Removable Platform for Gait Trainer

Team Members: Ananya Nandy, Vyshnavi Vennelakanti, Kanika Gakhar

Co-Designers: Jennifer and Julian

Thanks to the MIT AT Hack Exec Team and MIT Lincoln Beaver Works Center

This project was completed for AT Hack 2019 (the assistive technology hackathon at MIT). The purpose of this project was to design a base to support Julian's feet and allow him to be in a more seated position while in the gait trainer. This would increase the ease of transportation so that he would not have to be lifted up and down to move around. At the same time, the platform would be removable, allowing Julian to stand within the gait trainer when desired. The platform was designed to attach to Julian's existing outdoor gait trainer with no permanent modifications to the frame.

We traveled to Julian's house to take a look at the gait trainer and determine a simple and effective way to add the platform. From this, we learned that previous attempted solutions included soft velcro straps attached to the frame. However, with these soft straps, Julian's feet would fall out and end up in a bad position, with his feet too close together. Therefore, any sort of non-platform solution would have to allow for variable positioning of his feet.

We came up with some of the desired characteristics for the solution:

• Firm material rather than soft material - ideally something lightweight, like plastic
• Easily removable
• Level with frame height
• Supports ~120 lbs of weight
• Minimal addition of weight to the gait trainer

From this, we came up with a few ideas for the platform. The biggest challenge was being able to attach to the existing gait trainer without modifying it, due to the irregular sloping and cross-section of the framing. We then sent these ideas over to Jennifer and Julian to get feedback.

Paraphrased Feedback

Sketch 1 - Simple and easy to remove. Could require more stability to hold the platform - potentially a rod or metal plate in the front. Might not need pegs if the plastic was molded to hang over the frame.

Sketch 2 - Looks sturdy but would be hard to remove if there were too many screws. Ideally, the platform could slide into place without screws or pegs.

Sketch 3 - Might have too many moving parts, meaning too many pieces to keep track of. Having a permanent rod in the back would not work because that is how Julian gets in and out of the gait trainer. A rod could be attached to the front with no issues.

We chose the design that seemed the most reliable and simple.

For the platform, we used 1/4" HDPE with 1/2" plywood reinforcements. The back consisted of "wings" that would brace against the frame while the front would be resting inside a bracket. Due to material size constraints (and time constraints), the HDPE did not cover the part of the platform braced on the frame, but this would be covered otherwise.

The attachment relied on 2 tube clamps attached to the pipe on the frame. Due to the slope of the pipe (1.75" diameter), the clamps used were oversized (2" diameter). 2 brackets were screwed into place under the clamps on either side. Finally, an aluminum bar was screwed into place under the 2 brackets to complete the assembly.

In final assembly, 2 tube clamps of the correct size (1.75" diameter) were attached directly adjacent to the oversized clamps to prevent them from sliding forward.

• Tube clamps (2" and 1.75" diameter)
• Aluminum 6063 Rectangular Tube (1.5"x3" / 0.25" thick / 1' long)
• Aluminum 6061 Bar (0.25"x1" / 2' long)
• Marine-Grade HDPE Sheet (24"x24" / 0.25" thick)
• Marine-Grade Plywood Sheet (12"x24" / 0.5" thick)
• Wood screws
• 10-32 flat head bolts
• 5/16-18 flat head bolts

Machines Used

• Bandsaw
• Belt Sander
• Mill
• Power Drill

Platform

1. Cut HDPE sheet to size on the bandsaw, based on the inner dimension of the gait trainer.
2. Cut plywood pieces on the bandsaw for reinforcement (based on bending deflection).
3. Drilled and countersunk holes for flathead wood screws in the plastic.
4. Screwed plywood pieces into the HDPE sheet.
5. Sanded a corner radius on the platform assembly using the belt sander.

Frame Attachment

1. Cut two 1.5" pieces of the aluminum rectangular tubing on the bandsaw.
2. Cut off one wall of each piece on the bandsaw to create a U-channel (short side).
3. Used a mill to smooth the edges and increase the inside width of the U-channel (from 1" to 1.06").
4. Drilled and tapped a hole in the top of each bracket for a 10-32 screw (to attach tube clamp).
5. Drilled and tapped a hole in the bottom of each bracket for a 5/16-18 screw (to attach aluminum bar).
6. Cut the aluminum bar to size on the bandsaw, based on the dimension between the walls of the U-channel.
7. Drill clearance holes for the 5/16-18 screw in the aluminum bar .

Assembly

1. Attached the 2" diameter tube clamps to the piping on either side of the frame.
2. Screwed a bracket in to the clamps on either side using a 10-32 screw.
3. Flipped the gait trainer base upside down and screwed the aluminum bar to both brackets with 5/16-18 screws.
4. Attached the 1.75" diameter tube clamps right in front of the 2" diameter tube clamps to prevent them from sliding.
5. Slid the platform into the two brackets.

Although we had limited testing with Julian, he was able to comfortably rest his feet on the platform for the rest of the night. Further testing would be necessary to test the durability of the assembly throughout his daily routine.

Given more time and iterations, there are several things that could improve this prototype:

• We would have liked to cut off the extra plastic at the back so the platform was exactly the desired size.
• Using plywood as reinforcement keeps it relatively lightweight, but isn't ideal for outdoor use (in the snow and rain specifically). A better reinforcement material could be used.
• If plywood is used as final material, we would at least add a waterproofing finish.
• Similarly, aluminum parts for the frame attachment are lightweight and easy to machine, but are not as durable and less appropriate for outdoor use. A better material could be chosen.
• We were not able to test the load-bearing capability of the platform. Although it held up under Julian's feet and some extra bags during our testing, it would be important to see how much weight the attachment could hold before deforming.
• Some of the parts could be made more carefully with better materials (bigger size of plastic sheet to cover entire platform, better and more durable screws, etc.). More precision in creating the parts would likely ease the assembly process (drilling/tapping the holes in the correct locations within tolerance - not just relative to each other).
• We would have liked to add a hole to the platform for a rope/string so that it could be easily attached to the gait trainer when not in use.