Team 842 Testing Shots
 

Here are some different shots we were testing today:
http://www.youtube.com/watch?v=ldO02ByEn5o

How are you guys varying the pressure the cylinders launch at?

Re: Team 842 Testing Shots
 

I'd guess they have multi-stage pneumatic cylinders.

Re: Team 842 Testing Shots
 

The pressure is held constant for all of these shots - 60 psi. There are some tricks you can do in software to adjust the trajectory.

Re: Team 842 Testing Shots
 

I believe what they do is vary the air pulse timing in code- I remember hearing them talk about this in one of their videos.

Re: Team 842 Testing Shots
 

This is brilliant...

::rtm::

Re: Team 842 Testing Shots
 

Its a lot of fun!

Re: Team 842 Testing Shots
 

Yeah, and I think you have already scared a 1165er!

Re: Team 842 Testing Shots
 

This is awesome! You guys are hitting all of the shots we hope to, but without all the crazy mechanical stored energy.

Question, in your testing, how many tanks are you running with, and how many shots do you get before needing recharge? Is the compressor able to "keep up" with how fast you're taking shots? It looks like in a short time you are making some shots quickly, just curious as to how much air this shooting method requires.

Very cool, will no doubt be highly effective, and very simple!

Can always count on 842 to come up with some innovative solutions, and then share them in order to inspire the rest of us! Thanks!

-Mike

Re: Team 842 Testing Shots
 

Love this setup. That last shot, should be pretty much impossible to stop and completely repeatable. That has been on our list of shots we need to have.

Re: Team 842 Testing Shots
 

What are the bore sizes on those cylinders? Can't tell if it's 1.5 diameter or 1 1/16. Looks identical to what we have gotten so far. Good job guys! Looks awesome!

Re: Team 842 Testing Shots
 

We can shoot about 2-3 high goal shots from the middle of the field before the compressor needs to turn back on.

They are 1.5 in diameter.

Re: Team 842 Testing Shots
 

What kind (make/model #) of solenoid are you using?

I'm assuming it's a double acting. What is the center position of the solenoid? A and B both closed? Both to Exhaust? No center position?

How are you precisely varying the timing of the pulse to the solenoid? Are you just counting cycles in the teleop periodic loop? Does that limit you to about 20ms increments? Do you need anything more precise than that?

So many questions...

This is very cool stuff.

Re: Team 842 Testing Shots
 

Nope. :)

Here's a part number for you though (see mcmaster): 6124K511

I'll let Sergio get back to you on the pulse control... I'm not sure how fast his program loop cycles.

Re: Team 842 Testing Shots
 

Hey there, nice job you did there! Looks amazing, and very powerful :)
We wanted to ask a few questions:
1. What is the length of your chasis?
2. What is the length of your pistons?
3. Is there any specific reason why you put your pistons in such starting angle? Did you find that angle more effective than others?

Good Luck, and see you at the competitions! ;)

Re: Team 842 Testing Shots
 

With a motor, you use a gearbox to trade speed for torque.

With a pneu cylinder, you use leverage to trade force for speed.

Re: Team 842 Testing Shots
 

How are you guys loading the ball? Does the arm go down further?

Re: Team 842 Testing Shots
 

I basically use the Timer class. It does not seem to be having any issues with that.

Re: Team 842 Testing Shots
 

That pile of broken ceiling tile has nothing to do with the robot right?

Re: Team 842 Testing Shots
 

Robots*

Re: Team 842 Testing Shots
 

Could this be used to pass or catch?:confused:

Re: Team 842 Testing Shots
 

Could you please explain in greater detail how to implement this?

Re: Team 842 Testing Shots
 

Use the timer class to set the pistons to true for a certain amount of time then set them to false right after.

Re: Team 842 Testing Shots
 

The amount of inspiration this video has given me cannot be quantified.


What solenoid are you using? is there any special storage tank between the solenoid and the cylinder? Or is it just


Compressor ---> Pressure Sensor -----> Storage Air Tank ----> Regulator ----> Solinoid ----> Cylinder.

*Forgive me for my lack of pneumatic knowledge if that order is so wrong that I deserve to be flogged.

Re: Team 842 Testing Shots
 

Super cool!!! I look forward to seeing you at the AZ regional.

In the videos your team posted on Facebook you have another piston that goes up and down as you fire, what is the point in this and how does it work?

Re: Team 842 Testing Shots
 

Compressor, pressure sensor, primary storage tank, regulator, secondary storage tank, solenoid, cylinder

Re: Team 842 Testing Shots
 

That additional piston gives us the ability to adjust the trajectory further. Just by varying the pulse to the main catapult cylinders, we are able to make a relatively lofty truss shot and a pretty hard/flat high goal shot. The geometry of the arm for those shots doesn't work for the in-front-of-the-1pt-goal high goal shot, so we added another degree of actuation.

We did a few quick tests today that make a self caught shot over the truss look feasible using these additional pistons; it will be pretty neat if we can pull that off in a match!

Re: Team 842 Testing Shots
 

First let me say how impressive this design is. The flexibility is incredible! Can you please provide more details on how you implemented it including cylinder dimensions (bore & stroke), release, distance cylinders are attached from the pivot, pneumatic connections, are you using 2 tanks per cylinder? are you using separate solenoids for each cylinder? Our team tried to replicate your set up tonight and couldn't get anywhere close to the range you demonstrated.

Thanks...

Re: Team 842 Testing Shots
 

Our team used a different mechanical approach to varying our shots with the same shooter mechanism.
After seeing this thread early yesterday, we have already tried with great success the software pulsing of the solenoids instead.

Thanks for sharing.

Re: Team 842 Testing Shots
 

OK, we had similar size cylinders, similar sized catapult, and tanks directly connected to the cylinder ports (mechanical release - we didn't even get into large CV solenoid valves yet) and we could not make our shooter make long shots like yours. We clearly have some learning to do. I'm looking forward to seeing more of your system after build season!

Re: Team 842 Testing Shots
 

A very small difference in the geometry can cause a huge launch difference.

Re: Team 842 Testing Shots
 

So you used 1.5" bore cylinders, but what stroke did you use? We've looked at a couple ideas, but with our current configuration, ours couldn't fit.

Re: Team 842 Testing Shots
 

9 inch stroke