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Threads related to water balloon launchers.
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Silence
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Post by Silence » Sun Apr 30, 2006 5:14 pm

kevinthenerd wrote:I find that a standard can (from soup or vegetables or whatnot) fits 3" PVC well, and it's very good with a single layer of paper towel wrapped around it soaked in oil.
I was thinking about a more heavy-duty solution; for example, a wooden piston with a concave face carved into one base. If the balloon contacts the piston with greater area due to a more similar curve, then there will be less pressure and a lesser chance of rupture. Of course, this is all speculation.
joannaardway wrote:I'd like to do something like that for Cerberus when I've built it, but I have no editing software to do it with.
You would like to do something like what with Cerberus?

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kevinthenerd
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Post by kevinthenerd » Mon May 01, 2006 1:37 pm

SilentGuy wrote:I was thinking about a more heavy-duty solution; for example, a wooden piston with a concave face carved into one base. If the balloon contacts the piston with greater area due to a more similar curve, then there will be less pressure and a lesser chance of rupture. Of course, this is all speculation.
Ductile materials typically fail due to shear stress (if you look at Von Mises/distortion energy theory, etc.), but that's beyond the scope of the forum. If you don't understand solid mechanics, just trust me on this one when I say.............


As long as the balloon can mold itself into the shape of whatever container you're putting it in (with nothing too sharp to puncture the balloon), all you need to do is match the volume of water with the volume of the container. Imagine the container sitting on a table, and imagine if gravity were suddenly increased at and around the table. A balloon sitting in a can with more volume than the balloon's water is just going to sit down into the can more, but the balloon won't break because there will be equal compressive forces on either side of the rubber where the water and can meet.

If the volume of the holder is less than the balloon, our table experiment would yield a balloon that sags over the edges. In a barrel, this will cause parasitic loss as the balloon rubs the edges. (This is why I recommend a lubricated barrel, especially for a deformable projectile. Is a little bit of oil heading toward your target going to really ruin your water fight anyway?)

A soup can is quite a bit more durable than you might think. One key advantage over the wood idea is that it has a very good specific strength (high strength with a low mass). As far as the water balloon launching properties of it, I don't know... As I said, I'm not that interested in launching water balloons. My next launcher is going to be for water (so that's why I'm here), but my interest in launching solid objects extends to other things.

IF I were interested in designing a water balloon launcher, I'd be interested in something LIGHT and STRONG to hold the balloon during launch, and I'd want a parachute behind the balloon holder so the holder doesn't hit the intended target.

The weight of the balloon holder is important for more than one reason. First, you don't want the extra weight sucking up the finite amount of energy coming from your chamber. Second, you don't want your launcher to be cumbersome or tiring to use. Third, you don't want a heavy holder to hit a human target in the unlikely event that your balloon doesn't leave the can and the 'shute doesn't open.

I make no warranty, express or implied, on the safety of launching anything at a human. I would recommend paintball-style protection if you're crazy enough to do anything at close-range. (Close-range isn't why we're building our own launchers, from what I understand here.)
Last edited by kevinthenerd on Mon May 01, 2006 1:42 pm, edited 1 time in total.

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Silence
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Post by Silence » Mon May 01, 2006 8:16 pm

What ductile material are we talking about here? Is it the balloon?

I see your point about the volumes; so to prevent any possible shear stress, WBL builders should use buffers that have very large volumes. If the balloons can form the shape of the buffer without breaking, then size really shouldn't matter.

I did not intend for the buffer to actually shoot out of the muzzle. In fact, the whole reason I joined in this was to suggest something that does not get fired; in other words, the buffer is a piston plunger that is stopped before it exits the barrel; this would be much more convenient and much cheaper than conventional buffer uses. There doesn't even need to be a vent near the end of the barrel to release the pressure after the plunger has been stopped, as long as a pulley system or something allows the plunger to be pulled back or the barrel can be blocked. Otherwise, you would only have one shot!

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joannaardway
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Post by joannaardway » Tue May 02, 2006 6:54 pm

Something like the video. Maybe I can talk to a friend about using their PC for the editing...

Now I need to go and find a sabot for 1.5" barrels.
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Silence
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Post by Silence » Tue May 02, 2006 8:58 pm

Hmm...I have a good computer and its parts came with quite a few movie-editing programs that I never installed...

Maybe you could use the programs--but more conveniently, check out some websites. There is bound to be some good, free software out there.

I know the GIMP (a free image program similar to Photoshop, and about as good) has an addition that aids somehow with movies. I don't think it is a full-blown version of movie software, because I haven't used it, but somebody should do some research on that.

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kevinthenerd
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Post by kevinthenerd » Tue May 02, 2006 10:13 pm

SilentGuy wrote:What ductile material are we talking about here? Is it the balloon?

I see your point about the volumes; so to prevent any possible shear stress, water balloon launcher builders should use buffers that have very large volumes. If the balloons can form the shape of the buffer without breaking, then size really shouldn't matter.

I did not intend for the buffer to actually shoot out of the muzzle. In fact, the whole reason I joined in this was to suggest something that does not get fired; in other words, the buffer is a piston plunger that is stopped before it exits the barrel; this would be much more convenient and much cheaper than conventional buffer uses. There doesn't even need to be a vent near the end of the barrel to release the pressure after the plunger has been stopped, as long as a pulley system or something allows the plunger to be pulled back or the barrel can be blocked. Otherwise, you would only have one shot!
Hrmm... what if the balloon holder was simply tethered by a light but strong rope attached inside the launcher barrel?

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Silence
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Post by Silence » Tue May 02, 2006 11:52 pm

I thought of a pouch thing with, say, 6 cords attaching it to the barrel; but that isn't going to work because it will not create a seal. Yes, this would be closer to what we were aiming for, so it's unfortunate that it doesn't work.

Were you thinking of a method in which one can implement a parachute-like cloth while keeping a seal? If so, I am very interested...

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joannaardway
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Post by joannaardway » Thu May 04, 2006 9:15 am

There is a problem here - how will the pressures behind the piston part get released?

Tethered sabots tend to either not work as well as a discarding/ non-discarding sabot. They weigh more, often fly off, and are harder to make. Then again, if they don't dissappear, they are very cheap options - a one time cost rather than a one per shot cost.

I would use free software - but that might have spyware/viruses attached which I would prefer to leave off my PC.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

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Silence
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Post by Silence » Thu May 04, 2006 12:24 pm

If the pressures must be released, then you cut a few slits near the end of the barrel so that the back of the plunger just passes the slits before the plunger is stopped. Then, some sort of pulley system could bring the plunger back; however, if you're putting in a water balloon, then you might as well just let it slide down.

I think the tether on the sabot would just get in the way of the shot and be unneccessary. I wouldn't really worry about that option if I were you.

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DX
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Post by DX » Thu May 04, 2006 5:22 pm

I would use free software - but that might have spyware/viruses attached which I would prefer to leave off my PC.

I have never gotten a virus ever from a freeware program. Practically everything I have is a free program or from a friend.

Making this overly complicated is just going to cause headaches. One-shot sabots work well enough for the RM. We are pretty careful not to lose a can, but when we do, we just pull out another one. Water balloons can be stored in the cans, so there's another plus to bringing several. The solution to running out of cans is simply to eat more Pringles!

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Silence
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Post by Silence » Thu May 04, 2006 8:08 pm

I don't know...I really hate inconveniences such as needing more than one sabot, while you could just have one plunger. However, I don't want to theorize too much until I have actually built the Douchenator or another WBL.

Duxburian, are you ever going to start a thread for your ITWL in the Homemades subforum? Not to be impatient, but I simply can't wait :) . You might also want to think about the reservoir that you will use--unlike WBLs, this is going to require a lot of water.

kylemw9
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Post by kylemw9 » Fri Jun 16, 2006 3:13 am

[QUOTE=joannaardway]There is a problem here - how will the pressures behind the piston part get released?

Try this place it may help or it might not it has a picture of a piston here it is xinventions.com

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