SpudFiles

So heres the dream =P
Today I picked up one of those little 250psi 12V pumps from Bunnings for $11.. Before stripping it down, I tested it to see what it could do, and to my surprise it got all the way to around 190psi before I shut it off.. It could likely go farther but I didnt want to push my luck..
So then I got to pulling it to bits.. And inside I found EXACTLY what I had hoped for.. A compact piston system with a motor the same size as used in my electric RC cars, same mounting pattern and all..
I ran the pump again with my half charged 7.2V Lithium RC battery and again, up to 190psi.. just slower.
As usual I got to removing unnecessary bits with the good ol' dremel..
The picture below is the result of my hacking. I re attached the pump line just for now, though Ill be taking it back off to implement the final plan.

The Plan:
Firstly, I am going to replace the sucky motor with a high torque crawler motor like this
http://www.rcmart.com/catalog/rc-brushe ... th=293_945

Then I am going to mount this little pump unit inside a PVC chamber which has one screw cap end. Im going to attach the pump inside to the screw cap, so it can be pulled out for oiling and motor maintenance.
Power will be provided by the Lithium battery I mentioned earlier. A plug epoxied into the screw cap will provide the "power point", and a push button switch will control it all...
True portability is what Im aiming for, and Im thinking this might be my compact, cheap, and elbow greaseless(no hand pumping) way of achieving it..
As always, thoughts, criticisms etc are welcome


OH SNAP. I just had a realisation.. Where the hell is the air for inside the chamber gonna come from..
Looks like I will be needing a one way valve of sorts. Any ideas?

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more_eggs wrote:OH SNAP. I just had a realisation.. Where the hell is the air for inside the chamber gonna come from..

Aside from that, how are you going to keep the pump cool?

I would mount it externally, and stick a bunch of heatsinks to the cylinder.

Hmm that is a good point..
Plenty of oil! haha noooo..
External is ugly though.. and moving gear could eat my finger if im not careful.. unless i make a cover etc.. One of the biggest advantages of internal was that I wouldnt need any piping etc to stand up to the pressure..but we will see I suppose

You could house it in a perforated section of aluminium tubing that would protect your fingers, act as a heat sink and look bad-ass

Stick a check valve somewhere on the chamber, and you now have an air feed. McMaster has a lot of check valves.

Drilling a 6mm hole in a 1/4 plug then soldering a schrader with the rubber and core removed into it also works if you can't order from McMaster Carr.

You need to use a blowtorch to solder it, make sure that no solder wicks up the centre of the schrader, that happened on the second one I did.

Turns out I wouldnt need to run a valve... the cylinder head has a tiny valve in it, so if i ran an airtight tube from that hole to outside the chamber it would be ok... cooling is still an issue, but im thinking I might just try it and see how long it lasts before the piston ring melts.. I only stand to lose $11

If you do go with that setup, try to find vacuum-rated tubing. Any other tubing would probably just crumple.

Only $11? How much would it cost to replace the compressor?

Well the internal pump plans are a no go.. Cant find any piping which is pressure rated, large enough to house the pump.. So its gonna have to be external..

Only $11? How much would it cost to replace the compressor?

Im not sure I completely understand what your asking.. The mini compressor costed $11.. Which I got the little pump setup out of..

this looks promising, the pump setup could be attached to a bike ......
Which section of bunnings was the pump in? I've never seen one before. good luck.

Here's how I picture it...

That was the plan jack.. minus the QEV in there...
But it looks like it will be more effort than its worth.. So I think Im gonna stick to the soda stream bottle at a high pressure with a regulator idea.. will be compact and light

Another good way to get heat sinks is to rip apart on old TV or CRT screen. i only did it once just to see if there was anything usable inside, ended up with 8 or so different sized sinks. (was a TV btw a crt tv)