Hub vs Crank Drive Hill Climb

[Andy88]

Yeah, it make no odds really. It's still an MTB and handles well in the mud. That's what I really like about them. The fact that it's a pedelec makes going off road, off the beaten track, loaded with pedestrians, an effortless pleasure. I'm sure that you'll enjoy whatever you end up with.

Thanks, its given me a new lease of life become fascinated with the recent development of ebike options, last I looked was 2004, in those days all the ebikes resembled a chieftain tank lol.

Nice video, are u using a go pro to film?

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[LeighPing]

Nice video, are u using a go pro to film?

A cheap and cheerful TCL SVC 200, if you can find one to buy now! They were voted by 'Techmoan' (a UK cam reviewer) as being the best sub £100 cam in 2013. They went down to as low as £25 and appeared to have been all bought up. I've had mine over a year now. It has a slim profile and can take some hammer, as shown in the second vid below, when I lost it briefly.

 

[Croxden]

Please don't encourage him, it's enough with one vid each post but it's now two.

 

[Andy88]

Please don't encourage him, it's enough with one vid each post but it's now two.

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[LeighPing]

Please don't encourage him, it's enough with one vid each post but it's now two.

I agree.. but I'm housebound with man flu. When I should be out there saving humanity on my bike.

 

[Deleted member 4366]

That video is a bit misleading because they don't say how much power the motor controllers are allowing. The thing that will get you up hills is basically the product of volts and amps (volts x amps). The higher that number, the steeper the hill you can climb, but there's a proviso:

The motor has to be able to spin at the speed where it has efficiency. That speed needs to match its hill-climbing power (V x A). That's not normally a problem for a crank-drive because you can change the motor speed with the gears, but most hub-motors's speed is the same as the wheel, so there's more chance that the motor's optimum climbing speed doesn't match its power. If its winding speed is too high, so that it doesn't have enough power to reach its optimum climbing speed, it can't use enough of its electrical power for motive power. If its winding speed is too low, so that it maxes out on speed, it won't be able to use its available power to go any faster.

That means that a crank-drive and a hub motor with the same controller and battery will climb at the same speed provided that power needed for the speed of the climb matches what's available from the hub-motor at that rate of climb. In all other cases the CD will win.

Regarding the Bafang BPM motors and similar ones. The "250W" one can handle about 22 amps. After that, it becomes saturated, so increasing the current further doesn't make it climb any better. The 500w version looks the same, but it's different inside, and it can give the extra power up to at least 30 amps. You can get extra power from both of them by increasing the voltage, though that affects the speed and efficiency. As voltage increases, the zone of optimum efficiency moves to a higher speed in proportion to the voltage. Its better to run a low speed 36v motor at 48v, which will convert it to a motor with 33% more power and speed, and it'll then be a medium speed motor, i.e. a motor with best efficiency at a speed 33% higher. That's perfect for a hub-motor that runs optimally at 15 mph and you want to run it at 20 mph, though it doesn't work if you want to run a 15 mph motor at 30 mph because it needs four times as much power to go from 15 mph to 30 mph, but doubling the voltage only gives twice the power, so it'll probably run inefficiently.

 

[Andy88]

That video is a bit misleading because they don't say how much power the motor controllers are allowing. The thing that will get you up hills is basically the product of volts and amps (volts x amps). The higher that number, the steeper the hill you can climb, but there's a proviso:

The motor has to be able to spin at the speed where it has efficiency. That speed needs to match its hill-climbing power (V x A). That's not normally a problem for a crank-drive because you can change the motor speed with the gears, but most hub-motors's speed is the same as the wheel, so there's more chance that the motor's optimum climbing speed doesn't match its power. If its winding speed is too high, so that it doesn't have enough power to reach its optimum climbing speed, it can't use enough of its electrical power for motive power. If its winding speed is too low, so that it maxes out on speed, it won't be able to use its available power to go any faster.

That means that a crank-drive and a hub motor with the same controller and battery will climb at the same speed provided that power needed for the speed of the climb matches what's available from the hub-motor at that rate of climb. In all other cases the CD will win.

Regarding the Bafang BPM motors and similar ones. The "250W" one can handle about 22 amps. After that, it becomes saturated, so increasing the current further doesn't make it climb any better. The 500w version looks the same, but it's different inside, and it can give the extra power up to at least 30 amps. You can get extra power from both of them by increasing the voltage, though that affects the speed and efficiency. As voltage increases, the zone of optimum efficiency moves to a higher speed in proportion to the voltage. Its better to run a low speed 36v motor at 48v, which will convert it to a motor with 33% more power and speed, and it'll then be a medium speed motor, i.e. a motor with best efficiency at a speed 33% higher. That's perfect for a hub-motor that runs optimally at 15 mph and you want to run it at 20 mph, though it doesn't work if you want to run a 15 mph motor at 30 mph because it needs four times as much power to go from 15 mph to 30 mph, but doubling the voltage only gives twice the power, so it'll probably run inefficiently.

I had to read this several times but absolutely fascinating, great contribution in demything certain aspects.

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[Trevormonty]

Andy please turn "sent via huwaei phone" OFF. Its a setting in tapatalk.

 

[Andy88]

Andy please turn "sent via huwaei phone" OFF. Its a setting in tapatalk.

Has that done it?

 

[D8ve]

Has that done it?

Yes sweet

 

[Andy88]

 

[Croxden]

I agree.. but I'm housebound with man flu. When I should be out there saving humanity on my bike.

Do you watch Dave Gorman? He did a bit on 'man flu'. It's just a cold.

 

[Wisper Bikes]

Beware man flu!

On Thursday I went down with what I thought was at best a rare and particularly deadly tropical illness picked up on my recent trip to China! I was laid up for the whole day convinced this was the end! On Friday, of course, I felt a bit better but my wonderful wife pursuaded me (made the appointment for me without my knowledge) to go to the docs. It turned out I had been hit with Novovirus, it's rife at the moment and more contagious than flu. No cure just don't eat, drink loads of fluids and get over it. Today Sunday I feel great again but it was really dreadful.

If you do feel ill with head ache, stomach cramps and a temperature, the advice is to stay at home and use your own towel etc to stop spreading it. It should only last a few days.

All the best, David