pic: Team 8 T-Shirt Cannon

[jzajac]

Introducing Team 8’s T-shirt cannon, Skyline!

This bot was created as an offseason project for our team. It is 100% student designed and is the result of many weeks of hard work. That being said, we’d love to get some feedback from you all, as there’s always more to learn and improve upon.

Notable features:

• An 8 barrel revolver style launching system inspired by 254’s Shockwave
• Barrel indexing using a limit switch triggered by nubs on the rotating barrel assembly
• Up/down tilt powered by a mini CIM and Andymark wormbox
• A powered turret with 90 degrees of rotation in either direction
• 8 wheel drive, with the middle 4 dropped 3/16"
• 2 2 CIM WCP gearboxes
• No PVC parts anywhere near this robot

We are still working on the pneumatic setup. One scuba tank will act as a high pressure reservoir, and the other will be our low pressure accumulator. The accumulator goes to an electric solenoid valve which feeds to the shooter. We don’t have much experience with scuba regulators and non-FRC pneumatics, so all suggestions are welcome and appreciated.

[asid61]

Pretty nifty design, definitely looks very 254-inspired. How are you planning on launching the shirts? And is that a custom drive gearbox?

[dardeshna]

Pretty nifty design, definitely looks very 254-inspired.

254 inspired indeed. We liked the idea of a revolver, but wanted to mount it on a turret for an additional degree of freedom.

How are you planning on launching the shirts?

We are still researching which solenoid valve to use. We are looking for something with a very high flow coefficient (unfortunately these aren’t always published).

And is that a custom drive gearbox?

Nope, just a WCP DS gearbox. We weren’t too worried about running out of compressed air

[ASD20]

We are still researching which solenoid valve to use. We are looking for something with a very high flow coefficient (unfortunately these aren’t always published).

My team used:
http://valvesandinstruments.com/solenoids/solenoid/asco-8210g4-8210g004-12dc-2-way-brass-1-in-solenoid-valve-normally-closed-general-service.html
While extremely expensive, we ultimately chose it because it had a Cv of 13 and it was the best option we could find at the time.

This Valve:

3/4" 12V DC Electric Brass Solenoid Valve

has a Cv of 7.6 and is less than $50.

Thread: https://www.chiefdelphi.com/forums/showthread.php?t=149770

[GeeTwo]

We are still researching which solenoid valve to use. We are looking for something with a very high flow coefficient (unfortunately these aren’t always published).

Probably not a surprise, but look for a large-bore valve with a metal (probably brass) frame, and plumbing of the same or larger diameter from the accumulator through the valve tp the barrel. Using a 3/4 to 1 inch airway will let you launch shirts to the top levels of a high school stadium (or over them) from the sidelines with no more than 60 psi.

Nope, just a WCP DS gearbox. We weren’t too worried about running out of compressed air

Just curious, how are you compressing your air? We’ve been using a scuba tank, using a standard scuba regulator to get down to around 100psi and an FRC regulator to get down to 50-60 psi in a cast iron accumulator we picked up our rookie year. We get at least 200 launches from a tank, probably more like 400-500 when we programmatically regulate the valve time. If we were to ditch the scuba tank, we would probably have a high-pressure (120+ psi) tank that we charged using 110VAC and continue with the cast iron accumulator to reduce the number of battery changes.

[dardeshna]

Just curious, how are you compressing your air? We’ve been using a scuba tank, using a standard scuba regulator to get down to around 100psi and an FRC regulator to get down to 50-60 psi in a cast iron accumulator we picked up our rookie year. We get at least 200 launches from a tank, probably more like 400-500 when we programmatically regulate the valve time. If we were to ditch the scuba tank, we would probably have a high-pressure (120+ psi) tank that we charged using 110VAC and continue with the cast iron accumulator to reduce the number of battery changes.

We plan on filling up at a local dive shop when needed. One of us took a quick look and it appears its about $10 per fill.

[Richard_Wallace]

We are still researching which solenoid valve to use. We are looking for something with a very high flow coefficient (unfortunately these aren’t always published).

You could make your own. Our home-made valve is working well.

[dardeshna]

One question we do have is what sort of hose have other teams used?

We were thinking something like this: https://www.mcmaster.com/#1593n27/=1983z82

But the bend radius is 7", which would mean the hose would take over a foot to do a 180° turn from the tank to the barrel.

Are there more flexible alternatives?

[Arpit2206]

I love the amount of capabilities of your robot. Do you mind sharing the CAD file?

[GeeTwo]

One question we do have is what sort of hose have other teams used?

We were thinking something like this: https://www.mcmaster.com/#1593n27/=1983z82

But the bend radius is 7", which would mean the hose would take over a foot to do a 180° turn from the tank to the barrel.

Are there more flexible alternatives?

Large hoses at high pressure are going to have large bend radii. Note also that these sort of hoses do not take twisting well.
We eventually took out the freedom of a rotating turret so we could plumb everything with galvanized pipe and fittings. We looked in to swivel fittings, but at this size, the cost got out of our air cannon budget, especially for dry (non-lubricated) air.

[jzajac]

I love the amount of capabilities of your robot. Do you mind sharing the CAD file?

Here’s the link to the GrabCAD file, for anyone else who is interested:
https://workbench.grabcad.com/workbench/projects/gcjWVMmXPFvpeR0ilGS9Gc4fpZKZ8N6KgMgaoYSntR2kTb#/space/gch5aMk6D0BebVv1iK8qcdLYD26S7qWyYwu9gHzDJI0BPn