MagicPie Series Wheels Question

[Xntrick]

Hi everybody,

Am thinking of buying a GM pre-made MagicPie wheel.

I want to build a bike that, primarily, climbs hills well. Am I right in thinking that the 16" wheel would be able to climb steeper hills than the 28" ??    ( while giving no pedal assistance )

Also, is there any difference between the internal controllers of the various size wheels ?? Could I, for example, buy the 16" wheel and later remove the hub-motor and fit it into a 28" wheel without causing any problems ?


Sincerely,
Aging cyclist in Ireland

[Hardcore]

yes,yes
more torque with smaller rim
maybe the max rpm is different of the motor itself but this hasn't been seen so far.

[MonkeyMagic]

Hey xntrick welcome

I've used the 16" cast wheel, and have since changed to 20" mainly due to the ride height and a bit more top speed.

Yet to test, but I would say the 16" does have higher RPM than the 20" (I am only going by sound with this) and it has been mentioned previously in the forum.

It came up in another post recently, but I would say you could 'pop' (remove) the stator from the 16" magicpie and drop it into a bigger wheel diameter. I guess we would need to confirm the poles and magnets too, if they differ in some way maybe you cannot do it (the wheel may not drive properly)

Really need to test my 20" RPMmmm or ask GM what the go is compared to the 16"
My best advice is to really look into the bike frame you wish to mount this on.

A suggestion from me if you want a hill climber, is to look at a semi-recumbent or a folding bike of some sort that already has a 16" wheel.

I attached a picture of what a 24" bike looks like with a 16" cast wheel (my first install was neat right?? hehe) but this bike was VERY unpredictable to ride.

Riding with the bigger wheel up front was like it made my handling backwards/wrong. Definitely had to change that...

[Bikemad]

The internal controllers are supposedly the same, but the 16" Magic Pie was wound differently for higher speed (but with less torque), so putting the 16" motor into a 28" wheel would not provide as much torque as the standard 28" wheel, but it could well be faster, provided there is sufficient torque to actually achieve a higher speed.

The 16" Pie would require 33% more current in order to produce the same torque as the larger wheels

The 26" Pie wheel speed is 33.60kph@270rpm (max unloaded wheel speed)
The 16" Pie wheel speed is 37.44kph@480rpm (max unloaded wheel speed)

Performance figures obtained on 36V can be found here:
Standard Magic Pie performance data
16" Magic Pie performance data

If you want better hill climbing performance, you would probably be better to go for the external controller version and swap to a more powerful controller that is able to supply more amps than GM's controller will supply.
My Magic Pie's internal controller is non adjustable, and is unfortunately limited to ~20Amps, whereas a 40Amp Infineon controller would be able to supply twice the Amps, therefore enabling the same motor to produce twice the power! Plus they can be simply modified to accept a much higher battery voltage if a higher top speed is required.

Another alternative is to use dual pies (front and rear) to double the power for only a minimal increase in weight.

Alan
 

[Xntrick]

Many thanks, ALL (hardcore,MonkeyMagic and Bikemad) for your quick replies,

The bike I'm most thinking of going with is actually a 20" wheel folding bicycle.

Bikemad, you have pointed me towards 36V Performance figures for a Standard Magic Pie and a 16" Magic Pie . . . Does the 20" have the same performance figures as the Standard Magic Pie or is it different like the 16" ??

Also, can the 20" wheel take pneumatic tyres, and what type of braking systems will the 20" accept?


Thanks in advance.

[Bikemad]

As far as I know, it's just the 16" Pie that is wound differently and all the other Pies should be the same.

The 20" wheel does use pneumatic tyres, although Monkey found that 16" moped tyres seem to fit the rim better than his standard 20" BMX tyres. Check out this post for more details.
Hey Monkey, what happened to all your tyre pictures?

The 20" wheel is supposed to be able to use either disc or "V" brakes, but from the pictures I've seen, I'm not 100% convinced the rim is really deep enough for the brake blocks to have full contact.

I don't know whether Monkey has tried "V" brakes on his wheels or not.

Alan
 

[DirtyGinge]

HI all

can you take the "innards" of 2 x 16" , replace them into 2 x 26" innards,  and have a dual pie that is wound for higher rpm as opposed to torque ( as duals have so much torque to spare, rpm would be handy here)

regards

"clearly too much money on hand"
 
Dirtyginge

[MonkeyMagic]

Hey Monkey, what happened to all your tyre pictures?
Alan

I fixed that... I think it was because I changed the album name.

Hey about the V-brakes, I have not tried it as I would not even go there... With the 20" rim, it has around 5mm of rim for the brake block to grab onto.

The outer lip of the rim is rounded/smooth for the tyre.

BUT the inside lip is not rounded, and is straight edge so it would 'cut' the brake block much the same as if you ran your finger quickly around the inside of a 20" cast wheel you will slice your finger to bug#&!y.

Also - yet to be 100% sure, but I'm near certain the 2.5" tyre is the largest you can fit on the 20" cast rim. I was thinking my wheel might be out of balance, but the 2.75" could be a bit too big lol noooooooo