Introduction: Electric Powered Pedal Car Conversion
A pedal car can be a lot of fun but eventually your kids will grow out of it. I wondered if there was a way to power the car so they would get a little more enjoyment out of it. The pedal car had a lot going for it. It had real air-filled rubber wheels, a solid metal frame and a functional spindle and bracket steering assembly. Below explains how I converted the pedal car to an electric go kart using a small electric motor that can be found on many electric bikes and scooters.
Supplies
The main electronic components are a 250-Watt, 24 DC volt electric motor with a matched controller. The motor controller comes with a diagram of how to hook up the motor, power supply, throttle and other accessories.
Step 1: Disassembling the Pedal Car
· Remove the plastic covering around the pedal chain and rear axle assembly and discard.
· Remove the steering column plastic decorative piece and set aside for later.
· Undo and remove the pedal assembly from the aluminum frame.
· Undo the rear wheels and remove the two-piece rear axle with the disengaging lever mounted in the middle of the aluminum frame. It is important to save the wheel lock that was attached to the split axle. This piece of metal locks the left wheel in place by engaging the inner plastic wheel hub and then being bolted to the axle. Without this, the rear wheel would not turn when the axle turns.
· Remove the plastic seat and set aside.
Step 2: Adding the Threaded Rear Axle
· The split axle that came with the pedal car could not be used. The diameter of this axle was 12mm (almost ½ inch). A 12mm diameter threaded steel rod was purchased to be used in its place as the rear axle.
Threaded Rod, Carbon Steel, M12-1.75x1m: Amazon.com: Industrial & Scientific
· In addition, the plastic axle bearings that were used with this split axle were discarded. I didn’t feel these plastic bearings would hold up to the increased demand placed on the rear axle with an electric motor.
· To replace the plastic bearings, 12mm bore pillow block bearings were attached to each side of the rear aluminum frame with 10-24 diameter machine screws and nuts.
· The sprocket assembly was mounted to the threaded axle close to the right wheel and just outside the frame with 12mm lock nut.
· The sprocket was not mounted in the middle because I did not want to section the aluminum frame cross member that connected the two sides of the frame together.
· A pillow block bearing was also placed in the middle of the threaded axle and then attached to the underside of the plywood platform. This will give added support to the rear axle.
Step 3: Sizing the Bicycle Sprocket to Fit the Rear Axle
· A ½” thick piece of plywood was cut to a diameter slightly smaller than the drive sprocket. A 12mm diameter hole was drilled in the center.
· The sprocket was attached to the plywood disc with 10-24 diameter machine screws and lock nuts.
· On the opposite side of the plywood disc, a 12mm bore inner flange coupling was attached with the appropriately sized machine screws.
· I did a mockup on my bench and tested the sprocket assembly to make sure it rotated true and would work in the pedal car conversion. See the attached photo of my bench set-up.
· The sprocket assembly was then mounted to the threaded axle close to the right wheel and just outside the frame with a 12mm lock nut. The set screw was removed, and a hole was drilled through the axle to accept a cotter pin. Now the axle will rotate with the drive sprocket.
· The sprocket was not mounted in the middle because I did not want to section the aluminum frame cross member that connected the two sides of the frame together.
· The last thing needed to complete the powering of the rear wheels was to attach the wheel lock that we had set aside during the disassembly. This wheel lock will ensure the left rear wheel is attached to the axle and will rotate when the drive sprocket rotates and hence power our pedal car conversion.
Step 4: Adding the Plywood Platform
· Measure and cut to size ¾ inch thick plywood to fit to the aluminum frame. I used two pieces. One piece was measured to fit underneath the seat area. This will be where the motor, motor controller and batteries will be mounted.
· The underside of this piece had to be relieved so the hand brake would still function.
· A second plywood piece was cut to cover the remaining frame up to the front steering column. This piece was cut to provide safety and comfort for the driver's legs and to mount the stick shift, brake and speed pedals.
· The plywood was secured to the aluminum frame with 10-24 x 2” machine screws after a 3/16” hole was drilled.
Step 5: Mounting the Electric Motor, Controller and Batteries.
· The electric motor came with a sprocket already mounted on the shaft.
· The motor sprocket was lined up with the axle sprocket assembly.
· The motor was secured to the plywood platform through the mounting bracket with four ¼” bolts and locking nuts.
· The matching chain (25H) was then sized to the correct length and secured to both sprockets with a chain master connector.
· The motor controller was then secured to the plywood platform.
· A wooden battery holder was fabricated from ½” thick plywood to keep the two lead acid batteries from moving during operation.
Step 6: Adding the Pedals
· The acceleration/speed pedal was included with the motor control. It was attached to the proper terminal plug on the motor control and then mounted on the right side of the steering wheel column. The extended cable for the speed control was run underneath the wood platform and secured in place.
· A brake pedal was cut out of ½” thick plywood and mounted on the left side of the steering wheel column with a continuous hinge.
· I used the friction-based brake mechanism that came with the pedal car. It was hand operated and engaged the rear rubber wheels.
· I ran a bicycle brake cable from the manual brake handle around a plastic pulley to reverse the direction of the pull force.
· The cable was run underneath the wood platform to the brake pedal area. A ¼” diameter bolt was attached to the brake pedal and extended through the wood platform where a corresponding hole had been drilled. The bolt was about 4 inches long.
· Underneath the wood platform the brake cable was attached to the end of this bolt in such a way that when the brake pedal was depressed, the cable was tightened, and the manual brake mechanism was pressed against the rear rubber wheels. Another pulley was used to keep the brake cable close to the underside of the wood platform as the brake pedal was depressed.
· A spring was attached to the posterior aspect of the wood platform and the manual brake handle to ensure the brake mechanism would disengage once pressure was released from the brake pedal.
Step 7: Adding the Forward/Reverse Switch
· Switching the direction that the electric motor rotates is nothing more than reversing the polarity wires.
· This can be done with a 3-way switch that has an ON-OFF-ON configuration.
· I wanted to set this up like a center stick shift so I kept the disengaging lever that came with the pedal car for this use.
· I designed a wooden mounting brace to hold the 3-way switch in such a way that the toggle lever would fit through and engage the hole in the disengaging lever.
· Moving the lever would engage the 3-way toggle switch and reverse the rotation of the motor.
· Consequently, this changes the direction that the pedal car travels (forward and reverse).
Step 8: Adding the Rear Bumper
· A rear bumper was added by screwing two wooden bracing pieces to the rear of the wood platform and adding a 1” diameter dowel cut to the width of the wheelbase.
· The dowel was glued and screwed in place.
Step 9: Enclosing the Motor Compartment and Drive Chain
· The outline of the rear frame (that supports the seat) was traced onto ½” thick plywood. A right and left side were cut out on the band saw.
· The right side was a little tricky; it had to be fitted around the motor shaft and drive chain.
· The sides are screwed to the aluminum frame with 10-24 x 2” long machine screws. Holes were drilled like the plywood platforms were attached.
· The rear curved cover was formed from a 6” diameter metal heat duct section. It was cut to dimension with metal shears and screwed to the plywood sides.
· The front access door was cut to size and attached to the plywood floor with a continuous piano hinge. Cabinet clasps were mounted inside to hold it closed during use.
· The facing of the chain cover was made from ½” thick plywood that was cut to clear the sprockets and drive chain. The sides to the chain cover were made from 1 ½” wide plastic molding that was notched and kerfed so it would bend easily. It was held in place by air driven staples. The cover was finished with auto body putty and sanded smooth. Small L-brackets were added so the cover could be screwed in place.
Step 10: Finishing Up
· All that was left was to finish up the wiring and replace the seat and steering column cover.
· Two wires were run from the on/off connection on the motor controller under the plywood platform and up through the plastic steering column cover to a rocket panel type toggle switch. A ½” diameter hole was placed in the cover and the toggle switch was secured in place.
· There was a connection on the motor controller for a DC voltmeter, so I purchased a small one. I cut out the steering column cover to the dimensions of the voltmeter and pressed it in place. Again, two wires were run from the connector plug under the plywood platform and up through the steering column cover and attached to the voltmeter. One can monitor the battery usage with this voltmeter.
· One of the above photos shows the underside of the motorized pedal car. The voltmeter and on/off switch wires are run up through the steering column cover. The forward/reverse wires are run to the center stick shift. The black cable for the throttle is run up to the speed pedal and the bicycle brake cable is run underneath to the bolt extension on the plywood brake pedal.
· Lastly, the plastic seat was bolted back on to the aluminum frame.
Step 11: Video
The pedal car conversion to an electric motor driven go kart was complete. Attached you can see a short video of the pedal go-kart in action.
