Magic Pie Edge doesn't go fast enough 20 inch wheel 36 volt battery

[WCKrause]

Hello,

I am a new member.

Just purchased and installed a Magic Pie Edge on my Bacchetta recumbent bicycle.

I've taken it out for a couple of short test drives and I have an issue.

With a 36 volt battery, I am only able to obtain a top speed of 15.6 mph on level ground.  My motor is mounted on the front hub of a 20" wheel and the maximum RPM is set to 380 rpm (factory default).   This should give me a top speed of about 22.3 mpg.

Is there something wrong with my motor or do I need to go to 48 volt battery?   I have the acceleration set to 75% and it pulls away very strong.  Any higher and I'd slip the front wheel.

Thanks in advance for any advice.

Bill Krause

[Bikemad]

Hi Bill andto the forum.

The maximum motor rpm is also determined by the battery voltage rather than just the maximum rpm setting.

If your 36V battery is managing 15.6mph (~262rpm) then a 48V battery should allow you to reach 20.8mph (~350rpm).

There is nothing wrong with your motor, but after watching your video, I would say that your tyre seems to be poorly centred on the rim. 

Incidentally, using your 15.6mph as a guide, a 26" x 1.25" tyre on rear Magic Pie Edge should produce a top speed of ~19 mph on 36V and ~25.5 mph on 48V.

Alan
 

[WCKrause]

Thanks for the welcome and the response.

I'm using 3 12 volt SLAs, so I can easily add a 4th and give that a try.

What video are you referring to?

[Bikemad]

What video are you referring to?

I was referring to the video on Instagram (First running of the motor).

Another 12V SLA will definitely boost the speed, but it will also put 33% more strain on your battery rack.

Is your Bacchetta a Giro 20 with a steel frame, or a Giro A20 with an aluminium Frame?
I would be concerned if you did not have steel forks or suitable torque arms, as there is a lot of torque being transmitted through those dropouts.

Alan
 

[WCKrause]

The tire in that video wasn't even inflated.  My hand pump wouldn't connect to the presto valve  because of interference with the motor.   Did you notice it was spinning backwards?

It's the steel frame, and I have two torque arms up front.    The rack has a rating of 30 lbs, so the 4th SLA will push it over that.

I'll just try an extra 12 volts to see what I can get for a top speed.     My final battery is still T.B.D.   Probably a  48 volt LifePO4, but I wan't to match it's Ahr rating to the route I'm going to commute.

Thanks again for your help.   I'm an electrical engineer but not familiar with electric motors.  Would love to see a good description of how the sine wave controller works.

Bill