SpudFiles

The pipe nipples are already welded in place.
I did a lot of research on large PVC pipe fittings and found no pressure rated wyes (true wyes or manifolds) of the desired size, unfortunately.

Also, according to Toro, the manufacturer of the two main valves, using the valves as elbows actually minimizes losses due to friction.

Here's the product literature if anyone is interested:
http://www.toro.com/irrigation/com/down ... 0sheet.pdf

And regarding the connections, I planned on making the (slip socket) connection to the tee last.

It all worked out on paper, but we all know how that goes. Something will get screwed up, almost guaranteed...

I got the 3" nipple welded in place. Not too shabby. Despite what it may look like, it is actually in there almost perfectly perpendicular.

Looks like you have lined them out pretty well.

Are you leading the pipes all the way around the tank?
(not the most efficient design)

With 1 tank, 2 valves, and a tee, the shortest path would include 2 elbows (including the valves themselves). The tee is going to be parallel to the two ports, just about 6" above the tank. It would be a lot more efficient if I had a pressure rated wye or manifold, but they are nonexistent.

It's great to see a large project like this nearing completion. As Fnord said, not many project like this are as well documented.

If you ever plan on redoing this (I doubt you will), maybe you could try an air-driven butterfly valve? Correct me if I'm wrong:

A 4" butterfly valve and a small pneumatic cylinder seems to me like it would be the simplest solution needing the least amount of turns from chamber to barrel (and the least dead space). The fact that you have a 20' barrel balances the speed of a butterfly valve (making it air actuated would be even better)

This is all speculation, as I have no experience with the physics of this stuff. If I'm correct, while it may not help you, future readers of this thread my have a simpler option available to them if they're doing something similar.

It might be the simplest and efficient, but probably not as cost effective.

My understanding is that with larger and heavier projectiles, the speed at which the air dumps is not as important as it is with smaller projectiles (inertia of projectile, time spent in the barrel in relation to the opening of the valve). So everything kinda balances out.

I chose the valves that I am using for this project because of their relatively low cost and ease of use. Had i found any valve with full 4" porting at a similar price I would have gone that route.

Jimmy K wrote:My understanding is that with larger and heavier projectiles, the speed at which the air dumps is not as important as it is with smaller projectiles (inertia of projectile, time spent in the barrel in relation to the opening of the valve). So everything kinda balances out.

Indeed, heavier projectiles almost always result in higher muzzle energy for a given launcher.

This is all speculation

There's a definite seperation between members who do the math, and those who say, "Well it looks like it should work." I'm proud to say I'm smack in the middle.


The chamber looks good, Jimmy. I feel as though the next time you take any more pictures, you should throw in some sort of reference-able size comparison object. I'm reminded of DHalls picture of a person laying inside Vera's barrel, though obviously not to such an extreme.

Jimmy K wrote:I chose the valves that I am using for this project because of their relatively low cost and ease of use. Had i found any valve with full 4" porting at a similar price I would have gone that route.

How much did the two valves cost you? The link to the eBay auction no longer works.

I bought both of them, brand new, for about $80. Not bad considering Toro's retail price is about $350 per valve.

The 3 inch nipple is a good reference for me.

The chamber looks good, Jimmy. I feel as though the next time you take any more pictures, you should throw in some sort of reference-able size comparison object.

The 3 inch nipple is a good reference for me.

I was thinking more along the lines of a soda/beer can or bottle. I don't normally work with large pipe like that. Everyone can relate to soda/beer cans however.

A soda can fits a thin wall PVC 2.5 inch barrel


For reference his 3 inch pipe is the same size as the black barrel with the red an blue paint and white reflector tape. The 3 sizes of black ABS in the photo are 2 inch, 3 inch, and 4 inch. His barrel is 4 inch.



I found a good reference on a prior page.. The valve that fits the nipple is this one. It's big stuff.. He included a pencil and blowgun for size comparisons.

Here is the tank with the valves.

That is not the final position of the valves - they are on there simply for the ongoing pressure tests.

And I included a root beer can for comparison this time.

And I included a root beer can for comparison this time.

It definitely puts things in perspective.

Have you thought of putting some sort of wedge shape in the center of your Tee to help direct the airflow towards the barrwel and minimize turbulence?