Triangle Banding

Hey forum,

Can someone please explain how triangle tensioning works? I have read all of the applicable forum posts and none of them really explain it. I understand that the goal is uniform tensioning across the lift’s range of motion, but how does triangle tension achieve that?
Thanks

You may or may not have seen this but here is a post that I found useful.
https://vexforum.com/t/uniformly-tensioned-rubber-band-system-analysis-guide/28402/1
I’m not the best at math so i’ll try but correct me if i’m wrong.
When you have the lift down the angle of the rubber bands approaches 180, this means that the sin of 180 would approach 0. This could be explained as Tensionsin(theta) where theta is 180. So the force of tension times a small decimal gives you a smaller number. Now when the lift raises your angle decreases so you get more like tensionsin(theta) where theta is something around 100 or 90. When you do this your sin(theta) value raises but you’re tension decreases so the values of both heights should equal each other.

I hope this made sense and if i’m wrong please feel free to call me out on it.

Yep I’ve seen that particular post and I understand it for the most part, however the pictures there don’t show triangle tensioning as I’ve seen it this year, rather some other method that utilizes an extension behind the lift. I guess I’m not seeing what angle you’re referring to that is changing. All angles look constant to me in the triangle tension systems I’ve seen.

@917F I believe that it would act the same because the bottom piece acts as the extension.

Uh sorry that doesn’t really make sense to me lol. Maybe a diagram would help?
I really don’t want to just copy something without understanding why it works and how to build it most efficiently.

So something like this,

would be the same as something like this it would be like shifting the rubber bands outside the towers like the first example, don’t judge me on my paint skills,
Screen Shot 2017-12-16 at 10.59.26 PM.png

https://vexforum.com/t/browser-based-triangle-banding-visualizer/44609/1

Ok thanks, I actually found your visualizer before but it made no sense without the tutorial.

I think I’m starting to understand this. One more question though.
Is the distance between the lower bar band point and the secondary raised upper band point supposed to be increasing on the way up, until the halfway point, and then start to decrease again? Is that how triangle banding is supposed to help?
So basically, does that fluctuating distance counteract some of the tension on the way up to half, and then start to work together with the primary banding point to cause the rubber band stretch to decrease more rapidly?

-Ugh reading that over sounds very confusing but idk how to explain differently. Hopefully you understand what I mean.

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With all the hype for triangle banding amongst high level teams, does ANYONE actually know how to calculate the optimal positions on paper??

If you want the exact figure of the force, then it is pretty impossible - simply because rubber bands do not exactly follow hooke’s Law.

But what you can do is to do a simple resolving of forces (or tension) and see for yourself if the tension is balance, etc.