Help! Swytch Kit - Big Rolling Resistance - Xiongda, AKM hub - checking/help

[vfr400]

Another reason that the tiny motors don't freewheel so well is that they have very little mass and their mass is very close to the centre, so when you spin the wheel it has a lot less kinetic energy to keep the wheel spinning than a larger motor.

The moment of inertia relates to the square of the radius of the mass: I=MxRxR/2, so a motor twice the diameter and having the same weight will spin four times as long if the friction were the same, but that doesn't mean that it's better. The resistance at constant speed would be the same.

Some of what you lose in the friction, you'll gain back when accelerating. The much lower moment of inertia will mean a lot less energy is required to get up to speed - and you'll be able to stop quicker.

 

[Carbon.]

Another reason that the tiny motors don't freewheel so well is that they have very little mass and their mass is very close to the centre, so when you spin the wheel it has a lot less kinetic energy to keep the wheel spinning than a larger motor.

The moment of inertia relates to the square of the radius of the mass: I=MxRxR/2, so a motor twice the diameter and having the same weight will spin four times as long if the friction were the same, but that doesn't mean that it's better. The resistance at constant speed would be the same.

Some of what you lose in the friction, you'll gain back when accelerating. The much lower moment of inertia will mean a lot less energy is required to get up to speed - and you'll be able to stop quicker.

Yes, this is obvious. However it seems that Xionda has much bigger rolling resistance that others (because of big gear ratio 1:17,5).


Nevertheless it has no chance with this:
Cute Q85 250W - similar size and weight. Reduction ratio 1:12,6

 

[vfr400]

Yes, this is obvious. However it seems that Xionda has much bigger rolling resistance that others (because of big gear ratio 1:17,5).


Nevertheless it has no chance with this:
Cute Q85 250W - similar size and weight. Reduction ratio 1:12,6

That motor is quite a bit bigger - not the same size at all.

 

[Carbon.]

That motor is quite a bit bigger - not the same size at all.

As I can see the diameter difference is about 27 mm
(101 vs 128 mm).

 

[vfr400]

As I can see the diameter difference is about 27 mm
(101 vs 128 mm).

28mm is nearly 1/3 bigger. You don't need drawings: You only have to look at the motors to see the difference. Spot the Xiongda:

 

[harrys]

My Q128 is roughly 128mm beteen opposite spoke holes in the flange, My AKM100 amd Q100's are about 108mm with the same measurement. Wouldn't a Q85 and Q75 be closer to 80-90 mm?

And for the OP, one of my Q100's will take 12 seconds to spin its 20" wheel down from 20 mph. Another will take 7 seconds, but that wheel is severely unbalanced. I think all the slime in the tube congealed in the bottom with the cold winter weather.,

 

[Carbon.]

Yes, the advantage of Xiongda is its small size.
BTW I found also a video with similar dimensions front hub (there is no more details), please take a look just to compare.
(I think that free rolling is more than dozen seconds, starts 2'36'')

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I've tried just about every type of motor. I can't say that I've noticed that much difference when riding apart from power and noise.

In theory, AKM should be the most free-running because the clutch disengages every part of the motor when free-wheeling, though I had a MXUS motor that would spin forever, and the Cyclamatic motor, whatever it is, also runs very freely.

What you gain from the tiny Xiongda is its light weight. Every motor has advantages and disadvantages, but I' can't think of any that I didn't like.

The special controllers for the early high speed Xiongdas had an annoying delay because they were sensorless. I think I heard that they fixed that and they're now sensored. Do you get much of a delay between when you start pedalling and when the motor kicks in? How many pins in your motor cable?

This is a Xiongda plug (9 pin), so would it be possible to connect to other current front hub model like eg Q75, Q85, Q100, Mxus XF07, XF08?

 

[harrys]

The space between the screw holes on a disk brake rotor is 45 mm, so if I :compare that distance on the mini-me video, we;re looking at roughly 90mm between the spoke holes on the flange,far smaller than my Q100/AK100' at 108mm.

 

[vfr400]

That looks like a rebranded Keyde motor. tT

Bafang also make a mini motor, which you sometimes see on Aliexpress. I've been looking for the rear cassette version, which I've seen on some OEM bikes, but never at any resellers.

Most motors use that standard 9-pin connector.