2.5 inch QDV build

[Moonbogg]

Those are some SICK ports tech. My goodness, you're a MONSTER! What are you trying to do!?

::runs away in terror::

[Technician1002]

Those are some SICK ports tech. My goodness, you're a MONSTER! What are you trying to do!?

::runs away in terror::

From the original post.

This project is to up the power of my existing cannons. The t shirt cannon is built into a lightweight tank which is easily dented.

I want to safely go to 200 PSI in a larger valve cannon. There are a couple of experiments in line for this.

1 Test new ideas on bumpers that don't collapse like my current swim noodle and garden knee mats.

2 Test a large valve and a transition cone to up the COF on a golf ball barrel. Attempting Supersonic on 200 PSI with golfballs and marshmallows.

3 Test if a large valve on a large bore barrel with a sabot can launch golf balls faster.

4 Using the above test results, build the 4 inch launcher in a light gas gun configuration with a secondary piston, venturi into a smaller barrel and launch golfballs supersonic with just air using compression heating for the light gas.

5 Find out how hard it is to pull a larger piston under higher pressure. (o rings tighten under pressure) The larger cannon may need to have a pilot valve to trip it under pressure.

6 Launch big stuff.

7 Watch friends land on their butt.

[Heimo]

7 Watch friends land on their butt.

something well worth shooting for

[Technician1002]

I finaly got some pics resized to post. Enjoy

[tghhs]

Woah, can't wait to see the finished product. I love it tech, keep up the good work

[dewey-1]

Tech;
How do you plan to put the smoke back into those Radial Leaded Electrolytic Capacitors?
I have been trying to figure that out for over 45 years!

If you get a chance let me know piston/o-ring dimensions.
What is tank seam weld height and width.

This looks like a very promising high performance valve!

Here is the ported piston sleeve.

[Moonbogg]

I don't know if it can even be called a valve. Its like, the barrel is closed and then suddenly its just open as hell. It look like this thing is going to shoot really hard.

[dewey-1]

@Tech;

Here is preliminary tank and piston sleeve 3D model.

Need weld height and width on tank seam.
Otherwise I think the tank is complete.

Left side of tank has the ported sleeve.
Will need sleeve location.

Ready to do the piston next.

[Technician1002]

@Tech;

Here is preliminary tank and piston sleeve 3D model.

Need weld height and width on tank seam.
Otherwise I think the tank is complete.

Left side of tank has the ported sleeve.
Will need sleeve location.

Ready to do the piston next.

Sweet drawing. The weld bead on the waist of the tank is 0.060 inch tall and 0.305 wide.

The piston is now 2.33 inches long. Diameter is 2.46 in diameter. The piston is now larger around than it is long. O ring grooves are 0.230 inches wide. They are 0.224 inches deep. The piston body between the grooves is 1.45 inches long. The rear shoulder is 0.255 thick. The front one is 0.161. The front recess is 0.98 inches in diameter and 1.294 inches deep. The rod hole in the back is 0.365 in diameter.

[dewey-1]

@Tech; Thanks for dimensions.

Which O-ring do plan on using? A 330 or 331 number?

I see a potential air leak because the port is 1.5" and piston is 1.45".
Maybe I am just looking at it wrong from a pressurized standpoint.

I can show drawing of concerned area if you would like.

[Technician1002]

@Tech; Thanks for dimensions.

Which O-ring do plan on using? A 330 or 331 number?

I see a potential air leak because the port is 1.5" and piston is 1.45".
Maybe I am just looking at it wrong from a pressurized standpoint.

I can show drawing of concerned area if you would like.

I have no idea on the o ring part number. It is the 2.5 inch ring in the grab bins at my local hardware store. Is there a dimension I can measure to identify which this is?

The o rings do show some inside the centre area, but the edge of them do ride on metal and when the cannon is under pressure the rings do move away from the centre of the piston. It this leakage prevents filling, I may have to make another piston with a tiny bit more length. This was accidental as the slippery piston started creeping out of the lathe chuck as I was cutting grooves. This placed the grooves slightly closer together than I intended. I think it will work. In the worst case, I'll just make another piston.

UHMW is slippery stuff and difficult to secure in a lathe. If I turn another piston, I'm going to bolt it to a piece of round stock so it can't creep in the chuck.

[dewey-1]

Tech;

Go on McMaster Carr and you can see the numbering system.
Some hadware stores reference those numbers.

I get dimensions from their specs.

[Just1ChanceFree]

Tech, I would assume that the O-ring is 2.5" OD, so really all we need to figure out the part number is the thickness. For my 2" piston design I actually bought 3 different to play with different pistons: -032, -133, and -224-- .07, .103, and .139 respectively. I don't really have any tools per say to work with, certainly not a lathe, so I'm doing what I can with what I can find. I cast my own piston out of oven-melted HDPE using hair ties for the o-ring slits today and it turned out decently. I also found that 1.25in pvc end caps fit wonderfully inside of 2" pipe, and I was able to make sufficient runners on them for the -032 using a hacksaw and hand saw. Now if only the silly things will seal sufficiently.

Also, I found http://www.superiorseals.com to be a great place to buy o-rings for cheap in small quantities. The 5$ min. order got me enough to have a good few failed attempts...

[Technician1002]

I will have to measure my rings. I had a crazy week and didn't make any progress this week on the launcher. I'll get measurements later of the thickness.

[Technician1002]

It's time for this weeks update. First is some pictures on the distractions that kept anything getting done last weekend on the launcher. My order for some lighting came in so it needed installed. The band was having trouble with the stage lighting spilling on the video screen above the drummer. We ordered some spots that can be trimmed to keep the light off the screen and some dimmer packs to run them and some other lighting. Since I got my computer fixed, I have a photo of the pit BBQ to make you hungry.

Onto this weeks update, I got the valve welded in. It took me a little time because I am so out of practice welding (haven't done any in a decade). I selected a tip size to do the job and test welded a couple of the tank scraps together. It went well with good penetration of both base metals and a good fill. My hands were not too steady in the windy chilly weather so I don't have the pretty bead the professionals do.

I proceeded to start on the tank and ran into a problem. The tip was a size too small for the thicker pipe and I wasn't getting penetration on the pipe (would have leaked badly) so I went to get the next size larger. My second hand torch does not have that size, so I went up two sizes and proceeded to weld. It worked well but the puddle was too large and I melted through the tank twice welding it. I was able to close the holes fine as I filled in the valley (one of the reasons for it) The larger flame and puddle size did tend to remove the threads near the weld. An arc weld instead of the torch would have been a better choice. Anyway, it is together. I need to remove the scale and re polish the valve (why I wasn't worried about small pits, the scale will bring the exposed metal down to even it out. After the final polish, it should be in good shape.

Lessons learned, Too small of a tip is bad, so is too large of a tip. When flame welding near threads, the thin edges quickly melt off. I would have been better off to braze this and not melt the threads or burn holes in the tank.

On a safety note, the tank did release enough oil vapors to catch fire. I did have a flame dancing on the pipe while I was welding. The exhaust from the torch going in the tank purged the oxygen from the tank as I started so I never did get an explosion. An arc weld would have most likely have gone boom if a shield gas was not used. Don't arc weld a used propane tank without using something to prevent the build up of an explosive mixture. Heating the metal does release combustible fumes.