[Mike4703]

I have two solar panel arrays that are on a square frame that is hinged on the bottom front side and held up at the appropriate angle by two adjustable supports from the top corners to the base. Very simple, like a door laid on its side hinge on the bottom. I want to convert to a mechanism to remotely raise and lower the panels. We occasionally have high wind and like to have the panels down flat when this happens. I'd like to use a simple linear actuator but when I try to design this I run into a mechanical leverage problem. At the beginning of the lift from horizontal the angle of the lift causes the forces to mostly be in the horizontal direction which tends to rip things apart. The problem is that the base frame is only 10 inches off the roof so there no room to mount the actuator vertically so it would push up and down. The actuator needs a stroke of about 24 inches so it is a long one. How do you push upward with no room underneath for the retracted actuator. I've tried to think of all sorts of bell cranks, pullies, folded levers, etc and they all suffer from the problem of starting the motion with a unacceptable mechanical disadvantage which would break the framework.

[txcncman]

Why can't you use a scissor lift type mechanism built into its own steel frame?

[lukewarm]

The frame looks pretty rigid, what about moving the actuator connection point closer to the pivot point to cut down on the stroke you need. Use a 8 inch stroke linear actuator?

[lukewarm]

You could also mount the bottom of the actuator to pad of the leg closest to the pivot point and add a slight drop bracket on the panel to give better leverage. I'd sketch up what I mean but I'm away from the shop right now.

[Geof]

Do what I have seen on heavy dump trucks with the same problem; use two pairs of actuators.

One pair are very short stroke pushing straight up about one third of the way from the pivot point. These are not attached to the panel, only the frame and only raise the panel to a few degrees of tilt. By that point the mechanical disadvantage of the longer actuators is reduced so they take over and push the panel the full way.

[tjbaudio]

Do what I have seen on heavy dump trucks with the same problem; use two pairs of actuators.

One pair are very short stroke pushing straight up about one third of the way from the pivot point. These are not attached to the panel, only the frame and only raise the panel to a few degrees of tilt. By that point the mechanical disadvantage of the longer actuators is reduced so they take over and push the panel the full way.

This was one of my first thoughts.

The other was to use longer actuators and let part of them stick above the panel. When flat they would be 90 deg to the surface and have 100% lift available. You could play a little with the exact geometry.

I would also consider just moving the actuators closer to the center of the sides. Go from [\] to [|]

[Spencer Clayton]

Why can't you use a scissor lift type mechanism built into its own steel frame?

I like this idea, especially if it is just one set of scissor linkages on the edge to be raised with the base of the linkage mounted to a hinge running sideways.

Lateral thinking always amazes!

[vegipete]

How about a screw drive? Mount a hinged nut top center of the panel. Attach a 2 + whatever foot threaded rod to a motor. Hinge mount the motor to the roof frame under the nut. When the frame is lowered, the threaded rod will still be sticking up in the air. A long plastic nut would be preferred.

[TomB]

I'd mount the panel frame to a pivot rod and have a 6" long bar sticking down and out front when the panel was down. With a small electric motor connected to the back support and piece of allthread extending to a swiveling nut on the extension bar I would be done. Run the motor ccw and the allthread would pull the nut and end of the extension closer thus raising the panel. Reverse the motor an the panel would lay back down.

Somebody else can check my back of the envelop arithmetic but it seems to that the panel would need about 160 ft.lbs torque to raise. It seems to go about 40 degrees so a 6" long extension would swing +/- 20 degrees from vertical. That would mean the pull on the end would require about 341lbs. Using an acme .75" dia by 10 threads per inch rod would therefore require 22.5 ft lbs of torque. That is in the range of small electric motors and trivial to a small gear motor. A standard piece of 1/2" diameter allthread would work just as well as the acme rod but I couldn't remember the normal threads per inch and it would change the motor torque requirement.

Tom

[Mike4703]

I could use the threaded rod mechanism if I can find one made of stainless steel and I can make it lay down flat if needed. This is on top of a fifth wheel trailer and there can not be anything sticking up if it needs to move. I could make it so the panel attachment point can be uncoupled from the nut on the rod, and make the motor end so it can pivot. For wind protection purposes I suppose it doesn't matter if there is a rod still sticking up as it doesn't have any wind resistance.
I'll search for SS threaded rod. Stay tuned.

[Mike4703]

Plenty of SS threaded rod on ebay. The 1/2 in is 13tpi. As I thought this thru though I realized there is another reason not to have anything sticking up above the surface of the solar panels. These are high voltage panels and even a small shadow on one cell can cause the whole panel to fail. The shaded cell turns into a resistor in series with the rest of the cells and starts to heat up and can be ruined in a short time. Then the whole panel is trash. This could happen even if the panels are flat. I would have to remember to shut off the circuit breakers before lowering them or any time the rod would cast a shadow. So still looking for a way to push up from below.

[txcncman]

Don't park near trees or power lines that can cast shadows either. And hope a bird does not land on it or poop on it. Or wind blown leaves either.

[vegipete]

Plenty of SS threaded rod on ebay. The 1/2 in is 13tpi. As I thought this thru though I realized there is another reason not to have anything sticking up above the surface of the solar panels. These are high voltage panels and even a small shadow on one cell can cause the whole panel to fail.

The threaded rod can't cast a shadow on the panel it lifts because it is mounted on the wrong side. Ie, in the northern hemisphere, the rod would be due north of the center of the panel. (Assuming the hinge at the base of the panel is aligned east-west.)

[TomB]

I'd mount the panel frame to a pivot rod and have a 6" long bar sticking down and out front when the panel was down. With a small electric motor connected to the back support and piece of allthread extending to a swiveling nut on the extension bar I would be done. .....

Tom

I'm obviously not explaining myself clearly. (I wish I knew how to add a sketch to this note.) I was not suggesting anything that stood up like the current support post. I was imagining hooking the motor to the frame about where the current post connects but then laying the motor and allthread over so it was about parallel to the roof of the trailer and under the panel where it would remain. At the end where the panel pivots I would put two L shaped brackets, pivoted at the corner of the L. The long legs would hold each side of the panel and the short legs would stick down toward the trailer roof. Put a bar between the ends of the two short legs of the L and use the allthread to pull or release that bar.

I said the short leg of the L should point 20 degrees forward because the panel wants to point upward at about a 45 degree angle. If the L was made with a 130 degree rather than a 90 degree angle that would be the case. The downward facing leg of the L would swing from about 20 degrees behind vertical to about 25 degrees forward of vertical as the panel was rotated up 45 degrees. As the allthread pulled the panel up the end connected to the cross bar would follow a circular path so it would rock down from horizontal by about 5 degrees but it would never stick up.

Tom

[underthetire]

How about air bags?

[coolhand03]

i think i have an idea that hasnt been mentioned. in the picture in your first post it shows the solar panel with the single support rod holding it up. why not make another support rod with a hinge in the center? you could mount the linear actuator right near the hinge to pull it up and set it back down. mount the hinged support rod so it does not completly "close", when the panel is laid flat. that is, leave the hinge X degrees apart so the linear actuator doesnt bind up. i believe this design would reduce the amount of force needed to raise it as well, but i leave the load calculations to the experts.

[Mike4703]

Coolhand-Yes that is exactly what I initially designed and it has the initial lift problem. If the space between the folded flat panel and the roof were greater then the hinged arm (half of a scissors jack) could be left more open and everything would be easy
TomB-I wish I could picture your design a little better. It sounds like you are building an actuator which actually is a screw inside and usually mounted with rod ends to handle the angle changes as it moves instead of the hinged L brackets you suggest. But I'm still not sure I have your proposal right. After clicking post reply look down and there should be a more options window with an attachments option available. If not you may have to choose go advanced. If you step thru the attachments option a window opens and shows the upload menu and displays a list of acceptable file types. Make a drawing and upload it even if its just a paint document.

What I am going to have to do is make a lift with no play, no friction, and a lot of rigidity and enough strength to handle the initial lift. Which means careful design, machining, and more expense. I appreciate the suggestions but I don't think there is any way around this. I am leaning towards attaching the lift about 2/3 of the way out from the hinge which enough room for the actuator stroke without things sticking out and decreases the moment force (lift around the hinge axis) some. I'll have to find the right actuator(more money) or build it out of screw rod(more work). If I get something built anytime soon I'll post a picture of it here. Stay tuned and thanks.