Tension help

We have a double reverse 6 bar lift that works well however we are interested in where the best elastic tension points are. Currently we go on diagonals in each ‘section’ of the lift but we have seen another team that have their tension nearly perpendicular to each bar. It isn’t a problem we just have an interest to see whether it is better diagonally or perpendicular. Thanks

Testing many variations of an elastic assist is probably where you will find out what the best for your robot is. From my experience they are an increadibly fiddly thing to get right, So that you have the maximum assist, your lift is able to go down and the robot are in size.
Pictures of what you want help with/want to discuss would also be good for people.
What “bar” are you referring too on the lift, the lifting bars or the vertical ones? As both don’t seem like the best location for an elastic assist.
Also opening two identical threads won’t get answers quicker… :slight_smile:

Here’s an improvised diagram:

±-------1–+
|| ||
±-------2–±--------4-+
|`````````||`````````|


I assume that by "nearly perpendicular" you mean something like a rubber band going from 1 to 2, and your setup connects in a similar fashion as 3 to 4.

The 3-4 link is effective because the pull of the rubber bands will swing 3 towards 4, which will rotate the whole assembly around the central link and raise the lift. Having the rubber bands hooked up from 1 to 2 will do nothing at all; as the lift raises, the distance from 1 to 2 will not change at all, and thus the rubber bands have no effect. Your goal is to have the rubber bands rotate the hinges of the six-bar, and so you want the pulling motion to be as *parallel* to the main bar as possible, while still retaining a large range of motion so as to have a mechanical advantage. Ideally, you would want to put a force on 4 going directly to the left and a force on 3 going directly to the right, so as to have a maximum mechanical advantage and efficiency, but since that isn't possible (until VEX allows rockets or turbines of some kind) the more angled 3-4 connection is best.