It’s true, this unassuming little thing doesn’t look like much, but unless your robot has the capability to push the little trigger release valve up, you have no chance of moving it. (if we had thought of this earlier, we would have another one on the other side. drat.)
F.Y.I. It’s never good to use the rod of a cylinder for lateral support
I think you will also be suprised by the force of some of your opponents, in fact I know you will 
i really hope you’re not using the ability of a human to push your robot as grounds for these claims.
a robot can hit with much harder force than any human. you should take another robot and hit yours with it to test these things.
no one person could move a robot at our exhibition, but then another team’s bot rammed it and it slid 2 feet.
plus, i don’t think suction cups are going to be very effective due to the nature of the HDPE.
*jeremy
those aren’t jsut any suction cups, those are sheet metal holders, and they don’t slide, and are tested for about 300 lbs. Yeah, the pnematic might bend, but at that point, our robot will have fallen to pieces and we’ll be out for good (that wouldn’t be fun:( )
Oh, and they actually work best on smooth materials like the HDPE.
<edit> We are more worried about this monster bending our robot’s frame than we are of anyone else doing that.</edit>
Nice looking bot…but wouldn’t it be wise to somehow protect that cylinder? It would really suck if you guys got hit or ran into someone, and fubar’ed your suction system in the process.
They do work on smooth surfaces, but the HDPE will become very worn and will not be a flat surface after a few dozen matches, it will have pits in it. Just my opinion
i would add a lateral support beam, it wouldnt be too difficult, but i do believe you will be slideable… you aren’t drawing vacuum which will make your suction less effective.
those aren’t jsut any suction cups, those are sheet metal holders, and they don’t slide, and are tested for about 300 lbs. Yeah, the pnematic might bend, but at that point, our robot will have fallen to pieces and we’ll be out for good (that wouldn’t be fun:( )
That’s odd, because we had those (MSC right?) and they slid pretty bad, i can also tell you they didnt make it on our robot.
They look like Anver suction cups to me, and if they are then yes they do slide. They don’t slide very easily, but if someone like team 60 or 45 comes up the ramp at full speed, off the ramp you go.
FYI - The 300lb tested force is lifting force, the shear force (sliding) is probably going to be less that 50lbs.
Nice hatch for the controls.
I’m not sure if that cylinder will that very long. I can almost gaurantee the shaft will bend after 1 good hit.
Even that bracket that holds the cylinder looks weak, you may want to put it on the end of the cylinder where the shaft comes out. So as not to crease the wall.
The HDPE isn’t a very hard surface and will start to get scratched and pitted very fast. If you take into acount all the collisons and action on the ramp it won’t stay smooth very long.
I’m not saying you wont be able to stay on but I don’t think you stay on for long.
I can almost gaurantee the shaft will bend after 1 good hit
try this: flip the piston upside down. make a mounting bracket to connect it to a piece of extruded aluminum so the aluminum is flush with the back of the piston when the piston is extended. have the piston retract to pull the extruded alumiinum bar down, pushing the suction cups onto the ground. that way, the piston rod is inside your bot when you’re taking the force, and wont bend nearly as easily if you take a hit. other than that, not too shabby.
I get the vaugest feeling we prolly won’t want to take to many hits on this thing, but it is very cool to watch it lift the opposite side of the bot.
You just better hope you dont meet us cuz we push at well over 300 lbs and um suction cups arent stoping us.
You just better hope you dont meet us cuz we push at well over 300 lbs and um suction cups arent stoping us.
do you have any images up?
<edit> nevermind, I found it. It doesn’t look like you have enough traction to do that, are you sure you can push 300lbs.?</edit>
*Originally posted by Duke 13370 *
**do you have any images up?<edit> nevermind, I found it. It doesn’t look like you have enough traction to do that, are you sure you can push 300lbs.?</edit> **
It’s next to impossible to make any judgements about tractive effort by looking at a picture. Big tires doesn’t equate to big traction. Cool belts don’t equate to big traction, either.
In fact, this season, I expect many people are going to have to relearn all they though they learned about traction - especially where the HDPE is concerned.
As someone already mentioned, the 300 lbf. figure you have is probably for tension, not shear. Suction cups don’t really resist shear all that well, and there are robots out there that can exert well in excess of 300 lbf., anyway.
Against some robots, you’ll likely be fine. . . .well, assuming that your drivetrain has the oomph to move other robots with similar ideas out of the way. Against others, you won’t stand a chance. There’s always someone who does it better, or differently, or some way you never even considered.
It’s a bad idea to assume you’re immovable, or unbeatable, or that much more clever than the rest of us. 
Edit: Grammar. Also, do you understand the difference between pushing something that weighs 300 lbs. along a surface and exerting 300 lbf.?
the reason our team didnt want to use suction cups is that they are very finiky about their attatching surface…
dust, scratches, oils, moisture in the air all have an effect on how well they grip (or dont grip) the surface.
also: for a suction cup to operate properly the force on them has to be perpendicular to the surface in 2 directions.
when a robot hits it, it will be from the side.
we didnt think they would be a focused subsystem for our bot…
but good luck.
my 2 cents.
It’s a bad idea to assume you’re immovable, or unbeatable, or that much more clever than the rest of us.
Oh, i wish we were, but i know better. we spent mabye $20 dollars on the robot afte the kit and donations. Actually i think the zip ties were only $8, so we prolly spent more like $10.
Any way, I find the power that thing has very ammusing just because we’ve been testing this on dented, scratched tile, and it was very immpressive to see this thing pull us down.
This is a good idea and your robot will hold it’s position over MANY other robots.
Let’s look at this design and evaluate the impact:
It appears that the suction cups are being actuated up and down on a 2" dia cylinder (at 60psi, pulls at 170 lbs, pushes with 180 lbs).
Also, let’s assume that they have the same mechanism on the other side of their robot.
From our team’s experience, you can pull up on these suction cups with about 100-120 lbs of force before they let go (it depends on the cleanliness of the surface).
So… the cylinders push down, suction cups stick, and the cylinders try to pull up. They probably regulate the cylinder down to 40-50 psi in order to not pull the cups off of the floor. All of the force that they are pulling up on is being transferred to their wheels, and their robot essentially weighs much more than the actual weight of the robot. The downforce on the wheels is shown below in an equation:
Downforce on wheels = robot weight + left side cylinder/cup pulling force + right side cylinder/cup pulling force
Downforce on wheels = 130 + 100 + 100 = 330 lbs.
So… essentially, with both suction cups engaged and the cylinders pulling up, their robot weighs 330 lbs. Although it’s not best design practice to simply let the cylinder shaft support the side loads on the vacuum cups, it’s the wheels that are exerting the downforce, not the cups. An opposing team not only has to slide the suction cups, but also 330 lbs. of downforce applied to their wheels.
In order to push this robot, an opposing robot has to push with more force than this robot’s holding force (at least that’s what I call it). Their holding force = 330 lbs. x mu (their wheel’s coefficient of friction).
Now, with regard to scratches, these cups still do pretty well. If they had a lower durometer, they may even be more resistent to scratches.
Great 'bot… good luck!
Andy B.
not to complain…but i thought id help you out by telling you that your light shield is illegal…not that you can fix it now or anythign
not to complain…but i thought id help you out by telling you that your light shield is illegal…not that you can fix it now or anythign
HUH!?!?!?