Mares pneumatic pump seals?

Fibonacci · May 15, 2017

Found a cheap spare Mares pump, the bore and threads are OK but both the o-ring and the small cup seal are shot.
Cup seal measures about 9.8 in dia x 5.8 with a bore of 3.9 mm
Anyone know where to get replacements please...?

Fibonacci · May 28, 2017

After many emails I have determined that, incredibly, the pump cup seal is NOT available as a service part from Mares.
You need to buy a whole new pump at about $80 if a 50c seal fails!!

So I did a bit of web searching and stumbled across this Neken 0-300 psi pump meant to service air shocks etc.

http://www.ebay.com/itm/Neken-High-...hash=item5b0b6eb1a8&item=391033827752&vxp=mtr

With the right adaptor mounted on the hose end, could work on a range of pneumatic spearguns...

popgun pete · May 28, 2017

You could always replace the seal carrier with a piston and "O" ring, many pneumatic speargun pumps are equipped with that set-up rather than a cup type seal. Some hand pumps don't have air breather holes, they rely on the cup seal collapsing to suck air in past the seal as it is pulled backwards in the pump body, hence for those pumps you need to add air breather holes if you change the seal type. Mares pumps have breather holes, the main thing is that the breather holes don't cut the edges of the seal as it moves past the holes.

Fibonacci · Nov 30, 2017

popgun pete said:
You could always replace the seal carrier with a piston and "O" ring, many pneumatic speargun pumps are equipped with that set-up rather than a cup type seal. Some hand pumps don't have air breather holes, they rely on the cup seal collapsing to suck air in past the seal as it is pulled backwards in the pump body, hence for those pumps you need to add air breather holes if you change the seal type. Mares pumps have breather holes, the main thing is that the breather holes don't cut the edges of the seal as it moves past the holes.

On a hunch I ordered a couple of these Seacsub cup seals from Edosub... they fit the Mares pump perfectly!

The o-ring at the end of the pump appears to be ID 6.0 x 1.75mm

http://www.edosub.it/ecommerce/inde...rd=Guarnizione&option=com_virtuemart&Itemid=1

Diving Gecko · Nov 30, 2017

Good find.
Given your measurements, the o-ring at the end is probably a 6.07x1.78 o-ring (ID x W). Very easy to find. It's in one of the major standard series and often called "AS568-010" or at least "-010".
I should have the measurements somewhere as I made a pump adapter as one of the first things on my Mini Lathe not long ago. I based it on measurements taken from Seac and Mares pumps and it has worked flawlessly. Will check my notes later.

Fibonacci · Nov 30, 2017

Diving Gecko said:
Good find.
Given your measurements, the o-ring at the end is probably a 6.07x1.78 o-ring (ID x W). Very easy to find. It's in one of the major standard series and often called "AS568-010" or at least "-010".
I should have the measurements somewhere as I made a pump adapter as one of the first things on my Mini Lathe not long ago. I based it on measurements taken from Seac and Mares pumps and it has worked flawlessly. Will check my notes later.

Aha... thanks Gecko
That makes sense -010 o-rings are commonly used in SCUBA regulators for LP inflator hose (internal QD connector), and the 2nd stage hose (reg end)

Diving Gecko · Nov 30, 2017

Yeah, a lot of the o-rings in our guns come from that series.
The three big ones are a mystery, though. They are 2.15-2.2mm in section which I haven't been able to track down, yet.

I looked at my notes from when I measured the Mares and Seac pumps and my notes tell me the diameter of the o-ring groove is actually 7.0-7.35mm, while the Salvimar adapter for Mares is 7.5mm. So, the 6.07mm (ID) ring will be stretched beyond what is recommended - but other o-rings are, too in most of these guns. Perhaps to limit the amount of differently sized o-rings in the gun.
But I wouldn't be surprised if you could go with the next one up in the series which is 6.75 x 1.78mm (ID x W). There's even an intermediate that is 6.35mm (ID) but not always as easy to find.

Diving Gecko · Dec 4, 2017

I just checked the o-rings on my Seac and Mares pumps. I can not guarantee that I have not changed these o-rings, but anyways - both the pumps work.
The Seac one has a 6.75x1.78mm (ID x W) o-ring and the Mares pump an 6.35x1.78mm (ID x W).

Fibonacci · Dec 4, 2017

Diving Gecko said:
I just checked the o-rings on my Seac and Mares pumps. I can not guarantee that I have not changed these o-rings, but anyways - both the pumps work.
The Seac one has a 6.75x1.78mm (ID x W) o-ring and the Mares pump an 6.35x1.78mm (ID x W).

Thanks Gecko, good to know!

Diving Gecko · Dec 10, 2017

popgun pete said:
You could always replace the seal carrier with a piston and "O" ring, many pneumatic speargun pumps are equipped with that set-up rather than a cup type seal. Some hand pumps don't have air breather holes, they rely on the cup seal collapsing to suck air in past the seal as it is pulled backwards in the pump body, hence for those pumps you need to add air breather holes if you change the seal type. Mares pumps have breather holes, the main thing is that the breather holes don't cut the edges of the seal as it moves past the holes.

Hi Pete,
Since reading this, I am toying with the idea of making a hand pump - or at least a piston modification on an older one so I don't have to rely on those cup seals. I have a question which I think you can help me with.
Am I right in assuming that if the seal can't collapse then you'd be pulling a vacuum when you retract the pump handle? Let's say we are almost pulling a full vacuum so that, given the size of the piston, we would be in the order of pulling around 800g on each pull-back until you get to the breather hole? Does that make sense?
Now, if that is a lot or a little and will have any noticeable effect when filling a gun, I don't know.

Fibonacci · Dec 10, 2017

Diving Gecko said:
Am I right in assuming that if the seal can't collapse then you'd be pulling a vacuum when you retract the pump handle? Let's say we are almost pulling a full vacuum so that, given the size of the piston, we would be in the order of pulling around 800g on each pull-back until you get to the breather hole? Does that make sense?
Now, if that is a lot or a little and will have any noticeable effect when filling a gun, I don't know.

Hi Gecko
As someone who has restored a few pressure kero lanterns and stoves, I've often wondered why the pneumatic speargun pump cup design is so relatively crude.
The more sophisticated engineering found on the Primus integral pump involves the seal cup being mounted to a brass carrier with internal countersink which mates up against a corresponding external taper on the shaft.
The carrier cup is free to move forward and back about 1mm but is held captive by a nut... when withdrawing the pump rearwards, air rushes past the gap between the taper and the countersink in the carrier.
When pushing forward again, the two tapers close up and seal against the pressure so the pump cup can transmit the air past the one-way valve at the bottom of the integral pump tube, thus pressurising the tank and forcing out the kero.
Typically pressures are low in a kero stove or lantern, not sure if this would work at the much higher pressures in a pneumatic gun, but there may be some opportunities with a modification of this design using o-rings vs two tapers to seal.
Anyway be an interesting project... please keep posting updates!

Mares pneumatic pump seals?

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