I&E Wheelchair Design Seminar: Wednesday, October 8, 1975

  • I Project Definition and Goals
    Input from clients and all persons who use wheelchairs is needed, so that CIL can design and fabricate a wheelchair that will meet the needs of the disabled population. CIL hopes to produce a new wheelchair in quantity in order to offer a real alternative in mobility. Modifications on current wheelchairs can be completed before the final chair is on the market.
  • II Control systems
    • A On the EJ33B, Janice Krones has had problems with clicking relays and the chair takes off too fast.
      1. 1 The potentiometers in EJ33B have dead spots. The potentiometers were redesigned and provided larger neutral area. These potentiometers had no resistance. EJ changed from ceramic pots to wire-wound pots, but even with this change, the problems in the control system persist.
      2. 2 Janice K and John Hessler noted that plugs fall out. All plugs in a new chair should lock together, so plugs won't fall apart, which causes the chair to stop.
    • B Placement of control box
      1. If control box can be shifted, it will be easier to get through doorways.
      2. On Willie Winocur's Advanced chair, the control box is on the inside. The box is hinged, held by magnets, and can be moved outside whenever Willie needs to get in and out of the chair.
      3. John Hessler feels that a control box should be secured solidly. A control box laying in the driver's lap is not secure enough for many drivers.
  • III Battery and Charger System
    • A Should power chairs fold?
      1. John H. has folded his chair once for air travel. Travelling by air and by car is the major problem. The problem when travelling by planes, pilots can refuse to carry batteries, as batteries are considered "caustic" materials.
    • B CIL is investigating air-craft proof batteries. These batteries are seal-proof and won't spill if they turn over. However a problem is that batteries leak gas.
    • C CIL may construct a seal proof battery container to sell to air lines, so that batteries can be safely carried. John H. pointed out that another problem in taking the wheelchair on planes is that the airlines may object to the weight.
    • D Exposed wiring should be covered on the new wheelchairs.

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    • E Charger systems need to be improved.
      1. Janice K. felt that chargers should be built into the chair, so the chair can be charged anywhere. She used a golf cart that could be plugged in anywhere, and charged easily.
      2. Willie W. - automatic chargers sould have to be big in order to charge automatically whenever the chair battery is running low. An emergency charger can be smaller is size, and vibrations should not bother the small size charger.
      3. John H stated that any charger system must be a replaceable module that can be removed easily whenever it burns out.
  • IV Seats and backs
    • A What are the advantages of a hammock back over an upholstered back (like on the EJ chairs)?
      1. Doug B. - on EJ chairs, more support is needed for the lower back.
      2. John H - more support is needed than an upholstered back provides, even though with upholstery, the chair can fold.
    • B John H. - The power unit should be constructed. Then seats can be constructed to individual need.
      1. Willie W. - The seat on the "Advanced" is an improvement. There is three to four inches of foam. The foam can be pulled out and a pillow can be slipped in.
      2. Willie W has modified his seat. His seat was originally one hard sheet of plywood with three inches of sponge, but the foam in any pillow eventually bottoms out. He had a seat made with straps of rubber that are flexible and will give. Any seat structure with give is important.
      3. The seat should never touch the back of the driver's legs.
  • V The UC chair project now has seven prototypes that are being tested. The company that manufactured the prototypes is interested in manufacturing the chairs. The UC chair will come out in a year, and hopefully the price will be kept down to $3000.
  • VI Tires
    • A Inflatable caster tires provide a comfortable ride, more suspension, climbs curbs, but will puncture.
    • B Bill B -To avoid the problem of puncturing, a quick release device can be attached to the tire, (a modified part from a ten-speed bicycle). Then if a spare is carried, it can be easily substituted for a flat in case of puncture.
    • C John - Better suspension is needed for front and back of chairs. EJ chairs can be changed to spring suspension. Also it would be helpful to lock suspension when getting in and out of the chair to prevent the chair from tipping.
    • D Hitting curbs and sidewalks is difficult. Rear suspension is important to protect people's behinds.
    • E With casters, tires can swing out and get stuck in doorways or in walls.
    • F Ralph Hodgekiss is working on a ball system that can roll on its radius and will do away with casters.
    • G Willie W. - The advantage of an "Advanced" is that it is widest at the arms, so the person driving the chair can easily determine whether the chair can pass through a doorway or passage.

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    • H Are non-floormarking tires important?
      1. The grey tires don't provide sufficient traction.
      2. It would be nice to replace tires from a bicycle shop.
    • I One advantage of placing wheels under the seat is being able to transfer sideways.
    • J Willie W. - The problem with Advanced chairs is not with the small rear wheels, but with the front wheels when climbing curbs.
      1. Doug B. - An Advanced can climb curbs easier because of the extra power. He was able to bounce over a 5" curb.
    • K Should the solid wheels that don't turn be in front or in the back?
      1. The "IBAC" chair won't travel at high speeds.
  • VII Cushions
    • A John H. - An option for cushions is needed.
    • B Cathy Caulfield - A chair should be designed so the cushion won't slide.
    • C Naugahyde should not be used for cushions as it is too stiff; cloth is better for cushions.
    • D Molded seats are not a good idea, as people change how they are sitting during the day.
    • E Rehab Centers, ie Rancho Los Amigos, are researching different types of cushions.
  • VIII Footrests
    • A On footrests, is there a use for outer bars, or can a bar be placed behind the knees?
      1. For transferring, footrests should swing out. Adjustable footrests are needed, so they can be raised and lowered. One example is that footrests may need to be raised when going over curbs.
      2. Options on footrests are important. A pedal system with one rod is possible.
    • B A space between foot pedals is important, especially when pulling close to a table or desk. However John H. says he only had a problem once when trying to get close to a table (he has a single foot pedal).
    • C Padding on foot pedals should be a requirement to avoid pressure sores and to keep pedals warmer.
    • D The only advantage of half-length foot pedals is a shorter turning radius.
    • E The elevation of legs is an important consideration. Calf rests should be an option. The problem of heel straps, instead of calf rests, is that all weight goes on the heel.
      1. When driving low to the ground, there is the danger of feet falling off the side and getting caught in the wheel.
      2. All persons spasm differently, so the requirements for foot pedals will vary.
      3. Some persons don't spasm and may like to lift their feet off pedals during the day.
  • IX Arm rests and frames.
    • A The wheelchairs now separate walkies from wheelies, so a new chair should fit into the environment somehow.

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    • B Arm rests need cushioning.
    • C On the UC chairs, arm rests fold up backwards.
      1. Carrying pouches on the inside arms are useful. But with folding arms, the pouches would get caught up.
    • D Both arms need to be removed. Some people may prefer arms that lift out, but the pouches will remain in place.
    • E Arm length should be optional.
  • X Drives
    • A On EJ chairs, the belts slip, and don't provide adequate traction. Also belts break. However the EJ V-belts are sturdier.
      1. The belts squeak.
      2. With belts, it is easier to have a variable ratio.
    • B The chain drive on the Advanced is noisier. Willie W. thinks the advantage of noise is that it lets people know that a wheelchair is approaching. Also when the chair breaks down, people inside houses will be aware.
      1. The chain drive is safe as there is not any slipping in wet weather.
    • C MSE cog drive
      1. One problem is that when tires go flat, all braking power is lost.
      2. If cogs are moved away from tires, the only disadvantage is slipping, but the wear on tires is minimized.
        1. a. The cog drive wears tires. The problem is not puncturing, but slow leaks from wear. "Bike fill' may help to alleviate this problem of fast tire wear.
      3. The MSE has a harder ride, but with less slippage, it offers greater control over turns.
      4. The advantage of a friction hub, a hard rubber wheel running against the cog, is lessening tire wear.
      5. John H. rarely uses the 12 volt control. He feels that he has more control with the 24 volt, and it is more difficult to turn using the 12 volt control.
      6. John H. has a better range with the MSE.
  • XI Controller assemblies
    • A With small controller assemblies, overheating is a problem.
    • B On the Advanced wheelchair, transistors will not blow when going over curbs.
    • C A controller should be designed to recover speed of motors and balance, and to have positive front wheel steering (but would be very expensive).
  • XII Gear drives
    1. A. UC Project has a large worm gear mounted to the gears. This gear will add $100 to$200 to the cost of the chair. However the life of this worm gear will be longer.