Introduction: WSU GoBabyGo Modification - Ride on 12V Jeep With Big Mac Switch

About: Students at Wichita State University run a program that modifies off-the-shelf ride-on toy cars for kids with disabilities. Our cars feature more technical builds with joysticks and arduinos. We post our instr…

Fall 2018

Step 1: Step 1.1: Assess the Child's Needs

  • Assess the needs of the child based on their condition and abilities
  • Take note of various dimensions of the child such as chest width, midsection width, shoulder width, etc.
  • Determine any necessary supports for the child’s needs (trunk support, leg support, headrest, etc.)
  • Determine an effective control system (Big Mac Button, Joystick, Foot Pedal, etc.)
  • Take note of the child’s interests and try to incorporate those things into the modifications for the car.

Step 2: Step 1.2: Sample Questions

  • Would the child be able to reach the button comfortably?
  • Is the child able to steer the wheel under his own power? If not, what other control surfaces could be used?
  • Can the child get into and out of the car by himself safely?
  • Will the child require any extra stimulus (audio, tactile, optical)?
  • What position does the child like to sit in?
  • Does he need support around the waist and/or chest?
  • Do we need to put something in the car for leg support?
  • How was his head control movement?
  • What is his grip strength and circumference?
  • Can you transfer the car in your vehicle?
  • Where is the desired area of application (used outside or inside)?

Step 3: Step 1.3: Our Modifications

  • Big Mac Button as an acceleration pedal replacement
  • A kickboard for back support
  • LED lights to assist the child in learning how to operate the vehicle
  • a "texture" feature on the steering wheel to assist the child with hand placement
  • an emergency stop switch to stop runaways

Step 4: Step 1.4: Custom Aesthetics

  • Our child likes neon colors, so we elected to use bright colors on the car. This includes the use of polka dot decals on the car exterior and two bright LED strips that light up when the Big Mac Button is pressed.

The decals our team purchased can be found here:

The LED lights our team purchased can be found here:

  • The car also has the capability to play personalized music through the use of a cellphone attached to the car via a USB port in addition to the pre-programmed music.
  • Our team also laser cut the name of our child onto a piece of particle board to act as a license plate, and it was bolted onto the back bumper of the car.

Step 5: Step 2.1: Car Assembly

Link to the car:

Step 6: Step 2.2: Follow the Instructions

Significant observations the team noticed during assembly:

  • There are plastic wrenches made to put nuts on the axle.
  • When attaching the steering column be sure to run a bolt through the white terminal that controls steering for the remote control, but it should be left out in order to modify the electrical system later. The same applies to the small metallic pin located right above the "hook" part of the steering shaft.
  • Do not install the hubcaps until the axles are in place (They snap on, but are difficult to take off.)
  • Be sure to attach the loose red wire to the battery or the car will not run.
  • When attaching the motors to the wheels, check to make sure forward and reverse go in the correct directions.

Step 7: Step 3.1: Modifications-Emergency Stop Switch

Step 8: Step 3.1.1: Emergency Stop Materials

  • Toggle Switch (2 way) up to 120 volts
  • 22-16 AWG Female connector ¼” (2 of them)
  • 3 feet of 14WG wire (2 of them)
  • Wire strippers
  • Multi-meter
  • Philips Screwdriver
  • 2 wire nuts

Step 9: Step 3.1.2: Remove the Windshield

  • Remove the hood by removing the two black screws located on the front of the hood.
  • Remove the two black screws on the side of the windshield and the four located underneath where the hood would be.

Step 10: Step 3.1.3: Dash Removal

  • Remove the steering column.
  • Unscrew the 3 black screws behind the dash (underneath where the windshield was).
  • Remove the panel guarding the wires in the dash by removing the two black screws at the top of the panel.
  • Optional: Remove the charging port by removing the 2 large flanged silver screws; this allows the dash to be pulled out further for a larger workspace.

Step 11: Step 3.1.4: Trace Power Sources


  • There are two wires (brown and red) coming off the on button for the car; one is for the charging circuit, and the other is for the pedal control.
  • With the car off, test both wires with the positive end of the multi-meter, while the negative end is on ground (the brown cable should go to the charging circuit, and the red to the pedal control, but it is important to check anyway; the charging circuit should read 12V).
  • Check these wires again when the car is on; they should both read 12V.
  • If this is the case, trace the pedal control wire to a convenient location inside the hood compartment and cut the pedal control wire.

Step 12: Step 3.1.5: Wiring the Emergency Stop Switch

  • With two 3 foot lengths of 14 AWG wire, insert one wire in a wire nut with the cut pedal control wire, and the other in another wire nut with the opposite end of the cut pedal control wire (the toggle switch is wired in series).
  • Run these wires through a hole by one of the headlights to the location you wish to place your emergency stop switch; our team selected the left side of the rear bumper (a rear location is desirable so the parents of the child can kick the switch if the car is out of control of the parents).
  • Crimp female wire connectors on the opposite ends of the 14 AWG wires using pliers or similar tool to pinch the connector down onto the wire.
  • Run the wires to the back of the car, and connect the female connectors to the male ends on the toggle switch.

Step 13: Step 3.1.6: Position the Emergency Stop Switch

  • Measure the diameter of the switch threading, and select a drill bit close to the size needed (it is better to start off with a slightly smaller bit than the diameter, because you don't want the switch to fall out of the hole in the end).
  • Optional: Make a pilot hole if necessary, the plastic may not work well with the bigger drill bit.
  • Take the nut and "on-off" tab off the emergency stop switch, and make note of the slot on the "off" side of the switch.
  • Place the threaded end of the switch through the hole from underneath the car, screw the nut back on finger tight, and tighten with pliers if necessary.

Step 14: Step 3.1.7: Dealing With Excess Wire


  • Use duct tape to tape the excess wire from the emergency stop switch on the underside of the car to prevent them from being caught in the wheels.
  • DO NOT GET THE WIRE TOO TAUGHT, otherwise, the connection could break.

Step 15: Step 3.2: Steering Wheel Modification

Step 16: Step 3.2.1: Steering Wheel Modification Materials

  • Jigsaw
  • Masking Tape
  • Philips screwdriver
  • Electric Drill-select a bit wide enough for a zip tie to fit through the hole
  • Multimeter
  • Big Mac Button:
  • Wire Strippers
  • File
  • Superglue
  • 3 zip ties
  • 4 female wire connectors
  • 1 wire nut
  • Sanyou SARL -112DF (Single pole double throw) relay
  • Optional: colored string/colored tape

Step 17: Step 3.2.2: Cutting the Steering Wheel

  • Remove the steering wheel from the car.
  • Remove all the silver screws on the backside of the wheel.
  • Remove the electronic components from the steering wheel.
  • Set aside the back side of the wheel, use a jigsaw on the front half of the wheel to cut out the central portion of the wheel.
  • To clean up the cut, our team decided to use the jigsaw. It might be worth considering using a dremel tool with a cutting wheel versus the jigsaw.
  • Place the button approximately in the center of the wheel, and use masking tape to mark the edges around the button.
  • Taking the button off, any black areas will need to be trimmed off (the end goal is to have the button set into the steering wheel).
  • Trim, and then test the fit of the button.
  • If the fit is satisfactory, drill out one of the screw holes on the bottom part of the back half of the wheel to fit a zip tie through.
  • Reassemble the wheel with as many screws as possible. NOTE: Not all of the screws will be used again.

Step 18: Step 3.2.3: Optional-Adding Textures to the Wheel

  • Using colored string, tie a knot around the top left section of the steering wheel.
  • Wrap the string tightly around the wheel one section at a time (make sure the string is not so thick to the point where the Big Mac Button no longer fits in the wheel).

  • After the second section, tie another knot to prevent it from unraveling.

  • Our team wrapped only the bottom half of the steering wheel in order for the Big Mac Button to fit properly.

  • Use superglue on the string ends to prevent them from unraveling.

Step 19: Step 3.2.4: Attaching and Wiring the Big Mac Button

  • Feed the button wires through the trapezoid-shaped hole at the back of the wheel, NOT in the circular hole.
  • Zip tie the steering wheel at 10, 2, and 6 o'clock positions on the wheel. The 6 o'clock zip tie will go through the screw hole you widened out earlier.
  • Cut off the excess on the zip ties, make sure the cut ends are on the back side of the wheel, and file down the nubs as much as possible to prevent scratching of hands.
  • Find a wire that leads to ground, cut it, wire one end of the button to the ground wires, connecting them with a wire nut.
  • With the second wire from the Big Mac Button, crimp a female connector onto it and attach it to pin 85 on the relay.

Step 20: Step 3.2.5: Connecting the Pedal Circuit to the Relay

  • Flip the car over, remove the plastic pieces covering the backside of the pedal.
  • Test both wires with respect to ground, find the the wire with a positive voltage difference, cut this wire and attach this wire to pin 87 on the relay after crimping a female connector onto the end of the wire.
  • Cut the other wire and attach it to pin 30 on the relay after crimping a female wire connector onto the end of the wire.
  • NOTE: It is useful to use a two stage female wire connector on these wires due to their size. A two stage female wire connector works by having a large pair of pliers crimp the outside, then using the tip of a pair of wire strippers to crimp the center.

Step 21: Step 3.2.6: Finishing Connecting to the Relay

  • Cut 1 foot of 14 AWG wire, splice it into the wire nut that contains the wire coming back from the emergency stop switch.
  • With the other end of this wire, attach a female wire connector and attach to pin 86 on the relay.
  • To finish the relay, drill a small pilot hole with a small drill bit, then use a 1/4 in. screw to mount the relay to the wall of the inner hood compartment. Our team mounted to the backside of the front grill.

Step 22: Step 3.3: Modification-LED Strip

Step 23: Step 3.3.1: LED Strip Materials

    • LED strips (purchase link can be found in Step 1.4)
    • an analog potentiometer
    • wire strippers
    • a roll of electrical tape
    • 4 1-foot lengths of 14 AWG wire
    • 1 wire nut
    • wire connectors
    • soldering iron

    Step 24: Step 3.3.2: Potentiometer Setup

    • Drill one large hole approximately 3/4 in. into one side of the dash. Our team chose the right side just above the power switch.
    • Drill a second hole in the dash using a 3/16 in. drill bit, being careful to not hit any of the electronic components inside the dash. Our team made the hole offset from the steering column to the right about 3 in.
    • Drill a third hole in the hood compartment behind wherever you decided to place the first 3/4 in. diameter hole. This hole should be approximately the same size as the 3/4 in. diameter hole from the first bullet point.
    • The analog potentiometer connects to the dash of the car in a nearly identical manner as the emergency stop switch mentioned earlier.
    • To prepare the potentiometer, un-wire nut the wire nut with the red power button wire, one of the wires that goes to the emergency stop switch, and the wire that goes to the relay.
    • Un-wire nut the nut with the black wire that goes to ground and one of the Big Mac Button wires.
    • Look at the LED wire strips, note that the red (positive) and black (negative) wires are not long enough to reach the components that they connect to inside of the car.
    • For the next step, you can either do soldering or wire joining using wire connectors.

    Step 25: Step 3.3.3: Positioning the LED Strips

    • Select the point on your car where you would like to place your LED strips. Our team selected the top of the windshield for easy visibility.
    • Take the adhesive covering off the backs of the strips, and attach them to the selected location. Make sure to clean the surfaces of the car as the adhesive on these strips is not that great.
    • Take the two red wires from the strips and put them in one end of a wire connector after stripping them.
    • Strip the end of a 1ft length of 14 AWG wire and insert it into the other end of the wire connector. Pinch down both ends with pliers or with the end of strippers.
    • Repeat the previous two points with the black wires on the LED strips.
    • Feed the wires through the hole in the dash, and the hole leading to the hood compartment.

    Step 26: Step 3.3.4: Wiring the LED Strips

    • Take the end of the wire coming from the LED red wires, and wire it into the connection that contains the one end of the emergency stop, the red power button wire, and the relay wire. Do not put the wire nut back on yet, as the next step requires another wire to go into the mix.
    • Take the end of the wire coming from the LED black cables, and wire it into the connection that contains the one Big Mac Button wire and the black ground wire. The wire nut can be returned back onto these wires.

    Step 27: Step 3.3.5: Wire the Potentiometer

    • Soldering is required at this point: the connections on the potentiometer are too small to use a wire connector.
    • Insert the knob of the potentiometer through the 3/16 in. hole drilled earlier, tighten the nut on the knob finger tight.
    • Solder a 1 ft section of 14 AWG wire to the positive terminal of the potentiometer after stripping an end.
    • Solder the other end of the 14 AWG wire to the loose red wire/emergency stop wire/red LED wire cluster after stripping this end. DO NOT SOLDER THE WIRE THAT GOES TO THE RELAY, LEAVE IT ALONE FOR NOW!!! Wrap in electrical tape, do not use the wire nut.
    • Using another 1 ft length of 14 AWG wire, strip the end, and solder one end to the negative terminal of the potentiometer.
    • Strip the other end, and solder it to the wire that goes to the relay. Wrap this in electrical tape as well.

    Step 28: Step 3.3.6: Hiding the Wiring/Reassembly

    • Reassemble the dash and windshield.
    • Use electrical tape to cover the loose wiring running off of the windshield, and the wiring leading into the dash.
    • Electrical tape all wire nuts in the hood compartment.
    • Reassemble the steering column.
    • Reassemble the hood.
    • Note for reassembly: If you wish to have remote control of the car, bolt the steering column to the white motor from underneath the car.

    Step 29: Step 3.4.1: Back Support Materials

    • 2 1/4 in diameter carriage bolts longer than the PVC tube diameter
    • 4 1/4 in nuts
    • Measuring Tape
    • 7 ft of 1 inch wide PVC Pipe
    • Two T Joints
    • 6 90 degree elbow joints
    • 2 45 degree elbow joints
    • A can of PVC Cement (do not use all of the can, you won't need it all)
    • 3/8 in. drill bit
    • Drill
    • A small kick-board:
    • 6 zip ties
    • pointed file (to make holes in the kickboard)

    Step 30: Step 3.4.2: PVC Tube Dimensions

    • 5 ½ inch X 2 (piece 1)
    • 45 degree angle 3/4 inch (piece 2)
    • 4 ¾ inch X 2 (piece 3)
    • T-joint (piece 4)
    • 5 ¼ x 2 (piece 5)
    • Elbow 90 degree X 2 (piece 6)
    • 2 inch piece between elbow pieces (piece 7)
    • Elbow 90 degree X 2 (piece 8)
    • 2 inch piece between elbow pieces (piece 9)
    • Elbow 90 degree X 2 (piece 10)

    Step 31: Step 3.4.3: Back Support Assembly

    • Measure the width of the back of vehicle of where we want to put our pipes on the side.
    • Cut the PVC with a saw to the desire length.
    • Connect the pipes together with the T joints and elbow joints using the cement.
    • Follow the instructions on the cans to learn how to apply the cement.
    • Make sure that the support pipe is high enough that it is above the built in seat.
    • The orientation for the frame that we used is a 5.5 in. pipe at the bottom, then a 45 degree elbow joint, then a 4.75 in., then a T- joint, then a 5.25 in pipe, then a elbow joint (90 degrees). The first T-joint and top elbow joint should be facing backwards. This should be completed twice, one for each side. After that 2 in. pipe should be place in the T-joint and elbow joint, then elbow joints should be fitted on to the 2 in. pipe. Lastly, 17 in. pipe should connect the two sides together.

    Step 32: Step 3.4.4: Attaching the Kickboard

    • Use the pointed file to poke two sets of holes near the middle part of the frame and two single holes on the bottom part of the kickboard. Remove the two foam handles from the board.
    • Using 6 zip ties, attach 2 zip ties to the top of the board through the handles, 2 through the middle sets of holes, and 2 on the bottom, wrapping them around the 45 degree elbows toward the bottom of the frame.
    • Remove the middle part of the back roll bar, insert the PVC frame.
    • Drill a hole through each remaining pieces of the roll bar with the frame inserted, and put the carriage bolts into the holes. Fix the bolts in place with 2 nuts finger tight.