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Dchap-1

Dirt Cheap Homemade Air Powered

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#1 CaptainSlug

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Posted 06 June 2007 - 09:15 PM

I had this idea late last night after testing the push-button valves I got from Mcmaster. I was hoping to use them to make a homemade but their flow rate was way too low to be useful. I also had the dumb luck of finding at a dollar store near me the exact same pump 3DBBQ has been using all this time to make his homemades. They're $1 because they don't include a check valve. If you already have a spare pump you can obviously hook that one up to this design instead.
3DBBQ based all of his designs around a PVC check valve, which basically doubles the total cost of the gun. So instead of doing that I shopped around for the cheapest check valve possible and found a way to integrate it into the gun.
I'm VERY happy with this because not only does it work, but it went from concept to working gun in less than 24 hours.
Posted Image
This gun is primarily configured around the same size of parts that all of Carbon's SNAP series are using so that if you bought the supplies you need to make those then you already have the right sizes of pipe and fittings.

Pros
+ Cheap ($10-$15 total)
+ Adaptable
+ Push-button Trigger
+ Lightweight
+ Medium size
+ Very Durable
+ Can be disassembled for maintenance

Cons
- If the spring isn't tensioned enough the valve will leak during the first pump cycle. If the dart is already loaded this will push it out of the barrel. This can be fixed by adding a 1-1/4" washer to the spacer and screw added to the floor of the Tee.

McMaster part list
8745K41 - Gray PVC (Type I) Rod 1/4" Diameter = $0.48 per foot
8745K43 - Gray PVC (Type I) Rod 1/2" Diameter = $0.67 per foot

7757K43 - Polypropylene Spring-Loaded Ball Check Valve Buna-N Seat, 1/4" Barb X 1/4" Barb = $3.23
4880K21 - Std-Wall (Schedule 40) White PVC Pipe Fitting 1/2" Pipe Size, 90 Deg Elbow = $0.31
4880K44 - Std-Wall (Schedule 40) White PVC Pipe Fitting 1-1/4" Pipe Size, Tee = $1.28

90131A102 - 1/4" Screw Size, 3/4" OD, 1/8" Thick Large-OD Extra-Thick Reinforced Rubber Washer = $2.88 for 10
91090A101 - Zinc-Plated Steel Large-OD Flat Washer 8 Screw Size, 3/16" ID, 3/4" OD, .042"-.052" Thk = $2.80 for 100

4880K52 - Std-Wall (Schedule 40) White PVC Pipe Fitting 3/4" Pipe Size, Cap = $0.32
4880K54 - Std-Wall (Schedule 40) White PVC Pipe Fitting 1-1/4" Pipe Size, Cap = $0.72
4880K171 - Std-Wall (Schedule 40) White PVC Pipe Fitting 1-1/4" X1/2", Hex Bushing, Pipe End Male X Socket Fem = $0.99

+ #6-32 or #8-32 screws in 1" and 2" lengths
+ 1/4" length spacers for the size of screw chosen
+ Hex nuts for the size of screws chosen
+ 1-1/4" SCH40 Pipe
+ 1/2" SCH80 CPVC
+ Maverick/Scout/LS Front Gun Spring (or equivalent)

Construction
The valve consists of a few very easy to make and acquire parts. I will need to update this list soon because the washer I'm using right now is simply too large and offers too much surface area for the tank to push on. With that aside here's basically what you have to do to make one.
Posted Image
1/2" rod w/ 1/4" hole drill in one end -> 1/2" Pipe Elbow with 1/4" hole drilled in it -> 3" length 1/4" OD rod ->
1/2" rod with 1/4" hole drilled in one end and a 7/64" hole in the other -> 1/2" SCH40 Pipe -> 1-1/4" to 1/2" adapter bushing -> Rubber washer (trimmed to 1-1/8" outer diameter) -> #6-32 Hex nut -> Steel Washer -> 1" worth of spacers -> 1-1/2" length #6-32 screw -> Maverick plunger spring -> 1-1/4" Pipe Tee
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Valve assembled. Right image shows rubber washer trimmed to the correct size. Any size larger than a 3/4" outer diameter will work fine. Anything larger than 1" in outer diameter will need to be trimmed so that it's outer diameter is slightly smaller than the 1-1/4" OD steel washer.
Posted Image
Drill a 5/32" hole in the floor of the Tee and use a spacer, #6-32 screw and hex nut to fill it. This nub will keep the maverick plunger spring from sliding away when the trigger valve is pressed.
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+ Use and X-acto knife to trim the mold seam excess away from the underside of the bushing adapter (this ensures a good seal with the rubber washer)
+ Valve inserted into Tee with spring.
Posted Image
Now simply glue a short length of 1-1/4" pipe and a 1-1/4" Pipe Cap onto one end of the Tee.
Posted Image
Any check valve will do. You simply need to mount it solidly inbetween the cheap pump and the blast chamber (air tank). This is one I had on hand and the cheapest one available ($3.23). It doesn't seem to like PVC cement fumes though.
Cut the barbs off of the check valve and drill a 9/64" hole in the center of the 3/4" Pipe Cap. Insert the check valve into the hole you drilled into the pipe cap while making sure that the arrow molded onto the body of the check valve WILL BE POINTING AWAY FROM THE PUMP. Glue the check valve into the center using copious amounts of hot glue. I would recommend putting this in the freezer for a minute or two to cool the hot glue quickly.
Posted Image
Cut a 9" length of 1-1/4" PVC pipe and glue the $1 "BALLPUMP" into it.
Posted Image
After cutting or sanding the key off the side of the 3/4" pipe cap, glue the 3/4" Pipe Cap + Check valve into the opposite end of the 1-1/4" pipe + Pump.
+ Glue the new pump assembly into the Tee
+ Install the valve and spring back into the Tee
+ Either drill and tap two holes in the Tee and valve body (don't drill too far) or simply glue it in place. Using screws will allow you to service the valve later. If you do use screws to hold the valve in place you will need either epoxy sealant or teflon tap to seal them when they're installed.
Posted Image
And you're finished! Wait an hour or two for the PVC cement to dry completely. Your first dozen or so shots may be finicky. The more you use the gun the more the rubber washer will get deformed around the steel washer. This improving the seal between it and the bushing, and thusly will improve the reliability of the gun. If the valve is leaky then you need to take the valve back apart and make sure that the washers are centered properly.


Ranges
--------------
2 pumps = 30-50 feet
3 pumps = 70-90 feet
4 pumps = 90-120 feet

The total build cost for this gun is around $14, but since I had almost everything on-hand I only spent about $4. If you build just one you will have enough leftover materials that the next gun you make will only cost $5

Edited by CaptainSlug, 07 June 2007 - 10:19 PM.

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#2 Forsaken angel24

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Posted 06 June 2007 - 09:26 PM

Captain Slug, you have done it again.
Good work mate! I think this will be my first homemade.
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#3 CaptainSlug

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Posted 06 June 2007 - 09:33 PM

It's VERY easy to make and requires almost no tools. I did all of the machining work in a matter of 15 minutes and the rest of the work took about 30 minutes of glueing, assembling, and adjusting.
The rubber washer I'm using now has too large of a surface area and makes the trigger pull needed rather high. I need to go to the hardware store and get some 3/4" outer diameter ones to try instead. I chose adapter bushings specifically because they have multiple options for interfacing with a wide variety of rubber washer sizes. Anything from 5/8" to 1-1/4" will work.

My first thought was to use a 5/8" diameter rubber ball, which would also work but isn't as easy to assemble nor as cheap or easy to obtain.
If you were to make two of these valve you have the option of building a much larger air reservoir so you can get multiple shots from a single pumping cycle.

Edited by CaptainSlug, 06 June 2007 - 09:46 PM.

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#4 l337n3rf3r

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Posted 06 June 2007 - 09:43 PM

The SNAP is to springs, like the Dchap is to air powered.


~l337
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#5 Z-man12

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Posted 06 June 2007 - 10:17 PM

Now that is ingenous (sp?) I am going to have to give this thing a whirl later. CS you really need to be dubbed "the king of air".With a little teeking you could make this thing into just about any shape you wanted. <_< I like what I may be able to cram this thing into.

*goes to think about it some more.*
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#6 Carbon

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Posted 06 June 2007 - 10:20 PM

Beautifully done. I've been puzzling out a valve using a reducing bushing, but was stuck at how to properly trigger the thing. The elbow leading away to the barrel is a wonderfully simple solution.

I was wondering...considering the size of an AT2K tank and its relative ranges (90 feet with three pumps from a tiny pump) couldn't you use an elbow for your tank, rather than a tee? I could see 100' ranges with one or two pumps.
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#7 CaptainSlug

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Posted 06 June 2007 - 10:31 PM

I should be getting 100+ ranges with 3 or 4 pumps now since the pump outputs a decent amount of volume and the tank has the same internal volume as a Titan. I'll find out for sure tomorrow.
I could have tried to do it with an elbow. Keeping the spring from sliding away might have proved to be more difficult with one of those though. Maybe I should have just plugged off the other end of the Tee with a 3/4" pipe cap.
I wanted a cap because it's a very easy place to put a fitting should I want to hook this up to an external tank.

The main goal of this design was to test the valve in a complete and very cheap gun. A multitude of different configurations are possible and I look forward to seeing them all. All you need to do to move the valve from one gun to another is add the drilled and threaded holes in the sides instead of gluing it in place.

In the first post I did forget to mention that you DO NOT need to glue the 1/2" elbow in place. It has to be firmly seated, but you can loosen and swivel it if desired later.
Posted Image
Slightly better weight balance. Makes it look like a submarine though.

Edited by CaptainSlug, 07 June 2007 - 04:51 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#8 Prometheus

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Posted 06 June 2007 - 11:55 PM

Excellent work. Just a couple of questions though:
1) Did you bother with a seal around the extruding rod of the elbow?
2) How does the pump have a return of air if there is only one check valve?
3) Would it be possible to configure this as a pull valve (like Air Techs), by having the rod extend down through the elbow, and allowing you to pull it open?
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#9 CaptainSlug

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Posted 07 June 2007 - 12:01 AM

Excellent work. Just a couple of questions though:
1) Did you bother with a seal around the extruding rod of the elbow?
2) How does the pump have a return of air if there is only one check valve?
3) Would it be possible to configure this as a pull valve (like Air Techs), by having the rod extend down through the elbow, and allowing you to pull it open?

1. Nope. The fit is pretty tight since the hole is drilled to the same size as the rod. And the elbow doesn't really stay pressurized long enough for leakage to be an issue. If I wanted to be more of a stickler about sealing that part a rubber grommet could be used, or even a neck with an o-ring could be added. But both would have added to the overall cost so I didn't bother.
2. The plunger head on the pump has a check valve molded into it in the same way that stock Nerf pumps do. All it lacks is a check valve on its output. So you simply chop the end of the pump off to get rid of the dead space.
3. Sure, you would just have to have an o-ring sealing the outer surface of the rod before the point on the Tee where it would protrude out. The Maverick spring has a large enough inner diameter for this to be achieved with a 1/4" rod, but a 1/8" aluminum rod might make for an easier construction.
Doing this could allow you to turn this valve design into a tradition trigger pull instead of a push-button that you have to press with your thumb. I'll see if I can work up a CAD model and part list for it later. It would make the most sense to design this around a straight coupler rather than a Tee.

Edited by CaptainSlug, 07 June 2007 - 12:13 AM.

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#10 Pineapple

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Posted 07 June 2007 - 02:10 AM

We're having a resurgence of ingenuity in the Homemade department.

That's great, Sluggy. I'm getting some ideas about integrating that thing into a pump gun. Wowsers.


-Piney-
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<!--quoteo(post=209846:date=Feb 5 2009, 06:27 PM:name=boom)--><div class='quotetop'>QUOTE(boom @ Feb 5 2009, 06:27 PM) View Post</div><div class='quotemain'><!--quotec-->
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#11 CaptainSlug

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Posted 07 June 2007 - 03:10 AM

Prometheus has inspired DCHAP-2, which I will have a schematic of in a new thread in a day or two. It will have the options of being powered by any scalped stock Nerf pump, or a $1 "ballpump". It will also have a normal trigger instead of a thumb push-button.

I have also figured out which O-Ring I can use for the valve instead of having to use a rubber washer. I'm going to go to Grainger tomorrow to buy a bag of 50 so I can see if they will work. If they do then I'll have solved the hard trigger pull problem.

Edited by CaptainSlug, 07 June 2007 - 03:10 AM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#12 zaphodB

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Posted 07 June 2007 - 11:12 AM

This is perfect. I have a design for an impact trigger grenade, but i havent been able to design a cheap airgun. this is a perfect base for the launcher. As soon as i get the grenade working I'll let you know how it works, but it looks promising.
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#13 Prometheus

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Posted 07 June 2007 - 11:22 AM

Wow, I inspired one of the legends. Well, moving on, here is my design, but the measurements for length are still a little fuzzy. I was aiming for a more compact valve, but it can be longer (I want a small diameter valve so it will fit inside 1 1/4" PVC). I am still looking into whether or not I can use 1/2" PVC and fittings for this, but it is pretty self explanatory, as long as you use a base measure for your PVC.
Posted Image
To simplify, the left is a push-design, the right pull.

Grey: is the PVC (let's say 1/2") The black is springs, and endcaps (proper size, so in this case 1/2"
Red: PVC Coupler
Gold/Tan/Brownish: 1/8" rod, used to move plunger head.
Green: Plastic barbed fittings, epoxied into hold drilled into PVC or encap. Must be cut flush with inside of piece epoxied to.
Yellow: Smaller piece of PVC/CPVC glued into fitting, so than plunger head does not move to far. Also various lengths will help to set length of trigger pull.
Purple:Small rubber washer, or O-ring assembly (still working on design for it).
Blue: Air flow. These 2 air for push or pull-type valves, like the dchap-1 and -2, which inspired these designs.


So, I'm still looking for flaws. Not meaning to hijack your thread CS, but it seemed fitting to put this here. I'll move if ya like. Any questions, comments, and feedback are welcome.

Edited by Prometheus, 07 June 2007 - 11:32 AM.

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#14 CaptainSlug

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Posted 07 June 2007 - 02:17 PM

I fixed the trigger pull strength issue. It was a "duh" moment because it turns out I didn't need to buy another size of washer. All you have to do is trim it down to a diameter that's slightly smaller than the 1-1/4" steel washer.
Posted Image
Part list will be up later today.
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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#15 Jtcm

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Posted 07 June 2007 - 02:31 PM

Very creative design. After reading through I noticed zaphodB siad that this would work for his gernade laucher but that got me thinking couldn't this be the gernade? let me try to explain. if you removed the pump and just had a "refill" valve and if you put weight on the push trigger so it would land on it if thrown and then replaced the single large barrel with say four or five small vertical barrels? I dont know if it would work but that just what i thought.
Posted Image
Red-Trigger
Lite Blue- Tubing to the barrel(s)
Blue- Barrel(s)
Orange- Refill valve

Edited by Jtcm, 07 June 2007 - 02:49 PM.

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#16 CaptainSlug

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Posted 07 June 2007 - 02:39 PM

That would not be usable in a war and I wouldn't want to promote throwing something like this at people.

My check valve just stopped working for some reason. So, in the even that anyone else kills theirs somehow or would prefer to hook up a regular bike pump all you have to do is chop off or omit the dollar store pump. Then drill out where the check valve was and add a fitting. Then use a tube to stem adapter on the pump.
Posted Image
2 pumps = 120 feet

I will buy another dollar store pump the next time I am there and try to find a better way of adding a check valve to it.

Edited by CaptainSlug, 07 June 2007 - 03:20 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#17 zaphodB

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Posted 07 June 2007 - 03:03 PM

Any and all grenades should be light and spring powered. Well, the lightness requirement kind of necessitates the spring requirement. When I get the grenade working I'll post a new thread, but for now lets stop hijacking CS's.
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#18 Jtcm

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Posted 07 June 2007 - 03:09 PM

Sorry CS didnt mean to hijack the thread. Just a quick question how heavy is the gun?
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#19 CaptainSlug

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Posted 07 June 2007 - 03:19 PM

Depends on the pump used. With a dollar store pump it's about the same weight as a Big Blast.
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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#20 Guest_DarkInfection_*

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Posted 07 June 2007 - 04:14 PM

Well now that you fixed every bug in the design, I have to do this.... Can ALL of the parts be bought from Ace or Home Depot? Or do you have to order some of them from McMaster?
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#21 CaptainSlug

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Posted 07 June 2007 - 04:41 PM

I don't know what killed the check valve. It might have been caused by glue fumes or debris from the pump. But oh well it was only $3. I'm going to see if I can design my own.

Part list added to the first post. As well as a revised diagram showing the most reliable part arrangement.

Well now that you fixed every bug in the design, I have to do this.... Can ALL of the parts be bought from Ace or Home Depot? Or do you have to order some of them from McMaster?

The trigger valve itself was designed around parts I bought from Home Depot and a local hardware store that's similar to Ace Hardware. The the rest of the gun is entirely up to you as to how you put it together. I don't have any stores near me other than Grainger that sell check valves that are not PVC and I don't live near an Ace Hardware.
The answer is yes, but you'll have to figure it out on your own. The design configuration itself is very adaptable to whatever parts you decide to use. The only parts that HAS to be the same are the 1-1/4" bushing adapter and the 1/2" elbow. Everything else you can figure out what works. The first post is just a guide.

However I don't really see the point in insisting on spending so much time trying to hunt for the parts through multiple stores when ordering them all from Mcmaster is cheaper since their prices are lower for the vast majority of items.

Edited by CaptainSlug, 07 June 2007 - 10:55 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#22 CaptainSlug

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Posted 08 June 2007 - 02:58 PM

I was tooling about with the ghetto bike-pump version this afternoon. After four pumps with the 2-foot-long bike pump the valve is too pressurized to be depressed with my thumb. So I had to trigger it with my palm.
The aluminum barrel I've been using is still capable of firing the missiles from the Big Blast, but when I tried to shoot one of them at 4 pumps it split the missile in half near one of the fins.
Posted Image
That one went 70 feet.
The other one that didn't split in half went 100 feet.

The really large bike pump after 4 pumps had probably filled the tank to around 50 psi. And the speed at which the valve empties the tank equates to an absurdly powerful shot. So if you do hook this valve up to a normal bike pump I do not recommend (for safeties sake) trying to pump against the ground. Only pump it as hard as you can when held in both hands. Otherwise you're probably not even going to be able to depress the trigger with your thumb. For higher pressure operation you'll have to work out a lever system for actuating the valve.


One more thing I want to note
The slight leakage around the 1/4" rod that protrudes from the 1/2" elbow has actually been beneficial because it allows you to load a dart to the back end of the barrel by blowing into the end up the barrel. You don't really have to take the barrel off if you don't want to.

Edited by CaptainSlug, 08 June 2007 - 03:06 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#23 CaptainSlug

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Posted 08 June 2007 - 06:37 PM

Video is up:

I was only shooting trimmed streamlines in the video in the hopes that they could be seen on camera. They can, but not once they're uploaded onto youtube due to compression. Oh well.

Edited by CaptainSlug, 08 June 2007 - 06:38 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#24 3DBBQ

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Posted 13 June 2007 - 11:13 AM

very cool idea!
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