Our team has built.four bars in the past for “mechanical advantage”, but I was wondering if it is worth it for stability and structure, since our four bar often gets twisted from pushing agaonst stars.
It is typically easier to add elastics to a four bar setup for an assist.
In what way? We have a four bar and one of our biggest problems is finding a way to install elastics.
Definitely much easier to attach rubber bands on a four bar. You can attach them from near one pivot point to the opposing diagonal point rather than stretching elastics over and around the towers.
Besides elastics, is there anything else, good or bad, about four bars?
With a 4 bar, you won’t be able to self right if you tip over backwards, right? It’s fairly easy with a 2 bar dumper.
Our design can go far beyond vertical. I am most concerned about mechanical advantage and structure.
All you need to go backwards with a 4 bar is a non parallel structure. The easiest way to achieve this is extending the connecting bar between the top bar and the bottom bar.
As long as the two rotating bars are horizantally offset so that they do not hit each other, then you can go beyond vertical without offestting one bar. But I still would like to know if there if any mechanical advantage to having a four bar instead of a two bar.
Yes, but not in the traditional sense. A four bar allows for fuller utilization of the 18 inches. Aside from that, no, there are none.
Actually, there is a HUGE difference in what a four bar plays vs a two bar. A four bar will always keep the claw the same direction no matter what height, as a two bar goes from the claw in the front to the claw going backwards when it goes up. So what’s said, a four bar will be rather more useful for getting objects and dumping in the near zone, while a two bar can rather be more useful for getting objects and dumping in the far zone. For competitions, if you were to have a two-bar, pick a four-bar. If you have a four-bar, pick a two-bar. EDIT//: What this will do is that you can compliment each other greatly. Hopefully this helps 
We are using a four-bar and we are still able to get stars to the far zone. We collect stars at the the back of our side, and drive top speed towards the fence while raising the four-bar. We collide with the fence at the exact second when the arm is at its peak so the cube and stars can both fly into the far zone. Even if our timing is a bit off, the spin is still always in our favor because of how we release the cube/star. As for elastics, we have standoffs a bit off to the side on which we have a bunch of rubber bands to relieve tension on the arm. We have a standoff on the underside of the back of our robot too as an anti-tip mechanism. We also use the fence as support when we throw the stars back.
I wasn’t talking about dumping the stars, I was talking about intaking 
. When intaking with a 4 bar, you’d have to waste time turning to be able to intake the stars then dumping, and with a 2 bar, there’s no need for turning. With a 4 bar, it’s much better to intake objects in the opponents near zone (AKA the zone your robot’s standing on) then dump it because there’s no need for turning, because the robot is at the same orientation.
Oh. Yes. That is true.
I think you’re mixing up 4 bars with 6 bars…
Our current four bar lift is a reverse dumper. Just attach the claw to the top bar instead of the vertical bar.
Sorry, my mistake. On the 4 bar we built, we attached the claw to the top bar. So it wasn’t really a 4 bar, was more of a 2 bar supported by a 4 bar linkage.
4 bar is definitely more stable and less wobble-ly. It makes programming especially for skills a whole lot easier.
With a 4 bar depending on the geometry, it is very difficult to score in the far zone making the skills score limited