Our team (1566 The Ammoknights) is wondering if it is possible to “charge” a pneumatic ram. In other words, is there a way to store potential energy in a pneumatic ram and then release it very quickly?
Thanks,
Mitch Guzman
Team Captain Team #1566
if you have an air tank between the valve and ram, and a mechanism to release the ram after it has been pressurized, you can get the cam to move quite fast.
I believe team 360 used this in combination with a large spring to launch the trackballs during Overdrive.
also, if you need speed, lower the diameter of your cylinder. it won’t be as strong, but it will move much faster. if you add a weight on the end of the cylinder, the momentum will impart significant force.
The easiest way I can think of is to use a stop to hold the actuator whilethe cylinder is charged, then release the stop to release it… just like you would do using a spring or similar power source.
exactly, you just have to be extremely careful, as there are huge forces involved!
a 2 inch diameter cylinder pushes with close to 200 pounds of force at 60 PSI!
you can get a more instant oomph if you lock the piston at 1/3 extension b4 pressurizing and then releasing it. that way the gas can expand faster since it’s already in the piston.
Note: this accomplishes the same thing as having a piston extension lock and a tank between the solenoid and piston… just a tad faster.
wow! thats a really cool idea. Im gonna try that out this weekend and see what we can do.
Several teams used this concept in 2008 to launch the track ball. Also consider using an “over center” linkage design…so you don’t need to use a lot of force to release it.
We did something simmilar in 2008, where our catapult was held down by a pneumatic latch. We then charged the cylinder powering the catapult with 60 psi, and when we wanted to fire, we essentialy pulled the pin. This worked quite well and we were able to fire the ball over the overpass easily.
How many times can the piston crash against its end before it hammers itself apart?
Bruce
Most cylinders have ‘bumpers’ within them to prevent damage when being fully actuated.
How did you lock it in place? Did you use a piston to push a pin into the lock? Or did you just use the piston as the pin? If it was the latter, can you tell me what size your pistons were and how much damage was done to the smaller lock piston?
dont add weight to the end of the ram, remember, KE = (mv^2)/2
As a reminder to all teams and those that are reading this thread…
R01> Energy used by FRC ROBOTS, (i.e., stored at the start of a MATCH), shall come only from the following sources:
A. Electrical energy derived from the onboard 12V battery (see Rule <R40> for specifications and further details).
B. Compressed air stored in the pneumatic system, stored at a maximum pressure of 120 PSI in no more than four Clippard Instruments tanks. Extraneous lengths of pneumatic tubing shall not be used to increase the storage capacity of the air storage system.
C. A change in the altitude of the ROBOT center of gravity.
D. Storage achieved by deformation of ROBOT parts.
I don’t see why using a locking system and pneumatic cylinder breaks any of these rules at all.
It depends on how it is used. You could apply force to the rod of a pneumatic cylinder that had air trapped behind the piston by a closed valve. This could cause the air in the cylinder to exceed 60psi, which would be a rule violation. There are various ways to both do this sort of thing and prevent it, depending on what you are trying to accomplish
what is a over the center ,linkage system?
I’m kinda wondering - maybe this should be put on the FIRST Q&A. If we were to use a system that had the ability to use a pre-charged kicker cylinder it seems we would have to demonstrate to inspection that there is NO pre-charge condition prior to match start. I suppose putting a gauge on the cylinder circuit downstream of the valve could demonstrate there is NO pre-charge while the robot is in the fielded ‘disable’ mode.
What say you Al ? Should I put it to the Q&A ? We want to use something like this.
Ed
You could, but be sure to word it carefully.
As I see it, what you want to do is this (correct me where I am wrong):
Start the match with only the clippard tanks at pressure (allowed per <R01a>. Or don’t, and let them pressurize during autonomous)
After start, open a valve to extend a piston.
Mechanically limit the extension of that piston to something like 1/2 its stroke.
Allow the back end of the piston to completely pressurize to 60 PSI or so.
So far, are we OK? If not, I’d need to see a rule.
Using some mechanism, release the mechanical limit, allowing the piston to extend the rest of its stroke.
Still OK, right? Assuming you follow the rest of the rules (e.g, perimeter and safety), it still looks OK to me. (My opinion is worthless at any competition though)
We had the same idea actually. Although, we had the idea of using something like a trigger mechanism off of a control group on a firearm.
In our implementation, the air wouldn’t be trapped, only the piston would be trapped (somewhere) midway along it’s stroke. If there were a force applied to the pneumatic cylinder, it would back-pressure into the system and still be regulated to 60 psi. If I remember correctly from accidently putting the regulator backwards on the ‘high pressure side’, the pressure releases if it’s above 60. One of the first things we do every year is hook the regulator backwards and have our entire system never go past 60 psi, then someone remembers what happened the year before.
You could also prove that it is not pre-charged before a match by unlocking the triggering system, and the cylinder at this point wouldn’t fire.
Edit: Don’s question should cover the Q&A question that I’d even like to ask. Could someone submit that?
You got it perfect.
I just noticed that the FIRST website has not yet posted the pneumatics manual for this year so for the moment we are falling back on the 2009 manual even though that isn’t ‘official’.
And the KOP checklist doesn’t have the part number of the FESTO valve used in this years rookie kit and I’d like to know what that p/n is.
la dee da