what is the way to get the best torque at low speed (0-15 Km/h)?

[asker]

Hi!

The only way I know is a powerful motor mounted in a small rim. But I'm sure there are other solutions and I hope someone in this forum knows it.

I have a pedelec bike with 28" rim that is useless in the mountainous area where I live

Best regards from  S pain!

[Hardcore]

i don't know if goldenmotor has them, but there are two option I know of: a geared hub motor or buy an double drive 1000W GM gearless brushless hub motor(should be plenty of torque for mountainious area's)

[asker]

Thanks for your answer

I think GM has at least two geared models: minimotor & Magic Pie. Maybe the Magic Pie will be appropriate to me.
Do you know other geared hub motors slower enough and  powerful enough?

What will happen if I connect the 1000w 48v
motor to a 24v or 36v controller and battery?

regards

[Bikemad]

I think GM has at least two geared models: minimotor & Magic Pie. Maybe the Magic Pie will be appropriate to me.
What will happen if I connect the 1000w 48v motor to a 24v or 36v controller and battery?

The Magic Pie is not a geared motor! Although it's direct drive, I would expect it to have at least a third more torque than the HBS36F/R motors due to it being nearly 32% larger in diameter and probably has more magnets too.
Unfortunately torque figures for this motor are not yet available, so we will just have to wait and see.

If you connect the 1000w 48v HBS36F/R motor to a 24v or 36v controller and battery it should still work, but I would expect it to have the same or maybe even less power than the 500W motor at 24v or 36v.

Alan
 

[asker]

thanks for your explanation.

let's continue to explore options while we don't know more about Magic Pie torque.

My bike has a L-ion 37v 10ah battery.
If I install the Cycle Analist and set it up to limit the maximun current discharge to 20a, which is the best GM motor for me: 36v500W or 36v750w?

[Bikemad]

My bike has a L-ion 37v 10ah battery.
If I install the Cycle Analist and set it up to limit the maximun current discharge to 20a, which is the best GM motor for me: 36v500W or 36v750w?

Here's a little comparison between the 250W geared mini motor and the 500W Direct drive motor:

The 36V 250W mini geared hub produces 20.03Nm of torque @172.9rpm (23km/h or 14.3mph with 28" wheel).
To produce this torque it will draw 13.53Amps and consume 487Watts to output 362.5Watts @ 74% efficiency.

The 36V 500W non-geared hub produces 18.24Nm of torque @266.1rpm (35.5km/h or 22mph with 28" wheel).
To produce this torque it will draw 18.43Amps and consume 659.7Watts to output 508.1Watts @ 77% efficiency.

The geared motor will produce 8.68% more torque and use 26.2% less energy, but speed will be 35% slower.

At 362.5Watts output, the geared motor is working well above its 250W rating.

To answer your question, if you are limiting the available power to 740Watts (20x37) I think you might be better off running the 500Watt motor with an extra 80Watts than running the 750Watt motor with 235Watts less power.
(I've assumed the 750Watt motor will require an input of approx 975Watts to output 750Watts with same efficiency)

With a limited current of 20Amps, I would expect the geared 250W motor to give much better assistance up steep hills than the direct drive motors, providing it is able to cope with the strain. (My rough calculations indicate the geared motor would  produce 50% more torque than the direct drive motors)

If you had a single speed bike with high gearing and pedalled up a very steep hill, you would soon be exhausted.
If the bike had low gearing you would go a lot further up the same steep hill before you needed to stop for a rest.

The same applies to hub motors, lowering the gearing (by using a geared hub) will increase the torque and allow steeper hills to be climbed with the same amount of power, but at a slower speed!

Just something you might want to think about.

Alan
 

[14K]

Bikemad,
 Considering the pictures of a fried motor we've seen here, wouldn't the larger motor be safer for mountains?

Dave

[Bikemad]

Considering the pictures of a fried motor we've seen here, wouldn't the larger motor be safer for mountains?

Hi and welcome Dave,

You may well have a point there, but at slower speeds, the direct drive motor will be overloaded more than the geared motor.
If the gear reduction was 2:1, the direct drive motor will require double the power to generate the same torque at the same speed as the geared motor, and direct drive motors have also been cooked.

Unless you can provide enough power to keep the speed high enough to prevent the motor from being overloaded, an alternative is to limit the current to a low enough level to ensure the motor will not be damaged.

The ideal solution would be a hub motor running at its most efficient torque producing speed, driving through a integrated continuously variable transmission.
A steeper hill would simply mean a slower speed, while the load on the motor would remain constant.

As far as I know, nobody has produced one yet, but I'm convinced that someone is currently working away on this idea, and I suspect it will only be a matter of time before they are available.

Alan
 

[asker]

I found manufacturers that think about the low-speed torque, like the brushed geared hubs Heinzmann 6622: 50Nm,  13mph at 26” , but are a bit noisy and expensive
I'll wait to see the features of the Pie...