannym]

It's not only to assist in braking and recover some power, but I could have a little excess propulsion for extended periods. It's either that or drag the brakes which can be a high-wear thing. But also a significant portion of the time would be in neither mode and the drag of an engaged, but unused rotor during an extended period looks significant.

I'm just looking at the disassembly pic someone else took of the Cute:
http://endless-sphere.com/forums/viewtopic.php?f=3&t=13998&hilit=ananda&start=60

AFAIK the sun gear pops out when engaged, like a car starter's bendix. Could anyone verify that? I saw a pic of some sort of a popout mechanism on a similar motor but it was a Protanium in the description. If this motor doesn't have a freewheeling mechanism then obviously I need not spend time wondering how to control it.

Or... wait, I guess the sun gear itself isn't disengaging, but the SHAFT inside the sun's gonna be disengaging through some sort of tiny dog-clutch inside, right?

Seems like a mechanical lever could pop out that gear for regen.
I'm looking at the pics and it looks like a tight space. I'm not sure how an actuator could be built to DO that.

If a motor is already laced into the wheel, can it still be disassembled without unlacing the spokes?

 

[adigturbo]

Welding the one way bearing on the sun gear of my Bafang has worked fine for regen with a Kelly KBS48051E, though braking force is not that great.
Just fitted 900w cyclone with same controller, want to do regen with that instead, but with a Shimano alfine 8 hub.

Anyone got any experience with regen on internal gear hubs??