Instructions for Making a Four Bar Linkage Attachment for Center Mounted Footrest


Introduction: Instructions for Making a Four Bar Linkage Attachment for Center Mounted Footrest

Mid-drive power wheel chairs (PWC) have become more popular in recent years. However, due to the placement of the front casters, the traditional side-mounted footrests have been replaced by a single center-mounted footrest. Unfortunately, center-mounted footrests do not have a lift/lower mechanism that is easily operable by certain PWC users who transfer independently. Many PWC users have limited trunk strength and range of motion, decreased sensitivity in their lower body, and lack of fine motor function. This causes difficulty reaching the footrest to raise it. There is a need for a design solution that allows PWC users to independently lift and lower the footrest.

Step 1:

Replace hinge pin on existing footrest with round metal rod and drill set screws into the hinge to lock bar into place.

Step 2:

Cut two plastic pieces approximately 4" by 1" by 1".

Step 3:

Cut two wooden bars. One approximately 17" in length and the other approximately 5" in length. Width and depth should be 1" by 1".

Step 4:

Drill two holes into both ends of each plastic piece. Three of these holes should be of slightly bigger size than normal size screws. They should be able to have a screw slip in and out. The fourth hole should be the size of the metal bar used in the hinge and should hold it firmly. Insert metal bar into this hole and drill set screw in plastic piece to hold metal bar in place.

Step 5:

Drill a hole in the 17" wooden bar. Drill the 5" wooden bar into the top of the other side of the wooden bar.

Step 6:

Connect other two ends of plastic pieces together with screw and nut as shown.

Step 7:

Connect end of wooden bar to plastic piece with screw and nut as shown.

Step 8:

A hinge can also be added to the wooden bar to allow for clearance when bar is in maximum vertical position.

Step 9:

A casing such as the one shown can also be made to house the wooden bar.



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    12 Discussions

    Very nice. I have another suggestion, instead of using levers and hinges, have you considered running a steel cable inside a tube? (the same way as bike brakes work). Since the tube is flexible, it could be mounted anywhere on the frame with, for example, a ring pull attached that the user can grab. Obviously this will depend on the range of motion of the user though.

    5 replies

    What a cool idea. A lever handle on a hinge (i.e., exactly like a bike brake!) would permit "closed-fist" actuation. It's a slightly more complex design than the author's, I think, but a nice improvement for the end user.

    Interesting (and your colleague added it to our AT Group :-). I wonder if a paired lever system with countervailing springs (yeah, even more unnecessarily complicated) would be possible. For obvious reasons, expecting the user to push the footrest down with their feet, is not, um, appropriate.

    I would like to follow the work product of your design group.
    What do I need to do to accomplish this?
    I am particularly interested in ways to make everyday items more useable for people who use PWC chairs.

    You should probably repost your comment directly as a reply to user Kimberly8705, not to me.  Also, note that this discussion is a year old, and that user may no longer be active on Instructables.  Good luck.

    Cool! Looks like you have solved a major problem for some electric wheelchair users. Keep up the good work.

    3 replies

    Some of the most major problems for us is being able to even get a chair at a reasonable price. Most of the chair manufacturers, I think, are on drugs with their idea of priceing. Some of these chairs cost upwards of $30,000.00. They are not Rolls Royces. Want to make a nice living?

    Thank the medical insurance industry for the prices. "Whatever the market will bear," and they're the ones willing to "pay" (on paper, if not in reality) those prices. Some of the excessive cost comes from the "human safety" issues -- consider, as a metaphor, the cost differences per pound of payload for satellites or robotic space probes, compared to the Shuttle and space station. $10k and beyond for a power chair is still obscene.

    Here's a chance to make some money and reduce the cost of a chair in the process.

    Actually, we did, that should be coming up in another instructable, it is literally based on a bike cable.

    1 reply

    I think this was a reply "mechatronics" comment? Just so you know, if you click on the REPLY link immediately following a person's message (below the date-time stamp), your message will appear threaded below theirs, and they will automatically get an e-mail notification.