WillChair Build Page 3
Rear hubs. These were a much bigger pain to make than anticipated.
A short drive to my parents' to get my dad to weld it up.
Pressed in and welded. When you don't own a proper granite surface a 1/2" thick sheet of steel plate will do. The hubs were later put back in my lathe and lightly machined to make them run perfectly true as well as machine a lip to locate the center of the rim on.
That's a 3/4 id tapered roller bearing and not the el cheapo single roller type bearings found in typical powerchairs. It holds two. One at the top and one at the bottom. That groove below the bearing in the picture above holds an R sized O ring to seal up the bearings. You can see it installed in the picture to the left. These bearings should outlive me vs needing to be replaced every year or so.
Bearing caps machined from a solid bar of 6061-t6. Note the O ring groove on the right one and O ring installed on the left one. These O rings also hold the bearing caps in place. A little dab of grease on them and they seal tight. Water hose tested. Passed.
Assembled and welded on for testing prior to powdercoating. Note the surface rust from testing with the water hose. Direct blast from every angle and the bearings stayed safely dry inside.
The nut is used to set the preload on the bearings. I machined a set screw (can't see it) into the side of the nut to lock it in place. With no preload the casters rotate too easily. You get caster shake at speed. Ever got the grocery cart at the local Piggly Wiggly with the gimp foot? The one that shimmies uncontrollably as you make your way down the bread isle? That's caster shake. At 6 mph it's quite annoying. At 13+ mph it's downright scary.
This may not look impressive, but that was a big heavy chunk of steel to be mounted that far offset. Shake it like a salt shaker!
Boring to final size
Another moment where an independent 4 jaw chuck is irreplaceable - unless you have a mill. Which I don't at the time of making this page. Donations accepted....
Mount for the seat
Back to my dad's to beg for more slave labor. The one on the right has the connecting point for the linear actuator that controls the tilt. Look closely and you can see the snap ring groove in the right photo and the needle bearings in the left photo. No bushings here. All quality bearings throughout.
Annnnd my dad showing how to use the proper squinting technique. OSHA approved.
Lightly welded and installed for testing. The seat mounts on top of the 1x2" rectangle tubing. The actuator pulls forward on the bolt in the plates sticking down, which cause the seat to pivot and tilt back.
Most powerchairs use what's called "tilt in space" (TIS for short). There are many techniques to do it. TIS works by moving the bottom of the seat forward as the entire seat tilts rearward. This helps move the center of gravity forward, or moreso keep it near the same place, to make the chair less likely to tip over backwards while tilted back should you give it some throttle or lean back very hard.
I designed a TIS system then decided to forego it and rely solely on common sense instead to not flip over backwards. Like on all powerchairs with TIS, It would add several inches to the seat height. I needed to keep the chair short due to the high ground clearance and light weight of the battery. Any added height would decrease stability too much for use on the hilly terrain I frequent. It worked out fantastic.
These are the first caster forks made. I later remade some identical except 1/2" taller and 2.125" wide instead of 1" wide as these are. I bent one of them during some abusive hard testing. I hope the newer ones don't get bent. If they do I hope I'm not the one in the chair that caused it! Only one picture of the thicker ones being made. It was done the same way, just more force and cursing required.
I don't own any proper bending tools, so this little pattern below was made. Back to my dad's to burn up some of his acetylene. Simply heat where the bend was needed and fold it 90 degrees over the pattern. Ok, not that easy in practice. But, sounded easy before actually doing it.