when closing and opening to grab nothing, how is it that some claws shake the whole mechanism/structure so much while others, especially 1103’s, seem to be so stable? my guess: i have no idea, need help on this one.
when closing and opening to grab nothing or any game objects, seem to have a time lag between pressing the button on a joystick and the movement of the claw itself? my guess: the air takes time to apply pressure within the piston before having enough force to push and extend the piston.
( related to 2. ) is it better to have a shorter pneumatic tubing between the solenoid driver and the pistons? refer to https://vexforum.com/wiki/index.php/Pneumatics_Kit_2 my guess: this helps to reduce the time for which the air travels to the pistons from the solenoid, reducing the “time lag”
There is a light blue regulator valve on our pneumatic kit. This will control the amount of pressure with which the claw opens and closes. If you use too much pressure (and you usually don’t need much to pick up game objects), the whole frame will shake. And then there is the issue of how solidly built your frame is.
What kind of shaking? I would guess the intake is just not mounted very securely, but reducing the amount of energy per firing of the cylinder, either mechanically or with the pressure controller thing, should fix that problem.
We haven’t had any lag issues, but it’s probably not having to do with the air moving through the tubes, as that’s rather quick (there’s a lot of pressure).
The more tubing between the cylinder and the solenoid, the more air you will use/lose per firing of the cylinders. All the air between the solenoid and the cylinder is lost when you retract the piston (for a Kit 1 piston). Also, using less pressure will conserve air.
Thanks guys! the pneumatic kit 1 comes with a pressure regulator, but how do i use it? whichever way i adjust the valve, always give me the same amount of strokes before running out of air.
and by shaking, i mean… look at 1103’s for example. in this video, http://www.youtube.com/watch?v=Uqm-6UPl1zQ&feature=related when the robot misses the stack of tubes around the 32 sec mark, the claw closes but its lift/claw/structure seem to be very stable and don’t shake much. my guess is due to the “lightweight claw”. during the asia-pacific VRC i was in at taiwan, there were robots with tank treads on the claws. when the driver presses a button, there was a 1sec pause before the claw closes and when releasing, the claw shakes the whole lift/arm. comparing that “heavy claw” to 1103’s “light claw” i’d say there is a very huge difference in terms of weight
1103’s claw was pretty light, and it wasn’t moving very far. They also had a hard stop just smaller than the objects, so there wasn’t much difference between actually hitting an object and not. In general, if you want things to stay stable, make the claw symmetric and keep it light. Do you have a video of the shaking?
For the pressure regulator, look at page 5 of the Inventors Guide for pneumatics:
sadly, i do not have a video of the shaking and lagging. i guess keeping a claw light is the difficult part especially when you don’t want stuff to break or have another purpose. shall keep the lightweight claw thing in mind. thanks!
earlier this year we had a claw (before our first competition), we got it to work quite well by putting it on a four bar system to make it open and close without rotating - i didnt want it to rotate because i find rotating claws really really hard to drive and line up… so i just it so you drive until it ends up inside then close it…
1103’s claw looked super TANK (just like the rest of his robot)
the reason it was so light and sturdy was because he cut up aluminum c-channels to the correct lengths that he needed. that way its both light AND sturdy
(that is if you have the budget to spent on cut aluminum)
You have to specify: good for what? There is no questioning that 1103’s claw was well built and sturdy. It served it’s function spectacularly. What function do you have in mind when you ask whether it’s good or not?
So I take it that your arm can’t really lift up too many game pieces? If your strategy is to score the objects on by one, a claw might be a good option for you. The game objects aren’t difficult to grasp individually. If I remember correctly, Josh said that his claw got about 40 movements out of it before the reservoir ran out of pressure, so that might be a potential problem.
I would highly suggest designing your entire robot before building any of it. If you were planning on using a claw, that’s fine, but building a lift and then deciding what to put on the end of it just simply isn’t effective.
Claws dont have to only hold one or two, my VERY first claw design for this season (i never built it ) (yes, i have a ton of designs) is shown below. There is a small scissor lift at the back, which moves the whole claw and holding area up and down. For the first object, the claw is in the down position, and works as a normal claw, once the first object is picked up the claw raises to above the height of new objects. When it has one and is raised, another object can be picked up by driving into it, opening the claw and bringing the claw down on top then closing the claw and raising again ready for the next object. This all happens very fast as it is done in two puffs of pneumatic’s which would be a user control cuntion (one button picks an object up) so the claw would pick up objects reasonably fast. Hmmm, maybe i should build it…