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Any photos of said hole?Have disassembled something like 10 mares competition and jet guns. They all had the pin hole deformed and weared out.
The last one was rescued by replacin' the handle with a Sten one.
In the latest Cressi Saetta the manufacturer is using a very similar system as the one described above for the Competition/Jet Mares models. But I've had no direct experience with that speargun.
Will do so tmrw.You have mentioned the pump before and I am intrigued - can you share some pics, please? The more the merrier.
I think I know how the o-ring piston seal works. By the o-rings moving into a part of the piston with a small slot in it to allow "leakage" when retracting the handle, right?
The reason I am asking is that I was very close to making such an exact pump before a trip a while back but ran out of time. I have been burned 2-3 times before with shitty pumps breaking on me on trips. Once, the seal of my One Air pump disintegrated as I was filling up a 120 gun and a small piece of rubber from the pump seal got stuck in the inlet valve of the gun. As a result, the gun which I had just about pumped to 27 or so bar lost all the air and I had to take it apart, fix it, fix the pump and pump the gun back up. I was not happy. Another time, I cross threaded a Seac pump and yeah, my Mares pump has the pushed-in end wiggling loose.
I knew you would have this question. Little white thing does not move. It has to o-rings , one inside the body of the pump and one plays the role of that o-ring at the end of your pump (that thing that wiggles). It is used to reduce the dead space of the pumpThanks for the pics. But I can’t figure out what the little white plug/piston is for.
I’ve seen pumps where the o-ring seat is deliberately opened on one side so that when you retract the pump handle the o-ring is allowed to leak. And then, obviously in the “pumping direction” the o-ring flange is normal so that there’s a full seal. I guess you did that on the metal piston, too?
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No,I have nothing like that. Your original pump also has the air hole. But the piston is quite different - it is not serviceable. Mine is. Just replace o-rings and you are good to go.Here’s a pic of a bike pump showing the intentional cut outs to allow one-way leaking:
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Introduction of that white cylinder was necessary in order to move the thread to the body of the pump and thus fix the shit Mares created.
Exactly! I cut it out of delrin. It will last forever since it does not moveAh, of course! So, about half of it will stick out and seal inside the inlet valve of the gun.
Got it now.
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Unfortunately my pump is aluminum (the pusher is stainless). Since it is screwed into the end of the gun that is stainless it creates a chance of cross-threading. Thus you have to be careful. First of all it is difficult to find a stainless tube 14mm OD and 10mm ID and secondly cutting a 14x1 thread on stainless is a bitch. You need a proper die that is good for stainless and costs a lot. Or cut it on a lathe
I have a small lathe as well. Titanium would not be cheap - you need 18" length and 2mm wall. Go to aliexpress and look for stainless. You need only the part with the thread to be 14mm OD, the rest you can safely reduce to 1mm wall. Thus weight saving with titanium would be minisculeYeah, I’m lucky, I have a small lathe at home. I was even thinking of making the pump in titanium as I think I can get it cheap in China.
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Yeah, I’m lucky, I have a small lathe at home. I was even thinking of making the pump in titanium as I think I can get it cheap in China.
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You must look for a 'seamless' tube. They are smooth. But there is an issue of finding a proper o-ring given the ID of the tube. You must know before hand what o-rings are available to you. See here https://www.applerubber.com/oring-gland-calculator/ for referenceYeah. I have a few of those on my wishlist already;-). I’m actually based in China though I haven’t been back “home” for a long time now. So, I can get pretty much everything on Taobao within a few days at very affordable prices. The only reason I didn’t order the titanium tubes yes was because the seller couldn’t really tell me how well polished the inside of the tubes are. I might just buy one and see how they look and if I can polish them myself. Otherwise, the mirror polished SS tubes will be my backup solution.
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You must look for a 'seamless' tube. They are smooth. But there is an issue of finding a proper o-ring given the ID of the tube. You must know before hand what o-rings are available to you. See here https://www.applerubber.com/oring-gland-calculator/ for reference
If you get an ID of 10mm - you will find the o-rings. My pump's ID is 9.5mm - I could not find the 10mm one (to match the gun's valve ID).True. But I have reverse engineered enough bulkheads and other airgun parts by now and made a few of my own from scratch to have developed a good understanding of proper o-ring seat design. Definitely enough to see when the real manufacturers have not followed “the rules”.
I use two other online calculators one of which is Trelleborg’s and the other one escapes me now. But they sure do make it easy and I’ve learned a lot by using them.
Again, with Taobao I can literally buy pretty much any o-ring size piecemeal for very little money. But I’m sure a standard AS568 series or 1.5mm or 2mm section ring can work as long as you design the o-ring seat to give the ring the correct compression.
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