In lue of some of the hanging discussions going on, and some of the gloom and doom around the subject - I figured I’d toss the community an idea I came up with to show that hanging really isn’t impossible, that it can not only be made practical but that it can be done without that much extra added complexity to a robot that can already score in the high goal.
All in all it’s a low-tech solution, but with some tweaking (get the center of gravity right, lock the bar, etc) it might just work out for somebody.
So here it is …
Clicky clicky for high-res
As always run the numbers for yourself before considering this approach, I will warn that these numbers are somewhat sensitive. It only works with a lift that is already able to reach up to 24 inches (which doesn’t have to be a four-bar), but it eliminates the need for these super-lifts that can go all the way to 40".
Are you saying that it won’t be working out for you? It seems to be a solid enough design.
All I’ll say is that this same design is already “working out” for 610X, or rather, being worked out.
About some of the possible issues you brought up, in my experience, “locking the bar” is really simple, and C.O.G. isn’t as much of a problem as you would think, especially when its really easy to play with things like the placement of air tanks and how far forward/back you store the big ball.
This looks like a pretty solid place to start for hanging mechanisms. The only think that I don’t like is that it requires two power sources (one for the main lift, one for the hanging extension), so I made a few tweaks to make the hanging extension operate on the main lift’s power source assuming you use a chain bar/4 bar/6 bar/8 bar/etc. The following image depicts my tweaks, but like Cody’s sketch is by no means ‘build ready’.
The problem with that is that it requires MUCH more torque to use. So instead of an arm that is ~16 inches long, you increased it to an arm that is 28+ inches long (plus extra friction). Also, an additional power source could simply be a piston, which for one actuation per game isn’t much at all.
Last year I did some tests, and I know (by accident ) that a ~1:4 18 inch 4 bar is capable of lifting about 6-8lbs, depending on the battery level. Given that information, if you build light, I couldn’t see hanging being much of an issue this year doing it “Cody’s way”
How do you do the math for that? I’ve spent the last month trying to figure out what I could lift with different gear ratios and a four-bar, but I have no idea where to even start.
The numbers posted previously where from experience. I personally found calculating torque & gear ratios unreliable (to a point, what you can lift tends to be how well you build your lift). However, it can still be very useful especially early on in the season. You’ll want to look into how to calculate torque on arms and levers.
My first reaction when i saw this post was…
WHAT?! NAR IS FOLLOWING A MAINSTREAM IDEA?!?!:eek:
now back on topic, i had a similar idea to this but i had 1 addition
rather than worrying about center of gravity, i added fold out wings to the side to catch the robot. It should place pressure on the hanging structure so the robot doesn’t angle.
apparently other teams aren’t having issues with torsion or torque, so ill skip that. The next problem that arises is how to stay up after power cuts off. Long story short, a locking mechanism is needed, preferably one without pneumatics.
my instant thought was a carabiner which rests below the arm system. the arm system wouldn’t have the freedom on the ground or bump to reach it, but when hanging, maybe the lift can overextend to reach the carabiner and lock.
Another, less practical idea was powering the arm system via winch. Have it do an elastic raise and a powered descent.
for a moment i was like daaaang, new zealand does it again. Then i continued reading:p. Very very nice though:D. Couldn’t you modify your storage system to shoot bucky balls? it looks like it has a pneumatic lock and elastic attached to an arm which can overextend,
i’m given some relief that i wasn’t the only person to think about this. But i still don’t see the strategic benefit compared to the other alternatives which can influence more than 1/3 of the points.
Plus, isn’t it a bit unfair to consider this 1/3 of the points when you can’t build your own partner(s) and half of the hanging score comes from large balls? As you know, it’s a pretty tight squeeze for 2 teams to hang at the same time.
I realize that it’s somewhere around double the torque and I’m all for pistons, but for a while the teams that I was a part of did not use pistons and I know that there are still many teams that do not use pneumatics and this would allow them another option for hanging that would fit right in with other designs previously explored on this forum.
“I stand apart from the federation.” OK I can’t back that up, but yeah.
Mainstream? I can’t be mainstream!!! The week I FINALLY buy an iPhone I get called mainstream? Nooooo! ** melts **
Very impressive, but I haven’t seen it (I just tend to do stuff and ignore a lot of what other people are doing). I came to this conclusion on my own. Since NZ and I agree though the idea must be good. Simple is usually good.
So can we now (pretty please) all go build hanging robots without this “is it worth it” or “can it be done” stuff?
I believe the original poster was talking about how to control the hook so that it is down when under 12 inches, but will stretch upwards when the lift is all the way up. Interesting though that you erased some of the picture
Problem with this is that presumably you restrict to only one robot being able to hang at once. COG can be fixed by moving the hook back and forth a couple of inches until it’s right.
Well there are many ways to go about that, however pneumatics would make lift a lot easier.
For one, you can reverse rubber band the lift, so that it wants to stay down rather then up. I don’t know how effective that would be, but it would certainly help (robots like 1103 used reversed rubber banding)
If I were building for next year, I would lean towards a pneumatic assist, which would do a very good job of locking the lift into place, however I realize that’s not always an option for some teams
Finally an option could be to create a mechanical latch like 1103, however to my understanding that was dependent on the fact his lift could trigger back to an angle using pneumatics as well.
I know many NZ teams back in Round Up where able hang using 4 bars, but I wouldn’t know exactly how that worked.
Not exactly sure if its an NZ team, but a team used pneumatic pistons to jam up their gear tower. Others would use a pneumatic assist to mess with their rubberbands to make hanging easier.
it is a bit crude, maybe there’s a way to trigger elastic like catapults from clean sweep. ill need to think about it more
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i’m kind of envious of teams with pneumatics. However, you did give me a few ideas. Maybe it’s possible to have the tower shrink up and down with elastics. That way, you could shift your center of gravity and make lifting a lot easier. If not, maybe someone could just dead weight the end of a pneumatic piston to change the center of gravity a few inches. Power take off systems from the drivetrain to lift would be pretty cool. Maybe even an elastic powered hook with a pneumatic release to pull the robot up.
Because it was an unrelated doodle that had no relevance to robotics in any way! Surely.
What we did with our super stacker was a pin attached to the intake by string released a number of mechanisms once the arm was raised above a certain point. We knew that the arm would only ever be raised that high once (when scoring), so we didn’t have to worry about lowering the arm anymore. Here, maybe once the arm reaches full extension (a bit higher than the 24" goal perhaps), a ratcheting system locks in place. This allows the arm to lower, lifting the robot, but stops backdriving and doesn’t interfere with normal operations because the arm will only go that high once in the game.
Yeah, Free Range (2921 and 2921B) did it with a hook that folded out above the intake to reach up onto the ladder A bit like Cody’s idea They used rope to pull them over once the arms reached a certain height. I’ll have a look for a nice video of the hanging, if there is one.
To keep the robots up off the ground, they had 2 latches mounted on the chassis (one on each side) made of hinges, but there are other options too. And 2919 had pneumatics that locked the arms down, if I remember correctly.
EDIT: My opinion on hanging - do it. It doesn’t take much effort to add into a robot and is definitely worth it. We will be doing it this year for sure.
Depends which iteration I used a winch at Nationals (it was hilarious :D). And then for Worlds it was similar to yours George with hinges and rubber bands, yet added some pneumatics so it could un-hang itself
if i remember correctly, the engineering vs math match, 3rd round, posted by some user like dankutaiblahifogot, showed footage of you hanging. not exactly sure if it’s clear though
This is extremely close to what we have done for our hanging and latching mechanisms, except they do not ratchet into place so we can go up and down without them sticking up. Using elastics and rope we are able to actuate several mechanisms based on the height of our lift. There is really no sense in using a motor or pneumatics for such a simple task.
