Stacker Flipping

What’s the bets way to have the stacker flip out by itself? Right now we have our spinners rested on top of our two stage stacker, but when we lift the lift, the stacker doesn’t flip even though there are rubber bands connecting the back of both of the stages

more rubber bands. make sure they pull in the right direction.


Are they in an “X” shape? I believe that is the best way.


To add on that, I’ve had to deal with this before, and it’s all about the way you bands are positioned. You need enough of them so that its possible to flip out by itself, but they also tend to break alot; like Xenon said, they have to be pulling in the right direction. The China teams in their videos seem to cross their bands over the gaps, forming a big X. Try that, it seems to work well and allows the bands to not snap.


Why would you X band? It uses force in directions that are not needed.


I’m not exactly sure the physics of it, but it seems to be working best since a lot of good teams are doing it, and from personal experience, for some reason it helps the bands not snap as much, while still maintaining the elasticity it takes to flip out the tray. (In contrast to doing straight-up-and-down band mounting).

Can someone link a picture? Would be really helpful

By triangulating the rubber bands, you are stretching the rubber bands more and theoretically putting more strain causing more breakage

So X or no X might not be the problem. One team at our school uses BIG stand offs that stick like 3 inches out from the first tray, and their tray flips out nicely. Have you tried maybe making the bands stick out from the first stage?

Yes that is another thing to consider; leverage will help very much. have something that sticks out a little bit on the edge of the (stage of the) tray, and mount your bands on the end of that.

We aren’t triangulating them, just making them cross over each other, like this

| | -----> X

Best I could do on a keyboard lol :laughing:

1 Like

In terms of one singular rubber band, a diagonal is longer than a straight up and down rubber band

Can someone send a picture/illustration of the best way to do it?

X banding is not the best way to do it. The best way to do it is to loop a rubber band around itself around the tow connecting points, this essentially doubles the elastic force per rubber band. It’s not the same as just adding rubber bands because of the physics of a rubber band. The more you stretch it out, the greater the elastic force is. I hope that helps. Make sure the points are in a straight line across from each other as well.


One idea is this
20 Characters

If your bands are smack against the tray, there is no tension difference between folded and flipped-out. That why the bands need to stick out from the tray.

Can someone post an illustration of the best way to do it? Still confused, lol

I band like this:
I prefer using more rubber bands under less force, because then they won’t break as often.

I also don’t recommend x banding, because like @CNguyen425 said it pulls in unnecessary and potentially negative directions.

1 Like

Something that I’ve noticed about this version of tray banding is that once the tray bends past 100 degrees or so, the rubber bands kind of stop pulling it open. Would anyone be able to explain the physics behind this? And has anyone found a way to make the tray constantly want to unfold?

Typically, Banding will not pull your tray if the angle of two trays is inward causing the banding to no longer be pulling the tray out (as shown in diagram 1). Banding will pull your tray if the angle of your two trays are parallel or the angle of your 2 trays is outwards, which causes the bands to pull around the hinge and therefor deploy your tray (as shown in diagram 2). This can change with leverage and routing of rubber bands along your tray
20 PM - Edited