Chain Bar Rubber Bands

Currently, our team is building a chain bar that is going to rotate about 210 degrees. How are we supposed to attach rubber bands so that the bar remains stationary wherever it is?

While it is quite challenging to balance the chain bar the way you’re describing, it’s not difficult to add rubber bands to the chain bar to resist gravity. When building the chain bar, you want to leave a few holes below the axis of rotation. The rubber bands will be attached to those holes, pulling down. The advantage of this system is no matter which side the chain bar is on, the rubber bands pull the chain bar up, reducing the amount of force necessary to move it. (I’ve attached a picture to help clarify the way everything is laid out.)

Good luck!
Chain Bar Bands.jpg

Its actually a very interesting problem; you always want rubber bands to pull up toward the vertical position. There are a ton of ways to do this, but it has to pull to a center point not an end. I personally would do something like the attached.

Whoops, I just noticed @Anomaly 's response. It’s essentially the same except the roller on mine helps to normalize force at different positions. Then again, you might want lower force at the bottom so it can stay down without motors. I guess it depends on the exact situation.
rubberbands for forum.docx (788 KB)

Thanks guys! We’ll be sure to try it and tell you how it goes :slight_smile: