WillChair Build 4
Front Shock Mounts
Not many machining pictures. Nothing much to see. This piece was welded to the swingarm. The bottom of the shock attaches to it. There are four different mounting holes for the shock to attach to. Moving it farther rearward softens the shock and increases suspension travel slightly. Forward the opposite. Also useful in setting the sag (you'll know this term if you raced motocross) of the front end when loaded with 140 pounds of sexy.
After welding they went back into the lathe for final machining for bearings. A 1.625" od roller bearing fits into each side.
Assembled for testing.
An R sized O ring is sandwiched on the inside between the swingarm and mount and on the outside under that aluminum cap to keep the nastiness out. See the rusted bolts? Those are common black oxide coated socket cap bolts that come standard on powerchairs. Fail. All bolts were replaced with stainless bolts for final assembly.
Above: The tilt actuator mounting hole is slotted because the actuator itself moves in a slight arc as it extends and retracts while tilting.
Left: Testing the actuator fitment. Note the caster barrels aren't the same ones from the previous page. I originally made them the same size and used the same roller bearings as a powerchair I looked at. They lasted through about a month of my abusive testing.
A few crappy cellphone shots of more trial assembly
The rear tires and wheels are tubeless 145/70-6 from those cheap Chinese imported ATVs. My younggin has one of those ATVs I got her for her 3rd birthday. So, if I have a flat I'll have four spares. I'll eventually replace them with much better quality spun or cast aluminum wheels and Kevlar reinforced flat resistant tires.
The fronts are 3.00-8 made for those mini pit bikes. Much bigger and better than anything found on a manufactured powerchair.
Running the tires at a squishy 5 to 6 psi functions quite well as shock absorbers. The suspension covers the big bumps and holes. The large soft tires help smooth out the small stuff that cause vibrations. That's what triggers spasms and clonis more than big hits. Why can't the manufacturers realize this?
Add up how much ground clearance that will be. A 2x4, a 2x6, and a 4x4. Now it's clear why I needed to keep the chassis low on top and limit seat height. No weight down low = tippy!
Rear drive assembly
Note that the mounts are aluminum. These are the first ones I made. They were later remachined from steel at slightly different dimensions. Far too much work. These are also not the same motors used for final assembly. You can see the lip I machined into the hub to locate the rear wheels. After assembly there was maybe .001" of runout on the hubs. Far, FAR more accurate than anything you'll buy and more concentric than the stamped steel wheels they hold.
Yes, that's 1/4" steel. They are a bit heavy. I wanted to add some extra weight way out front to help offset the weight of the motors since they are mounted behind the rear axle centerline. Kind of like a counterbalance or pendulum. With the seat mounted in a proper location instead of too far forward, like on stock powerchairs, the chair's center of gravity is just in front of the rear axles. This makes wheelies and steering easier. Plus, lessens the strain on the drivetrain trying to overcome the resistance of the front casters. That bit of weight out front helps make wheelies smoother. You can see the mounts from the pictures a few pages back.
Mostly assembled for testing. I ran it like this for several months to work the bugs out before powdercoating and final assembly. Fortunately, I didn't have to change much from my original design. Most stuff worked out quite well.
The hard parts pulled back apart after a few months of testing and tweaking. All ready for the powdercoaters.
A few weeks later and here they are! Now the fun part of running a tap through each of the bolt holes as well as polishing all of the bearing press fit surfaces. That alone took several days, but the results were worth it.
Getting' there! This is a higher quality fit and finish than you will ever see on a manufactured powerchair. All steel parts and some aluminum are powdercoated, the rest of the aluminum is polished to a near mirror finish, all fasteners are quality 304 stainless, all wiring soldered and heat shrink applied, etc. There was a lot of attention to detail. Too bad it won't be this pretty for long. I USE/ABUSE this thing.
Note: Bright sunlight and a dark subject with shiny accents doesn't play well with the camera. These are the best I could do.
The covers were made from 1/8" thick Kydex. It's a heat formable plastic. Cool stuff! Thinner sheets are used a lot in the gun industry to form custom holsters.
Covers are most definitely necessary. You don't want a wrench or screwdriver falling down inside with the battery. The LiFePo4 battery chemistry is actually safer than the common lead/acid currently used. However, the way the cells are set up with open ends leaves a lot of hot area instead of just two conductive terminals up top. SPARK SHOW! Don't ask how I know....
The aluminum parts are polished to a bright finish. I intentionally dulled the photo so that the details could be seen. The chain is common 420 sized as used on mid sized ATVs and motocross bikes. Too bad you can't see all of the goodies hidden inside. There was a lot of intricate machining. Hidden beneath the pretty surface are four 1.625" roller bearings, several C clips for locating, a 1.25" od needle bearing, a Torrington bearing, and O ring seals. Note the stainless bolts now instead of rusty crap. That one bolt in the sprocket mount is all that holds everything together. Remove it and everything slides apart in 30 seconds for easy maintenance should it ever be necessary.
Look at that sexy butt! I need to learn how to make a Sir-Mix-A-Lot song play on mouse hover.
See all those motor wires? There's 11 instead of the simple 2 wires on brushed motors. Definitely ups the complication going brushless. But, what you lose in simplicity you gain back in efficiency. It was like removing a band aid. A pain and scary at first then all good once finished.
These are custom wound brushless motors. Currently and as far as I know, there are no off-the-shelf brushless motors made that are suitable for a wheelchair application. I simply did the math to come to the specs I needed, lubed up my bank account, and searched online for a vendor. Several places blew me off because they want high volume orders without much work.
I could only find one company that was willing to even acknowledge my inquiries for just a few units. Albeit it wasn't cheap. $1,700 later and motors were ordered (cheaper than you'll pay for a similar or lower quality motor from a wheelchair thief/vendor).
Those gearboxes are SWEET! Permanently lubed planetary reductions. They were a bit loud at first, but have gotten quieter with use. No louder than a standard low efficiency worm drive gearbox in typical powerchairs if they were run at this rpm or power level.
The wheels and hardware were whittled out of a solid bar of 6061-t6 aluminum. The "tires" are simply big R sized O rings that fit into grooves I machined into the wheels. The soft aluminum wheels will eventually get dinged up pretty bad. Once that happens I'll make some more tires. For now they look pretty!
The bolts are stainless. The rod is also stainless. It doubles as a tow bar. Believe it or not, this chair will pull a load. It pulls my 14hp 60" tow behind mower without issue. Try that in your standard powerchair.