MWU:OFFENSE-101 'The Geek Breech Cannon'

Discussion in 'Weapons & Pneumatics' started by Tugboat, Jan 29, 2011.

  1. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    OR more precisely, the geek-breech, ball-bearing interrupter cannon... [this design is based on/derived from work by Bob Sloan, the teachings of Bob H, and quite a bit of trial and error. Thanks to The 2 Bobs!]
    The HTML version of the CPOE cruiser class and follow-ons will be a little broken up (pump- and gun-building classes will be separate from boat-building classes, but will be linked to as seems appropriate). With that in mind, Model Warship University presents the first Offense class :)
    ZO! Schtudentz! Hyu vish for POWER, ja?! Ser goot! Ve must be able to zhoot ze enemies, ja? Vissout gunz, ve are nossing more zan convoy zhipz! Und zo, to class...
    You will need the following tools: Blowtorch, solder, and flux paste. Drill or drill press with bits. Tubing cutter and bender. 1/2" countersink bit (used for deburring the ends of the copper tube after cutting)
    You will also need the following parts/materials for EACH gun that you want to make: 1/4" copper tubing (1 foot), the following brass pieces for 1/4" OD tubing: 1 Ander-Lign Compression Tee (part # A-12), 1 Ander-Lign Compression Union (Part # A-10), 2 Compression Caps (Part # A-5). Part numbers are from the packages I bought at Lowe's, they are color-coded with a pink bar on the top of the package. Also 2 delrin sleeves for 1/4" OD tubing. Additionally, you will need a package of Panther Products large silicon fuel tubing (like for RC planes), some 7/32" stainless steel ball bearings, some Clippard 1/16" hose, some 5/32" aluminum or brass tubing and one Clippard 1/8" hose barb (thread type unimportant, it gets soldered).
    First, cut the 1/4" copper tubing into three lengths: a 9" piece for the 50-round magazine, a 2.25" for the uptube, and a 1/4" long piece that'll be part of the breech. You do this with the tubing bender; don't try to tighten it too much between rotations! just a little, give it a turn, tighten a bit more, give it a turn, repeat until the tubing breaks at the cut line. Use the countersink tool to clean out the ends of the tubing where you cut it; this will help encourage BBs to pass freely thru the ends of the tubes. (That's important!)
    Lay out the parts and it should look like below. Note that the 2.25" piece of tubing has been bent in a nice curve. It's not quite a 90 degree turn, more like 60 degrees. You must use a tubing bender to get a nice kink-free bend! I use a cheap 'spring'-type bender, there are several different types that can do the job. The two compression fittings with holes in them came from the Tee (you get 3 with it, and 2 with the coupler). These compression fittings originally come with a brass compression sleeve in them. You will need to remove that, using pliers and some ingenuity. We will be using delrin sleeves in place of the original brass ones, which leak gas when the guns are fired. The delrin won't leak nearly as badly, so we get more power :) [Thanks to Bob of Port Polar Bear for the education on this!]
    [​IMG]
    Now, we drill out what will be the bottom of the Tee. Put your 1/4" drill bit in your drill press, and hold your Tee upright with a vise (best), vise-grips (less good), or a pair of pliers (least good). I have used all three with good results. Just pay attention to what you're doing! :) I marked my drill bit with tap 9/16" up from the tip, so that I don't rill too far. Go too far, and you just slagged a $6 Tee, at least for our purposes. 9/16" is it. You can go a little less, but not too far. NOTE: Do NOT use a 'pilot-tip' drill bit. it will create a funky-shaped hole that will grab the ball bearing, jamming the gun after one shot. Use a plain-ole drill bit like in the picture. I killed two tees before figuring out that little factoid...
    [​IMG]
    Below, an obviously-staged photograph showing the bit 9/16" into the Tee. In case you're wondering, the vise has been removed from these two pics, for clarity's sake.
    [​IMG]
    Next, we are going to make the bottom end of the breech, where the CO2 will enter the gun... Clamp one of the compression caps into a vise (or something to hold it steady for drilling and soldering), so you can drill down into the inside of the top. We do this because 1) it lets us clamp the cap by the solid 'crown', where it's strong and inflexible, and 2) we can use the little dimple in the inside of the crown to center and guide the drill bit. Pick a drill bit that is just bigger than the threaded base of the Clippard 1/8" nipple. I'll post the size tomorrow when I can check it in the shop.
    [​IMG]
    Below, the hole has been drilled, and the nipple inserted. You can't see it very well, but there is a bit of solder flux paste around and under the nipple.
    [​IMG]
    Rar! Kree-gah! Fire! Heat both pieces evenly, and solder them together! Try to keep the nipple straight up and down :)
    When it's good, let it cool while we play with the other parts...
    [​IMG]
    After the gas fitting cools, grab the 9" magazine tube and the compression coupling. We will be soldering those together, too! I clamp the tubing in the vise, and sit the coupling on top, then solder. It's pretty straightforward, but if you run into problems, email me.
    [​IMG]
    We need to provide a means for gas to enter the rear of the magazine, as this promotes good ammo feed to the breech of the gun. We do this by drilling a 5/32" hole into the coupler that we just soldered onto the magazine tube, as seen below. More on this later!
    [​IMG]
    Below are the parts laid out more or less as they relate to one another...
    [​IMG]
    Take the Tee, and insert the ball bearing into the bottom (where we drilled the Tee out), followed by the 1/4" length of copper tubing, and then thread the gass fitting that we made onto the bottom of the Tee. Screw it on as tight as it'll go. Flip it upside down and look into the hole where the magazine tube will go, you should see a fair bit of the hole (20-30%) obstructed by the ball bearing. The bearing should freely move back and forth if you invert and revert the Tee several times. This is the time to check for jams :) Below is a pic of the first step, completed.
    [​IMG]
    Next, take your remaining tubing, and slide a compression fitting (the ones with holes, obviously) and then a delrin sleeve over the end of each piece that'll go into the Tee. You can see what it looks like at this point, below:
    [​IMG]
    Next, thread the compression fittings onto the Tee, and tighten them both hand-tight, then use a wrench, and tighten them more. I don't have a torque spec for these, just get them tight enough that rotating the tube is difficult but not impossible.
    [​IMG]
    That's it for part 1 of Offense-101, part 2 is tomorrow! In part 2, we will connect the barrel and silicon tubing to the rest of the gun, and run 1/16" tubing from the breech to the back of the magazine, followed up by function testing!
    All schtudenten vill be in zer seatz promptly vhen zee klass schtarts! Heil Fluegel!!!

    *I am especially interested in feedback from people who have 1) Never made a gun in their life, or 2) Have made lots of guns, for themselves and others. Does a part of the lesson seem hard to follow, or need more pictures? Constructive feedback is greatly appreciated.
     
  2. thegeek

    thegeek Well-Known Member

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    Uptake to the barrel should be of a more durable material, like 1/4" brake tubing, not copper.

    I made the first "geek" in 1983
     
  3. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    I cover the copper with plastic split-loom stuff, it does okay. Obviously, the brake lines would be more resistant to incoming rounds.

    I have part II pics to upload, after I feed my face!
     
  4. thegeek

    thegeek Well-Known Member

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    It's not the outside that blows out, The BB's going up and around the bend with stretch
    the copper and make the uptake oval.
     
  5. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    Hmm... in your experience, how many battles can I expect to get out of the copper tubing before it causes jams from the reshaping? (i.e. how long do I have to go get brake line tubing, and a bender for it?) I'm assuming that the metal lever-type bender we use for copper will do brake lines with a little more oomph?
     
  6. thegeek

    thegeek Well-Known Member

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    The copper will deform but it will take time (2000 rounds?)
    Then it will hang fire a bit.
    But if you use steel brake line it is very stable, you can bend it with your thumbs
    in a long radius. Tight radius requires a spring bender or lever type bender.
    I buy 6 foot lengths of 1/4" at the local Auto parts store.
     
  7. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    Sounds like a plan! Thanks for the input! :)
     
  8. Kotori87

    Kotori87 Well-Known Member

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    Indeed, Brake Line is delightful stuff. 1/4" works great for .177" bbs, 5/16" line is ideal for 7/32" shot, and 3/8" makes for an excellent shotgun blast for 1/4" rounds. It is a somewhat soft metal for Big Gun barrels, so it does need to be replaced every two years. In fact, it's about time I replaced mine again...
     
  9. DarrenScott

    DarrenScott -->> C T D <<--

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    I use stainless hydraulic tubing for my 1/4 barrels....overkill, I know, but hey.
     
  10. froggyfrenchman

    froggyfrenchman Well-Known Member

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    I think Carlo may have introduced me to that cannon way back when.
    Salt Lake City. Meet the Geek cannon.
    Geek cannon. This is the Salt Lake City.
    Salt Lake City. Meet Davey Jones' locker.
    Or something like that.
    Mikey
     
  11. froggyfrenchman

    froggyfrenchman Well-Known Member

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    Oh yes.
    Nice thread Tuggy.
    Mikey
     
  12. SteveT44

    SteveT44 Well-Known Member

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    Performance wise:

    How does the restrictor tube breach compare to the Foster breach?
    How does the ball bearing selector compare to the piston selector?


    Steve
     
  13. mike5334

    mike5334 Well-Known Member

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    I can answer the first question ...

    The restrictor tube (aka Geek Breech) does not seem to shoot harder than a correctly tweeked o-ring (aka Foster or BC) breech. I haven't seen a FPS for the Geek style, but we have measured Foster style breeches tweeked for reliability (vs hardest hitting) at 240'ish fps. Of the hardest hitting geek breaches I have seen, they are still more than hard enough to put belows on a ship.

    The Geek style breeches are no tweak, perfect for the type of person that dislikes tweaking (me) and for ships that need a "set it and forget it" low maintenance cannons such as loaner ships or ships for captains new to the hobby.

    Some of the northeast guys have been collecting cannon data for a while. Maybe they will have an FPS for some restrictor style breeches.
     
  14. thegeek

    thegeek Well-Known Member

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    Geek breech is not as "good" as a "O" ring breech and has significantly less FPS (20-60 FPS less).
    But is much more reliable and easier to set up than a O ring breech, much better for a rookie or loaner boat.
    Piston selector is much better than a Ballbearing selector (prone to doubles).
     
  15. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    In my limited experience, my geek breech guns are slightly different than those that have gone before it. The only major change in my guns is that I change the gas supply from a tiny 5/32" OD tube (fed by 1/16" line) that sprays sideways into the breech, to a 1/8" supply hose thru a large Clippard fitting that sprays the CO2 straight up at the bottom of the ball bearing, assuring that it blocks the magazine tube, preventing doubles more effectively.

    Neither of the test guns had any doubles in 600-odd rounds, regardless of rate of fire. So I disagree on the propensity for firing doubles (in this setup), based on limited testing. Not to say that they couldn't happen, but all testing was with my old lightweight reg that only makes 110#. A newer reg making like 140# would be even less prone to doubles. My max rate of fire was probably 2 to 3 rounds per second, so not as high as some solenoid-equipped ships are capable of (Mike Mangus, take a bow!). But the gun did fine, as fast as I could mash the MAV's button. And that's acceptable for a gun presented in an article aimed at new battlers (or people like me who suck at aiming hihi).

    Power-wise, I have no idea how many FPS they generate, but I can't imagine that they'd be any different than previous geek guns. But they do well enough to penetrate balsa at range (tested at 12' against 1/32" balsa), the limit of which was my ability to aim (see above). I plan to make several North Carolina battles, and I know Rob S has a chrono so when we have numbers, I will post them.

    If this sounds defensive, I don't mean it to; you guys, especially Ming the Merciless, have given me valuable feedback for improving the guns. I was just trying to explain why I feel differently than a few things that were brought up. I didn't post this for a long time relative to when I built the test guns because I wanted to get in a bunch of shooting with them, and to get some local feedback from Brian and Pete. Pete is VERY sceptical of 'new and improved', so I really wanted him to test the guns (less chance of bias). Both of them were impressed, and given that I'm driving on THEIR team this spring (with these guns in my KGV), I don't think they'd blow smoke up my arse. I hope :)
     
  16. thegeek

    thegeek Well-Known Member

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    Down angle below water shots have been a problem with geeks, the difference now is 1/8" line and
    large oriface solinoids. The more gas you use the better cause it tends to solve the double and FPS
    problems.
     
  17. Evil Joker

    Evil Joker Member

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    i made some of these but i went with the Piston selector
    i can shoot through a beer/soda can

    Tug will test EQ out on February 12 speed test fire guns
    most likely will not battle unless my #1 ships failes

    thanks for the class
     
  18. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    Good hunting, Joker. Glad it helped, still got a bit left to do for the other class members :)
     
  19. djranier

    djranier Well-Known Member

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    I tried geeks for the last couple of years, copied one of Pete's D gun's. They worked very well when first set up, but I found that after I set them up here in Florida, and then traveled to different parts of the country, they became inconsistant, due to the temp I would guess. The silicone tube would become either more rigid, or more flexable, leading to jams or weak guns.

    Last year I went to the Foster type breech, and started using silicone o-rings, and are way happer with how they function. Just pull along side and see for yourself. Tug-a-glug-glug-glug what are you doing switching side's, trying to ruin Don and my fun it sounds like.:)
     
  20. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    Think of it as inspiration for finishing that Nagato!

    I wanted to run Big Scharnie, but after seeing that it's an old Swampy hull, I want to reinforce the ribs before it re-enters battle.

    For you and Don, I will stick an Imperial German naval ensign on it and refer to it as 'Konig Georg der Funfte'. Heil Fluegel!

    Testing so far has been from November (~70-75F) to January (~35F). Admittedly no testing has occurred under the hot Georgia sun, but my time machine project is not making good progress. All I've been able to do is get it to make time go forward at a rate of 1sec/sec. But that's progress!