SpudFiles

I was thinking about using ping pong balls for my 1.5" barrel and i thought of a great idea... With a dremel or whatever drill a decent size hole and put in a piece of string and let it hang out about an inch. Fill the ball full of concrete and let it set. Get a cup of hot wax and a cup of cold water. With the string hanging out just dip the ball into the wax and dunk it in the cold water. When its done just snip the string off. The reason for the wax is because the ball is about a millimeter too small for the barrel but the wax makes the diameter bigger so that it'll fit. I haven't tried this out yet but i'm sure it'll work wonders.

With a decent powered launcher, this ought to be capable of some serious damage. When completed and tested, please post pics.

You know, this is not limited to cement. Why not buy some balls by the bulk and experiment with different fills.

Also, that is a pretty good idea about making the ball to fit, although a sabot would have worked, too.

Have you seen my cannon... it would be perfect ammo for it.

You talking about The Best Cannon On This Website?

If so, I do believe this ammo would suit that quite well.

That'd be it...

I've tried filling ping pong balls before, and with one small filling hole, concrete / cement has a real hard time drying. The drill hole just isn't enough to let enough moisture out. Granted I was using water for a liquid, you might try alcohol or something else that will evaporate quickly . . . .keep us poasted.

Well how long did you let the concrete set? I was thinking more like a full 24 hours for mine, mabey longer... I could go with something else thats like concrete if that doesnt work, or anything thats dense really. I dont think sand would work too good, since the ball will spin too fast and if i were to have like a piece of tape on the hole, maybe the momentum would cause the sand to come out... Anyone try this...? I could be wrong. Or maybe if i fill about 9/10ths of it up with sand ill fill the rest with gorrilla glue or something.

Well first of all, the sand shouldnt fly out because since the ball is goin so fast, the air pressure outside it would keep the ball in. This would be kindof an example of bernoulli's (spelling?) principle. Because when there is a air flow, that creates lower pressure. Since high pressure tends to equal out with low pressure, the surrounding are would push in, cause in the sand to stay in. But if that airflow isnt fast enough, meaning if you projectile isnt flying fast enough, then the sand wouldnt stay in. But the tape should be fine anyway. Its like swinging a bucket of water in a circular motion. Just as you all know, the water stays in, so the same can be applied here. But sand would obviously not perform as well as concrete because it is not as dense and hard as conctrete, but also there are little gaps between sand grainules that are air pockets and will decrease performance. So i really wouldnt use sand at all.

more than a week, it never dried. A small plug dried where the hole was and the rest never dried. I got bored waiting and broke it open. Cement dries when a large amount of it is exposed to the air. When a tiny little bit is exposed, it just won't dry.

I would mix fiberglass epoxy and sand 50/50% that would dry inside a ping-pong ball easily, its what I do. I never thought of candle dunking one to take up the extra diameter.

Should work better than just sand itself

You could add baking soda to the concrete powder.

For each cup of concrete powder you mix up, add around a 1/8 teaspoon of baking soda. Then mix with appropraite amount of water. If you really want fast set times, replace water with denatured alcohol (look by the paint thinners). Do not use rubbing alcohol as it is a very different concentration and more expensive.

When you mix in the liquid of your choice, make sure you THOROUGHLY mix. Otherwise you negate the ability of the baking soda. It cut my dry time down to around 6-10 hours (depending on humidity, warm dry places work faster).

Thanks to Grumpy for the tip to me: seen here Tip and info on page 2 of this thread.

BTW, portland concrete powder is uber destructive with any sort of good seal in the barrel. Make sure of what is behind your target!!!!!! Be careful, but its worth it.

Instead of wax... Which I guess would only allow them to be shot once maybe twice before unusable...
Why not try some fibreglass resin? Same method just dip in resin...Maybe a bit messy...

Or perhaps... Some non-shrink construction grout might be a substitute for the plain cement.. You do mean cement not concrete don't you? Being that concrete has aggregate in it... which would negative affect your projectile's centre.

williamfeldmann,
i don't know why i did not think of this earlier (old age i guess) but you can use hydraulic cement if you need something to setup realy fast, most hardware and home improvement stores will have it. to better understand what i am talking about read this. http://www.swepcousa.com/bpsite/bppdf/j11089.pdf

Fill the balls up with piss tape em up and bombs away!!!