I’m pretty sure your problem can be explained by this
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Yep exactly what i said but with fancy pictures 
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what type of hinge system do you use? because if its a custom made one then the issue could fall under friction.
It looks like his/her robot is using custom hinges.
Try to lossen your screws on the hinges slightly, just make them loose enough where you can spin the screw and nylock with your fingers, this ensures that there isnt a lot of friction on the hinges
Most teams that I observe are wrapping the rubber bands around the back of the hinge where there isn’t much mechanical advantage. I am curious if anyone has considered using an offset fulcrum. My example shows overlapping c-channel but anything that would change the angle of the rubber band should require fewer bands and have more power to overcome the static load.
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So if you put rubber bands farther up the tray it will fold out
I will try out some of these solutions tonight and get back to you guys
We had this same issue with our tray. What is happening is that when the tray gets bent to about 180 degrees the robber band start to pull the tray closed. The best way to fix it is to have your rubber bands pulling from a point further back than the hinge point.
Looking at your picture you should more the cross bracing c-channel on the upper stage back a few holes, and add something to the cross brace of the lower one. We added a 5-hold c-channel sideways on to the cross bracing of the lower stage as something for the rubber bands around.
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I’m afraid I’m not understanding your solution. I did move the rubber bands away from the hinges and it still doesn’t open.
I tried copying the design from one of our other teams which has a successful three-stage fold out and it still didn’t work? The rubber bands are away from the tray slightly to provide more torque. See picture
Can you show us a picture while its folded down?
Let me explain clearer. Let’s say if you were to run an axel through the two hinge points, the rubber bands need to wrap around behind it.
Red= hinge point
Blue = current placement of c-channel that runs across the tray.
Green = the blue channel moved back a few holes
Gray = small piece of c-channel we added for the bands to wrap around.
Orange = points that the rubber bands attach to.
If the bands wrap around something further up than the hinge than it will fix the issue you are having.
So I tried this and it worked, however there was too much vertical separation between the angle iron of each stage that cubes cannot slide up it.
@Toadally, I actually found success with less bands. The principle is that when the joint is all the way compressed, the bands actually want it to stay in the closed position. Thus, less bands will allow the momentum of the first stage deploying to deploy the final stage.
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I’m not sure how that causes vertical separation? if you move the top channel moves up two holes, and then you put a small piece of c-channel attached to the bottom one, it leaves it in the same position as it was.
The angle iron wanted to stay almost a quarter-inch above the second-stage, so that couldn’t work. I tried it a different way and it wants to stay closed instead of open.
@bobmarlinjr Nothing happens with less bands. Can’t even get it to open in the first place
if its a quarter inch above, add some 1/4" spacers as stoppers.
Also, i think i see from the video that the third stage is somewhat stuck on the second stage even before deployment. let me know if you are not able to get the two pieces completely in line.
I am able to get both pieces in line.