Tuesday, December 14, 2010

Trying a new center wheel idea

Well, here we go again!

R2-D2's center foot uses two 2.5 inch casters to roll around with.  Anything small gets snared up when I try to drive R2 onto or off an elevator.  If I go with a 3 inch wheel, due to the larger size, it tips the outer feet back too far, making it difficult for the front-wheel drive to carry the full weight load.  To date, I have been using the casters from Lowe's with good results.  However due to the weight of R2 and the amount of driving we do, we wear thru them within a few months.  

We've also experimented with various shock-dampening ideas, so that when R2 does plow along over uneven surfaces, our little metal buddy doesn't chime like an over-sized bell!

One idea my local Aubuchon Hardware guy mentioned was trying a rollerblade wheel.  I had a youngster mention that once a while back but I never followed up on it.  Just down the road is Gunn's Sports Shop, the local mecca for all things hockey!  (That's where I bought all my pads, skates and stick back when I played!).  I stopped by and explained what I was looking for and what I intended to use it for.  The gentleman there had seen the various media coverage on what we have been up to on the Pediatric Floor and was pleased to help.

We found some rollerblade wheels that game very close to 2.5 inches.  The wheels we found are 64mm which breaks down to 2.51 inches.  Nice!  He was also able to install ball bearings and found some long hinges that we thought might work out.

I had some spare casters that already had the wheels removed.  These were my original attempt to use 2 inch wheels.

As you can see, the axle for the rollerblade is too short and does not make it across the wheel mount.  Also, its a lot thinner than the mounting hole, another issue that will need to be addressed.

Here's what I am using for parts...a 2.5 inch long graded 1/4 inch bolt, lock nut and some nylon spacers and a bronze piece that I will use to shim the mounting hole, so the axle fits snug for smooth rolling.

As you can see, it fits but will require some sanding down to do so.

This shot gives you an idea how everything will work.  The spacers make contact with the wheel bearings, not the wheel.  The bolt will have to be trimmed down some as well.

This was tricky to cut in a vice.  Set the vice too tight and you no longer have a round piece!  I just went slow and used the hacksaw to remove .25 inch piece to use as an insert in the wheel mount.

In this shot, you can see I have used a hammer to pound the bronze inserts into the wheel mount.  To make sure they were fit smooth, I used the dremel to remove any excess material from each side.  I also used a 1/4 inch drill bit to make sure the holes were uniform, so that the bolt would pass through easily.

The axle bolt is trimmed down after the wheel and nylon spacers are installed.

Here's the end result tonight.  I'm pretty optimistic to see how these perform.  The material is softer and should have a lot better wear.  Tomorrow we'll look at installing them into the center foot and try them out.