BOTTLE ROCKET + GANTRY

myminifactory

Here is the rewritten text: Human: 2 Liter Bottle Rocket and Launching Gantry. Please read all notes before building any of the kit. Bottle Rocket and Launch Gantry The most basic rocket would include the MK 1 cone SHORT FINS and BUNG. A half a tennis ball taped to the top (bottom) of the bottle gives it more inertia and provides a shock absorber for landing. A good stirrup-type pump with a gauge is best for pumping them up with air. A good introduction to Bottle Rocketry. The CONE will screw on to a standard 2 Liter fizzy drink bottle. Fill 1/3 with water, fit the bung, and pump away. The bottle with water in will stand on its fins, but please don't fill more than 1/3 water as it will fall over and could be dangerous. The shorter fins will be more stable. Take great care with kids around any rocketry. The bung is designed to let the bottle off around 60 psi (4 Bar). Print the bung with Ninjaflex slowly at fine Z resolution, no infill - solid. You should get three or four bungs from a 10-meter sample reel of NinjaFlex. I print the bungs at high resolution but that is a fine art; be prepared to print a few. Keep all the bungs if you go on to make the gantry - a loose bung is good for that. The bung may feel a little loose in the neck of the bottle, but when the Schrader valve is pushed through the hole, it gets tighter. Trim the rubber round the valve so it fits in the recess or make a punch with a 12mm 1/2 inch metal tube - it needs a bit of a flange. To fit the bung in the bottle, push it in a bit then give it two pumps of air; this makes the bottle rigid. Then the bung can be pushed in without buckling the bottle - upside down, of course, after charging it with water. I print the cones at medium resolution and speed with PLA. The MK1 cone has some spikes sticking out to hold it to the bed; they are cut off after. I print the fins as fast as I can get away with in PLA again. The fins can be solvent-glued to the cone. I have used hot glue, but sometimes it gives up and is not really something you can take in the field. In later models, I have printed fins with holes to zip-tie to the cone. Unfortunately, it spoils the lines of the rocket, but it's a repair that can be done in the field. If the gantry is used, the bottle can be pumped to higher pressures - don't pump bottles beyond 100 psi. Always make sure the rocket is not tugged about by the pump. I mounted my pump on a board and tied the airline down so it couldn't make the bottle fall over. The MK1 rocket will go off spontaneously, so that's why it should be set to go off at low pressure by using a bung that's not too tight. It should go 60 to 80 feet in the air and not too far downwind. Rocket Developments include nose cones that can hold payloads, altimeters, or parachutes. I found that an all-up nose weight of 60 grams was enough to get the rockets much higher as they now have some more inertia - please be aware that they have to land, and it may hurt someone badly. A simple 8-string parachute made with very thin plastic dust sheet from a shop where everything costs £1 will do. The parachute is about two feet in diameter - any bigger and it will drift a long way; we only want to slow the descent a bit so the rocket doesn't get wrecked. Fly in open spaces. I've had one launch land 180 yards away and one 1 yard away - it depends on the wind. Rockets can't be targeted as the initial jet of water is a little random on the bung. Launch Gantry My early launches were with a double-barreled foot pump, but I got myself a floor (stirrup) pump, but it has a double-sized connector for the valve, so I have two different configurations for the gantry. With a single outlet connector, use the reinforcing ring under the bung ring. If your pump has a big connector, you will have to print the legs and pads that have a chamfer on them to let the connector through. I could have used a valve extender, but the whole gantry would have to be made taller - it works, I don't want to do any more designing for a while. Have Fun! Keep it Safe!