This is my 11 year old, "Booger". She had a bout with SCFE, (https://secure.wikimedia.org/wikipedia/en/wiki/Slipped_capital_femoral_epiphysis) which landed her in a wheelchair for 3 months. These 3 months included Maker Faire NC, which we had been planning to attend for at least a couple months before this happened. Knowing we were still going to go, wheelchair be damned, we needed a way to carry the inevitable SWAG without piling it all on her lap or my back. Here is my solution. This is my first instructable, so be gentle... critical, but gentle!
Step 1: Convienience items
Since the wheelchair was rented I couldn't affix any more permanent modifications, plus a permanent attachment of the rear mount basket would have rendered the chair unable to fold. After sewing her some tush cushion and adding a way for her to tote her water bottle, it was time to figure out how to attach a milk crate to the back of the chair.
Step 2: Found a basket... now what?
the old milk crate I "acquired" was a little too narrow to rest atop the kick stubs on the chair. After removing the rubber bumpers on the kick stubs, I found pre-drilled holes.
Step 3: Measure!
Measured the basket. it was 13 3/4 in x 15 3/8 in
Step 4: Gathering supplies
We were in Lowe's and I saw these 2' sections of PVC for between $1.50 and $2 each and decided that would be the best thing to build a removable carrier for our "basket". I got 5 sections of 1/2" PVC and 4 sections of 1". Not being an engineer and not really all that adept at math, I made rough guesstimates as to the lengths and used a power miter saw to cut the PVC to my guesstimates. I also picked up 2 1" to 1/2" 90 degree adapters, 4 1"X1/2" tees, 2 1/2"x1/2" tees and a 1/2"x1/2" cross. After my initial guesstimates were wrong, I remeasured and basically cut to fit. The final cuts were 2 2" sections of 1", 4 6" sections of 1", 6 7" sections of 1/2", and 2 6" sections of 1/2". My initial cyphering failed to include the adapters.