E-mini pit bike

Related:
Create New Tag

2/22/2019 1:15 PM
Edited Date/Time: 2/22/2019 1:21 PM

Wanted to share a little project I have going on. Building some small pit bike sized electrics for my family to come trail riding with me. I am not too far away from having the first one ready. I am building 3 of them back to back. All 3 will be different sizes but using the same frames. One will have 10"/10" wheels and be real low and light for about 5-9ish aged kids, one with 12"/12" wheels midsize for about 9-15ish aged kids but can be ridden by and adult, and then a larger 14"/12" wheeled version that my wife will ride. I should be able to keep the same frames and just make them bigger through the fork and wheel sizes as my family grows.

They will use 18650 based battery packs and brushless motors and controllers with power ranging between 1kw up to about 7-8kw depending on the motor/controller/battery combo. Looking for the kids bikes to be able to go 30-40 miles or so on a full frame of battery. They will also fit a smaller pack for yard riding which is what I am testing with first. It should make for an expandable battery pack that can be maintained as modules and charged and stored in safe locations and hot swapped at a track if need be. I am targeting a top speed on the biggest bike of about 45mph or so with enough torque to easily wheely the bike at lower speeds.

Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo
Photo




|

2/24/2019 9:59 AM
Edited Date/Time: 2/25/2019 9:23 PM

|

2/24/2019 9:59 AM

Way cool! I wish I had fabricating skills like that.

|

3/19/2019 4:54 PM

I finished the first bike and we did some riding. Really satisfied with the power. I had to turn down the max current down to 35% on the Kelly to make it appropriate for my son who is still learning. The KBS controller I am using will do 100amp burst for 30 sec. I tried riding it like this and it was really fast with 160lb person on it. Picks up faster than my big bike despite the big bike having 130amp burst KBS controller and a much larger BHT motor at a much higher 72 volt nominal. The tire size on the bigger bike and less reduction have a big impact. The little bike is only at 52v but the smaller tire and more reduction really make it kick off the line. Enough to power straight into a wheelie with me on it when turned up. It is only topping out at about 27mph which is about as fast as they need for now. With it turned down, the max I have seen is about 29 amps battery current measured through the Luna meter. I can't wait to see what the bike with the larger motor and 72 volts going in is going to feel like.

150amp main breaker and a 300amp disconnect switch tucks inside of the frame.
Photo
Photo
Photo

hall throttle sensor pulled by standard cable throttle.
Photo

bike with shaved seat
Photo

chain adjuster
Photo

Programming controller
Photo



2 more to finish now!

|

3/20/2019 4:01 AM

Nice!

|

4/10/2019 12:53 PM

Your boy is pretty good for just learning! Cool build!

|

4/19/2019 1:51 PM

Beautiful! I like it cool!!!

|

4/20/2019 9:07 AM

How much does it weigh in at?

|

4/22/2019 8:58 AM

He picked this up pretty quick because of riding BMX. This first version of the bike with 12" wheels and heavy enduro tires weighs just under 100lbs. The smaller version with 10's will be about 70lbs I think. The biggest version should be around 130lbs. My son and his cousin rode this in the yard throughout this 3 day weekend on a single charge. About 15-20min at a time about 10 times going at it. Seems pretty good for just the small battery pack still. Need to start doing some more scientific range testing so I can size the larger battery pack.


|

4/23/2019 9:56 AM

Where did you source the electric goodies? I have a JR 50 chassis I am going to convert to electric for my 3 year old. I have a 24v razor scooter I sourced parts off of for now just for a prototype. I would like some better parts like this for the final product.

|