My team is on edge on what lift we want to do. Currently, we are leaning towards the 6 bar as it takes less space, less weight, less time to build, and can get the job done. The DRB can definitely go higher by a mile but it doesnt seem that we need to go as high, as the 6-bar should be able to get to the high post and you obviously aren’t allowed to push high flags.
I wanted to talk to you guys before we I finalise a decision.
Thank you all, and good luck on a great season!
A lot of teams are coming to the table saying that DR4Bs take up too much space. They don’t have to. You don’t need to make it 5 feet tall like from ITZ. If you just shorten everything up, it won’t be much bigger than the 6 bar, and you get the added benefit of having a linear lift.
I would use neither, the six bar expands horizontally, putting you at risk of leaving the expansion zone and a DR4B takes up too much space. I would use a cascading lift that is 3 stages.
The expansion zone is marked by the tiles. No matter what your lift does, so long as at least one wheel is touching the ground inside the zone, you cannot leave it.
To add on to what @jwwood13 said, the six bar’s horizontal expansion will actually make it erasure to not leave the expansion zone
Every time I mention a double reverse, all of the teams from in the zone think of that height. In reality, a very small and slim 2 ft double reverse is totally viable and with linearity it’s a no brainier for more simplistic driving.
This year you have to consider what will happen when you try and get on the ramp. Almost all of the DB4Bs at worlds were top heavy. Also, what would happen if you got tipped over on the ramp. Are there any lifts that could be used to right side your robot?
uhhhHhHhHh…your teammate? I imagine it would be very difficult for the taller lifts…so maybe some passive horizontal stabilizers that fling open when the match starts? That may be your best bet…
I would stray from 6 bars and other types of non-linear lifts, because they change your center of gravity and make it harder to maneuver when they are up.
That’s why there’s cascading lifts… To have linear lifts.
agreed. we will either do a small dr4b or some sort of multi-stage elevator lift.
Seems a good decision
Yep, and a DR4B accomplishes this pretty well, too.
Sure, non-linear lifts change your center of gravity. But every linear lift I’ve seen does as well. Very few linear lifts I’ve seen only move the center of gravity upward. Most lifts, including DR4B and the like, move the center of gravity both vertically and horizontally. One of the bigger issues for teams, I suspect, is an issue of angular momentum placed into or taken from non-linear lifts causing the robot to tend to rock.
Okay, but it’s a much bigger issue with nonlinear lifts than a DR4B. I’ve seen 8-bars turning around a point outside of the chassis, whereas my DR4B in ITZ created no noticeable effect when turning. Also, elevator lifts have very little horizontal change in center of gravity, if any.
Right, elevator and cascade type lifts mostly just move the center of gravity vertically. I think you would be surprised how much horizontal shift there is with a DR4B, but yes, that shift would tend to remain inside the wheels more readily. However, generalizing this to linear lifts v. non-linear lifts is going to far in my mind. I’ve seen plenty of linear lifts cause more horizontal change in the center of gravity than some nonlinear lifts.
I don’t think I would be too surprised, considering I drove a DR4B-based lift robot for… well, the entire season. If there is a lot of weight, just make it lighter. But I promise you that it does not compare to a nonlinear lift of the same height, with the same weight at the end, etc. Here is an image that includes the back section of our DR4B. Pretty darn light.
You may not want to make that promise. Consider this: DR4B that has lengths of 12" for each arm v. the same design with 8" on the lower arms and 16" on the upper arms. They’ll lift to the same height, but the second isn’t linear. However, in the case of the second, all those motors, gears, etc. on the back move horizontally less than with the DR4B. So depending on what you’re holding and the weight of the claw, this non-linear lift could go to an equal height and move the center of gravity less horizontally. Edit: Actually, what is being lifted will move back slightly, counteracting the forward motion of the midsection. So there will be a lot of leeway on what claw/load weights are lifted for this non-linear lift. (For clarity, that is bottom to top and so a sort of average. In the middle the claw/load will be forward a little.)
Yes, with most typical lifts your preference should be correct. But if you’re moving lightweight things, there may well be surprising differences.
I dont know I used an 8-bar at state last year and placed 10th and went 4-2-0 and if i would have used the last 10 seconds of a match differently and pulled my partner away from the mogo they were touching, we would have been 5-1-0 and got about 6th or 4th. it was fairly efficient as a lift and since i had it for the whole season i was used to how i needed to position so it set the cone on right. I also had a mogo lift inside the U-drive
My driving strategy for using a 6-bar would be to bring caps to the expansion zone and only extending then. I would have a launcher in the middle of the bot for shooting so caps isn’t our only scoring method.