Jonny69's inventing shed: Giant Spudmatic gun

[Jonny69]

On another forum I'm being pestered to put some more of my toys online so I'm going to run a series of threads and show you what I've got in my garage. I'll start with the spudmatic gun I made today and move onto some of the older stuff as my bandwidth allows

So, plan is to make a little reservoir out of steel tube that I can pump up with a bike pump and have a ball valve at the other end to let it all out at once. No fire, reliable and repeatable tried and tested method which I used last week on one of the gags at work, for firing a model Polaris missile.

Start with a bit of 75mm tube, this bit is 250mm long:



It needs two endcaps, one with a hole in it. Cut these out with a 1mm blade in the angle grinder, then clean them up with a flap wheel. The hole is cut with a Screwfix holesaw which has lasted just 3 holes in 2mm steel:



(I'm not all pro using engineers blue but the way, the steel I had happened to have it on already)

Through that hole is going a brass tank fitting, a common plumbing fitting for 15mm copper pipe:



Fits through the hole like so:



I've drilled a hole in the side so I can squish through a tyre valve that I got from the local tyre place:





This is the only difficult bit for most people, welding the ends on:



The tank fitting needs to be tightened up before the end is welded on so I cranked it up paggin' tight with some PTFE inside, welded in short stitches and cooled in water each time to stop too much heat getting to the brass:



It's assembled with a lever ball valve tap thing, again, another common plumbing part with compression fittings so no tapping or soldering needed:



And this is how it works, fairly self explanatory:



Testing.

The good news is it works pretty well. The pump is a bit rubbish but 40psi sends a 15mm slug of potato clean over the 3 stories of flats in my building. 100psi sends it right over the block adjacent and 160psi which is pretty much all I can manage with all my weight on the pump goes about 75 metres down the road with a bit of recoil.

I'm chuffed, first toy for the camping trip in June is complete. Better stock up on potatoes

[Fayshun]

AWESOME!!

[Burble]

I want to live next door to Mr. 69!

[Belmit]

Originally Posted by Burble

I want to live next door to Mr. 69!

I don't, the lawn would just be littered with chunks of raw potato!


I think it needs to be adpated to have a superheater at the end so it makes instant chips.

[Fayshun]

Originally Posted by Belmit

I don't, the lawn would just be littered with chunks of raw potato!


I think it needs to be adpated to have a superheater at the end so it makes instant chips.

With a salt and vinegar dispensing "afterburner"!

[Belmit]

Food always tastes better when it's fired point blank into your face at 160psi.

[Feek]

You want to borrow my 300bar divers bottle?

(300 bar = around 4300 psi!)

[Fayshun]

Originally Posted by Feek

You want to borrow my 300bar divers bottle?

(300 bar = around 4300 psi!)

Sub orbital spuds anyone?

[Stan_Lite]

Originally Posted by Feek

You want to borrow my 300bar divers bottle?

(300 bar = around 4300 psi!)

That could get a little messy

The SWP (Safe Working Pressure) of a typical 15mm compression ball valve is around 16bar (approx 230psi). If the ball valve came from Screwfix, like the hole saw, I'd be wary of putting the 160psi through it that Jonny did.

[Jonny69]

Originally Posted by Bigstan

That could get a little messy

The SWP (Safe Working Pressure) of a typical 15mm compression ball valve is around 16bar (approx 230psi). If the ball valve came from Screwfix, like the hole saw, I'd be wary of putting the 160psi through it that Jonny did.

That's good to know. Is that for the ball or the compression fitting? This was from a plumbers merchant, not Screwfix.