THE PIT BIKE PROJECT
THE INTRODUCTION
The idea came about on a Monday afternoon with a phone call from my mate Dave my fellow partner in the Mini-z group, The call went like this. My son's petrol pit bike has just blown up, and would it be possible to convert this pit bike to Battery power, straight away I said Yes !!.
So that afternoon text's and phone calls were going back and forward for the next few hours with ideas, requirements type of power source and what sort of motor, with what is the goal for the finished item.
With what sort of motor will we use how big will the power of the batteries be, what sort of voltage and best of all what is the finished goal when completed.
MOTOR TYPE
There are 3 types of motor' that could be used, they are -
Rear hub version with a choice of 250w motors up 1kw versions, and higher.
Front wheel hubs once again from 250w upto 1kw and some a bit higher, but this is my least of the 3 types.
The third type is the mid motor version which is my favouite type as I found that the mid motor version is the best for power use of the three, it means you can keep the wheels, that is a money save in our eyes.
After reading about each motor and talking over what sort of motor we want to use and what sort of power we require, our choice was either 1000w, 2000w and 3000w motors.
we ruled out the front hub motor because of some experience people I know have had in the past, the rear motor would put a lot of weight at the rear of the bike so we throw that out , so we was left with the mid motor style motor that puts the weight in the mid of the bikes frame mounted on so bracket style mount. The motor kit comes with chain , sprocket key switch and motor controller for under £220.00.
BATTERY POWER
There are many choices when it comes to batteries, but the only 3 that was worth considering was Onbo Lipo batteries , 18650 batteries and Tesla 21700 battery cells. All that I have had years of use in other projects. Lipo are good but the time to charge all the Lipos that would be needed , there is to much mucking around, so the next was the 18650 I have made plenty of battery packs for my MTB and other bikes batteries, the problem I have found with the18650 batteries is they have a small pcb under the positive cap that releases the contact to the cap if the cells get over heated of the resistance goes to high. So the choice for this new project will be the Tesla 21700 battery cells that I have already used a few times in making long range battery packs for my bikes. The cells will be 5amp cells and a total of 160 pieces to give the 60v and 50amps that we want for the motor.
Onbo Lipo
Samsung 18650
Tesla 21700
THE STRIP DOWN
Here is the Pit bike been stripped down to the bare frame, the motor that blow up has been removed along with the exhaust and all the cowlings and petrol tank, ready for sizing up for the motor and battery pack, and try and work out the best place to fit everything.
The bracket hanging down in the empty engine bay will have to go, a battery box will need to be made along with a motor mount.
The rest of what you see will stay, also the motor controller will be fitted under the seat.
Now for some measurements to see where everything will go. now the sizes are got and put on to a picture this gives a good idea what you have to play with or not in some cases. best place for the motor to give the chain a straight route is marked in the picture and the battery box will be in front of the motor in its own case. the front width shows 23cm well i will be coning out another 1cm either side on the frame, this will allow me to make 3 rows off battery stacks to give the 60v we want for the motor.
We will mount the motor first before any thing else because we still have not worked out what type of bracket system is required, as the motor is the main item to make this bike work. Welding will be the best way to go for any type brackets as making holes in t the tubular frame this would we find weaken the frame.
Here is the motor kit we have choose for this kit bike, this then will take about 3 weeks for delivery and then the serious work starts.
