Hi all,
As I keep taking my guns apart all the time - yeah, I have too much time for that and too little for diving - I have been thinking about a way to not have to pump the guns manually.
Obviously, the fridge pump solution is great and affordable and I will likely make one in the future but I also wanted something portable.
For a while I tried to see if I could find a small electrical pump that could get to the pressures needed and would be small enough to travel with but no luck so far.
I realized, thinking back, that when I travel I am never far from a scuba tank so I want to use that as a source.
Both Mares, Omer and Salvimar offer commercial versions of a scuba inflator but they are not cheap. Mares' is actually the cheapest (around E 100) but you need a first stage regulator to make it work. The others work as they are, but are 2-2.5 times more expensive.
I am a bit in luck since my older brother works in a small company which services and builds air-conditioning test units, so he had some parts lying around which could be put to good use.
This is still in the FrankenRig phase and could be tidied up a tad by swapping some parts. But for now it works and has been tested to about 45 bar. But the first change I will do is to change the hose to a proper high pressure hose.
The main ingredient here is the over pressure relief valve. It is adjustable and I set it to vent at 34 bar - as I would need this setup for my Mirage(s), too. This is an important safety function as the scuba tanks often hold about 200 bar.
Oh, almost forgot - what made me finally go for this was when I realized that Salvimar sells the pump inlet valve fittings as loose items. This is perfect because it meant, I did not have to get one custom made and it also means, if you have, say, both Salvi, Cressi and Mares guns it is easy just to swap the pump fitting and one inflator (or fridge pump) will work for most guns.
The pump fittings cost E 15 each.
In the end, making this yourself is actually not that cheap, but I did it because I could source many parts for free.
I had to buy the yoke connector to the scuba tank but I got for about E 15 in China.
This particualr over pressure relief valve can be had for 10-20 USD on Ebay.
The whole thing weighs about 900 grams. Not too bad, but I wish it was even lighter - but def lighter than lugging a fridge pump with me;-)
Here is the beast in all it's FrankenBeauty.
The hose will be changed to a proper high pressure hose next.
The over pressure relief valve is made out of brass and seen to the left of the pressure gauge. You adjust it with an allen key but there is no scale, so it's a bit of trial and error but nothing major at all.
I had to do some quick and rough trimming of the Salvimar pump fitting as it was just a tiny bit too big to go straight into the Mirage.
A few practical notes if any of you are setting out to make something similar:
The Salvimar fitting is a straight G1/4 female thread (not NPT/tapered).
The relief valve I used is a SWAGELOK B-4CPA2-350.
As I keep taking my guns apart all the time - yeah, I have too much time for that and too little for diving - I have been thinking about a way to not have to pump the guns manually.
Obviously, the fridge pump solution is great and affordable and I will likely make one in the future but I also wanted something portable.
For a while I tried to see if I could find a small electrical pump that could get to the pressures needed and would be small enough to travel with but no luck so far.
I realized, thinking back, that when I travel I am never far from a scuba tank so I want to use that as a source.
Both Mares, Omer and Salvimar offer commercial versions of a scuba inflator but they are not cheap. Mares' is actually the cheapest (around E 100) but you need a first stage regulator to make it work. The others work as they are, but are 2-2.5 times more expensive.
I am a bit in luck since my older brother works in a small company which services and builds air-conditioning test units, so he had some parts lying around which could be put to good use.
This is still in the FrankenRig phase and could be tidied up a tad by swapping some parts. But for now it works and has been tested to about 45 bar. But the first change I will do is to change the hose to a proper high pressure hose.
The main ingredient here is the over pressure relief valve. It is adjustable and I set it to vent at 34 bar - as I would need this setup for my Mirage(s), too. This is an important safety function as the scuba tanks often hold about 200 bar.
Oh, almost forgot - what made me finally go for this was when I realized that Salvimar sells the pump inlet valve fittings as loose items. This is perfect because it meant, I did not have to get one custom made and it also means, if you have, say, both Salvi, Cressi and Mares guns it is easy just to swap the pump fitting and one inflator (or fridge pump) will work for most guns.
The pump fittings cost E 15 each.
In the end, making this yourself is actually not that cheap, but I did it because I could source many parts for free.
I had to buy the yoke connector to the scuba tank but I got for about E 15 in China.
This particualr over pressure relief valve can be had for 10-20 USD on Ebay.
The whole thing weighs about 900 grams. Not too bad, but I wish it was even lighter - but def lighter than lugging a fridge pump with me;-)
Here is the beast in all it's FrankenBeauty.
The hose will be changed to a proper high pressure hose next.
The over pressure relief valve is made out of brass and seen to the left of the pressure gauge. You adjust it with an allen key but there is no scale, so it's a bit of trial and error but nothing major at all.
I had to do some quick and rough trimming of the Salvimar pump fitting as it was just a tiny bit too big to go straight into the Mirage.
A few practical notes if any of you are setting out to make something similar:
The Salvimar fitting is a straight G1/4 female thread (not NPT/tapered).
The relief valve I used is a SWAGELOK B-4CPA2-350.
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