1. 1 10 ft section of 1 inch PVC pipe
2. 4 45 degree angles for PVC
3. 1 piece of 3/4 inch plywood sized for your laptop
4. 1 piece 3/4 x 1 inch wood as long as your plywood is wide
5. PVC glue
6. 6 1 inch drywall screws
Drill bits and screw bits
Pencil and permanent marker
Step 1: Design Your Desk to Fit Your Bike
On my bike there is a bar that wraps around the back of the seat to form handles that you can hold on to while you exercise. The handles are a little less than 1 inch in diameter and the end sections are about 5 inches long (see photos). This design made it easy for me to attach the desk to my bike by simply slipping 1 inch PVC over the existing handles.
If your bike does not have a handy attachment point you could design your desk to be free-standing or such that it attaches to the bike in some other fashion (maybe with screws or clamps?).
Step 2: Acquire the Materials
In addition to the PVC supports, you will need a piece of wood to make the desk surface. I used some 3/4 inch plywood that I already had. You will also need a piece about 3/4 inch thick and 1 inch wide to attach across the bottom of the desk (like a wrist rest) to support the laptop on the desk. It will need to be as long as your desk is wide.
Step 3: Cut and Dry-fit the Support Pieces
Using the 45 degree angles as a guide, measure the length needed to provide adequate clearance for your legs and knees on the bike. When measuring you may want to consider others who may also want to use your desk and bike and design your desk appropriately.
Cut the risers to the length indicated by your previous measurement and dry-fit them into the 45 degree angles attached to the handles. Dry-fit the second pair of 45's on the top ends of the risers.
Cut two more support pieces to attach to your wooden desk surface. They should be about the same length as the desk. Dry fit the desk supports into the 45's at the top of the risers. At this point you should be starting to get an idea of where the desk surface will be. As you measure, be sure to allow for the length added by the 45 degree angles. It is a good idea to sit on the bike and hold the complete dry-fitted supports in place to determine that everything is coming together correctly. Do not put any weight on the dry-fitted pieces at this point. The PVC joints will not be stable and will not support and significant weight.
Step 4: Glue Up the Supports and Attach the Desk
Once you have the dry-fitted pieces configured the way you want, mark the fit of the straight pieces to the 45's so that you can put it back the same way when you glue it together. I used a permanent marker and made a couple of marks on each piece. I varied the distances between the marks so that I knew which pieces fit together and was able to recreate the necessary angles to support the desk in the correct position.
Glue the PVC pieces together using your marks as guides. PVC glue has a very strong smell and is a sticky, drippy, mess, so cover your work area and have some rags handy.
While the PVC glue cures, cut, sand, and screw the wrist rest to your desk piece. I used 1 3/8 inch drywall screws to attach mine. As an afterthought I wish that I had screwed from the bottom of the desk into the wrist rest so that the screws would not show on the top. Using some wood glue in this step is probably a good idea.
After the PVC glue is cured, attach the desk supports to the desk top. I used 1 inch drywall screws for this job. To do this, first decide where you are going to put your screws. Drill holes in the bottom surface of the PVC only large enough to allow the screw to be inserted. Drywall screws will cut themselves through the other wall of the PVC and into the wood. Be careful not to over-tighten the screws or they will strip. Once the desk top is attached to the supports, you are done.
Step 5: You're Finished! (but You Can Customize It If You Want)
To make the PVC look less like plumbing you could buff it down with some fine sandpaper and paint it. If you want to do a bit more work and like a more industrial look, you could drill holes in the PVC to make it look like an exhaust pipe or machine gun barrel heat shroud. 3/4 inch holes in an offset pattern should do it.
If you just want to make it look a bit more like furniture, you could paint the PVC black and stain the wood. Adding some trim around the edges of the desktop would really dress it up.
If you want to go farther still and style it in some particular fashion you could use a router or scroll saw to cut a design out of the desktop. Designs that might look nice could include the Federation or Klingon logo from Star Trek if you are a fan. The possibilities are almost limitless in this area.
Any of the modifications mentioned here should not affect the strength of the structure and will make it lighter, so they would be functional as well as aesthetic improvements. Cutting designs from the desktop will also improve ventilation to help keep your laptop cool while you are working.
I hope that this instructable helps you to build your own laptop desk for your exercise bike.