Double Reverse Four Bar


#1

I know it’s late, but my team is curious if anyone has experience with a double reverse four bar. We think that it can reach the scale quickly and is relatively simple.

Here’s a link to a VEX double reverse four bar: https://www.youtube.com/watch?v=CSvqpYRSb0k

What does Chief Delphi think?


33's parallel bar mechanism
#2

That was one of my first ideas. But we’re doing something else…just a normal 4 bar, with a wrist to get the rest of the motion needed.


#3

Chill Out! 1778 is doing a double reverse four bar!
We had an FTC prototype very similar to the video posted, and are in the process of building it now. Good CG profile.
Rob


#4

Our team had initially came up with that idea as one of our prototype ideas.
As a program that does VEX, it was very doable for us.
We didnt end up choosing that design because other challenges of the game created integration issues for other portions of the game.
Good luck, hope it works out for you folks.


#5

It’s a good idea- in theory.

We had something similar to that prototyped up in 2016 to fit inside our form factor, but eventually ended up scrapping it because it was too unreliable (liked to bind up) and ultimately too heavy.

This year we’re just going for a two-stage forklift made out of 80/20 extrusion. Mechanically simple and robust, just the way we like it.


#6

I wanted to do an arm rather than a cascade forklift because you can backload a lot of your weight, but my team decided they liked the forklift more (and it looks like it’s going to work great as long as we don’t try to drive around fully extended.)


#7

I’m pretty sure Lancer Robotics in Hawaii is doing a reverse double 4 bar. You might want to get in contact with them and see what they are experiencing.https://uploads.tapatalk-cdn.com/20180209/651fa7906224c5bfad14cca25ea1add4.jpg

Sent from my Moto Z (2) using Tapatalk


#8

Glad to see they at least have clamps locking the arms before getting under them like that.


#9

we’re considering something like this for this year. can anybody comment on using this as opposed to a traditional elevator? we haven’t had much experience with either.


#10

From 148 build blog last year

You also have lots of examples from last years game to reference.


#11

our team did one last year and it was quick and fast, but you should make it like 33 or 59 not us
it would jam and it was impossible to balance the weight. we looked at that exact video but without making the bars go up at the same time things will get stuck.


#12

This is a pretty general question. What specifically do you want others to comment on regarding DR4B’s?


#13

I was hoping somebody could give me some pointers about design. some challenges they experienced with either an elevator or dr4b. just overall “recommend/don’t recommend” for either one. I don’t have specifics in mind. a friend told me about “auto back-driving” to compensate for pushing. how difficult is that to implement and what does that mean exactly?


#14

Does anyone know of FRC robots that did a double reverse four bar? I know 33 did last year to great success, but I honestly can’t think of any others. Lots of VEX and FTC robots on youtube, but I am having trouble finding documentation on FRC sized robots.


#15

Team 59 was very good with it last year: https://www.thebluealliance.com/team/59/2018


#16

5407 was pretty good at FMA Champs.


#17

1778 had a double reverse four bar.


#18

935 used a double reverse 4 bar.


#19

Yeah there were a few of those, if my memory serves me, I think team 33, the Killer Bees did a pretty baller one, and team 935 Raile Robotics definitely did one, their pit was next to ours at a regional last year, their robot was pretty good, but it didn’t quite have the speed of the better lift bots. They were still a pretty big contender at the regional tho. They tipped over in their first match because the design is kind of top-heavy, but that was the only time and it didn’t end up being an issue


#20

Our team, 3495, did a double reverse four bar last year. Worked out pretty good of your design team makes absolute sure the lift is stable.