Write-up: The HydroBreech

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Write-up: The HydroBreech

Post by C-A_99 » Fri Mar 19, 2010 3:47 am

Seeing as how practical WBL's are in fair demand, yet are somewhat difficult to figure out how to do, I'll do a write-up right here on the breech I have on the launcher I made last summer which can be found in this thread.

Pictures are limited for the time being and I apologize but that's how it's going.

Important part needed: A threaded 2" pipe coupler. Contrary to what I mentioned about it being available in Home Depot, it is also available at Lowe's. What it is, is a pipe joint with threaded caps at each end as well as black rubber seals. You should recognize them fairly easily; they are often placed near the PVC check valves and/or the various lengths of PVC pipe in Lowe's. This piece is needed to cover the breech hole. The coupler is a somewhat long cylinder with threaded parts and rubber seals, one at each end, and there is a grove in the plastic to accomodate the seals. (with a little creativity, you could make this piece look almost like a pipe bomb; that may help you recognize the coupler)

See the pictures in the other thead. (they're the best I have right now)

First, you need to designate a 2" pipe as the barrel. Before cutting it down, remember that you will need extra barrel length to accomodate for the nasty dead space caused by the barrel. The dead space on my launcher is far too large and unacceptable, but it's what I'm stuck with. (originally I was implementing a bolt action design but found out that it wouldn't work, yet the barrel breech was already cut and was cut far too long.)

The breech should be cut much like here (though you can have it a bit shorter; how short depends on the coupler; the coupler should ideally be roughly 1" longer than the hole cut):


To do this, use a pencil and draw along the cut to be made. There should be no sharp edges drawn, only semi-circles and straight lines. The cut should NOT go completely halfway around the pipe; leave some space (roughly 10° or more) around the edge of the half-pipe area or the pipe can weaken.

There are several ways to make the cut but you'll definately need some power tools. What me and my dad did was to use a drill with a relatively small bit equipped (no larger than, say 1/4" though the smaller the easier as long as it's not too small) and drilled small holes around the area to be cut. Be sure the center of the holes drilled are inside the marked area, so that the holes are roughly tangent to the marked line. The holes should be spaced very slightly so the whole thing holds together, or they can intersect; I don't think it should matter.

After the holes, break the resulting scrap piece out. If that's not possible, take out a dremel (with a cutting/grinding wheel attached) and cut at the areas in between the holes. After that, replace the wheel with a grinding stone to smooth out the whole thing and make it clean.

Make sure to work in a well ventillated area, preferably outside. PVC dust is particularly nasty so wear safety glasses and a mask.

Now take the coupler out, unscrew the coupler's "caps", and remove the rubber seals. The coupler should slide very easily over the pipe and should be longer than the cut you made. If it's at least 1" longer, then you have a very good cut, but if not, you can resort to the trick I did as depicted in the other thread. More later as I explain the seals.

For the seals, I used weather strips. You want to pick weather strips that are able to squeeze to a very tight space easily: around 2mm to 3mm. If the strips are too thick, the movement will be very difficult. However, the ones I picked were considerably soft and they seem to wear out a bit quickly.

Now if your breech hole was cut well short enough to fit the coupler, here's how you want the weather strips (use the pictures in the other thread for assistance):

- There should be a set of one or two strips wrapped completely around each end of the hole, wrapped in a way as if you were marking the pipe to make a vertical cut. Avoid overlapping the strips; they should "blend" together at the bottom of the pipe. (not the top where the hole is)

- There should be two strips on the sides, one on each side, as a boundary around the cut breech hole. See pictures.

- There should be one strip on the very bottom that runs beneath the hole. The purpose of this strip is only to keep the coupler piece in place so it's not really necessary (as long as the coupler makes it to both sets of strips at the ends) but it doesn't hurt to add it.

Now if your coupler does NOT fit over the hole nicely, resort to the pictures. I used a rubber seal to help hold up some weather strips at one end, but the problem with this setup is that the coupler may get blasted open when firing. (this design problem was my fault) If you cut your breech hole short enough you should not encounter this problem. The rubber seals can also act as stoppers so the coupler can only slide in a limited range. The additional rubber cylinders attached are flexible rubber couplers (which included clamps at each end that I removed) and are there from a failed attempt at finding a cover piece for the breech earlier. Now, I use them as grips and support, and not only do they make a nicer grip to the pipe, they also look cool.

Now, the back end of your pipe should hook up to a PVC coupler (a regular coupler that you have to weld together w/ primer/cement) and that coupler should go into a reducing brushing that goes to the size of the pipe that the firing valve will use. After that, attach to the PC's as you see fit. I had my PC on the bottom in an over-under setup, and if you go with a single PC like in my design, you may want to use a flexible air hose instead of PVC. (your choice; if your assembly is rigid and better than mine, PVC could be a better choice, but if it's crappy like mine, you may want to use an air tube; don't forget the clamps!) Another option may be to have the valve on the bottom but the dead space that creates is even worse.

I hope this helps anyone looking to build a breech. This isn't much of a beginner's guide, but it consolidates the steps/parts to what I did to build mine and I hope it's a widely available solution that's not just restricted to me. It's not as good as the launcher made here, but I had much difficulty trying to find out what parts and pipe were being used. (I believe they used regular couplers with their inner centers grinded out in order to hold the rotary breech in place)

Edit: Updated post regarding the threaded pipe coupler.
Last edited by C-A_99 on Thu Jun 03, 2010 9:17 pm, edited 1 time in total.

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