Area 42

The Wheelchair's Drive Train (First Fit-Up)

Chasing model airplanes. That’s one of the first mental images I had when I decided to build myself a power wheelchair. Whatever I came up with, it would have to be able to roll off into the tall grass without getting mired in mud or sand, or upset by lumps, bumps, branches, or other small obstructions.

So this was to be an all-terrain wheelchair. That meant big drive wheels with fat tires, as big as would fit under the seat.

The actual tires would have to be non-marking nylon, so I had little choice but to obtain that part from a wheelchair supply source. But in general I wanted to avoid assembling off-the-shelf wheelchair parts—that’s no better than buying an off-the-shelf wheelchair. My wheelchair is built up mostly from go-kart, mini-bike, and electric scooter parts.

Bad Bearing: Tap a Wedge Under/Around Flange to Remove

In particular, I used 8″ aluminum mini-bike wheels with size 400-8 power wheelchair tires. This makes a nice 16″ overall tire diameter with a fat cross-section. For a narrower tire, a 10-inch rim with 300-10 tires should have about the same overall diameter.

The wheel model I used came with bearings installed, but required a little drilling to accept a drive sprocket/brake drum. The provided bearings are a rather cheap “flanged” style with a stamped ball race; I’ve had to replace one pair already. Fortunately replacements can be ordered from several sources, some claiming “heavy duty” construction, and they’re not very hard to replace.

Now for the hard part: clear away all the other distractions and start flying model airplanes! Yeah, right.

Part Numbers and Sources

At my wife’s suggestion, I’ve moved some gory details here, where they’re easy to skip.

Bad Bearing: Distorted Race

Wheels: Azusa part number AZ1177, modified by drilling to mount the AZ2218-ID 72 tooth sprocket/drum assembly. I got mine at gokartparts.com. These wheels have 3/4″ ID, 1-3/8″ OD bearings.

Tires: size 4.00-8 knobby gray non-marking, edmond-wheelchair.com.

As an alternative, you might try the Azusa AZ10155 10″ steel wheel/drum/sprocket assembly with Edmond’s size 3.00-10 wheelchair tire (which I believe should fit). This setup would need no modification to mount the drive sprocket.

Good Bearing: Tap Gently Around Flange To Insert

The following are some replacement bearings I found that are claimed to work for the 3/4″ by 1-3/8″ flanged bearings:

• Northern Tools/Martin Wheel #13682 (”Low speed.” I’ve tried these; see the comments)
• K&T Parts, LawnMowerParts, or ReliableGoKarts #6573 (”heavy duty”)
• PressureParts or TheOEMPartsStore, #215-079 (”heavy duty”)

None of these are claimed to be “precision” bearings. Some day I might try fitting a 5/8″ x 1-3/8″ precision bearing into my wheels. (And changing my wheelchair’s axles, of course.)