Kevin Warnock

I am continuing to work on my RTS bus conversion on weekends and in the evenings.

My current project is designing a sliding window shade that insulates the window when closed. Sadly, the RTS has single pane windows, and double pane windows are not available. For most conversions, one can buy factory new double pane replacement windows from Motion Windows. You send them a tracing of the original windows and they ship you a wooden crate with double pane windows that fit perfectly. That is possible because most buses used for conversions have flat glass in the side windows.

Airplane window. Photo by Hajime NAKANO.

But my RTS was designed by General Motors, and they wanted a curvy modern shape to the vehicle like a car would have. The glass panes are curved, and Motion Windows can’t make a double pane curved pane window.

As a result, I will make sliding window shades that fit in a track lined with wool felt. Passenger airline windows are the closest example of what I envision. When you raise the shade, the shade disappears up into the inside of the ceiling, so that most of the shade is parallel to the roof when raised.

I built a prototype some time back, and the idea worked, but the sliding of the shade was stiff, and it sometimes got stuck and needed to be lowered and raised again in one smooth action. The cause of this was the complete lack of suitable bearings on the shade, which was a piece of unmounted countertop Formica plastic laminate.

My new version uses Delrin ball roller bearings on the sides of a 1/32″ thick sheet of 5052 aluminum, which is bendable such that it can conform to the curve where the wall meets the ceiling.

I envision that the bearings will roll against 3/8″ square aluminum bar on the left and right of the shade, perpendicular to the floor. What’s been troubling me for a long while is how will I form the gentle yet variable radius bend into the aluminum so that I can install it. Today on YouTube I discovered the machine I need. I don’t know if TechShop has one of these, but if they don’t I suspect some machine shop in San Francisco has one and that I could have them bend the 20 pieces I’ll need to complete the shades. It would seem these could all be bent in an hour or three by someone who knows how to use the machine.

It may also be quite practical for me to simply build a wooden bending form that incorporates the varying curves I need, and just bend them with my own arms, as 3/8″ is not that thick. I suspect this is the way I’ll go. However, the machine I found is so impressive I wanted to write a post about it and show you the video.

I will insulate the aluminum shade with Reflectix brand reflective ‘bubble wrap’ style insulation. This insulation looks like bubble wrap sandwiched between two layers of aluminum foil. It’s very flexible, and the foil part is a plastic foil, not real aluminum foil, so it can be bent many times without cracking. Reflectix is also thin, so it will be able to glide up into the ceiling cavity without binding. This tight fitting shade with its Reflectix backing will probably insulate as well as the costly Motion Windows, and I get a built in window shade that should look high tech and sleek. My prototype certainly looked sleek, and I believe the improved aluminum version will be quite handsome. I’ll keep you posted on my progress.