2 Liter Bottle Rocket and Launching gantry.
Please read all the 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 guage is best for pumping them up with the air .
A good introduction to Bottle Rocketry.
The CONE will screw on to a standard 2 Litre 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 dont 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 arround any Rocketry.
The bung is designed to let the bottle off arround 60 psi (4 Bar).
Print the bung with Ninjaflex slowly at fine Z resolution no infill ie solid .
You shoud get 3 or 4 bungs from a 10meter 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 Shrader 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 ridgid then the bung can be pushed in without buckling the bottle. Upside down of course aftre charging it with the water .
I print the cones at medium resolution and speed with in 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 some time it gives up and is not realy something you can take in the field.
In later models i have printed fins with hole to zip tie to the cone.
Unfortunatly it spoils the lines of the rocket but it is a repair that can be done in the field.
If the gantry is used the bottle can be pumped to higher pressures.
Do not 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 could not make the bottle fall over.
The MK1 rocket will go off spontaneously so that is why it should be set to go off at low pressure by using a bung that is not too tight..
It should go 60 to 80 feet in the air.and not to far down wind.
Rocket Developments include nose cones that can hold a payload , altimeter or parachute . 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 it may hurt someone badly . Simple 8 string parachute made with very thin plastic dust dust sheet from a shop where everything cost 1GBP . Parachute about 2 feet in diameter any bigger and it will drift a long way we only want to slow the decent a bit so the rocket does not get wrecked.
Fly in open spaces. I have had one launch land 180 yards away and one 1 yard away. It depends on the wind. Rockets cannot be targeted as the initial jet of water is a little random on the bung.
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 diferent configurations for the gantry.
With a single outlet conector 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 will have to be made taller. It works i dont want to do any more designing for a while.
Have Fun Keep it Safe