For my youngest son I made a simple NERF-Bazooka. Of course they can also be charged with other projectiles, but then the danger is increaded.
The following parts are required for the contruction:
* a PVC HT-pipe
* a Fitting sleeve
* a bicycle pump with a pressure gauge
* a 1.5 Liter PET-bottle
* a bicycle valve
* a water hose (13 mm)
* a 50 cm long plastic tube, diameter approximately 13 mm suitable for the NERF-cartridge
* 2 x Gardena 1/2" Adapter
* a Gardena water rocket Adapter (you can use your 3D-printer for this)
* a 12V 1/2" valve like you find them on ebay for some bucks
Step 1: The Assembly
As you can see on the plan the two gardena-adapters are screwed on both side of the valve. The waterrocket-adapter is screwed on the bottle and connected to the valve using the water hose. On the other side of the valve you fix the plastic pipe with an inner diameter suitable for the NERF-cartridges.
On the bottom of the 1.5-liter-bottle you mount a long bicycle valve. Then everything is put into the HT-pipe. On the outside of the HT-pipe the bicycle-pump is fixed with pipe clamps.
Step 2: The Electronic
For the electric valve you'll need a 3s-lipo-battery (11.1V). But using this voltage the valve will not open very precisely and fast enough. Therefore I use a step-up-transformer to Charge a capacitor with about 30V. So I first have to push the charging-button for 1-2 seconds and after this I can push the fire-button. The higher voltage will guarantee a more precisely and faster shift of the valve...
Step 3: The Final Assembly
To create a more realistic look I painted the pipe using spray cans and Camouflage-colours. To shoot with the Bazooka you'll first have to pump. But caution, don't use a pressure higher than 6 bar (about 100 psi) to avoid an exploding bottle. This might be very dangerous and loud....
For the first test I took iron-balls as a projectile instead of the NERF-cartridges. The estimated Speed was higher than 200 km/h and the energy should be about 20 Joule. But for my son I'll load the bazooke only with the original and soft NERF-cartridges.
Thank's for your interest. Maybe you'd like to take a look at my other YouTube-Videos: www.youtube.com/user/stopperl16/videos