What do you guys think the best lift is for this game? We don’t need to go very high (the highest object , the pole and wall, are at 24", I would like to go 30" to get a little leeway).
I have always thought the best lifts are scissor lifts because when they are built correctly, they are fast and efficient. 4, 6, and 8 bar lifts are okay too. They go very high but when my club has tried them in the past, they have burned out some motors and aren’t too fast. It has been a little weird. I would at least prototype the scissor lift.
We’ve found the exact opposite. We tried to make a scissor lift for toss up and skyrise and had serious stability issues with it. The lift requires substantially more torque to lift, especially in the lowered position, than a 4 or 6 bar, and needs much more material to make.
In Skyrise, we had a clawbot on steroids that reached 30 inches high without stripping gears or twisting axels, so thats doable. This year is about moving fast, grabbing and getting it over. I would think any lift with the exception of an arm would make a bot too unstable and slow down scoring. Additionally, a forward reaching arm on a speed bot would win the race to the wall in autonomous. Our skybot also had a great design for a passive scoop (no claw)… design an effective passive scoop and you are speedy gonzales on the points board. Take three jax and you will find that they neatly stack on each other. An initial drawing in sketchup implies three 14" long stars could neatly stack and be liftable with a 10" fork. Getting them to align quickly appears to be doable as well.
I think what we’re going to do is make a rd4b with 4 motors that can lift fairly high (so that we can reach over other robots on the other side of the bar) and then have a 4 motor drive with 2 motors that transfer to the lift for hanging.
A Scissor lift sounds useful if you want to hang, a as I could see 4/6/8 bars having trouble attaching to the pole because they also extend horizontally. Inversely, if you want to reach the jacks on top of the fence very quickly and easily, 4/6/8 bars would be better fit for that task than a scissor lift because of the horizontal extension of the 4/6/8 bars.
Double reverse 4/6 bars seem a bit overboard to me, as we only need lifts that go 24 inches high (the height of the fence), but I could see them being useful in the same ways that a scissor lift would in this game
I’m mainly thinking of an rd4b because if built right it can be faster than a scissor lift as well as lighter. However, I do see your point. However, rd4b’s don’t extend horizontally if they are built right, right? Someone please correct me if I’m wrong.
what is a rd4b?
RD4Bs do not extend horizontally. That was one of the benefits of it for Skyrise; an opponent couldn’t crowd your lift and make you move to raise it. That only holds true if the segments of the top and bottom 4 bars are the same length, however (there’s no reason to build it any other way).
Reverse double 4 bar
Yes they do not extend horizontally if they are built correctly ; that is the reason why I said that their benefits in this competition would be pretty much the same as a scissor lift. I was just thinking that a scissor lift may be better than a double four bar because many teams back in skyrise opted for a reverse double four bar because of its ability to reach a high height while still being more stable than a scissor lift (as scissor lifts seem to be much more difficult to stabilize as you try to create a lift that extends to a higher height).
Really, it all depends on what the builder is more used to. I just believe that if a team wishes to focus on hanging this year, their best options for a lift would be either a scissor or double reverse four bar (and choosing between the two really comes down to which one you are most comfortable with building).
rd4b is a good way to lift yourself because it wont fall over and is very strong and fast due to torque gear ratios
Reverse double 4 bars are complicated, harder to build, and heavy.
30in has been done before with a 6 bar. A lot of them were during gateway. Six-bars can be done really thin and really high without much struggle, yet also retain a low weight.
I like the idea of building a six-bar lift. In my first year, Skyrise, I was able to build a six-bar that almost could build five skyrises. As long as the six-bar lift is built with aluminum, it is very light. If someone figures out a way to hang with a six-bar, I believe that scissor lifts and reverse double four bar lifts will be practically obsolete by the end of the season since a horizontal lift is important to get the stars off the fence.
With a six bar you have to have more torque and it will be slower because you have horizontal distance to cover also, it was the same way in skyrise, a lot of the faster robots had scissor lifts and not very many had six bars
There are still some advantages to having some horizontal movement. Like not having to launch as far if you can stick the launching mechanism over the fence. Then you won’t have to have a super strong launcher to get far goals.
I’m still debating a 6 bar or a scissor for my first prototype this week. Anyone else want to weigh in with their opinion before I start building?
LKStevensT.G. 49 seconds ago
But if you use a torque scissor lift you go straight up, and depending on your launcher you may only need a small torque gear ratio, like if you have an x-chassis with a forklift slip gear catapult it will be very light, about 6 lbs. and a 25 in. x chassis with a 60 tooth to 12 tooth gear ratio on it you can lift 13lbs. (Skyrise test) before your robot starts slow down and about 19 lbs. before burning out the 4 motors
Sorry if its worded weird, got it from one of my other posts
No thanks for the input, I actually might go with this instead, before i was leaning towards 6 bar but now I’m leaning towards this. Still not 100% sure yet. I’ll give it a night before deciding what to prototype first tomorrow.
The reason why this worked so well is that there was a horizontal and vertical component to the bar they were climbing. So friction is proportional to the normal force, and the coefficient of friction. With a slanted bar, gravity helps you by providing a normal force, and in the case of their robot it was enough. As far as a vertical-plastic bar goes, creating the friction required to lift yourself with a wheel would be pretty tough with vex parts. I’d imagine you’d have to use a wheel on the other side as well, and apply a lot of force between the climbing wheel, and the roller wheel. Doable, but difficult.