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Topic: Ammo is the key for automatic weapons
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Member
Registered: 06-12-02
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While I have no objection in principle to the Junkyard Warriors attempting to replicate a fully automatic weapon, I have to point out the the tolerances in such weapons are extrmemly precise, far greater than are likely to be achievable in the junkyard shops.
Any weapon that can rock 'n roll would have to be made to fit the specifications of ammo provided by the show. Even the first and simplest automatic weapon (the hand-cranked Gatling gun) was not achievable until the advent of mass-produced cartridge ammunition. Whether you used the purely mechanical approach of Gatling, the blowback principles of Browning and Garand, or the open-bolt system of Thompson, you still have to design the weapon around the ammunition you propose to fire.
I truly don't know if that kind of thing can be done in the junkyard given what they have to work with, even if they are using a smoothbore barrel and relying on volume of fire to make up for the lack of accuracy. Even the comparatively simple Bofors action would be hard to make. Heck, even a Mauser-type bolt action would be hard to make!
My bottom-line opinion? Build a breechloading cannon that uses a shell and powder bags, set off by a blank cartridge... possible. Construct shells to fit in a breech-loading action fired by a blank cartridge set into the base as a primer... well, maybe. -Build a cannon that is belt- or magazine-fed? Unlikely to impossible in 10 hours.
But DAMN, I'd like to see them take a shot at a true breechloading cannon of, say, 1840 vintage!
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Member
Registered: 06-12-02
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Oops; this was to reply to terranfury in Ballistas
Sorry, I hit the wrong button. This was menat to reply to terranfury's proposal to build modern automatic weapons in the Ballistas thread.
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Member
Registered: 07-05-02
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It's all right; it probably belongs in a new post anyway.
You're right, of course: Just about any automatic weapon that I can think of requires regular cartridges. And almost all designs require precision machining.
But I'm not so sure it's impossible. We just might need an unconventional design.
So I'll post back, after giving it a little more thought, about possible bodged-together automatics.
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Member
Registered: 06-12-02
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Okay, a new challenge it is! Automatic weapons! Ba-da-da-da-dah!
terranfury, I think you are right. It's a move from muscle power to chemical power, and that does make it a new challenge.
The catch is to come up with a device that does not need a lot of machining. This lets out the Thompson, the Maxim, and probably the Browning systems. We might want to take a look at the Suomi, which only had one moving part (the bolt), and possibly at the Sten and the Schmeisser systems; also the US M-3 'grease gun.' The latter three have few moving parts and are mostly made out of stampings. I'd look at the Suomi first because it was designed to function is a very harsh subzero climate. That means it has to be a fairly forgiving action and fairly simple to maintain. The Bofors action might also be worth a look because of its gravity feed; it's one less problem to solve as opposed to a spring-loaded follower in a magazine.
Also, what about the Gatling action? That is a purely mechanical action with an external power source doing all the work, whether it is someone cranking a lever to spin the barrels or an electric motor driving the gears.
Once we can agree on which two actions are the simplest to construct, we can start looking for a way to begin building them from scrap. However, I think we had better plan on using low-powered loads rather than milspec loads. Perhaps black powder instead of cordite as the propellant. That would keep the gas pressures the teams have to contend with down lower, and therefore safer.
What do you think?
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Member
Registered: 07-05-02
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You seem to know a lot more about guns than I do!
Before I launch into my rapid-fire ramblings, I'll say I agree with you that small charges of black powder should be used for safety purposes rather than full-size cordite charges.
Now, the important stuff!
I don't know very much about the individual models you mentioned. But since it only has one moving part, the Suomi sounds promising. I'm assuming it uses a recoil action? My biggest concern is how the shells are extracted. How might you build one?
The Gatling actually sounds like it would be comparatively easy to build - but only comparatively.
One problem is that both need to be built essentially from scratch. I can't think of a way to adapt any component you'd likely find in a junkyard to make either.
Or maybe we don't even need shells, or even gunpowder for that matter. If you can build a coilgun, it should be pretty easy to pour metal bits into the coil. Or what if you just get a large flywheel spinning very rapidly, build some simple guides around it, and pour ball bearings onto it? An old Ninja Turtles toy shot plastic pizzas that way!
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Member
Registered: 07-05-02
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A simplified Gatlingesque gun.
Maybe we can get somewhere by reinventing the wheel.
One idea that I think is interesting comes from something I saw a shop class build once: A gumball dispenser. The design was simple: A large hole was drilled through a wooden block from the top. A second hole was drilled through the side of the block at its middle so it met the first one. Another hole was drilled halfway through a dowel, deep enough to hold just one gumball. The dowel was inserted into the second hole in the block, and it divided the first hole into a top and a bottom part. Gumballs were poured into the top of the first hole in the block to load the machine. To dispense a gumball, you gave the dowel a single turn. When the hole in the dowel was pointing up, a gumball from the top part of the first hole fell into the hole in the dowel. When the dowel was rotated more so the hole was pointing downward, that gumball fell out into the bottom part of the first hole, and out into a dish. One revolution resulted in exactly one gumball coming out. Replace wood with metal and gumballs with shells. You can see where I'm going with this. It ends up being a sort of single-barreled Gatling gun with a single firing pin, in which RPMs correspond exactly to shots per minute. There are fewer parts to find, and that also means fewer to break.
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Member
Registered: 06-22-02
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I gotta agree with basically everything said thusfar. I spent hours last night designing a rapid fire cannon in my head out of all junkyard parts, comming away with a pnumatic carriage bolt fire'r, but it all fell apart when I realized one tiny little part of it wouldn't work, and I couldn't come up with a way to replace it. Shucks.
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Member
Registered: 06-12-02
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Gumball cannon
I like it. A point you haven't mentioned, however, is extracting the spent case from the firing chamber. How is that accomplished? Or are you predicating the gumball cannon on caseless ammo such as was used in the 1960s Gyrojet rocket pistol?
Or, if we could cross your gumball idea with blazefire84's pneumatic idea, we might end up with an interesting variant on the paintball gun that actually fires full auto without doublefeeding the chamber. Keep working on it!
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Member
Registered: 06-12-02
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blazefire84, keep on thinkin'!
Don't be discouraged because your Zen pneumatic cannon doesn't work yet. Sketch it out and see if you can re-engineer the problem part. I think you are onto something. I especially like the idead of not having to rely on show-provided cartriges or shells. Don't give up on that idea!
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Member
Registered: 07-05-02
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Complete gumball cannon.
Caseless ammo! Why hadn't I thought of that? That certainly would make things easy. But I guess we'd rather use something more common, right? So let's see...
For a second I'm going to drop the original gumball idea and try something new (but similar, and inspired by the gumball idea).
Imagine two concentric pipes, snug within one another. The central one is free to rotate, and is sealed at one end. Cut a hole in the outer pipe at its top and at its bottom (towards the back end). Cut a third hole of the same size in the inner pipe. Now, rotate the inner pipe within the outer one. When the hole in the inner pipe is aligned with the top hole, a shell drops in. Ninety degrees from here, it is not aligned with either the top or the bottom hole, and is therefore sealed. This is where the gun fires. Ninety degrees more bring the inner hole into alignment with the bottom hole, so the bullet can drop out. One hundred and eighty more bring it back to the beginning for another shell to drop in.
Pretty simple! The only thing I've left out is the firing pin.
I guess you could use a simple blowback mechanism to force the pin back (but not to operate the rest of the gun). With some simple physics the teams could determine the RPM required to synchronize the rotating feeder/extraction machanism with the pin. But this strikes me as unreliable. Things could probably get out of synch too easily.
You could use a gatling-style circular ramp to force a spring-loaded pin back. When the pin gets to the end of the ramp, it comes forward striking the cap. Since the barrel is stationary, though, the pin would have to be off center (or at least the part that protrudes through the back of the barrel would have to be off-center). This might make constructing this particular part difficult.
I'd like a simpler idea for a firing pin. If you have one, put it here.
Of course, maybe we don't even need a firing pin. Go with the pneumatic idea for a moment. Add another hole to the inner pipe that lines up with an otherwise-sealed hole that leads to a compressed air tank. As long as the compressor can compress the tank as fast as the cannon decompresses it, you've got rapid-fire.
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Member
Registered: 06-12-02
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Don't forget the mighty cam
terranfury, you could fire the cannon or release the airblast to propel the gumball by using a cam that will permit the firing pin/air valve to work ONLY when the conditions are right, that is to say, when both the top and bottom holes are not open. It is the basis for the Fokker interrupter gear that was used to permit machine guns to fire through the propeller arc in World War I fighter planes. The pilot pressed his trigger, and a cam connected to the engine driveshaft would permit the machine gun to fire only when there was no propeller blade in the line of fire. The same principle would work for your gumball cannon, I think.
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Member
Registered: 06-22-02
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Well, let me tell you where I was headed.
Ok, the first, most esential thing is the ammo. Carriage bolts are very good for this. See, since they have a round head, you don't have to worry about to much air escaping around the sides of the head like you would a standard bolt. We also need nuts (Preferably acorn) to support the oposite end so it sits level and gives it nose weight. If possible, we should also drill out the center of the nuts to lighten them.
Next, we need lengths of good, small bore tubing. Close to the size of the carriage bolt's head, just slightly smaller (like, listed same but measures different for some reason), smooth interior. Get three circular steel disks, cut holes for the barrels and a central rod. Weld the barrels and central rod in place. Now, we get some bits of beam and assemble a frame with two stands for pillow bearing blocks. Mount the barrel system on the frame. Add an additional piece to the frame that will hold the third sheet, but not let it spin. Put a rubber seal on the hole from which you will be launching, and grease both plates so you get an airtight but mobile seal. On this plate, you also need to mount a thick ring that will cover the rear ends of each of the barrels as they spin, so your ammo does not fall out on its way from the loader to the launcher. Also at this stage mount a system to spin your barrels, likely a geared down electric motor system. In a dream senario, you might be able to push this system as high as 60 RPM, which, assuming 8 barrels would output 480 shots per minute.
Next we need a good, strong compressor, and a solid air tank. Since we don't have the ability to make an air tight seal on the carriage bolts, we will need a lot of pressure to move them. Mount the compressor with an engine to power it, and good lengths of hose to attach everything. We also need an auto closing valve, with a lever switch on top. Mount the valve behind the barrel system so that the switch is just a bit higher than the barrel you plan to fire from, on the same angle. Now attach a length of hose to the hole on the rear plate that has the seal to the second. Weld some bits of rod onto your barrels that come far enough rearward to trip the switch on your valve. There, your firing system is done. Pump up your storage tank nice and high, activate your spinning barrels, and as each barrel comes by the firing hole, it activates your valve, which closes again after it has passed.
And wait, I just came up with a loader system. Geeze, ok, this thing is theoretical, but likely impossible.
Take some extra lenths from the earlier pipe and cut some squares (will be arched) from them. Now cut some holes out of the top of each launcher pipe that are just slightly smaller than the ones just cut. Mount some little brackets onto the pipes that can guide the larger "door" sqares and hold a spring. Also, just at one side of the "door" system, mount some little ramp pieces that go a little higher than the "door" both in front of and behind it. What this accomplishes is a door that can be pushed open from the side, but the will close again when the impediment that was keeping it open is removed.
Now build an additional setup that will hold a "cartidge" in sliders above the top of the gun. As the gun barrels rotate, the "cartidge" forces open the "door" and drops in a carriage bolt, and then is forced up and over the door by the ramp pieces, allowing the door to close back over the top.
There, now your gun loads and fires, with only enough human intervention to activate the spinning barrels and start the compressor's engine.
See, simple
 right? "He asks self mockingly" |
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Member
Registered: 06-22-02
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I thought my idea seemed a bit confusing, so I made a quick and dirty side sketch of my plan, which should help simplify it to some extent. Take a look <a href=http://members.tripod.com/blazefire84/id99.htm>here</a>
or at http://members.tripod.com/blazefire84/id99.htm if it doesn't allow html coding on these boards.
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Member
Registered: 06-12-02
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You are on to something here
This looks like it would work. The interior diameter of your barrels only needs to be a dew thousandths larger than the bolt, just enough to drop it thru the hatch without binding.
Question: do you think we could solve the gas seal problem with a grease injector? At the next stop after loading the bold, just injecting a glob of fluid grease before the inlet seals? Centrifugal force ought to spread the stuff around enough to give a brief gas seal before the air hits the bolt to send it out the muzzle. I recall that the riflemen of the Revolutionary War period used greased linen patches to get a good seal in the muzzleloading Pennsylvania rifle that the Brits feared so much. It was the grease and not the linen that provided the gastight seal.
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Member
Registered: 06-22-02
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That might just do the trick! Man, now I kinda feel like building the thing myself because it looks like a lot of fun.
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Member
Registered: 07-05-02
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Drawings!
royjaruk: I thought of cams too, but initially dismissed them because I thought they would be moving too slowly. However, at a high RPM, they probably would work, and they'd be relatively simple.
Now, about drawings: Blazefire, I like it! It's an interesting looking design, and I think it really could work.
But here's an alternative!!
Following blazefire's lead, I drew up a simple diagram of my design from my previous post. Here's the URL: http://www.crosswinds.net/~terranfury/automatic.gif
I mention in the picture that the design can be used or modified in several ways. Here they are:
Small Machinegun (Pneumatic firing pin)
The blue-green tube connected to the gun is connected to a compressed CO2 cartridge. A small electric motor (like the one powering a toy radio controlled car) spins the device. Small cartridges are used. This is the vanilla version.
Pneumatic launcher
Cartridges are replaced by makeshift bullets (bolts, as blazefire suggested, or anything else that fits the tube), the small CO2 cartridge is replaced by an air tank and compressor, and the firing pin is removed. The bottom hole in the gray tube is unnecessary, but can be left in the design if needed. Think pumpkin chuckin, but with bolts, and rapid-fire.
Small Machinegun (Electric firing pin)
The blue-green tube connected to the gun is replaced by an electrical wire. The blue holes are replaced by insulated electrical contacts. The firing pin is attached to a solenoid. The circuit is completed by using the body of the gun as a ground. It's a simple alternative to the pneumatic pin system.
Gas gun
The blue "holes" are electrical contacts, as with the last variant. The solenoid, however, is replaced by a spark plug. As with the pneumatic launcher, makeshift bullets are used instead of cartridges. The hole at the bottom is connected to a compressed propane/air (or oxygen) mixture. Remember potato cannons? Well this one's serious!
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Member
Registered: 06-22-02
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Now that I like! Far simpler than my setup (though it doesn't look as cool
 ) and still very effective looking.But I just realized that you are gonna have to go with the pnumatic option on that one (which is ok, I love pnumatics) because the heat from any kind of explosion in there is going to expand your barrels, and in a matter of a couple shots, the barrels will be locked together by their increased size. Just an observation. You could make it work if you could reduce the size of the inner barrel, but then you don't get the tight confinement you need for proper channeling of the explosion.
Hey, wait. We now have two totally feasible junkyard ideas which do not necessarily have to relly on show provided cartidges. This is a doable comp! YEHAA! Lets see it!
Oh, by the way, anybody else with an idea, if you want to put up a drawing, just send it my way ( thefish77@hotmail.com ) and I'll throw it up on the site for you and post the link.
[This message was edited by blazefire84 on September 03, 2002 at 11:20 PM.]
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Member
Registered: 06-12-02
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RDF Productions Will Have Kittens...
... but we now have a legitimate weapons challenge to offer them! Lots of noise, lots of innovation, lots of problems to crack on the set, but damn if these ideas won't work!
Actually, I think it will be the insurance carrier that has the hissy fit. Cathy Rodgers and the RDF gang will just sit quietly in the corner twiddling their thumbs and toes while they wait for the nice men in the white coats. They are used to the innovations and insane-looking suggestions that later turn out to be quite doable.
 Re: the combustible gas propellant system. Can we increase the oomph if we mate the gun with an oxyacetylene welding rig to provide the explosive gases, and control the gas injection with injectors and a mechanical governor similar to what was used in the old stationary reciprocating steam engines? (See the biopic Spencer Tracy did of Thomas Edison; they show the machines in the sequence where he undertakes to electrify a New York City neighborhood, if you don't know what I mean.)
Re: heat expansion. We could solve this by adding radiator fins to the barrels, or by incorporating a partial water jacket around the weapon as the Army did for the M1919A3 Browning .30 caliber machine gun and for early versions of the .50 caliber M2 machine gun.
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Member
Registered: 07-05-02
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I agree, blazefire, that the pure pneumatic idea would probably be the simplest. But I'm starting to like the combustion idea. For one thing, it would contrast more with your design in a competition.
When I said that for a gas combustion cannon, you would use the bottom hole to admit gas, I was not entirely correct. You'd have to reposition the holes in the design such that the order in rotation would be: Load, Fuel, Spark.
Now, about oxyacetylene: Among potato cannon enthusiasts, its use is considered suicidal. Then again, they're using PVC, and we're using steel - steel which didn't fail even when we detonated black powder inside in one episode (though the judge was sure it would). So it actually does seem relatively safe. It also has a few key advantages: First, it is an existing system for creating a good fuel-oxygen mixture. Second, the teams already have one: I wonder if attaching their tools to their machines is against regulations? (Seeing that a team was once allowed to cut apart the set, I think not!). As for a seperate governor, I'm not really sure, but I assume you mean a device to inject the appropriate amount of gas depending on the RPM of the gun, royjaruk? (I haven't seen the Edison film.) If so, I think it's unnecessary. Design it to run at a single constant speed; simpler is usually better. If you mean something else, tell me.
About heat expansion: You're right, royjaruk; any cooling system would go a long way to combat the problem, and most would be relatively simple to make. In the end, though, blazefire is right: The gun may have overheating problems.
But, whatever details we work out now regarding our designs (or maybe a third alternative, someone?), we do have two different, workable approaches (whether one combusion and one pneumatic or both pneumatic) which could really be done. I'd love to see this!! Let's continue to improve our designs though, and come up with new ideas. I like this thread.
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Member
Registered: 06-12-02
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Technical Issues
There are three ways to deal with the heat produced by combustion: rate of fire; radiation; and convection. We could control the heat issue with any of these.
A slow rate of fire will permit the heat produced by firing to dissipate before the barrel fires again in a gatling-type weapon. The movement of the barrel through the air accomplishes this.
Installing or cutting radiation fins in each barrel will act as a heat sink and also dissipate the heat to the air.
Installing a water jacket would absorb the heat by convection and permit a higher rate of fire for at least a limited period. However, getting the jacket watertight (more or less might do) around the spinning barrels could be a real chore.
What I was trying to address with the governor/injector issue is a way of insuring that the gas is injected only into the loaded barrel. I'm sure there are other, better ways to accomplish this. What we DON'T want to have happen is for the combustible gas (and blazefire84 is right, propane or a propane-oxygen mix would probably be good enough and not as risky as acetylene) to be set off prematurely, by leaking or being injected into the barrel before it is loaded.
Basically, I think we are well on the way to solving this problem and being able to present the production team with a valid challenge for the Junkyard Warriors.
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Member
Registered: 06-22-02
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Another Idea!
Ok, I got another one. This is kinda an adaption of terranfury's idea. This one utilizes 2 barrels, one inside the other, and a cam to cause a reciprotcation action between them. What I like about this one better is 2 things.
One, it utilizes a true valve instead of aligning holes, which I think will provided a better burst of air than holes which would provide an unregulated flow over the course of contact.
Secondly, it adresses the issue of making sure only one "bullet" attempts to enter the chamber at a time. An issue we forgot to adress in all the previous posts is that although we make room for only one "bullet" in the main chamer, another one could try to drop in and cause binding. Now, this is correctible in terranfury's origional idea since we have round amunition and the thing is spinning, all we have to do is make the cuts into the outer barrel angled edges instead of flat, and the ammo will be forced to roll right back into it's holder.
This one prevents any problems at all with individually cased ammo and a system on the cam that pulls out each case with each retraction allowing the next to drop down, but not to soon.
The pic is on the same link as before, second one down. (Note: the red cartidge support beams are not supposed to be attached to the outer pipe.)
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Member
Registered: 07-05-02
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I _really_ like this idea, blazefire, even more so than your first one (which was itself very good). I like it because it's simple. That's an important asset in a junkyard! I also agree that a valve is better than aligning holes. It also eliminates the need for tons of grease, a big plus.
You mentioned a problem with my design, and that the corners would need to be beveled. You're right, and I assumed from the beginning that those corners would need to be more angled than they appear in the drawing. But there's another issue that I hadn't thought of, and I now think it might really be a problem with my design. The shape of the inside of the barrel may be a problem. When closed, the "hollow space" of the muzzle "sticks out" where there's the hole to let the bullet in. The barrel is wider here. The bullet might still catch here when the gun fires. I thought the problem could be solved by making this a gentle slope rather than a sharp edge, and it might solve the problem, but I'm really not sure.
I'm still thinking about designs too, blazefire. I'm also going to look at yours some more too, and I'll post again when I have more ideas.
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Member
Registered: 06-22-02
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I think we will need to revisit this idea again and again to get it right.
You know what Edison said: "There's a better way to do it. Find it!"
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08-30-02 09:51 AM 08-30-02 08:51 AM 
