GM Magic Pie 500km test

[Hardcore]

hey all,

I now have the MP for several weeks and I got 500km on the speedo.
It is amazing that this hub motor was so easily to install( I got no experience at all )
I drove an average of 38km/h with 43.2 top (no pedalling)
No overheating yet.


Any questions, don't hesitate:


greetz,



kevin h (the Netherlands)

[ggielen]

Hoi Kevin,

I understand from one of your previous posts that bike + rider is 80kg, and assuming that's still the case, that's pretty light
Is the 38km/h the average of the entire 500km? That's quite fast.

By now maybe you also have an indication of the range you are getting out of one battery charge? Considering that I think you are pretty much maxing out the bike -all- the time, that would be a pretty good max load stat.

Gijs
Meeuwen, Belgium/ occasionaly Delft, NL

Edit: nearly forgot to ask, what tire are you using to get these speeds? I'm mainly interested in the circumference, as using that we can determine what rpm your Magic Pie is running at 

[Hardcore]

26inch big MTB tires, I did not gain weight if that's what you're asking. it's still around 80kg.
Range is 35 km on 12ah full throttle,
Range on average 25km/h is 48km,
GOD bless cruise control

circumference: (26/2)*2.54*2*(pi)= 207.5 cm
                                               = 2074mm
                                               = 0,002074km
38km/h
38/0,002074=18322,082931533269045323047251688 rph
18322/60= 305rpm
 
is this correct

[Hardcore]

also my top speed, according to the datasheet it should get 350rpm

350*60*0.002074=43.554km/h
_________________________________________

??: [78.0%]
??: 12.77 (N.m)
??: 320 (r/min) almost 305rpm
??: 11.45 (A)
?: 428.27 (W)

i am drawing 11.45 A so almost 12 A so 1 hour on max speed, range would be 38, I got 35 so pritty acurate.

[Bikemad]

Hi Kevin

Those figures certainly look good to me, with the exception of your anticipated top speed.
The maximum rpm of the Magic Pie at 48V is shown as 357rpm, but this is the no load speed.  When you put a load on the wheel the rpm will decrease accordingly. This is particularly noticeable with wind resistance, ground conditions and hills etc., the harder the motor has to work, the slower the top speed will be.

Your calculated max speed of 43.554km/h would be achievable with no wind resistance or frictional losses from the tyres etc.,but unfortunately we live in a real world where friction and wind resistance are always present, so don't expect to achieve this speed without a long steep hill, or a very strong 45km/h+ tailwind, or your legs providing the required power to get you there!
Because at 350rpm the Magic Pie will not be providing much assistance at all.

Here's a rough guide to the data sheet figures:
Efficiency:     78.0% (Power Out/Power In)
Torque:         12.77 (N.m) (turning force needed to balance the applied load)
Motor Speed: 318 (r/min)   (actual wheel speed)
Current:        11.36 (A)  (current drawn by the motor)
Power Out:    425.27 (W) (energy produced)
Power In:      545.3 (W)   (energy consumed)

Alan
 

[Hardcore]

wel my top speed of 43.3 was with wind so...

[ggielen]

Your calculations are correct, good information! I plan to use 700c wheel size on mine with balloon tires adding to the total circumference, together with a more aerodynamically optimum design I'm targeting 45 km/hr, so these numbers really seem like I might get there. Bikemad is absolutely right about your top speed, you won't achieve that without some form of assistance, at top speed (rpm) the Pie is only putting out 64W, not even nearly enough to sustain that speed.

Range and ride time are pretty awesome too! And maybe you didn't gain weight, but maybe your bike got some extra parts, I remain diplomatic 

[Hardcore]

haha nice, 700c is 28inch right,

305*60*0.002234= 40.8km/h on 305 rpm

45/0.002234/60=335

you need to get 335 rpm to go 45km/h

[ggielen]

Yes, that's 28", but using Schwalbe Big Apple tires (ETRTO 60-622), the effective circumference of the wheel + tire will be 2350mm, so:
45/0.00235/60= 319 rpm

At 319 rpm, the Pie is still delivering about 530W, which I think will be sufficient to sustain the target speed for my lowracer trike. The effect of the increased tire size makes a small but noticeable difference, at least on paper  . Those tires are huge, but for rolling resistance they should actually be pretty good! They weigh a lot more, so acceleration will suffer of course. As an added benefit, they will act a bit like 'suspension', delivering a smoother ride, which at those speeds is definitely a plus.

And the 45km/hr target speed means I would theoretically be able to comply with the 'motorfiets' regulations (small motorcycle class, limited to 45). This won't be an electric bike, no pedals, it will be an EV: electric vehicle!

[dajsino]

Here's a rough guide to the data sheet figures:
Efficiency:     78.0% (Power Out/Power In)
Torque:         12.77 (N.m) (turning force needed to balance the applied load)
Motor Speed: 318 (r/min)   (actual wheel speed)
Current:        11.36 (A)  (current drawn by the motor)
Power Out:    425.27 (W) (energy produced)
Power In:      545.3 (W)   (energy consumed)

Alan
 

Yes, very good,

but I think that diagram "Motor performance curve" is missing something,
I wonder what is performance on width range rpm ,max load
somewhere should be that 1 kW power
maybe power and torque depending on rpm, starting with 0 rpm

in this case it is 425 W on 318 rpm, and it would be somewhere at the end of that diagram