E Mini Bike with NuVinc 171 Auto Trans

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bigoilbob
10 W
10 W
Posts: 96
Joined: Sep 06, 2015 8:33 am

E Mini Bike with NuVinc 171 Auto Trans

Post by bigoilbob » Jun 29, 2017 6:44 pm

This is a frame rescue, and I wanted an e mini bike that could climb any hill with enough traction. By the numbers:

Prime Mover:
BLDC, 48 volt, 20 amp in, 750 watts out. 2880 rpm @48 volts, reduced to 480 rpm. 14 tooth, #40 sprocket. Output torque after 6/1 gear reduction, ~11 ft*lb.

BMI Jackshaft, with 14 tooth, #40 sprockets in and out.

NuVinci 171 Developers Kit, Auto Transmission:

27 tooth input sprocket, 44 tooth output sprocket. When motor output increases to 350 rpm (approximately 3 mph), the auto trans changes gears in 64 steps, maintaining the output motor gear reduction speed of ~350 rpm, to ~10.5 mph. Controller is preprogrammed for this, and speed is sensed from the speed sensor installed on the disc brake. Actuator is originally from a Ford automatic window opener, and moves the ceramic balls into and out of the visco-elastic fluid to effectively change gear ratio.

Transmission torque rating, 48 ft*lb, input. Max required, ~21 ft.*lb.
Transmission rotational velocity limit, 1000 rpm. versus maximum required of ~500 rpm.

Rear sprocket, 60 tooth, #40.

Rear tire, 8", with effective radius of ~7.25"

Battery: 720 watt hour, 48 volt, Cal Bike

Rear brake - disc, via the drive chain, from the NuVinci transmission

Front brake, drum, via a "pay it forward" benefactor, from Old Mini Bikes.

Front light - rescue, from 12 volt Night Ryder with bad battery

Right chain guard, modified trash can top

Left chain guard, modified refrigerator shelf.

It will go for over 14 miles in South St. Louis, and winch over 200# up any gravel hill (i.e. it will lose traction before stalling out). Top speed ~13.5-16.5 mph, depending on state of charge. Vids will be posted after nieces/nephews shake it down in the country, during annual 4th of July family reunion/fluids replacement event....

https://www.youtube.com/watch?v=AWEJPqJtZsk
Attachments
E Mini Bike 750 watt, 48 volt BLDC Motor.jpg
E Mini Bike 750 watt, 48 volt BLDC Motor.jpg (48 KiB) Viewed 951 times
E Mini Bike NuVinc Transmission with input and output sprockets and chains.jpg
E Mini Bike NuVinc Transmission with input and output sprockets and chains.jpg (53.97 KiB) Viewed 951 times
E Mini Bike with Disc Brake and trans controller and 48 to 12 volt controller.jpg
E Mini Bike with Disc Brake and trans controller and 48 to 12 volt controller.jpg (60 KiB) Viewed 951 times
E Mini Bike with NuVinci Trans Actuator.jpg
E Mini Bike with NuVinci Trans Actuator.jpg (61.36 KiB) Viewed 951 times
E Mini Bike with NuVinci Transmission Disc Brake.jpg
E Mini Bike with NuVinci Transmission Disc Brake.jpg (53.69 KiB) Viewed 951 times
E Mini Bike wth NuVinci Transmission and Cal Bike Battery.jpg
E Mini Bike wth NuVinci Transmission and Cal Bike Battery.jpg (62.37 KiB) Viewed 951 times
E Mini Bike wth rear basket.jpg
E Mini Bike wth rear basket.jpg (67.6 KiB) Viewed 951 times
Last edited by bigoilbob on Aug 10, 2017 8:09 am, edited 1 time in total.

Mugenski
100 mW
100 mW
Posts: 37
Joined: Aug 02, 2015 9:03 pm
Location: Toronto

Re: E Mini Bike with NuVinc 171 Auto Trans

Post by Mugenski » Jul 03, 2017 9:32 am

Great build. I just changed the oil and fired up the old gas mini bike. Looking to sell it but I can't say an electric conversion didn't come to mind :roll:
Giant Glory Tangent ∞kw @ 52v

bigoilbob
10 W
10 W
Posts: 96
Joined: Sep 06, 2015 8:33 am

Re: E Mini Bike with NuVinc 171 Auto Trans

Post by bigoilbob » Jul 03, 2017 11:22 am

Mugenski wrote:Great build. I just changed the oil and fired up the old gas mini bike. Looking to sell it but I can't say an electric conversion didn't come to mind :roll:
Thanks, but it was hard for me to figure out where to put everything. And I'm NOT dissing traditional 4 cycle/clutch builds. Even with torqueverters, they're simple and fun

FYI, acquiring a Nuvinci 171 Developers Kit might be hard, but not impossible. They are burlier than the modern Nuvinci's they put on some bikes, and were discontinued because they were heavy enough to be a drag on pedalers. NUVinci put their remaining stock on clearance sale several years ago, and I now own this one and one other. If you buy anything similar, do the torque/speed arithmetic to see if you're within limits. Several builders shucked theirs when they didn't......

crxgregmiller
1 µW
1 µW
Posts: 1
Joined: Jul 11, 2017 7:32 am

Re: E Mini Bike with NuVinc 171 Auto Trans

Post by crxgregmiller » Jul 11, 2017 7:40 am

Looks good. Iam also make a mini bike e bike. Just wating on parts to finish it.

bigoilbob
10 W
10 W
Posts: 96
Joined: Sep 06, 2015 8:33 am

Re: E Mini Bike with NuVinc 171 Auto Trans

Post by bigoilbob » Jul 11, 2017 6:35 pm

crxgregmiller wrote:Looks good. Iam also make a mini bike e bike. Just wating on parts to finish it.
Good for you. ASAP, please provide us with some specifics. FYI, I am in a VERY small minority by including ANY kind of multi speed transmission. If you know what you want, hill climbing or speed, you can get by without one. But I wanted SOME speed, LOTS of hill climbing ability, and a motor usually in the efficiency "sweet spot" of motor speed.

Do your motor speed/sprocket gear/ tire diameter arithmetic - not just for "rated" motor speed, but - if possible - with motor power/torque/efficiency versus rpm data. It's worth the time and happy to help - pretty geeky that way...

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