rcman50166 wrote:I have a full unviersity machine shop, CNC mill, lathe, drills, saws, torch, mig welder etc. The problem is just the fact that raw materials cost so much, Schedule 80 everything is expensive, but still cheaper than steel
It fully depends on where you shop. I should post a price list for the little cannon. I belive the entire bill for that cannon came to under $50 for a nice steel cannon that tosses shirts 200 feet. The tank is under $5 if you decide to buy one new and use the contents. It is safe at 100 PSI and still has the original safety relief valve. I think the relief valve opens at more than 300 PIS, but I haven't tested it.
My large cannon is also steel and uses a free tank. The pipe nipple is the most expensive component in the cannon. If I didn't spend so much on a wide selection of barrels for it, the basic cannon can be fully built for less than $100.
It's a free tank, a $35 custom cut and threaded nipple, plastic at $3.75/lb, 2 70 cent o rings, a goodwill fireplace poker, a golfball, a $6.00 garden kneeling foam pad, a few pieces of brazing rod and welding rod, welding gas, a few parts for the fill and gauge, and several cans of spray paint.
There is no reason for it to be expensive. I'm starting my 3 inch. I already have a free obsolete propane tank (7 gallon) with the old style POL valve they will no longer refill, another fireplace tool for the shaft, the HDPE, etc. I'm shopping for a 3 inch pipe nipple 24 inches long. This is my high expense item for this cannon.
A $400 dollar budget, access to all those tools, and a little resourcefulness, and your set. You should have more than enough left over for lunch for the team. Steel is much higher impact resistant and fatique resistant than PVC. I highly recommend it. As a bonus, my steel 2 inch cannon is about 1/3 the weight of my 2.5 inch PVC cannon. I'll plan on weighing them both later. One is bulky and awkward. The other is a pleasure to use.
I do fully agree that schedlule 80 PVC parts are very expensive. My Dragon Cannon has several PVC fittings that were over $30 each.
I took a good look at your GGDT. The little cannon above outperforms that cannon on 100 PSI. Using the same shirt weight, the larger barrel and smaller valve provides a higher launch speed.
I think if you figure out how to eliminate the huge dead space, things will work better. Lighter pistons open faster. Are you sure that dead space is really that big?
GGDT below shows a more powerful launch using about 10% of the air volume. If you want multi shots, work on effeciency and gas consumption per shot. I could launch 100 shirts with the same supply you use to launch 10. My actual chamber is smaller than shown. I used round numbers for size. I don't have the actual size at work.
I took the liberty of modifying your design and plugging the numbers into GGDT. This mod will use less than 1/5th the air per shot, add 50 FPS to the shirt and cut the KE in the piston down to 1/4 so the possibility of breakage is much less. I enlarged the barrel so the cross section on the shirt is much better for the air launch effeciency and better flight. Overall this reduced the cost. A faux chamber can be added from a form tube for cosmetics if desired.
@ spuddytyrant; The full size cannon used in the contest was able to tag the retired numbers above the 300 section of the Rose Garden Arena in Portland OR on just 35 PSI.
) will be 100 psi at most. The help I need is with the piston. I'm not sure what to use to cover a 2" bore and still be nice and light. For that I was thinking of using pine wood for the body of the piston. I also need help deciding the material to use for the seal. I was thinking of silicon caulk. Any ideas or comments? I have a budget of $400 for the entire gun.