Major Disappointment

[Graybeard]

Thirteen folks signed up saying they'd support this forum if it was set up.

So far we've had a grand total of two I think post here and the Moderator who asked for it has not even bothered to stop by so far as I can tell.

That's really about what I expected but did hope some of those 13 who voted to get it might actually use it.

I'll give it to the end of April but if it still is dead it's GONE.

[Bornsouthern34]

I have a bunch of 2" steel tubing and would love to build a 6 to 8 foot trebuchet. However, before I start I would like some input on the arm. Would an 8 foot section of the 2" tubing handle the forces of the weight basket or would I need to reinforce the pivot point top and bottom?

[carronader]

I have to agree Bill,it is disappointing and end of April is fair.I hope it takes off though because there is a lot of scope in this type of stuff for generating interest and just not turning into a t.v. addicted vegetable.Maybe someone should have tried to sneak this stuff under your radar into exotics section.

[Victor3]

 I didn't see there was a vote, but I'd like to participate...





 Just a suggestion Graybeard (and tapwater), but if you were to modify the title, it may catch more guys' attention.

  "Air cannons, catapults, slingshots, etc." would be appealing to a wider audience than the current title, and those all fall under the same general 'non-powder, large projectile' category that I know a lot of people are interested in (The addition of slingshots might even gain some advertizers).

[briarpatch]

Victor3, That air cannon looks as though it is fired with a solenoid. What do you shoot in it.
I quess what I am asking. What is it? looks interesting.

[Graybeard]

OK title changed. It matters not to me what the title is so if it helps fine.

[Bornsouthern34]

Carronader,

What size projectile will your catapault launch and how far?

[jamaldog87]

i have been hunting with a slingshot for years now(got my first one at 14). This always happens with slingshot groups, were everone says it a good idea but no one joins in. just like this group: http://thecatapultkidslingshot.myfastforum.org/index.php

[tapwater]

   Ok everyone and GB, I'm truly sorry for not checking in. Being a farmboy, we're gearing up for planting, and I just haven't had time to play online much. I'm sure we can all learn from each other. Our compressed air punkin chunker and my golf ball cannon both use butterfly valves. Victor's gun uses what looks like a solenoid valve. I'd like to know more about that application.
    I hope we can keep interest in this forum going, however if it dies, well so be it. (I hope not)

[tapwater]

   Bornsouthern....For the length you're thinking about, 2" tube should be fine.....HOWEVER, what is the wall thickness of your tubing? I would think that 3/16" or heavier would be OK.

[Bornsouthern34]

Actually, I think my tubing is 1/8 wall thickness. Will it still hold?

Victor3, we tried a solenoid valve on a compressed air cannon once and could not get enough air through it. If I recall correctly, our solenoid was reduced internally as compared to the inlet and outlet sizes. We eventually gave up and put a 2" ball valve on it. With 125 psi on the air tank, it would shoot a potato pretty good. Have you had better luck with yours?

[Victor3]

Victor3, That air cannon looks as though it is fired with a solenoid. What do you shoot in it.
I quess what I am asking. What is it? looks interesting.

 The tank is a stainless fire extinguisher. Barrel is ~5' of 3" ID aluminum tube. The valve is a large diaphragm type. It originally used a solenoid, but I removed that and modified the valve so it could be used with a pilot exhaust valve. There's a safety valve set to open at 100psi so it can't be overfilled. 20oz plastic soda bottles (2 7/8") fit it well.

 When I can find the pics, I'll show a Co2 golf ball launcher I built 

[Victor3]

Victor3, we tried a solenoid valve on a compressed air cannon once and could not get enough air through it. If I recall correctly, our solenoid was reduced internally as compared to the inlet and outlet sizes. We eventually gave up and put a 2" ball valve on it. With 125 psi on the air tank, it would shoot a potato pretty good. Have you had better luck with yours?

 Bornsouthern,

 My valve is designed for water, but one can be used to rapidly dump an air charge if you modify it. Lots of guys use sprinkler valves for smaller cannons, and mine is just a big version of those.

 Problem with this type of valve (like you found) is that it's designed to somewhat slowly 'leak' water back into the sealed line as it's opening the diaphragm. It doesn't need to open quickly to function as designed. For air, you want it to open quickly, which it does if you ditch the solenoid valve, block the internal 'leak' orifice (which you don't need, since you're exhausing the air above the diaphragm into the atmosphere) and use some kind of external valve to trigger the main. I use an air gun like you find on the end of an air hose in most shops (it's not shown in my pic).

 That said, you can use some valves having a solenoid. Just have to make sure that it will open fast enough to dump your reservoir immediately.

[Victor3]

i have been hunting with a slingshot for years now(got my first one at 14). This always happens with slingshot groups, were everone says it a good idea but no one joins in. just like this group: http://thecatapultkidslingshot.myfastforum.org/index.php

 I suspect that one's got a bit less exposure and traffic than GBO