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The Problem with High Efficiency WBLs

Written by sbell
Last updated on 2008-01-23

When the Douchenator water balloon launcher was first introduced, many people (myself included) were in awe. Here was a simple device, made out of a few bits from the local plumbing shop that was pretty much a water balloon bazooka. Ranges of 500 feet or more were common.

However, as time went on and these were actually battle tested, a few flaws were found. Mainly, because of the large air tank it took a long time to pressurize with a bike pump. Also a long barrel was necessary for efficiency, making a pretty unwieldy device. This started a quest to find a more battle practical and efficient WBL.

The best fix to both of these problems was a better firing valve. The Douchenator uses a ball valve, which has an opening time of around 200 milliseconds. This means that by the time the projectile had left the barrel, the valve was only partially open, making poor use of the available compressed air. Having a more efficient valve meant that you could decrease the size of the chamber and barrel, without sacrificing performance.

Currently, the most efficient valve available for this use is the Mauler Valve, which is a commercially available piston valve. It opens in around 5 milliseconds, and has a full 2" opening for the air to flow through. Using a Mauler Valve, it would theoretically be possible to create a launcher a little over a foot long with performance similar to the average Douchenator. It would be extremely easy to carry, and pressurize very fast even with a bike pump. This would be the ideal battle practical WBL.

I had built my own cannon using a Mauler Valve, however it was not compact like I have described above as I was more interested in pure performance than shooting water balloons. However one day when shooting water bombs, I noticed something. I was using low pressure to prevent popping the balloon, yet no matter what pressure I tried, I couldn't shoot a water bomb anywhere near the same distance that my previous Douchenator-based launcher could. Each time, the balloons would pop on their way out. This got me thinking. Despite being far more powerful, couldn't you just lower the pressure and get the same performance as a Douchenator? Why were the balloons breaking anyway? I had often thought how neat it would be to make a tiny, but high performance WBL with a Mauler Valve. Then I finally realized why this wouldn't work. I'll explain below.

Let's assume that you have 2 different WBLs: Gun A and Gun B. For the purpose of this explanation, both guns have the same muzzle velocity which should translate into both having the same range. Gun A is a regular ball valve pneumatic, like the Douchenator Gun B is a Mauler Valve pneumatic, a much smaller high efficiency design like I have described above.

As both guns have the same muzzle velocity, the Gun B is going to be far smaller than Gun A, thanks to it's higher efficiency. So automatically, you'd think that Gun B is better. As mentioned above, it'd be much faster to pressurize, and far easier to carry. I was reading some of last year's discussions from WWc Forums, and this was one of the points brought up. A higher efficiency valve would make a better WBL. However, there is one problem that I believe no-one has factored in: Acceleration.

Now looking back at Gun A and Gun B, we can easily see that Gun B is going to subject the water balloon to a lot more acceleration than Gun A. This is how it achieves the same muzzle velocity despite the smaller barrel and chamber. Now what is the one thing that kills water balloons shot from a WBL? Force from acceleration. Because the Mauler Valve opens so fast and puts through so much air, there is a huge acceleration spike at the beginning of the shot which pops the balloon. On the other hand, a Douchenator has a much more gentle acceleration 'curve' because the valve opens more slowly.

So unfortunately from this we can see that WBLs not only have limits in power, but they also have limits in efficiency as well. The super compact WBL idea is simply not possible. I would think that a sprinkler valve is the limit in terms of efficiency, and any form of piston valve probably wouldn't work.

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