We used to have a couple that we brought out for family reunions and gatherings, we had a farm and a huge garden, hence many disposable potatoes. They would regularly launch them 300-400 feet, we used to set a couple rubbermaid cans out in a field and see how close we could come to them.
Fuel them with pretty much any aerosol, but hair spray gums up the threads, and the igniter sometimes, and WD-40 works very well, but if you use too much, it will get oily, obviously. Keep some paper towels handy. Wear safety glasses, just in case, a shard of Sch. 80 PVC pipe in the eye would definitely ruin your day. We never had a problem whatsoever, and they make a very satisfying "pooomp" when fired. We used the rotary lighters, like for gas lanterns, they were problematic, but a grill lighter, piezo style, would probably be more reliable. Cheap, loud, entertaining. What else do you need? Crexrun
We did shoot some raquetballs out of one, their inherent round-ness makes them fly a very long ways, but not very cost efficient, and it's no fun having to walk and get them. A golf ball launcher was suggested, but "shot down" for the sake of not wanting any children walking around with golf ball shaped holes in their craniums. I suppose you could launch nearly anything out of them, providing you had a large enough chamber and barrel. Come to think of it, there are a couple cats that my parents have out at the farm that wouldn't be missed. Has there ever been a cat in orbit?
Crexrun
PS I dont' believe I'd be party to launching concrete filled caulk tubes, either. That seems like an awful lot of backpressure in the chamber.
Here's a question, how did you progress to concrete filled tubes, anyway? Did you read that in "How to kill yourself with JUST a potato gun!"
Crexrun
