Since securing the support of Olivier to design and manufacture a wheelchair almost completely out of plywood, we have met on 2 separate occasions.
First meeting with Olivier.
I mentioned that I had bought a wheelchair and that it was fundamentally a sound design. After explaining the wheelchair to him he thought it sounded good but was curious about the detail of the wheels/bearings/axis etc.
We decided the best move would be to emulate this exact wheelchair but using plywood. As a starting point. He mentioned two suppliers of bearings, Igus + MSC.
So at the end of this meeting we had decided that we would focus on the mechanicals first and then move on to aesthetics later. Olivier agreed that the design seems good, it is more the materials used that we want to question.
Dylan came along and mentioned that he went to university with the guy that designed the safari seat. Said he can put me in touch with him, which is a good avenue to explore.
Olivier then said I should look in the store room to see if any bolts we have could be used. his whole thing is that this needs to be easy to produce not only in its assembly and technical design, but in that the necessary components are easy to find and order.
After this I went on to research Igus as a company and it seems a great place to purchase the bearings from. they also have a great page on past projects that have used particular bearings or components that they produce and in searching through this I have stumbled on a useful precedent, the plywood wheelchair designed for a hospital in Tokyo.
Whilst working on saturday Olivier said I should find out from either supplier if they have an axis solution. I think at this point he thought it was far more complicated than it was.
once I had found the time to actually look at the bearings and the axis on the current wheelchair I found it to be actually quite simple. For instance, I did a rough measurement of the front castor, in situ, and ordered some bearings I had found for a skateboard on amazon. Again this is something to note as in my quest to paint mobility tools as vehicles, or personal mobility/I am discovering that the components are similar to that used in bicycles/skateboards and abstractly to the components used in cars.
I have since spent a morning taking the wheels apart, i found this incredibly satisfying, really beginning to understand how the wheelchair is put together and how it functions. I now have all of the measurements/specifications for each bearing.
Rear wheel requires,
M12 Hex Head Bolt x 100mm in length. (This acts as the axle) with nut
2x 6201ZZ Wheel bearings per rear wheel.
32mm Outer Diameter,
Type, Deep groove/shielded.
For Front Castor
M8 Alan Head Bolt x 75mm in length with nut
2x 608zz wheel bearings per wheel,
30mm Outer Diameter
For swivel Mount
30mm bearing outer – measured across the top which includes the flange
inverse of this is 28mm domed body of the bearing which means 1mm flange on both sides.
12mm inner so this dictates that will have to purchase another m12 x 75-100mm bolt with nut to act as the rod to which is slid through the housing of the two bearings and secured at the top. depth wise at least around 15mm but anything deeper will be bonus in terms of purchase.
Wheel sizes are as follows,
Rear wheel is 560mm in diameter with a 70mm hub incorporated into the mould (achievable in ply)
front castor is 172 in diameter with a 32mm hub incorporated into the mould of the wheel (achievable in ply)
During my second meeting with Olivier we looked at the plywood chair in tokyo + he gave me a list of things to get on with. Learnt another advantage of this material is that the wheelchair would be airport friendly and could go through scanners etc without setting off alarms.
included – List all hardware necessary for us to design a wheel and then order them. in other words generate a kit. and tyres also – find out where to order them from. and take tyres off both wheels and measure profiles carefully.
look up alternate resin bolts to use as axles.
He then mocked up a wheel very quickly that I can machine at a later date and use it to test how we will construct the wheel out of two pieces of ply to create a domed forged rim. So I will do that sometime soon ( this weekend whilst at work hopefully)