A scooter board can be customized for a particular child. These come in all shapes and sizes (depending on the size of the user). Some have leg stabilizers or arm stabilizers built in. The one demonstrated here has an anti-tip bar. This one is small, but so is the user.
faux leather fabric / Naugahyde
1" nominal thickness foam padding
Velcro (both hook and loop, not adhesive)
Casters (I collect casters from discarded office furniture, desks, etc. for just such an event)
#10 screws, 1/2" (4 per wheel, in this case)
Step 1: Take Measurements
He measured 8" wide and 16" from neck to crotch. The board will be made to this size.
This instructable actually covers two boards, the original prototype and an upgrade.
The second one is a little bigger; more on that later.
Step 2: Cut the Board, Add Casters
Next, cut a 45° chamfer on each of the corners for a rounder look.
I rounded all the edges; this will be easier both on the kid and the upholstery.
I positioned four casters on the board (in this case, I aligned them on the corner bisectors on a whim).
The main point here is to try and position the casters so that the radius of revolutions don't touch - you should be able to spin the casters without them banging into each other. The other point is to spread out the load as uniformly as possible.
I drilled pilot holes for the casters, then screwed the casters into place.
In this case, I used a 7/64" drill bit for the pilot holes, and used #10 - 1/2" metal screws to attach the casters.
I collect good casters for such projects. Whenever I see a junk <desk, chair, etc.> with casters, I try to rescue the casters before the rest of it goes to the dump. You can also buy casters online, at the hardware store, etc. I am experimenting with using ball transfers as casters for scooter boards.
Step 3: Upholster the Board
Lay out the scooter board on top of a piece of foam padding. Lay the board and the foam on top of faux leather or other upholstery fabric. The foam should be bigger than the board on all sides, and the fabric should be bigger than the foam. This gives space for the fabric and foam to wrap around the edges.
The wheels are on in this step because the wheels all need to spin freely. With the wheels attached, this can be easily tested.
Wrap the fabric and the foam around a straight edge.Staple into place. Repeat on the opposite side, stretching the fabric tight; staple into place. Repeat for the other sides, then start on the corners.
Trim the foam and the fabric as needed. The corners are especially tricky. I am using the corner technique from http://littlegreennotebook.blogspot.com/2012/07/how-to-upholster-bench-corners.html
Step 4: Attach Velcro
Also on this step I added a stabilizer bar. Normally this is not needed, most children have more arm and leg and can right themselves if they tip. "A" needs a little more help - he could tip over and not be able to get back upright. The bar can be removed once he learns to balance by himself. Think of it as a set of training wheels.
I think the stabilizer bar used to be a sign stake or a tomato stake (i.e. scrap wood I had on hand) that was rounded and sanded smooth so he wouldn't scrape himself.
Step 5: User Testing
1) He is top-heavy. Since he is missing some leg, his head is the heaviest part of him. If he is positioned so that he can reach the ground, he tends to nose-dive. He figured out how to balance, and was able to move with his back wheels and feet in the air (like a wheelbarrow). We will fix this by adding a nose wheel to prevent tipping.
2) It would be easier if he had more use of his arms. We will fix this by making a tapered nose on the next model.
Step 6: Version 2 Cutting
I mapped out the shape I needed, and marked off 1" from the edges for upholstery. The rotation of each wheel (except for the nose) is marked. The board is cut, the holes are drilled, and the casters are attached. I had initially considered a smaller wheel for the nose, but later decided to make them all the same size. I used the same size bits and screws for this build.
Step 7: Version 2 Upholster
This time, I tucked the fabric under and stapled through both layers. It results in a much cleaner look. Pull the fabric tightly before stapling the material.
I made sure to have extra padding in the nose and on the tail, as these are the areas most likely to be involved in collisions.
Step 8: Version 2 Velcro
I moved the stabilizer bar from the first model to the second.
I also ran out of black Velcro so I switched over to using white for one strap.
Step 10: Update: Ball Transfers
They can mount from the bottom of the deck (like the casters). Since there are no swinging parts, we don't have to worry about a radius of revolution like with the casters.
The best part is that they can be mounted from the top of the deck. This means cutting a hole through the wood, then screwing the ball transfer into the top of the wood deck using the provided mounting holes. This dramatically lowers the height of the scooter board. For someone with poor leg and arm length like "A", this means the legs and arms are closer to the ground and thus more useable. For this design, hugging the ground also removes the need for an anti-tip measures. It becomes impossible to tip as the scooter board rides 1/2" from the ground. I had to make sure the upholstery was nice and tight to prevent it dragging on the ground.
The two scooters shown in the pictures using the transfers - one is a "booty scooter" (sit on it), and the other is prone (lay on it).