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Thunderbess, Edit: Major Update!

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: chinnerz » Tue Sep 28, 2010 9:42 am

wow man!
The effort you invested really payed off, your rifle looks really exceptional now.
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Unread postAuthor: Lockednloaded » Mon Oct 04, 2010 10:06 pm

the homedepot ones are rated to 250, but it still seems unsafe to have that hooked up to unregged co2 without a pop-off for safety
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Unread postAuthor: Big-E » Tue Oct 05, 2010 1:29 pm

It doesn't run off CO2, it runs off compressed air. The CO2 cylinder is my airtank; I use a stirrup pump to fill the launcher to 200-250 psi, which the bottle can handle with ease. I had some paintball parts which fit the bill for my build already, so it was a no-brainer.

I could easily adapt it to run off co2, I just need to add a co2 reg on the tank to step the pressure down before I screw it in.

The current reg wasn't ever intended for use with unregged co2, which would be nearly four times the pressure I currently run.

You see, in the old build, pressure would drop with each shot, now, with a regulator, it keeps the shots at a consistent power level. In other words, the pressure will be the same for every shot until the bottle pressure drops below the regulator's set pressure.

Besides, it has a schrader valve on it; If I were running co2, I wouldn't need one of those :)

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Unread postAuthor: Lockednloaded » Tue Oct 05, 2010 4:53 pm

I see, I thought the schrader was for when you wanted to up the pressure a bit. I think the regulator may work with a needle valve and a pop off for safety, but for some people that may be pushing their safety limits.
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Unread postAuthor: Big-E » Wed Oct 06, 2010 10:55 am

Lockednloaded wrote:I see, I thought the schrader was for when you wanted to up the pressure a bit. I think the regulator may work with a needle valve and a pop off for safety, but for some people that may be pushing their safety limits.


understandable. I did build Thunderbess in such a way that if I wanted to run co2, I could with minimal changes. but for now, air does fine.

Incidentally, I can use the schraeder to top off the tank as well, but it is also used for filling the gun and additional cylinders. That's right, I can fill a tank, unscrew it from the receiver, spin on an empty tank, and then fill that too. That way, I have cylinders pre-pressurized, ready to go. When the cylinder is empty, I just swap it for a full one, meaning less pumping between shots. it works great! I just wish I had more cylinders!
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Unread postAuthor: Lockednloaded » Wed Oct 06, 2010 9:36 pm

How many shots are you getting with a 20oz pressurized to max pressure, whatever it is, and with the regulator set at 200 psi?
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Unread postAuthor: Big-E » Thu Oct 07, 2010 5:29 pm

At 200 psi, I get 3 full power shots, after which the pressure drops to around 180 PSI, then around 160, etc. I would usually take a moment to put about 30-50 pumps in the cylinder to bring the pressure back up. Doesn't sound like much, but it's good enough to check groupings at max power, so it works for me.

If I set the regulator to about 150, I get about 5 or 6 shots before the pressure drops. With the reg set to 50-60 psi, I get 10 shots easily, sometimes I get 12 shots, but I get 10 shots consistently. it all depends on whether I pre-pressurize the chamber or not, and what pressure I use (generally I fill to 200 or 220 psi)

I haven't tried it at all the power levels with the cylinder pumped to 250 PSI yet; It may yield a few extra shots turned all the way up. That's the maximum I'm willing to put in for now, but my pump can go higher than that. So far, the regulator seems to handle it okay, I may try 300 PSI, since that's the maximum pressure most compressors go to for the reg I'm using.

Most of the time, I'm either plinking at a low power setting, or it's around the 120-150 PSI mark if I'm trying to destroy things like plywood, tin, etc.

I'll try to take a video or something tomorrow, so long as the weather is nice.
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Unread postAuthor: Big-E » Wed Oct 13, 2010 2:51 pm

Here's that frequently requested damage video people have been asking for. Enjoy! As always feedback is welcome.

[youtube]http://www.youtube.com/watch?v=0N9ogq5-ugE[/youtube]

:D
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Unread postAuthor: jackssmirkingrevenge » Wed Oct 13, 2010 7:20 pm

Nice choice of music :)

You should be going through that lunchbox like it was made of warm butter, shame about the sub 300 psi pressures... but good accuracy at 50 feet for a smoothbore and homemade rounds.
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Unread postAuthor: Big-E » Thu Oct 14, 2010 10:32 am

Actually, it was going through easily enough, part of the problem was that the lunchbox had the hinged side towards the back for most of the shots, The first shot almost ripped the hinged side off entirely. Another factor was my backstop, as the lunchbox was usually placed directly against it, so I have a feeling that hindered full penetration.
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In that last shot on the video, you can see where it just started to punch through the backside, I also wised up and put the hinged side in the front for that last shot, so it wouldn't just pop open when I shot it. Next time, I'll be sure to watch for little things like that.
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Just another tidbit of info: The last shot was actually about 190-195 PSI, as my bottle's pressure had dropped. I filled it to 220 PSI for the shoot, all those shots were on a single fill. I also took two shots at a can, but cut it out of the video because I completely missed the can both times and was just punching holes in the plywood behind it.

I think because I made the barrel longer in the latest revision, accuracy improved but power dropped a bit; the shots seem quieter than they were before the changes. I may have to swap in a longer firing chamber to compensate, but honestly, my property isn't all that large, and I don't need to be hitting any of my neighbor's property by accident, so at this point, it's still up in the air. I could always see if I could get a different regulator that would let me up the pressure a bit, but then I'd need to add another cylinder for that extra air.

I'm limited by my pump too. I've further reduced dead space at the bottom of the piston stroke, so it's performing much better, but I've encountered a flaw: when I pass the 300 PSI mark, the o-ring partially pops out of it's groove in the piston, so I can't build any more pressure on the downstroke due to a bad seal. I can re-seat the o-ring easily enough, but it doesn't want me to get very far past that 300 psi mark. so it looks as though that's going to be the maximum amount of pressure I can run for a while, until I either get a fridge compressor, or make a new piston for my pump that fits a bit tighter.

This is why my projects are always a work in progress. :)

Anyways, in a nutshell, my hot glue/bolt combo slugs seems to be the most stable and accurate. The pellets are good too, but use lighter bolts, which seems to effect their accuracy a bit. I plan on getting some .54 caliber Lead balls to see how they work, I have a feeling it'll probably be an optimal choice.
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Last edited by Big-E on Thu Oct 14, 2010 11:15 am, edited 2 times in total.
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Unread postAuthor: Technician1002 » Thu Oct 14, 2010 10:43 am

I am a fan of not leaving space for the o ring to leave the groove. Good luck on your new piston. I am sure you will improve.
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Unread postAuthor: chinnerz » Sat Oct 16, 2010 2:51 am

So its fairly accurate is it?

That is some nice work mate, you have made something which you should be really proud of; looks good, its powerful, and its fairly accurate. good job all round.

i actually really like the look of this rifle, are you going to do any more modifications in the near future?
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Unread postAuthor: Big-E » Sat Oct 16, 2010 10:12 am

chinnerz wrote:
i actually really like the look of this rifle, are you going to do any more modifications in the near future?


As I said earlier, It's a project that will probably continue to be fine tuned. I am considering a bigger chamber to bump the power up a little since I swapped in a longer barrel. I have some other ideas as well. Time will tell what I actually do in this regard.

I can even tune the pellets, by tightening or loosening the bolt, you can make the seal tighter or looser in the barrel, and adjust the forward weight of the pellet.

When I have reached the limit of what I can achieve with thunderbess, I'll probably start on a new launcher. For the moment, however, I'm quite pleased with it.
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Unread postAuthor: chinnerz » Sat Oct 16, 2010 7:17 pm

sure, OK, that makes sense.

Big-E wrote:For the moment, however, I'm quite pleased with it.


And you should be :)
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Unread postAuthor: Selador » Tue Nov 09, 2010 4:57 pm

Is that a 1/2" deep socket, for the bolt handle ?
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