Introduction: Linear Glide Arm Trough for Children With Disabilities

By REAR laboratory
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Problem Statement

Some kids with upper extremity limitations have difficulty using a tablet. This may be because they cannot keep their forearms off the tablet surface or do not have adequate strength to slide their arms on the table surface. We were asked to design and fabricate a simple arm trough that supports the forearm and allow adequate range of motion to use a tablet or other table-mounted device.

Design Parameters

The device should be able to cradle the user's arm while allowing them to move their arm linearly and have a full 360 degrees of rotation. This range of motion will allow the user to operate a tablet with greater ease of use. The device should also be comfortable to the user, simple to use, and easy assemble.

Step 1: Materials

Gather all necessary materials depending on whether you are making the small or larger version. Use the charts shown at your own discretion as particular parts may be substituted. Most parts you can find at your local hardware store or craft store. However, the linear glide and turntable need to be ordered from these specific vendors:

Turntable: http://www.mcmaster.com/#6031k16/=vxr170

Linear Glide: http://www.sugatsune.com/products/ProductDetails.c...

Step 2: Tools Needed

1. Handheld drill

2. Set of drill bits

3. Tap and die set (recommended but not necessary)

4. Band saw or jig saw

5. Scissors

6. Belt sander or Dremel tool

7. Tape measurer (preferably a tailors tape measurer)

8. Super 77 spray glue

Step 3: Fabrication of Parts for Assembly

Larger Assembly:

  1. Cut pieces of acrylic to size, both 1/16” and 1/8”. They should match the dimensions of the turn table, 3”x3. Make corners of acrylic pieces rounded using a belt sander or Dremel tool.
  2. Cut the “feet” out of aluminum, 3”x1”. If you do not have access to aluminum, acrylic can also be used. Make sure to use thicker acrylic (+1/8”) in order for it to hold a screw to be used later. Make the corners rounded using a belt sander or Dremel tool.
  3. Cut out pieces of the rug gripper material to match the size of the “feet”, 3”x1”.
  4. Drill a hole into the center of the “feet” so they can be secured to the linear glide. In our case, we used a #8 tapered machined screw that had to be grinded down to fit our exact needs. The hole was also tapped to fit this specific screw.
  5. Using the hand drill, make a small hole on either end of the linear glide in the center. The holes size should correspond with whatever you are using as a stopper. In our case, we used a #8 bolt after the whole was tapped.
  6. Take the 1/8” piece of acrylic and turn table and line them up. Mark the acrylic with a sharpie where the 4 outer holes on the turn table are. Drill these holes on the acrylic using a drill bit that corresponds with whatever type of screw you are using. Repeat the above step with the 1/16” piece of acrylic.
  7. Using the same 1/8” piece of acrylic, line up the glide in the center and mark where the two holes should be. In our example, we countersunk the acrylic so it would fit a #8 tapered screw as to not interfere with the turntable above it.

Smaller Assembly:

  1. Cut 1/8” piece of acrylic to size, it should match the dimensions of the turn table, 3”x3. Make corners of acrylic pieces rounded using a belt sander or Dremel tool.
  2. Cut 1/16” piece of acrylic to size, 3”x2. Make corners of acrylic pieces rounded using a belt sander or Dremel tool.
  3. Cut out a piece of the rug gripper material to match the size of the turntable, 3”x3”.
  4. Drill a small hole on either end of the linear glide. The holes size should correspond with whatever you are using as a stopper. In our case, we used a #8 bolt after the whole was tapped.
  5. Take the 1/8” piece of acrylic and turn table and line them up. Mark the acrylic with a sharpie where the 4 outer holes on the turn table are. Drill these holes on the acrylic using a drill bit that corresponds with whatever type of screw you are using.
  6. Using the same 1/8” piece of acrylic, line up the linear glide in the center and mark where the two holes should be.
  7. Take the 1/16” piece of acrylic and line up the glide of the linear glide in the center of the acrylic and mark where the two holes should be. Drill through the acrylic using the appropriate drill bit.

Step 4: Creating the Arm Troughs

NOTE:We decided to use different width and length of arm troughs in order to accommodate a wider range of people. If you are creating this to be used by one specific person, then you can tailor it to fit them, using these steps as a guide

  1. Cut each diameter of acrylic tube you are using down to 9” in length using a band saw or Dremel tool. We used 3.5”, 2.5”, and 2” diameter acrylic tubing.
  2. Cut the tubes directly in half so you have 2 semicircle pieces. Do this for each diameter.
  3. Measure 6” and/or 3” on the tube and cut so you have both a 3” and 6” piece. Do this for each diameter.
  4. For each piece you have, in our case 6, cut the semicircle pieces down so the total height is 1.25”.
  5. Round off the corners of each piece using a belt sander or Dremel tool.
  6. Using a belt sander or Dremel tool, grind down the center of the trough on the outside of each acrylic piece to create a flat surface for a strip of 3M Dual Lock to adhere to.
  7. Cut strips of 3M Dual Lock for each acrylic tube. Some strips of Dual Lock may have to be cut in half width wise in order to accommodate the smaller acrylic troughs.
  8. Apply the 3M Dual Lock to the bottom of each acrylic trough.
  9. Measure the inner circumference of each trough, the length should either be 3” or 6” and cut out pieces of spacer fabric and vinyl that correspond with the measurements you just took.
  10. Glue together the pieces of spacer fabric and vinyl, let dry for a few minutes.
  11. Glue the spacer fabric/vinyl combo to the acrylic trough, apply pressure, and let dry for a few minutes

Step 5: Assemble Your Parts

Assembly for Larger Model:

  1. Attach feet to linear glide. Make sure the screws do not interfere with the glide
  2. Glue pieces of rug gripper material to the bottom of the feet using the Super77
  3. Add a stopper screw to one end of the linear glide
  4. Attach the glide to the 1/8” piece of acrylic. Make sure the screws used do not interfere with the linear glide
  5. Attach the 1/8” piece of acrylic to the turntable using the pre-drilled holes and appropriate screws
  6. Attach the 1/16” piece of acrylic to the other side of the turntable, again using the pre-drilled holes and appropriate screws
  7. Take the 3”x1” piece of 3M Dual Lock and apply it to the middle of the 1/16” piece of acrylic
  8. Insert the glide into the track and attach the second stopper screw

Assembly for Smaller Model:

  1. Glue the piece of rug gripper material to one side of the turntable
  2. Add stopper screw to one end of the linear glide
  3. Attach the turntable to the 1/8” piece of acrylic. Make sure the screws used do not interfere with turntable
  4. Attach the 1/16” piece of acrylic to the glide using the predrilled holes and appropriate screws
  5. Take the 3”x1” piece of 3M Dual Lock and cut it into 3 pieces so that it fits around the screws on the 1/16” piece of acrylic
  6. Insert the glide into the track and attach the second stopper screw