Best lift configuration for a double reverse n broken bar

My team wants to do some type of double reverse broken n bar because we can utilize the four-bar on top as sort of a chain bar. That saves motors if part of our lift was also our chain bar mechanism. Now, what should we have on the bottom? I was thinking a six-bar on the bottom and a four-bar on the type. Or should we go with a four-bar? What would you pick? I personally would go for the six-bar on the bottom because it’ll give us some more height and we have the space to build it. Thank you in advance.

I’m sorry what do you mean by broken n bar ?

Yes. A bit more clarification would be nice.

I’m sorry, maybe I should clarify on the idea of a broken n bar. A double reverse 4 bar is a lift made of two lifts if you think about it. A double reverse broken n bar is two lifts, but they are mechanically separate. The ‘n’ refers to the number of the lift (i.e. 4 bar, 6 bar, 8 bar, etc.). You can control the top lift separate of the bottom lift, and vice versa.

Ok, those lifts are called things like R6B-4B for Reverse 6 bar - 4 bar, and so on. Is your robot an internal stacker?


I would do a 4 bar if you are going to have a CB on top. You could consider a 6 bar, but for what I can make out of your situation, speed will make you go further on in the season than high stacks. I mean, look at 929U and ALBA’s (I know I mention them a lot, but credit where credit is due).

Okay, I see what you mean and it makes sense. Thank you for your input!

4 bar 4 bar gives you enough height for 14 cones, but I would really encourage you to choose another design. The issues are too numerous to explain here, but you will end up with a needlessly complicated robot. Two top teams in Cali and one in Texas have used this design for months and we are all switching because of the complication introduced by the linkage.

My team used to have a RD4B with a 4B on top for internal stacking, but we are scraping that design for a much simpler internal stacking CB. We feel that the speed and reliability of a CB outweighs the limit of a 5 or 6 cone stack, at least for these early season competitions.

All of these are terms made up by the VEX community. The only real mechanical engineering term we use for arms and lifts is 4-bar link (no, there isn’t a 6-bar link in the real engineering world*). I wouldn’t scold someone for using a term that is virtually unknown outside this forum.

Haha us VEX people are centuries ahead of engineers with our correct 6-bars!