SpudFiles

VH_man wrote:I see we disagree on how piston bounce exists... Leaving me to wonder..... Whos right? to the testing board!

Like you said it is a complex process with lots of variables involved. In addition to the increasing pressure from the rapidly moving piston you also have to consider the rapidly falling chamber pressure (which is what you were describing I believe). In simplest terms if pilot pressure is greater than chamber pressure the piston will want to close again, so you want to avoid that by having a sufficient exhaust valve or by sizing your valve such that you get as much air out of the pilot as you can before the piston starts moving. The latter method is usually what I prefer, but I didn't have the luxury of selecting the dimensions on this valve.

starman wrote:...With that built-in seat, it's almost like it was designed for this application....

I would have consided a little larger diameter chamber just to keep the length down some, but I know you were just using a chamber you had a around.

Yep just slap in a piston and go. I also ran across some check valves that are built in wyes and use pistons, so all you would have to do is modify the piston to turn it into a piston valve, but they aren't as common as strainers so I never actually got one.

Here is an example of the check valves http://www.haywardflowcontrol.com/pages/pro_cv_05.html There are clear ones out there too.

The chamber was partially because it was something I already had, but also because I didn't want it to be too front heavy. Letting the chamber extend back a ways helps balance it out some.

jackssmirkingrevenge wrote:Nicely done as always it would be great to have it filmed with a reasonably high speed camera to assess piston behaviour with different pilot valves vis a vis performance.

This design is outstanding. I now consider this to be among the best cannons I've seen. Cleanliness, innovation, this thing has it all. Nice work, Clide.

clide wrote:

jackssmirkingrevenge wrote:Nicely done as always it would be great to have it filmed with a reasonably high speed camera to assess piston behaviour with different pilot valves vis a vis performance.

Does that mean... "coming soon"?

May I recommend smoke trails or other particles flyin around being recorded on highspeed?
It would be very interesting to see the flow of the air.
We could learn alot from it, as the opening of a piston valve is now just a theoretical idea of what is going on. But how things really work (in slow-mo) would be nice to see.

There may be a few effects going on we didnt think about yet. (for example: the last shot in the video shows that the piston bounces/gets sucked/pushed back to almost seated position after firing. WHY? and HOW?)

Heck, it could lead to a new type of valves which are even better or optimize piston valves as they are.

Drool.....
Nothing else to say but beautiful work Clide. You are an artist with your cannons.

Nice very nice. Although I think piston valve bounce is caused by yours and VH_mans theories the venturi effect in VH_mans theorie I think couldn't work without the pressure behind the piston (chamber pressure holds piston back) and clides couldn't work because there would need to be some other force to pull the piston towards the barrel because of the higher force inside the chamber(venturi effect). But maybe it has somthing to do with having a very short piston travel which I don't think would be your problem clide

I can't believe I missed this post. But I guess I know why now, seeing as it was posted the same day I was moving...

I am always amazed at your ability to turn random things we never looked at before into a cannon. As far as innovation goes, I would put all of my money into betting that you are the #1 spudder in the department.

Every time I saw those strainers, the only thing I could think of was iron deposits, toilet paper/feces, and other unpleasant things of that nature. I never dreamed of a valve.

Also, I think you downplayed the whole exhaust setup, with the chamber-sealing pilot built into the cap. I had to look twice for it. Something on that level of craftsmanship would frustrate me no end.


Once again, great cannon. Monumental cannon. Usually, people say "I can't wait to try that!", but I don't think I am. It would go completely against the spirit of invention and all the virtues I just pointed out, so all I can say is good job.

I hope to see more of you. Get working on that web site!

nice this cannon inspired me to start making my own piston cannon

Thanks guys.

This is the same one I've had up for a while, but I figured I should add this link into the thread for completeness sake. Here is the flipbook of the clear valve firing recorded with my high speed camera. Not the best view. I'll try to get some better ones eventually.
http://gbcannon.com/projects/flipbooks/clearvalve.html

Mark, yeah I know I need to get on that. I'm not sure why am having such a hard time getting myself motivated to work on my website. I probably spent as much time building that flipbook measurement tool just for kicks as I spent on content for the rest of the site.

Ahh, it's okay. Take a look at my website for the epitome of incompleteness (although I do have several pages written that I haven't uploaded yet).

Incomplete website is very incomplete.


Whats with the picture of the buildings?

Clide, you always did have the most innovative cannons. Good work.