considering a gearless hub kit

[trex]

Hi everyone,

Hub kits like the Bafang CST or BPM seem like the way to go but I thought there are a few disadvantages with geared hub motors:

1. wear and tear of the clutch and gearbox.
2. motor torque and efficiency drop after 10mph, this is where wind resistance becomes significant.
3. limited to 270 RPM.

I've been reading up on the Swiss GoDrive motor (cannot afford it but no harm in checking) and thought that perhaps if high power motors coupled to 36V 20A controller are not illegal as long as speed is restricted, the gearless motor seems to be a better choice if you ride mostly at over 10mph.

I have no experience of this type of motor and would appreciate if any member of the forum likes to share his/her knowledge.

 

[Deleted member 4366]

1. Wear ant tear on the clutch and gearbox is not a problem. When was the last time you heard of a problem.
2. Motor efficiency drops at low speed, but torque increases
3. Speed only depends on the winding, but the higher the top speed, the worse the low-speed efficiency.

Non-geared motors (DD) tend to suffer from points 2 and 3 worse, so no advantage at all. DD motors are a bit quieter and you can get regen, but on the negative side, they have more drag when power's off, and they have to be much bigger and heavier to get the same low-speed torque. If you want regen, you won't be able to free-wheel down-hill at much more than 15 mph, so, if you ride with friends, you won't be able to keep up unless they also have DD motors.

 

[flecc]

The BionX is also a direct drive, as is the Sparta Ion, both ridden. They are generally in the rear wheel due to ther larger size and weight. In general direct drive motors are consistently quiet throughout their speed range and the motor part very reliable as you'd expect. Torque for hill climbing is often lacking compared with an internally geared motor, especially at low speeds, but that can be offset to some degree as in the BionX with various switched power modes. The downside of that can be high consumption in a high power mode, for example in the BionX maximum power mode 4 continuously the range can slump to below 18 miles from their 36 volt 10Ah battery.

However, if you are in a fairly flat area where the highest power modes are not needed, spend most of the time over 10 mph as you say and don't want to ride without power or beyond the assist speed limit, a direct drive is a great choice for silence and reliability. It would be my choice in those circumstances. Note that there is always some drag if riding without power since the motor has no freewheel.

N.B Crossed with d8veh's post.

 

[trex]

Thank you d8veh and flecc.
I also agree with d8veh that gearless motors suck at low RPM.
I am using the ebikes.ca Hub Motor and Ebike Simulator to compare various motors at around the legal speed limit 25kph but the site does not have the latest gearless motors from leafmotor.com, the one I am most interested in because they have the lightest gearless model.
Xiongda and 9continent.com also have new lighter gearless motors but no datasheet to help to compare them.
If I go for the CST or BPM, battery and controller will have to be of similar performance so it's down to the choice of motor. Some gearless motors have 5 year warranty because there is not much inside that can go wrong, especially the hall-less models, geared motors have only one year warranty. So which one?