Wooden Electric Mini Go-Kart

I wanted to fabricate a small electric powered wooden go-kart for my youngest grandson. I decided to try a half-scale model based on a full-scale plan I researched on the web. This will be a learning project to eventually making a full-scale build. I measured the wheelbase of a small pedal car that my grandson could handle to come up with the scale. The wheelbase was about 28 inches axle to axle. The rest of the wooden go-kart was designed, based on this measurement. 

Supplies

A spreadsheet of all supplies and materials used in this project is attached.

Step 1: Chassis

The go-kart chassis was made from ¾ inch thick plywood. See the layout in the photos provided. This layout was traced onto the plywood and cut out with a bandsaw and hand-held jig saw. All saw cuts were sanded and smoothed. Two 1 ½” square laminated plywood support braces were attached to the chassis 1” away from the chassis center line. They were secured in place with #6 x 1 5/8” wood screws. This was to reinforce and give strength to the chassis.

Step 2: Steering (Spindles)

See the drawing for the dimensions of the left and right spindles. Two pieces of ¾” thick plywood were glued together to give an adequate thickness for ½” diameter bolt to be placed horizontally, down the middle, to serve as axles for the front wheels. Once the glue had set, two patterns were traced on the plywood and then cut out on a bandsaw. The two spindles were cleaned up and sanded smooth. They were then taken to the drill press so ½” diameter holes could be drilled to accept the threaded rod lengths as described above. These bolts where held in place with ½” lock nuts and washers.

Plywood braces and a ½” lower spacer (attached to the plywood chassis) were designed to hold the spindles and position the front wheels at the same height as the back wheels. A center point hole was drilled on the right and left side of the bracing pieces, with the spindles in position, to accept a 5/16” diameter machine bolt. This bolt will be the pivot point.

Step 3: Steering (Mechanics)

A 1” wide x 1/8” thick metal stabilizing bar was fabricated to fit between the spindles at their neutral parallel position (straight ahead) and connect to the movement arm of each spindle from below.

The mechanical steering column was made from a 5/8” diameter threaded rod. A lower 5/8” diameter bore pillow bearing was used to stabilize the bottom of the steering rod and a regular 5/8” bore bearing was countersunk (1 3/8" hole) into a wood bracing piece to hold the top of the steering rod. Both bearings were attached to wood blocks that had been cut to match the 30-degree angle of the steering column (see photos). The steering rod was positioned at a 30-degree angle to the plywood chassis using a temporary wood support while the bearings and wood steering column brace were positioned and secured in place.

Next, I bolted on a ¾” thick plywood steering wheel, I had cut out for a different project, and a bottom steel plate to accept the tie rod. The steel plate is shown in the photo. It was a standard steel bracing plate with one of the holes widened to 5/8” diameter so it could be bolted on to the bottom of the steering rod with a 5/8” lock nut.

To complete the steering mechanism, I cut an 8-millimeter diameter threaded rod to size (6 inches) and screwed two tie-rod ends on to each side. Once the exact length of the tie-rod had been achieved (neutral parallel position at straight ahead), each end of the tie-rod was attached to the right spindle and the steering rod plate with the appropriate length 5/16” diameter bolt and lock nut.

Step 4: Drive Sprocket

My first design concept was to use a live axle for my mini go kart, but without the use of a welder it was almost impossible on a threaded rod. Therefore, I had to attach the drive sprocket to the right back wheel to propel the mini go kart. It was a 68-tooth sprocket that a 25H chain fits on. It was approximately 6 inches in diameter. Two plywood disks were used to fit the sprocket to the wheel. The first disk was cut to a 6 ¼” diameter from ¾” thick plywood to attach to the inside spoked hub of the wheel. It had to be routed out to fit the plastic ribbing of the spoked wheel. See photo.

The second disk was cut to 4 ½” diameter from ½” thick plywood and secured to the sprocket. The disk had to be of a small enough diameter to allow for the drive chain to engage the sprocket. These two subassemblies were then bolted together after being aligned at their center points with 1/4” x 3” machine screws.

Step 5: Rear Axle

Two ½” diameter bore pillow bearings were attached to the top rear of the plywood chassis using 7/16” diameter bolts and lock nuts. The midline for the axle was 4” in from the rear of the chassis. A ½” diameter threaded steel rod was placed through the bearings. This will be the rear axle. The right wheel with the drive sprocket attached was secured to the rear axle with a ½” lock nut and washer. A 3/8” diameter x 1 ¼” long black pipe nipple spacer was slipped on first to provide clearance between the sprocket and the right side of the plywood chassis.

Step 6: Motor and Controller Installation

A back vertical ¾” thick plywood piece was attached to the plywood chassis to serve as a platform to mount the motor and the accompanying electrical components. It measures 18” wide (to match the width of the chassis) and 10” high. The DC drive motor was positioned in line with the drive sprocket and attached to the plywood back with (4) 8-millimeter diameter screws. The scooter motor used was a 24-volt 350-watt DC motor that was purchased on Amazon. It came with a 11-tooth motor sprocket already attached.

The matching chain (25H) was then sized to the correct length and secured to both the motor sprocket and drive sprocket with a chain master connector.

The motor controller and lithium battery holder were also attached to the rear plywood platform with #6 x ½” wood screws.

Step 7: Seat

Two seat frames were designed, not only to support the seat bottom and back, but also to brace the back motor mount platform. The frames were designed with a 70-degree angle to the back for the seat back and a 10-degree angle to the rear for the seat bottom. The back of the frames had a 90-degree angle to hold the back plywood motor platform square so it would not tilt forward over time and loosen the drive chain.

These frames were made from ¾” thick plywood. Pine strips that were 1” wide and ¾” thick were attached to the bottom edge of the seat frames with wood glue and screws to serve as a means for securing the frames to the bottom chassis (#6 x 1 ¼” wood screws were used). The frames were positioned about 12” apart. The back motor platform was secured to the vertical segment of the seat frame with #6 x 1 5/8” wood screws.

The actual seat and back were cut from ½” plywood to match the width of the plywood chassis. They will be secured to the frames with #6 x 1 5/8” wooden screws but were set aside for now so the brake system and electrical connections could be installed and finished.

Step 8: Brake System With Rear Fenders

A braking system was devised using the rear fenders. The rear fenders were made by gluing up 4 pieces of ¾” thick plywood that gave an overall thickness of 3 inches. Once the glue had set, the fenders were cut out on a bandsaw in a half circle configuration at a slightly larger diameter then the 8-inch diameter wheels. The fenders were cut to approximately a ¾” thickness. They were sanded and then finished with a couple coats of varnish.

The braking surface will be the inside of the rear fenders pressing against the outside of the rear wheels. It is the sprocket driven drive wheel that I’m most concerned about stopping.

I used two threaded steel rods to hold the fenders in place. The rods spanned the width of the mini go kart and will be hidden by the seat. The front rod will be the pivot. It is 5/16” in diameter and will be firmly secured on top of the two middle bracing beams and left and right axillary bracing pieces of wood positioned near the outside of the plywood chassis. The bottom of the seat will hold this rod firmly in place.

The rear threaded steel rod is 3/8” in diameter for a little more rigidity. It will be positioned through the two seat braces where the braces meet the back motor support platform and then continue out and be secured to the fenders. This will serve to provide support for the back of the fenders. A vertical slot is placed through the seat braces so the rear rod can move up and down.

A 3/32” diameter hole is drilled in the midline of the back rod to accept a 1/16” diameter brake cable. Springs are attached so the rear rod holds the back of the fenders in a normal position above the rear wheels. When the brake cable is activated, the rear of the wood fenders are pulled down, and apply friction and pressure to the wheel wheels. Rubber was placed on the inside of the left rear fender to provide a little more gripping power. Please see the photos.

Step 9: Electrical

All electrical hookups were completed using appropriate size wire and matching connectors to the motor control box. Instructions for each connection are included with the motor controller. An On/Off switch and Forward/Reverse toggle switch were placed on the steering column wood brace below the steering wheel. Switching the direction that the electric motor rotates is nothing more than reversing the polarity wires. The Forward/Reverse toggle switch was a 3-way switch that has an ON-OFF-ON configuration. 

Step 10: Pedal Installation and Steering Column

We needed a brake and speed pedal. The speed or acceleration pedal was purchased from Amazon and simply screwed into the right side of the plywood chassis. A hole had to be placed in the chassis to allow the rheostat portion of the speed control to work when you press down the pedal. A wedge of wood was also used to increase the angle that the rheostat operated at. The cable running back to the motor controller was run underneath the chassis and brought back up behind the seat and attached to the motor controller. You may have to purchase plastic wire housing connectors to match the connectors from the motor controller.

The brake pedal was made from ½” thick plywood. It was attached to the left side of the plywood chassis with a standard 2” hinge. A ½” x 4” metal bracing plate was screwed into the back of the pedal with one hole left exposed on the right side of the pedal, toward the top. This hole will accept the 1/16” diameter brake cable that was attached to the back 3/8” diameter horizontal threaded rod. It runs down a small copper tube to direct it down the middle of the go kart, under the seat, and through the steering column brace. See the photos.

Lastly, the wood vertical steering support column was enclosed with thin 1/8" thick plywood. The thin plywood could be bent to the curve of the column. It enclosed the electrical switches and wires and gave the mini go-kart a cleaner look.

Step 11: Enclosing the Motor Compartment and Drive Chain

At this point, the seat bottom and back were screwed into place covering all the electrical and braking components. It is important to cover all remaining moving parts by enclosing the rear of the go-kart. Plywood sides (1/2” thickness) had to be measured and cut to fit. The left side was sized between the seat back and the rear plywood platform and to fit around the pillow bearing. It was secured in place with #6 x 1 5/8” wood screws.

The right side was a little trickier. It had to be fitted around the motor shaft and drive chain. A cardboard pattern was traced and cut out to ensure clearance for the sprocket and chain. The pattern was then traced onto a piece of ½” thick plywood and cut out on the bandsaw. This right side was then smoothed and sanded. I found that the ½” thickness of the plywood was not enough to cover the motor sprocket so a 1/8” thin piece of plywood was sized and glued over the sprocket to complete the right side. This side was again screwed in place with #6 x 1 5/8” wood screws.

A top access door was cut to size and attached to the rear vertical motor mount plywood with a continuous piano hinge. A cabinet clasp was mounted to secure the lid in place when riding the mini go cart. This top will also serve to hold the lithium battery in place.

Step 12: Finishing Up

The front wheels were bolted in place with ½” diameter lock nuts. I used a painted color scheme of blue stain and natural wood grain. The light blue stain was placed on some trim and accent areas and then leaving some wood with its grain unpainted. Two coats of varnish were then used to protect and seal the wood. The seat was painted black. The steering wheel was already painted a blue enamel. Finally, the 24-volt lithium battery was snapped into the plastic battery holder.

I have not been able to test the mini go cart outside yet since it is January in Chicago and very cold and snowy. I was able to have my grandson test it in the basement, and it seemed to work fine. He likes it a lot.