A few months ago a student from New Hampshire emailed NuVu looking for help. Juan has cerebral palsy and can only move his arms. Juan's favorite activity in school is gardening. Juan can’t participate in gardening because he is not able to bend down to touch the ground. Stefano and Ethan started to design a wheelchair that could safely lower Juan to the ground, so that he can garden. They designed a 1/6th scale of the wheelchair. Ben Four weeks ago picked up this project from where Stefano and Ethan left it. For the last two weeks Ben, Reed and Ethan have been working on making it a reality for Juan.
The newest version of the wheelchair is a 1/3rd scale model that fully functions. The wheelchair is a mechanical foot pump to operate. The wheelchair has gears that are a 1/4th scale to cut down on weight. The small gears is connected to a ratchet. That ratchet has pawls to help hold the weight and lock it in place. The ratchet has a foot pump that turns the gears to push Juan up into the normal configuration for a wheelchair. The smallest gear has a gears shift to let Juan lower to the ground that is slowed down by linear dashpots, so juan doesn’t get hurt lowering to the ground. Reed and Ben have been talking about what parts, material, shape, size, and how to use the parts for the past week and have decided that the wheelchair will have a frame made of aluminum and square shaped. The padded chair from his normal wheelchair will be removed and bolted onto the lowering wheelchair. Also, to water jet steel gears to make the gears strong. One challenge that was faced was that juan can’t have his legs straight, so we have to have his legs slightly bent when his is lowered to the ground. The wheelchair has its chair not completely on the ground so that juan can have his legs slightly bent.
One iteration that we did was to take out one of the supports with a gears that was not essential to the wheelchair. This support beam was getting in the way of the gears and foot pump. That gear on the support was then attached to the second support with a gear. This iteration cut down on weight, amount of material and complication.
The second iteration was the original ratchet was made of wood, bolts, nuts, and springs. The problem with the wood ratchet and pawls was that the wood started to dull and brake. The newest version of the ratchet is 3D printed. The pawls, small gears shifts, and ratchets were 3D printed to create more strength and weight capabilities for the wheelchair. On the final product, all the gears will be water jetted from steel for strength.
The third iteration we redesigned the foot pump. The original pump was not strong enough to have someone use it. The first time the foot pump together it broke and split the thin wood parts. So, we redesigned the foot pump and laser cut the pieces in thick wood. Also, we added pilot holes for the screws to go into to stop the wood from splitting.