I’m in the middle of a LONG project. I wanted a motorized outdoor shade that is about 15’ long. It would cost about $3,000 to purchase one, and $1,000 for a non-motorized one. My first prototype was essentially a sail shade connected to ~17’ of 1/2" steel pipe. I installed a bracket on each end. The brackets each held two ball bearings mounted in a 3d printed case to support the pipe. I’m attaching the .f3d file for the model. On one side, the bracket included a collar for one end of the pipe to be inserted. On the other side, the bracket included a 12v motor. The motor was connected to the pipe using a 3d printed part and a flange coupling. I installed my first prototype, and it broke shortly after due to (as I suspected) sagging in the middle of the shade (see second figure in drawing). That is where I need your help. I’m trying to engineer a support bracket in the middle. But the bracket has to be able to support the shade when it is rolled up (and therefore a bigger diameter), as well as when the shade is rolled down and only the 1/2" pipe needs support. With a stationary bracket, it seems there would be a gap between the 1/2" pipe and the support when the shade is down, which would allow the pipe to sag (see bottom figures 3 and 4 in drawing demonstrating that problem).
The 1/2" x 17’ pipe sags causing drive problems, so the center needs support
Fixed center support rollers: The diameter of the pipe+shade reduces as the shade unrolls leaving a gap between the fixed support rollers and the bare pipe. This results in sag in the pipe which is what the support was intended to correct.
Can you use two shorter sections of shade driven from either end or is the gap between the two shades a problem?
Stagger two smaller shades one in front of the other with bearings in the middle?
Some sort of spring tension on the rollers that bias them upward as the shade unrolls?
A nonabrasive centered hook that pulls from above under tension
You nailed the problem. I’m trying to avoid the two-shade solution. I also considered the spring tension idea, but it seems like it would be very hard to dial in the spring. I’m not even sure where I would begin with that. The hook is a good idea, and would be easier than a bracket. But it suffers from the same problem as the spring: how do I dial in the proper tension so that it raises the appropriate length as the shade unrolls? Any idea, or should I result to trial and error.
I would love to know how the $3000 ones solve the problem!! (titanium or carbon fiber pipe, which may explain the price??)
Sometimes things you know work ends up being better in the long run
I also wonder about the spring tension problem. I was thinking that the spring keeps upward tension on the roll all the time as it unwinds. The spring would need to be strong enough to hold just the pipe at the end of the unwind. The hook material would need to allow the shade material to slide easily against the hook under tension. I would create a model and run some tests to see if the spring adjustment is that critical.
I was unsure where the rollers could get their mounting, above or alternately behind like your drawing.
I think having the weight of the bar applied vertically on its restraint would be the most reliable.
I wonder if this approach, whose force on the roll is at an angle will cause the rod to be pushed out and the rod will want to walk down and off the rollers.
The devil is in the detail… time to proto a few ideas
Not that I have any ideas, but is this just extending vertically like a window shade? Or is it a retractable canopy like you see on RVs? Seems like the core on the canopy on our RV is about 3" diameter, extruded aluminum most likely.
Oh BTW I have a shade outdoors in our Gazebo that I made from PVC with an internal piece of conduit.
You drop and stow it with cables and pulleys affixed to the frame … :).
I’ve seen hollow pipes with added internal X material to provide strength and limit sag. It’s like an “I” beam inside the pipe. Not sure how you would create one to fit inside your pipe… maybe a long piece of roof flashing trimmed and folded to form a triangle?
Interesting problem but I think you are correct in that there is some form of internal structure which handles the sagging forces.
