big water cannon

The step files of the water cannon are uploaded for better understanding of the model.

BOM:

98x   M4x16 screw          (14 less if the pipe_barometer is not used)

98x   M4 cap nut             (14 less if the pipe_barometer is not used)

196x M4 washer              (28 less if the pipe_barometer is not used)

2x     C-coupling 2" IG    (or other 2" coupling)

4x     O-Ring 48 x 3.5

2x     M3 locknut

2x     M3x10 screw

68x  6 mm stainless steel balls       

1 mm rubber mat             (for cutting seals)

some lubricant, i used vaseline 

total partcount: 496

Weight of the printed parts:

joint: 163 g (2x)

start_pipe: 230 g

center_pipe: 440 g

end_pipe: 420 g

pipe_barometer: 102 g (not necessary)

total weight: around 1600 g of filament

Print settings (I used):

Material: PLA

Layerheight: 0.1

Perimeters: 100     (very important at higher pressures. You can see the results below if it is printed with normal walls and low infill after pressure tests)

Toplayers: 50

Bottomlayers: 50

Seam position: random

Infill: 100%  (but no infill is used, due to the high number of perimeters)

Print time: too much (a few days)

Assebly instructon joint

1. Take joint_upper and place joint_lower_turn around it. 
2. Fill the 34 6 mm stainless steel balls into the gap between those two parts
3. Screw joint_upper_turn onto joint_upper
4. Install the two joint_rotation_protection in the designated holes
5. Put the two O-rings on the joint_lower
6. Lubricate the sealing surface between the O-rings and joint_upper
7. Put the M3 locknut into joint_lower
8. Stick joint_lower into joint_upper
9. Screw joint_lower_turn onto joint_lower
10. secure joint_lower_turn with the M3x10 screw

Things i have learned from my second water cannon design

I testet this design, filled up with water with a bicycle pump at around 12 bar.

I was not able to print a pipe in two halfs. I tried multiple glues and even copperpins molten in the material with a soldering iron. It was never fully water tight at pressure. The big advantage would have been a saving in support material and it resultet in a by far better surface quality. Here some pictures from my attempts.

At the beginning i printed the parts with normal walls and infill. That resultet in some failures during pressure tests. After printing with many perimeters my parts can withstand a pressure of 12 bar and dont explode anymore.