Maybe once winter settles in I'll have time for more detailed instructions. Since the frame is glued together, I cannot disassemble to provide the exact tube lengths used. Meanwhile, given the photos of my prototype you have a good template representation to work from.
Start by extracting the foam sheets from the exterior side panels and use the large grey sheets as templates for the outer shape of the PVC frame.
- The entire stock of 1/2" white Schedule 40 PVC pipe and non-threaded T-connectors needed for this project is really cheap. Visit Home Depot, Lowes, etc. in their irrigation section You'll need 5 or 6 10' lengths of tubing, plus 32 Ts (buy in bags of 10 at HT).
- The curved grey 1/2" PVC from the electrical section in HT matched the bottom radius close enough so I used this instead of custom bending. The built in joint on one end is stronger too.
- The 1/2" metal U-brackets for securing the frame to the case bottom are available from the HT plumbing area. Use 5/8" #10 screws, nuts, etc to fasten.
- Also needed is a PVC primer & cement kit (<$10), a good respirator mask, hack saw or a PVC pipe cutter and a heat gun (HT or Lowes paint dept) to bend the PVC sections for the top radius.
On the topic of heating and bending the PVC for the top curves, it is best to do an entire radius and then cut it into sections later, than to try creating smaller sections. Using the grey foam as an outline, trace the curve onto a piece of plywood. This is the outer part of the pipe curve. Create an inner arc line by using a piece of PVC pipe or simply measure, then along this inner line add a row of long nails or screws. This is the inner bend radius. At the arc ends, add a couple nails/screws on the outer line which will act as pipe holders. Be sure to provide enough pipe length to allow the ends to run straight. Use a heat gun on 6-12" sections at a time and slowly wrap the pipe around the inner curve of nails/screws.
- Add however many S&S compression towers you wish to support the middle of the case. I used 2 of these, trimming the pipe to fit the inner case space. Initially I thought of building in PVC supports as part of my frame, but later opted for the movable S&S towers to accomodate gear placement flexibility.
Once this is all glued up, you'll be surprised how rigid the frame is and the entire case when loaded. With the PVC frame, the case maintains its shape regardless of what is piled on top (even I was guilty of tossing our main suitcases without much care onto the top of the tandem case in our rental cars)... not a problem. As a bonus, the case looks completely standard from the exterior and actually tracks better on its wheels.
Total cost of materials for these modifications is about $20 for the pipes, connectors, etc, $14 for the PVC glue kit, plus a few dollars more for however many S&S compression towers you use (btw, these are simply 1/2" PVC pipe with a couple end caps - not sure where to source those from to make my own).
Last edited by twocicle; 10-03-12 at 09:02 AM.