Pedaling an x5 - need an explanation.

[lazarus2405]

So a week ago, I was doing the first capacity tests of my batteries, and I ended up two miles from home at my (self-imposed) LVC and without a way to charge. So, I pedaled back home, using as little power as I could on hills and to fight the drag from that big huge 5304.

Oddly, I found that it's far easier to pedal without any assistance above 12-13mph than below that speed. It was very noticeable. Since it was a 26" wheel, that comes out to about 150rpm. Why should it be easier above this value and harder to pedal below it? Can anyone offer an explanation?

 

[Ypedal]

Momentum i think.

At low speed, any resistance is felt the most between pedal pushes.. but once you get moving all that weight, the bike, you, battery, act like a flywheel effect and smooths things out lol...

But i know what you mean.. i've seen this as well.. and sometimes i think i'm just a little krayyzee.. ... but i feel better now.

 

[Ypedal]

Also.. a weird thing i've noticed ( among other things.. )

If i spin a hub motor manually, the bike being upside down.. it will buzzz to a stop..

If i spin this same hub.. REALLY hard.. it will lock up and STOP suddenly..

I'm sure some EE can explain this in a more scientific way.. :wink:

 

[D-Man]

Also.. a weird thing i've noticed ( among other things.. )

If i spin a hub motor manually, the bike being upside down.. it will buzzz to a stop..

If i spin this same hub.. REALLY hard.. it will lock up and STOP suddenly..

I'm sure some EE can explain this in a more scientific way.. :wink:

I'm glad that its normal for the hub motor to "lock up" when spun. I noticed this from the beginning and worried one day I might be fipped over the handlebars. I assume its normal anyway. :|

 

[Link]

If i spin this same hub.. REALLY hard.. it will lock up and STOP suddenly..

Interesting; my BD36 does nothing of the like. Was this with or without the controller? Mine IS brushed, though...

Lazarus: My hub does the same thing. I'm also inclined to think it's a momentum thing. The extra weight in the wheel is more noticeable. If I switch gears a lot, I don't notice it.

 

[fechter]

Also.. a weird thing i've noticed ( among other things.. )

If i spin a hub motor manually, the bike being upside down.. it will buzzz to a stop..

If i spin this same hub.. REALLY hard.. it will lock up and STOP suddenly..

I'm sure some EE can explain this in a more scientific way.. :wink:

When the controller is powered off, the FETs are off, so you only have the magnetic cogging of the pole pieces. If you spin it hard enough, the motor generates enough voltage (like regen) into the main capacitors on the controller so it powers up long enough for the FETs to turn on. When the FETs turn on, they basically short the motor windings, causing a braking effect.

That's just a wild-ass guess BTW.

 

[Jozzer]

And "one of fechters wild-ass guesses is worth a thousand tests" :lol:

 

[Mathurin]

I'm glad that its normal for the hub motor to "lock up" when spun. I noticed this from the beginning and worried one day I might be fipped over the handlebars. I assume its normal anyway. :|

Well played!