- Joined
- 3 May 2004
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- Kapitalist Republik of Surrey
Jonny69's inventing shed: Giant Spudmatic gun (video added)
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
Edit: video is in post 36
Edit 2: more silly video in post 68
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
Edit: video is in post 36
Edit 2: more silly video in post 68
Last edited:
You must really trust those welds and fittings (nice welds, BTW). That kind of pressure scares me. I get nervous pumping up bike tyres. 