Im trying to figure out what to do for an arm for this years game. Any unique ideas other than a 6-bar or elevator?
A scissor lift, eight bar, or double four bar would give you plenty of extension for reaching the Hanging Bar. A four bar, six bar, or chain bar would also work well, and with the lift extension Cody proposes in his thread a wile back (https://vexforum.com/t/possible-hanging-design/24105/1) hanging would be an option with these lifts as well.
I’d suggest a chain bar, since they’re the lighter option, plus you could use the extra tilt from different sized sprockets to your advantage if you wanted.
I did some testing with CADing chain bars and 6 bars, and it seems that 6 bars can drastically change angle without taking as much space the same angle change on a chain bar would with different sprockets - just something to think about when you guys design your robots.
4 bar needs some major innovation to work. That picture shows 25" height, but it’s also an 18" 4 bar. The bars need to go almost vertical to make it work.
One way to make the linkage vertical could be to offset the bars, so they are not directly under each other.
It really doesn’t need major innovation. Not a lot needs done to a standard 4-bar to get it to reach 24"
I’ve always fancied the idea of making a lock and elastic type lift system. It’s applicable to any lift system. The idea is having a lever or winch of some sort to pull on elastic and store force. Then use another set of motors to release a lock to make your lift raise nearly instantly.
-you can lift early by storing energy while you drive
-you can overtorque your system(while protecting axles as necessary) to lift large loads without being penalized on speed
-needs surgical tubing
-needs routine inspection
other than that, i highly recommend a chain bar
I am unsure on the strength of the chain bar when you are trying to hang. Have you tested lifting a 10+ pound robot with a chain bar?
You would probably want to design a lock release that doesn’t require motors; having a motor just for locking would be a waste of a motor that could go on another subsystem. In fact, you can probably cleverly design the lift so that it passively releases without even pneumatics That would depend totally on you robot design though, and it might not be reliable enough.
I think we’ve already seen this with the Tabor Lift. And seen what it can do (GER at Sack Attack worlds)
I’ve always dreamed about that but i need a higher level of work efficiency to work out the kinks.
mind posting the tabor lift? if i remember correctly, GER could only lift once
It is hard to find a lift that does not have a place in this game in my opinion. Having to lock the lifts for hanging seems to be somewhat of a challenge for all types of lifts.
Winching an elastic lift back down again could take more time and add more complexity than it’s worth, unless there is a need for the fast elastic movement.
One good application for a re-tensioning elastic lift would be a catapult, like this one.
1103 had something similar to that for Clean Sweep as well. If I remember correctly it lifts 4 or 5 pounds suspended 8 or 10 inches using two old VEX motors at 1:25 for power.
that’s very similar to the video i had in mind:)… i was actually thinking this VEX Cleansweeep, GaTSA Qualifer, 1235A - West Forsyth, member of the Forsyth Alliance F1-1 - YouTube. The thing i thought was pretty cool could be seen at 0:45 bottom left corner. the robot could constantly reload while driving. In Toss Up, i think this would be especially helpful when driving across from the goal to the hanging zone or vice versa. Of course, you would only do this if you had an unreliable ally. As for fabrication, i think it kind of counterbalances. For many years, people have experiences with drivetrains, lifts, and intakes from gateway. Might as well carry and continue your knowledge to younger members so they can step it up when their time comes
Currahee was actually where i first saw something like that. At first i never equated it to a lift, more like a catapult, but realized it would be really awesome if a lift could do that.
By old vex motors, do you mean 3 wires?
Yep. I forget the specs on them are but those are the ones.
I believe they have a bit over 6 inch pounds of torque and 100 rpms. I dont pay attention to electrical stuff, but i would think it’s too low to make a big deal on most robots
It’s quite ironic though. Last night, i realized if we made a carabineer to hold the catapult and extended the lever further, we could possibly make a lift that locks and slings with a single point of rotation. As for fleshing it out into vex pieces, i need more time to think more about that.
Question though. With the force and speed of a shooter. What do you guys think about using a same properties for hanging
Through numerous trial and error we decided to go with a pneumatic 4 bar