Build: Cramming An X5 Into A 20" Wheel

[xyster]

Sounds great fun. Any plans for a 16 inch wheel

There's no spokes available for a X5/16" combo. Ypedal tells me the 16" wheels have 28 spoke holes, and the X5 of course has 36. But all hope is not lost! There is a 5304/12" for sale (which I'd like to put on my scooter...):

http://www.poweridestore.com/Scooter-Hub-Motors/12-Scooter-Motor
<img src="http://www.poweridestore.com/images/5304scooterhubmotorwithtire.jpg" width="600">

HubSim says it should be good for 35-40mph at 120 volts 35 amps, with 200 lbs of thrust! Look out, Lowell! (No doubt if I tried that he'd outdo me by running his 5304 without any tire or wheel Gotta keep up with the Jones's, eh?..)

 

[Ypedal]

Like this !

 

[NickF23]

hehe can't wait to to see someone try that. Could you fit it in a bicycle frame?

 

[xyster]

hehe can't wait to to see someone try that. Could you fit it in a bicycle frame?

Let's pester Lowell to do it -- he'll try anything with a bike.

I could do it on my bike, but I might have to ditch the derailleur; and would certainly have to extend the rear shock even farther so the pedals maintain ground clearance. The bigger challenge would be feeding it sufficient voltage to maintain an adequate top speed. 35mph would require meeting the motor's supposed 120 volt ceiling.

 

[xyster]

This project complete, now I can move on to the next big mod project...

 

[The7]

Beauty Machine!!

Performance???

 

[xyster]

Beauty Machine!!

Performance???

Thanks.

I'll run acceleration and hill climb tests with the new wheel soon.

Top speed: 40mph
Range: 100 miles @ 20mph on the level, no pedal
Pack: 2,500 W-H Li-ion; 84 peak volts; R=0.15 ohms (5V sag @35A); 15 kg

Motor-related characteristics and motor/overall efficiency:

 

[The7]

Noted that you are using 84V pack.

The following suggestion may improve the overall efficiency and the life of the battery:

1) Wire it into two 42V packs.
2)Use a DPDT switch (or relay) to switch the 42V packs in parallel to get 42V with double Ah and in series to get 84V for feeding the controller.
3)Then you could select parallel 42V for Soft-Start/Low Speed; and series 84V for High Speed.

This is only possible if your controller could work at 42V and 84V.

In fact, this parallel/series method was used for traction dc motor in the olden day before the advent of power electronics.

 

[CGameProgrammer]

But is that really any better than just using partial throttle? The only advantage I can imagine is finer low-speed control, but I'd be surprised if it really affected range.

 

[The7]

But is that really any better than just using partial throttle? The only advantage I can imagine is finer low-speed control, but I'd be surprised if it really affected range.

From the no-load test of my ebike working at 24V and 36V battery:
When both were throttled at the same no-load speed 30.7km/h, the power input for 24V and 36V were 29.3 W and 34.2 W respectively.
There was 17% more input power due to the higher PWM current loss in the 36V case.

The % age of input power would be higher if 48V were used (not tested because I am not sure if the stock controller could stand 48V)

Under load at low speed, I think the % age difference would be higher.


Please see:
http://endless-sphere.com/forums/viewtopic.php?t=1611

 

[xyster]

But is that really any better than just using partial throttle? The only advantage I can imagine is finer low-speed control, but I'd be surprised if it really affected range.

You're correct. The only advantage to 1/2 voltage @ 2X AH is finer throttle control. In my testing, with my pack at 36 volts it requires 10 amps to cruise at 20mph (no pedal, on the level). At 72 volts it takes 5 amps to cruise 20mph. Higher voltages are more electrically efficient since fewer amps are drawn on the battery side, but there's a little bit more controller loss from the lowered duty cycle. The two effects cancel.
If this worked as The7 says, we'd see switching schemes on cars. But instead we see very high voltages used. The hubmotor sim doesn't show any efficiency gain either.
http://www.ebikes.ca/simulator/

 

[Lowell]

I've done similar tests at different voltages, and couldn't find any statistically significant difference in Wh/km numbers. The biggest savings with lower voltage is simply not going as fast... :lol: