2 bar vs 4 bar

I haven’t seen a thread specifically on this (nothing showed up when I searched for a few related terms):
What advantages or disadvantages does a four bar linkage have over a two bar, and vice versa?

Context: My team is rebuilding our lift after our axle candy-caned and messed everything up.
Thanks in advance!

  • Vince of 7589B Kiwi

@Kiwi (7589B) 4 bar backwards dumper or 4 bar forwards dumper?

we are doing a back dumper

Generally 4 bar lifts are easier to attach elastics to, while 2 bar lifts are lighter with slightly less friction.

Ok so I will start with a 4 bar. One of the two types of 4 bars is a reverse 4 bar meant to invert at the top of the swing of the arm to actually allow you to flick the claw and making sure you score in the 2 point zone. There is also the other 4 bar type which is just used to add rubber bands on the lift rather than over the pivot point. This is essentialy a 2 bar. A 2 bar is far and away the simpliest but figuring out a way to mount rubber bands onto it is the only limiting factor given you go for tourqe ratio faster than 1:5 (5 rotations of the motor to one rotation of the lift) or have a really heavy arm. As I said on a 2 bar the rubber bands are typicaly mounted over the pivot point meaning the higher above the pivot point the more tourqe the rubber bands will give. This could also be solved with the use of tons of rubber bands. For this reason many teams go with that extra linkage to allow for easy lift assist but it does limit your lift to about 100 or 120 degrees of movement rather than the full 200 degrees some bots can get allowing for them to flip them self back over.
Hope this helps.
This picture is the setup of the 3 types I mentioned