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Theories on blowgun design

9271 Views 13 Replies 6 Participants Last post by  Lobohunter
Not sure where this belongs, I am rather new to this forum...

to me, a .625 cal PVC blowgun 5 feet long, crafted in a odd way, seems to be the perfect blowgun.

Most of my friends and I have trouble getting enough air into the 5 footer fast enough to get good velocity(150 FPS+)

I was reading Geezer's Corner two days ago, and saw his article on this blowgun-

(its not easy to read, but if you download the HTML code, you can easily read the text by opening the HTML as a text document OR by opening it in browser and inserting spaces where they belong)

I decided there must be a better way than the valve on the end of the pipe.

And there is.

Make your dart cones roughly 1/16 inch bigger than the ID of the pipe. You should BARELY be able to blow them down the pipe normally. it is pretty hard to do right.

Then take some 2" PVC and an end cap for 2"PVC. Drill a 7/8ths inch hole in the center of the end cap. It should slide over the 1/2 inch PVC pipe(actually .625). Then cut a 10" section of the 2" PVC and push it into the end cap. Slide that over the pipe. Then roll some paper tubes roughly 1" in diameter. Don't make them too stiff. Make them 1" long.

Then, make it so the end of the 1/2 inch PVC is 1 1/2 inches in from the end of the 2". Duct tape the end cap to the 1/2 inch PVC well... if it leaks this doesn't work. You should be able to use the 2" of the PVC as a mouthpiece, but not be able to touch the end of the 1/2 inch PVC with your mouth or lips. you might be able to touch it with your tongue.

OK. so now we have what looks a little like a potatoe cannon.

Put your paper tubes between the 2" and the 1/2 inch PVC so it supports the 1/2 inch PVC, and keeps it centered.

Once this is all done, MAKE SURE the end of the 2" has no sharp edges. it WILL cut you.

then put the dart into the tube. Here is the secret. It should NOT actually be in the tube. The cone itself should have a slight air gap with the 1/2 inch PVC. So if you blow GENTLY into it, the dart will seal the tube. AKA you get a headache from trying to blow into it.

The dart should fall out if you turn the gun upside down.

replace the dart into the tube(1/2 inch PVC) and then point at your target. Then huff into the 2" PVC. If there is an air leak between your face and the tube... it won't work. Well, it will, but the dart will drop roughly 10" in 10 feet.

If you do it right, it should send the dart really moving. As in, 3" drop at 10 yards.

Why it works-

With a normal blowgun, you are limited by the amount of air you can get into it before the dart leaves the barrel.

With this blowgun, you are only limited by what pressure you can build in the 2" PVC before the dart is pushed down the barrel.

The 2" PVC acts as an air reservoir that you pressurize to roughly 25-40 PSI. It has a volume roughly 1.5 times that of the barrel. When the dart's resistance is finally overcome enough to compress the cone, forcing it into the barrel, the air is suddenly released behind the dart into the barrel. @40 PSI it is enough to propel the dart extremely fast, probably over 200 FPS. I don't have a chrono... but I can compare with my experience with other ballistic weapons of known FPS.

just try it.

Not too hard.

It does help to chamfer the end of the barrel. It allows you to use a larger cone, therefore getting more pressure.

That probably made no sense.

Well, ill get pictures up soon.
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I'm really interested in what your talking about. I'm a visual picture guy so I look forward to the pictures for clarity.
Yea.. the discription sounds very wierd.

As in, it doesn't make sense.

But you'll see.
I was intrigued with Geezer's design when I first read it and will at some time probably build one or two.

Question/Suggestion? Instead of the 1'' round 1'' long pieces of paper being used to keep the barrel evenly supported within the 2'' pvc, why not make a disk like the guys do for dart making and make it out of something like 1/2 '' foam, or cardboard, or perhaps another smaller end cap that might fit within the 2 inch pvc?

As all of us who have made paper cones know, paper can absorb water and become soft n mooshy and therein loose it's ability to support the barrel inside the 2'' pvc. Other material might provide better long term support if the material used is not affected by water.

Geezer used a bunch of smaller diameter tubes of short length surrounding the barrel that acted as spacers to support the inner barrel and air passageways into the 2'' pvc cavity surrounding the barrel. I have found that small diameter pvc pipe like that is very hard to find in my area but I'm sure a person could use something like drinking straw or something of similar size being a little bit stiffer/stronger to achieve the same affect.

Like Treefork, I too am interested.
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I would have to then drill multiple holes in the disk.

I do have a bearing race that might work though.

paper is what I had. It is cheap....


I don't recall if I said all credit for the innovation goes to Geezer.

Except his air chamber was the length of the pipe, greater volume... but less preassure.

mine is the opposite.
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Well there is always something else you could try with re-purposing in mind. Providing you have the abiltiy to drill a few holes.....I kinda got the idea you did not have a drill from your last post but........why not try something like a screw off/on lid from a plastic gallon milk jug? It's gonna be close in size, if not surely there is something else like that could be used in plastic that wont absorb moisture. I'd look at some other things before considering using the bearing race lol. You could cut the top off a 2 litre pop bottle and cut it like a mouthpiece but keep it round. The barrel could go into the opening of the bottle and the 2 inch pipe could be supported by the shoulder section of the pop bottle. I mean that's just an example. Lots of stuff like that can be had for free. Free is pretty cheap!
I think that you missed the point of this design.

The 2" PVC is full of air.

When pressurized, it has greater volume than the barrel

once the dart starts moving into the barrel, the air flows from the 2" PVC into the barrel.

Said air needs to be able to move easily into the barrel.

I do have the ability to drill a lot of materials- but drilling thin plastic is extremely annoying.

And the # of holes requires is quite large- at least 6, preferably 10. and there is then the problem of support and centering- the paper rolls tend to keep the tube centered because they all have equal or very near equal bend strength. Although you have a very good point. I might try some thin steel.

Hence the bearing race

if I were to cut some holes into the pop bottle mouthpiece, it would probably work.

This design only works because the pressure in the 2" pvc is transferred to the barrel behind the dart.

It only works because the air is able to move between the two.

yep... I do work on a near-zero budget.

A consequence of being young and broke.
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Nope, understood it perfectly. This was what I was referring to - you wrote;

I do have the ability to drill a lot of materials- but drilling thin plastic is extremely annoying.

And the # of holes requires is quite large- at least 6, preferably 10. and there is then the problem of support and centering- the paper rolls tend to keep the tube centered because they all have equal or very near equal bend strength. Although you have a very good point. I might try some thin steel.

If the drilling is problematic, you could always melt through it with a hot nail or other metal object. the inside does not have to be pretty to be affective. As long as air can pass through into the 2 inch area at an equal or greater rate than it can into the barrel.

This disk would look something like the face of a revolver cylinder - a hole in the middle for the barrel and an outside diameter equal to the inside diameter of the 2 inch pvc. In the space surrounding the barrel and between the 2 inch pvc holes would be made (however you prefer) all the way around so it would end up again looking like chambers in a revolver cylinder. A material that would be ideal for this and is extremely easy to obtain for free is chloroplast which essentially cardboard made of plastic. It's used a lot for signage. Any sign shop would have scrap pieces that size for the taking free.

Re the bottle top, it could look something like this;


The outter diameter would be cut round and of the same OD as the 2 inch pvc ID. The circles indicate how the holes could be oriented.

This was just a suggestion of how an end result of not using paper "could" be done. Not necessarily how it should be done. Best of luck.
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I forgot about the heat method. my problems of drilling thin plastic are now solved ;)

I will have to try that.

Well... I know what I am doing this weekend

a 2 liter shouldn't be too hard to obtain...
Following this thread with great interest.

.40 I have no breath problems I can drive them hard.

.50 and up its another story.

Would you be able to go up to say a 3" pvc air chamber around a 1/2 pipe blowgun?
.40 I have no breath problems I can drive them hard.

.50 and up its another story.

Would you be able to go up to say a 3" pvc air chamber around a 1/2 pipe blowgun?


50 and up require you to take a deeper breath to start with. Otherwise the technique is the same. You'll have more back pressure with 40 than with 50 and 625 but thats only because the of the smaller diameter of 40 cal.

I won't say you couldn't go to 3 inch but I suspect there are pressure advantages with the 2 inch. Besides, do you really want a length of 3 inch diameter anything on your BG? It's really not nice to hold onto. Even 2 inch is getting into the uncomfortable range especially if you have to carry or hold onto it for any length of time and I have BIG hands.

There is no reason a person could not do this to a standard metal blowgun barrel using 2 inch pvc for the air chamber and silicone them up to get your seal and if you did not like it the silicone could be removed and you'd have your blowgun back the way it was before. I'd personally use 3 or 4 layers of chloroplast glued together for the round bushing with holes drilled/melted through it rather than the pop bottle seen above. Chloroplast would be lighter and much stronger than say paper like above here or pop bottle. either way you will have fun experimenting.

I'm the opposite to you ghosthawk. I find .40 cal has much more pressure requirement and just find the 50 and 625 easier to blow to get the same performance. :startle:
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2" isn't exactly nice either.

I dunno if you can go to 3". I don't have any 3" PVC to test it with either..

Its an idea inspired by Geezer. Test it!!!

Well, I got some thin, stiff plastic sheet.

Not pleasant to work.

I am probably going to try some chloroplast.

I like the idea.

Rubber cement works great for sealing, or pine pitch if you have access to it- it is far superior and sticks better too.

I also got some 16d nails... :)

and some other assorted big nails.

I just noticed these great things called spiral roofing nails ;)

I should have bought some thin alumnium sheet.

Its easy to work with, and very strong for its weight.
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Geezer worked for IBM for decades - he's most likely a genius, especially concerning his blowguns - but he got away from the sport about a decade ago. Pity. Would have loved to see more of his innovations.

Here's one he shared with me ... Go buy a pack of party plastic straws. Get a pack of #11 X-Acto blades. Some plastic trays (or the kinds of foam take-home trays from a restaurant, or what used to be used for fast-foods (burgers, etc.) and two hole punches. One the ID of your barrel, the other the OD of the straw. Get a gluegun. Glue the back end of the blade into one side of the straw, be sure to seal that end with hot glue, and push the blade in, so that there is an air seal. Slip three of the plastic rings onto the back end of the straw (about 1/2 inch from the back end, each about 1/4 inch apart). Shoots well, great for small game close hunting.
Love the backdraft blow guns I have two
Really though now I came up with a .62 cal six footer made from carbon fiber and that's my go to gun these days
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