Quick question(s)

Specter · Post by **Specter** » Wed Jun 13, 2007 11:38 pm

ok so i glued the valve in from the inside. i also put some glue around it on the outside, i put some primer on it before the glue just to be sure. I primed and glued it to the air chamber so in the morning i can try it out. i hope it works!

i also found this random can of orange spray paint that i asked my dad if i can use it to paint my cannon and he said it was ok. It actually fits the name well- Afterburner, fire, orange, get it?

I will also probably take more pictures of it tomorrow and maybe some with me holding it. i hope it turns out well.

Specter · Post by **Specter** » Thu Jun 14, 2007 3:13 am

SilentGuy wrote:Looks good.

You can probably use anything to lubricate the barrel...the sabot (like a tennis ball can or a Pringles can) should be loose enough to not need any lube though.

i don't think those will fit in a 2 inch barrel... i can always wad paper in it right?

and it wasn't a screw-in valve, as you can sort of see from the pic.

Specter · Post by **Specter** » Thu Jun 14, 2007 3:14 pm

sorry about triple post. I just air-tested my canon today, its so cool. The first 2 times, my bike pump wouldn't let me get past 80 psi for some reason. The 3rd time, i was able to get 115 psi, and shot a foam ball(stress ball?) out of it. Another problem i had, was that the 3rd time i connected the pump to the valve, the glue broke, so now the valve slips in and out, but it still holds air in the chamber due to i don't know what. I told my dad that ACE hardware has screw in valves, so if he can take me there i can get a better one. It is possible for me to get the current valve out, by pushing it through and pulling it out from the male adapter at the other end.

edit:
Ok so my dad took me to an auto parts store and i got a MUCH better schrader attachment. it has a rubber seal on the inside and the shaft is all stainless steel or something. It also has a metal cap instead of plastic. Its much better than the cut off bike tube one. It should perform much better. (pics maybe later)

Specter · Post by **Specter** » Fri Jun 15, 2007 12:40 am

wow... sorry about the quad post, but this topic needs its own post.
I just fired the cannon about 5 times with a water balloon now. It doesn't get real far because my bike pump only can get to 85 psi, then it won't (and I'm too lazy to add the apostrophe!) let you pump more, and goes down to 60 psi, so i have a feeling that it is regulated, (for bike tubes).
I was able to shoot the balloons ~100ft range (i think, i have no way to measure) as of now. When i can get it to 120psi I believe i can reach around 300 ft or more. Even though the water balloons are small for a 2" barrel, they can still be affective. The way i was able to get them to shoot, was i cut a small plastic cup so that it fit in the barrel, and the balloon fits in the cup. (like a bullet in a casing) Its pretty amazing for such a "small" canon. The 1-ft PC fills up quick, just hope that it can get to my wanted 120psi (it is rated to 280).

Silence · Post by **Silence** » Fri Jun 15, 2007 12:59 am

The range vs. pressure relationship isn't linear. In fact, it's probably closer to logarithmic or square root. Doubling the PSI is going to less than double the range.

Make sure you flip the ball valve open as quickly as possible.

I don't know why air is being leaked out. Maybe there's a problem with a seal somewhere. Put soapy water on all the joints, or just immerse the water gun in water, to see if anything bubbles.

And make sure your sabot slides easily but fits fairly tightly into the barrel. As it is, you have the potential for several hundred pounds of force pushing on the projectile - a little friction won't hurt. Better tight than loose.

C-A_99 · Post by **C-A_99** » Fri Jun 15, 2007 1:04 am

Well you're not supposed to go higher than 120 (the 260 PSI rating is for water, not air), and you shouldn't even need more than 80. 60 in fact, should perform fairly well. I think the problem is because you aren't opening the valve fast enough; build a torque arm like I said, it'll allow you to open it faster.

This is the torque arm me and dad built for my launcher:
http://img157.imageshack.us/img157/3194 ... eszfp6.jpg

However, something simpler like this should do: (pics from ben's supercannon)
http://www.sscentral.org/images/superca ... g_0191.jpg
http://www.sscentral.org/images/superca ... g_0253.jpg

Here are both my homemades, with both torque arms shown.
http://img187.imageshack.us/img187/6899 ... eszbm8.jpg

Of course, there are better valves you can use, but if you don't want to deal with them (i.e. getting something expensive and/or something you have to modify), you don't have to.

Specter · Post by **Specter** » Fri Jun 15, 2007 1:49 am

SilentGuy wrote:The range vs. pressure relationship isn't linear. In fact, it's probably closer to logarithmic or square root. Doubling the PSI is going to less than double the range.

Make sure you flip the ball valve open as quickly as possible.

I don't know why air is being leaked out. Maybe there's a problem with a seal somewhere. Put soapy water on all the joints, or just immerse the water gun in water, to see if anything bubbles.

And make sure your sabot slides easily but fits fairly tightly into the barrel. As it is, you have the potential for several hundred pounds of force pushing on the projectile - a little friction won't hurt. Better tight than loose.

I just hope to reach further than it is right now. And my valve opens pretty quick. (i have fast hands, considering i play drums, i need fast hands)
why did you mention air leaking out? i dont remember saying anything about it in recent posts. I did mention that i got a better schrader.
and the "sabot" i made is a small plastic cup cut down some to fit in the barrel. It works just fine. and i also figured out how to make bigger water balloons fit.

@CA-99:
as i also said to Silentguy, My valve opens pretty quick, because i can open it fast. i dont think i will need a torq arm. Also 60 psi on my cannon doesn't perform well. 85 isn't that great either. thats why i would like to get it to 120 to see what it can do.

to anyone:
I haven't finished painting my cannon orange. so i might not take more pics until its done. It's been a hectic week because i've been helping my brother make 20 DVD's, case labels, and the DVD labels for a slide show for my sister's 8th grade graduation which is tomorrow. So i most likely won't be doing much on Saturday, so i may take more pictures then.

Silence · Post by **Silence** » Fri Jun 15, 2007 1:56 pm

I mentioned air leaking because you mentioned the PSI dropping.

Also, I still doubt you can move your hand fast enough. The problem is opening the valve as much as possible before the projectile leaves the barrel. You have only a few milliseconds to do so. And opening the valve is very different from playing percussion - with ball valves, you have to exert a lot of force, and you have to move your hand a lot.

The PVC can take either air or water at that pressure. What it can't take is industrial water pump systems that have the water hammer effect. These pressures are perfectly safe (the PVC is probably safe to 500 PSI), at least unless you drop the launcher.

Anyway, good luck, and I hope you get more good results in war!

C-A_99 · Post by **C-A_99** » Fri Jun 15, 2007 3:13 pm

Yup, the valve opening has to be nearly instantaneous, the air flies out of that thing fast. As a drummer myself, I know regardless of that, you still need much more speed to open the valve. Considering how long it took to open the valve with my bare hand (before putting in the torque arm, it would take at least 500 milliseconds, which is way too long), it's definately a good idea to put the arm in, as it opened it up much faster. Even then, I've seen people who don't really know how to use the launcher operate the valve, opening it about as slowly as I would before putting in the arm. The performance was horridly compromised to say the least. Since you're using a 1ft PC, that might make it even worse since it takes less time for the air to escape.

As to PSI, I would choose not to go above 80 because it's not even necessary, and takes longer to charge up, lowering your rate of fire. (well I'll still admit I'm a little paranoid with the launchers, but I like to stay safe with it anyhow)