My new project: Converting my Cargobike to a E-Cargobike

[krelle52]

Hello

I'll make my cargo bike to an e-cargo bike. But is slightly in doubt. Which motor should I choose. I've looked at ProKit 901 750W, but it is a good choice?

My setup is a motor on each front wheel (20"), each with a 36V/16Ah battery.

I do not care about speed. I just need to be able to bring myself, the bike and up to 150 kg of load (a total of around 278kg max) effortlessly up hills and start easily.

I've looked a bit on the different motors. Magic Pie has a bit more torque. But I do not like the price and appearance and I do not want a built-in controller.

So if it was you, what would you buy?

I would also like to hear about the pros and cons of the two motors

I have enclosed two pictures of my bike. Taken from the manufacturers website: www.ladcyklerweb.dk/bakfietsen/model-030-db-b-1.html

thanks in advance

/Krelle52

[Bikemad]

So if it was you, what would you buy?

I would go for a pair of 20" Magic Pies with external controllers. The external controller will make it much easier to reverse the motor direction on the left hand wheel to match the right hand wheel rotation.

Pros:
The cast rims will be much stronger than a spoked double walled rim and will handle the lateral side forces much better. As there are no spokes to work loose (or break) the wheel should remain nice and true, even when subjected to the extreme side-forces that are present when negotiating tight bends at speed (especially when fully laden).
The larger width rims can also be fitted with heavier duty tyres for load carrying.
The Magic Pie can easily handle 750Watts each on 36V, and the larger hub diameter (with additional magnets and coils) will provide more torque for acceleration and hill climbing (and the regenerative braking effect should also be stronger too).

Cons:
Each Magic Pie front wheel kit will cost $5.00 more than the HBS 36V500W kit.
The Magic Pies will be heavier, slightly slower, and may produce more resistance to pedalling when they are turned off, but I would expect the motors to be used most of the time on this particular type of vehicle.
From an aesthetics point of view, the directional cast wheel pattern will be reversed on one side compared to the other.
The rim area is quite narrow where the "V" brake blocks are forced against it.

Please remember this is just my own opinion, but ultimately it is your choice, and you must decide which motor you will be more content with.

Alan
 

[krelle52]

A rookie question: Why are there less torque at 48 volts than at 36 volts on a Magic Pie. When the torque is much higher at 48 volts than at 36 volts on a ProKit 901

MP Data Sheet:
Max torque @ 36V: 29.73 N.M
Max torque @ 48V: 27.66 N.M

http://www.goldenmotor.com/magicpie/MP-performance%20data%2036V.pdf
http://www.goldenmotor.com/magicpie/MP-performance%20data%2048V.pdf

Golden Motor lists:
Max torque @ 36V: 27.3 N.M
Max torque @ 48V: 34.4 N.M

http://www.goldenmotor.com/magicpie/compare.html

Maybe it's a stupid question but I can not quite see the logic.

If HBS48F is a stronger motor than the 48V Magic pie. Should it then not be the HBS48F I used for my project?

I just need to be able to bring myself, the bike and up to 150 kg of load (a total of around 278kg max) effortlessly up hills and start easily.

I want to be sure that I have chosen a sufficient powerful motor before I buy. It's a lot of weight!!!

/ Krelle52

[Bikemad]

A rookie question: Why are there less torque at 48 volts than at 36 volts on a Magic Pie. When the torque is much higher at 48 volts than at 36 volts on a ProKit 901

MP Data Sheet:
Max torque @ 36V: 29.73 N.M
Max torque @ 48V: 27.66 N.M

On the dynomometer test which produced those results, the torque (and current) increases as the wheel is loaded.


The 36V test was loaded to a lower speed than the 48V test, hence the higher torque.
If the 48V motor had been loaded to the same 202rpm, the measured torque would have been much higher.

If you compare both motors at similar current readings you will see that the torque is very similar:

23.15Amps @ 36V = 27.2Nm of torque @ 202rpm
23.16Amps @ 48V = 27.4Nm of torque @ 280rpm

Although the torque is similar, producing this torque at a higher rpm equates to more power.

If the torque output from the 48V motor was put through a 100% efficient 1.386:1 reduction gear, it would produce an output torque of 37.98Nm at 202rpm, which would be 40% more than the 36V motor.

I've just done a quick stall test comparison between 24 and 48 Volts using 14Ah SLA batteries on my Magic Pie.
With a digital luggage weighing device attached by a strong piece of cord so that is is pulling right on the outer edge of the tyre (Maximum Diameter on a 26 x 2.35 tyre) I get a reading of around 31lbs/14kg @ 24V and 32lbs/14.5kgs @ 48V.
My spreadsheet calculates this to be just over 45Nm of torque @ 24V

Unfortunately, my Magic Pie's internal controller only allows around 20 Amps max, regardless of voltage, which is why I'm keen to try dual internal controllers for double the torque (hopefully).

Increasing the current mainly increases the torque, whereas increasing the voltage mainly increases the speed.

I hope this makes sense.

Alan
 

[krelle52]

Hi Alan

I think it makes sense.

Originally I had decided to use a Magic Pie with external controller. But when I saw that Prokit 901 had more torque and was cheaper, I became somewhat in doubt. But I think I stick to my original decision and go with a MP.

The problem now is to find a place to buy MP with external controller. The only place I could possibly find MP with external controller even mentioned, is a order form on goldenmotor website. But no prices on the website as there are with all the other motors they sell. I asked a dealer in europe, but they do not have any. But they could offer a motor which is very similar. So maybe I go with that motor  

So if there is anyone out there using a MP with external controller. Help .. Where did you buy yours?

I would like to buy in Europe, so I avoid surprises with customs and tax.

/Krelle52