Introduction: Adaptive Infant Crawler

There are conditions, such as spina bifida, that prevent the use of a person's lower extremities. With an infant, this prevents him or her from crawling as infants typically do. This obstacle denies the infant the ability to explore his or her surroundings, an important part of the child's mental development. One of the goals with these instructions is to create a product for these infants so that they can better explore their surroundings. The other is to do it in such a way that it allows someone to be able to recreate this product with commercially available materials and tools that you can find in your backyard shed.

Step 1: Materials and Tools

Next to the materials are either a URL to find the item online or the McMaster-Carr product number

  • 1/8” Hardboard 2’x4’ (1)
  • 12"x28"(1) 1/16" PVC or other plastic sheet (optional)
  • 12"x12"(1) 1/8" Acrylic sheet or Hardboard
  • 14”x2”(2), 12”x15”(1) Pieces of ½” Thick Polyurethane Foam 86375K224
  • 12”x14” Piece of ¼” Thick Polyurethane Foam (1) 86375K234
  • 2”x2” Piece of Ethafoam
  • 12”x1½”x1½” Wood Block
  • 1½ Shoulder 5/16” Shoulder Bolt with ¼”x20 threads (2) 91259A587
  • Washer with a 5/16” Inner Diameter (2) 91860A029
  • ¼ x 20 Hex Nut (4) 94804A029
  • ¼ x 20 Bolt (2) 93190A542
  • ¼”x20 Tee Nut (2) 90973A415
  • Skate Bearings (4) (Used: Bones Reds)
  • Skateboard Wheels (2)
  • Omnitrack Omnicaster OC50 (1)
  • M10 Hex Nut (1) 94223A103
  • Wood Glue
  • Double-Sided Carpet Tape
  • Gaff Tape (optional)
  • 1/2 yard Polyurethane Laminate Fabric
  • Black Spray Paint (optional)
  • Super 77 spray adhesive


  • Drill
  • 9/32” drill bit
  • 3/8” drill bit
  • Hammer
  • Bandsaw
  • Small Paint Brush
  • ¾” Hole Punch
  • Hacksaw
  • File
  • Scissors

Step 2: Assembling the Wheel

  1. Put a skate bearing into each side of the skateboard wheel. A hammer may be required to properly seat the bearing into the wheel.
  2. Feed a shoulder bolt through the bearing on each wheel.
  3. Feed a washer through the thread end of the shoulder bolt.
  4. Screw a ¼”x20 Hex Nut onto the thread end of shoulder bolt.
  5. Repeat for the other wheel

Step 3: Making the Axle Block

    1. (Optional) Spray paint the wood block to give a nicer finish.
    2. Designate a bottom and a top of the 12”x1½”x1½” Wood Block.
    3. On the ends of the 12”x1½”x1½” Wood Block, make a horizontal line ½” above the bottom of the wood and a vertical line ¾” from one side of the wood. Repeat on the other end in such a way that the holes would line up.
    4. On the intersection of the two lines, drill a hole with a 9/32” bit so that the depth matches the length of the Tee nut.
    5. Put enough wood glue in the hole to properly secure the Tee nut.
    6. Place a ¼”x20 Tee nut in the hole and hammer it to make the face of the Tee nut flush with the end of the wood.
    7. Allow the glue to dry.
    8. Repeat Steps 3-6 on the other side of the block.
    9. Screw the threads of the assembled wheel’s shoulder bolt into the Tee nut
    10. Repeat for the other side.

    Step 4: Assembling the Main Board

    1. Cut the hardboard in half parallel to the longer edge, so that you have two 1’x4’ pieces
    2. Cut out (2) Main Board shapes and (2) Ribs from the hardboard.
    3. (Optional) In the bottom of the two main board pieces, cut a 14” slot starting 2.5” from the front centered along the longitudinal axis. This is to better hold the rib after gluing.
    4. Glue the two main board pieces together and the two rib pieces together with wood glue. You want the laminated sides on the outside. The wood glue will take time to dry, so clamps are suggested.
    5. Drill a 3/8” hole 3½” from the sides and 1½” from the front.
    6. Glue the two rib pieces together with wood glue. You want the laminated sides on the outside. The wood glue will take time to dry, so clamps are suggested.
    7. Put a thin strip of wood glue on the rib's long edge and place it on the board starting 2.5 inches from the front. You will likely need to use two pieces of scrap wood to keep the piece perpendicular to the board as the glue dries. You may also need to put wood glue along the edges.
    8. Cut approximately 5/16” off of the top of the Omnitrack Omnicaster’s threaded stud (Suggestion: File the edges of the newly cut side for safety purposes)
    9. After the wood glue has dried, put the Omnitrack Omnicaster into the main board from the bottom and screw the M10 Hex Nut into the thread until it is tight.

    Step 5: Assembling the Extension Board

    1. Cut the extension board out of hardboard or acrylic using the measurements in the previous step.
    2. Drill (1) 1/4" hole 1.75" away from the edge and (1) 1/4" hole 3.25" away from the edge of the board to fit the bolts for adjusting the board
    3. Drill (2) 1/16" holes 2.75” from the back and 3” from each edge for the axle block
    4. (Optional) Use Super 77 to attach 1/4" foam to the top of the extension board for added comfort, then cover in fabric.
    5. Using wood screws, screw the axle block onto the extension board.

    Step 6: Assembling the Foam

    1. Punch a ¾” diameter hole in the middle of the 2”x2” Ethafoam.
    2. Use Super 77 to adhere the Ethafoam to the front of the main board so that the nut on the Omnitrack Omnicaster fits in the hole in the foam.
    3. Use Super 77 to adhere the two 14”x2” Polyurethane pieces of ½” foam to main board along the sides so that the pieces are flush with the back edge of the main board.
    4. Cut the 12”x15” piece of ½” Polyurethane foam so that it matches the shape of the front of the main board. Use Super 77 to adhere the newly shaped piece of ½” Polyurethane foam to the front half of the main board.
    5. Use Super 77 to adhere the 12”x14” piece of ¼” Polyurethane foam to the back of the main board so that it goes on top of the14”x2 pieces of ½” foam.

    Step 7: ​Upholstering the Board

    1. Layout your fabric nice side down and place the assembled board on top of it.
    2. Remove the extension board by unscrewing the nuts and leaving the bolts in the main board.
    3. Apply carpet tape to every edge of the main board’s underside
    4. Wrap the fabric tightly around the sides of the foam and board, attaching the ends of the excess to the carpet tape.
    5. (Optional) Secure the raw edge of the fabric with Gaff tape.
    6. (Optional) Cut a piece of 1/16" sheet of PVC to the same shape as the hardboard and secure with screws for a nice finished look.
    7. Replace extension board, securing it with the nuts.