Instructions on Completing Mock-Up of Track Slide Design for Lift/Lower of Center-Mounted Footrests on Power Wheel Chairs

Step 5 Creating the Slotted Footrest Moment Arm

Now we must create the actual attachment from the track to the footrest. This will require two relatively long hinges.

I have labeled them as A and B in figure 8, 1st Image

First, find a long hinge(A) that is at least as long as your chosen moment arm length. Based on the length of the moment arm (of your choosing), you may need to cut one side of the hinge down. (If you don't want to deal with the physics for moment arm calculations, just find a hinge around a 4.5 inch length.) For my mock-up, I left it at 4.5 inches (Fig 8, 1st Image). '

Next, you will need to create the slotting mechanism. This mechanism increases your moment arm length, during lift, as well, so this must be taken into account for optimization.

Find a set of small bushings. These will be used as your rollers in your slot. Take your hinge, and use the mill to create a slot of width dependent on the diameter of your bushings (use calipers). See Fig 9, 2nd Image. You must make many passes with the mill and use lubrication, because the hinge material is steel.

Third, take your second hinge (B), and you must attach the bushing rollers to this hinge.

The bushings must either be cut or filed down to the height of the thickness of the hinge A. Please see Fig 9, 2nd Image for reference. Find two bolts which fit within the inner holes of the two bushings. Drill holes corresponding to bolt size through the hinge (B). The distance between these two holes also dictates how much extension your moment arm will have. You may want to consider drilling more holes for testing purposes.

Now fit both bolts through the holes in hinge B, then the bushings, and finally through the slot of hinge A (Fig 9, 2nd Image). Make sure that the bushings move and roll easily within the slot and creates an extension motion.

Lock in the bushings now with washers and wing nuts/nuts/locknuts.