My favorite is probably the multistage linear/elevator lift because it keeps the intake at a constant angle, a predictable height, and can reach great heights. Problem is it’s very hard to build well.
Out of all the robotics competitions I’ve participated in, the most common system I’ve used was probably the arm. I’ve used it in round up, logomotion, get over it, bowled over, ring it up, and block party.
I’ve worked with arms, boom lifts, linkages (4, 6, 8, peaucellier, reverse double 4 bar, shifting, offset), conveyor belts, linear lift (multi stage, cascading, fold out, inversely powered, rack and pinion, winch), and scissor lifts(inversely powered, and 5 stage)
I like the six bar because it’s easy to build doesn’t require a lot of parts to build and can be mostly used in any game up to this point. Any bar lift (4 bar, 6 bar, or 8 bar) are kind of easy to build and are easy to teach to new robotics members.
The elevator linear lift we did last year was a true thing of beauty, although I may be bias. The biggest downside was that it was heavy and ridiculous to maintain. We spent many hours at worlds trying to correct just the slightest bit of friction that would make or break our performance. It’s definitely not ideal for this year’s game, where robots need to be as light and fast as possible.
Six bar lifts are probably the most common lift I’ve ever seen, and rightfully so: they’re easy to build, maintain, are cost-effective, and easy to conceptualize. They make a really good reliable and consent lift. They are hindered primarily by the fact that they can take up more space than other lifts, but aren’t tremendously bad. They also usually suffer from center of gravity changes, causing the robot to be more susceptible to falling over. Chain bars duplicate the functionality of six bars with the pro of being more lightweight and having a smaller footprint, although they have a tough time lifting themselves (because the chain slips).
Scissor lifts are the dream lifts in vex. They theoretically are the best lift, in my opinion as they offer excellent lowered:expanded height ratios. The problems VEX has is that these lifts require lots of power to move, friction can both save and ruin these lifts, and are oftentimes wobbly when extended. I toyed around with the idea of a pneumatic scissor lift, but it didn’t get very far because of the stated reasons. They’re kinda like linear lifts when it comes to their issues, as one might expect. Although linear lifts are much easier to pull off. But basically everybody wants to make them, but very few can effectively do so
See I liked my scissor lift for its center of gravity. But in the end the maintenance was more than we liked so we scrapped it. I’m loving it. We have a new 6 bar built and have like 4 extra aluminum c channels left over so for me I am loving the efficiency of the 2 motor 6 bar. It can even high hang. But we need to work on some kind of latch to hold it.
Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar Chain bar!
I’ve tried 4 bars, 6 bars, scissor lifts, and linear lifts, and none of these worked as well for me as a chain bar. Because my team could never afford aluminium until this year, we always tried to reduce lift weight by ridiculous amounts (which is hard to do with a 6-bar). Being only a single bar, the relative weight of a chain bar is very low, especially with aluminium. I haven’t had a problem with the chain slipping, especially with tension points in the right places. It’s a bit vulnerable to impact and stress, but it makes up for its instability with its capabilities. It can go completely vertical, which is something rare for 4 and 6 bars. This is my favorite feature. It’s also very reliable. Where a 6 bar can catch on its connection points, the chain bar does not.
I’m not saying that other lifts are bad options, it’s just that I prefer this one and have had the most success with it.
My all time favorite is probably the chain bar or 6 bar. Actually… chain bar hands down. Love it. I also love scissor lifts, no matter how complex they are. I have seen a successful pneumatic scissor lift, and it’s quite interesting.
For competition, definitely four bars and six bars: they just work so well. Other kinds of lifts can be cool, but rarely perform as well with the same amount of effort. My favorite lift for the coolness factor is probably the peaucellier linkage.
We finally got our scissor lift working with 100% reliability, but the trade off was speed due to not being able to get the gearing to the point that it is fast and dependable. Even being 100% aluminum we have gotten close to 20lbs.
6 bars require little to no “tweaking”. I wish we had gone with a 6 bar last year and started this year with one as well. Just look at the skills ratings and with the exception of 9090C you will see 6 bar robots dominating the top 30.
I personally feel that that over the last few VRC games (even before I started competing), arm linkages have become the most foolproof design as they can be applied effectively to every game in one variation or another. They are extremely versatile and can be modified/customized just enough to suit a new game (e.g. mounting it lower to meet the de facto height restriction this year) without having to start from scratch with an entirely new system. The only game I can think of in recent years in which a standard 4-bar or 6-bar wouldn’t be as effective would be Round Up (their lack of linear motion poses a problem for descoring tubes on the movable weighted bases), but a reverse double 4-bar definitely solves any issues that its simpler counterparts had in that game. Thus, the category of arm linkages in general are my favorite lift mechanism due to their versatility. If I had to choose a more specific favorite design, it would likely be the reverse double 4-bar, although I have seen teams struggle with making them run smoothly, so I would not advise newer teams looking for a good foolproof design to take this route. Rather, I would recommend a 4-bar or 6-bar, possibly even a chain bar, to newer teams.
I have always liked the chain multistage elevator because even though they are hard to build, when they work they are fast, compact, and all of the motors are located in one spot.
I also like this kind of lift that our club uses a lot
My team and I put a lot of time and effort into perfecting a scissor lift but as previous posters have mentioned the amount of time simply isn’t worth it and when you do get it to work the speed isn’t comparable to what you can get out of a 4/6 bar lift.
I think for Toss Up simplicity should be one’s goal; the game is all about speed and weight. I have seen some amazingly complex and interesting designs over the years and at the World Championship but my goal this year going into build season was simplicity and to analyse the necessity each and every screw, nut, or axel. With that said my team is working on a 6-Bar lift. Are only problem, well challenge really, is to devise a mechanism that will hold our arm after hanging.
I saw a team (i do not remember who this was) that had a loop of redundant chain in their lift mechanism. When they lifted themselves onto the hanging bar, a pneumatic piston went through the links of the chain loop, stopping the lift axles from rotating. Just an idea, I guess.
One lift that I loved (though a bit hard to pull off really well) was the linear chain lift that 1103 had in Round Up. If I remember correctly, it locked itself mechanically after the robot was high hanged on the ladder, though I don’t know how.