I printed up one last Piston Seal mold just to try to get a finished Seal-Geometry that fell between the shape of the factory Piston Seal and the aftermarket Piston Seal I bought from the Australian vendor I was dealing with a while back. One of the things I wanted to change also on one of the mold-halves is the vent-holes.
On my initial 3D printed molds I had put three small vent-holes on the bottom half of the mold-set. This worked OK but I found that whenever I got a badly cast Piston Seal it was due to the fact that the casting resin was being sucked in and deformed in the areas of one or all three of these vent holes. I ended up eliminated two of those vent-hole and just going with one smaller hole.
After several failed casts I got to where I'm getting good useable Piston Seals. It took that long to figure out the correct mixing procedure for the casting resin and when I tried mixing in some Powdered Graphite that procedure required a slight alteration to my mixing procedure.
Right now I have eight Piston Seals that I've successfully cast and I plan on testing them in my first-gen Umarex Octane air rifle next week. I have a not-to-busy week next week so I plan on setting up my chronograph and re-testing the velocities of the existing factory replacement Piston Seal I presently have in my air rifle. I'll then swap it out for one of my new DIY home made Piston Seals with the Powdered Graphite mixed into the casting resin and then I'll test one of those same home made Piston Seals that I cast without the Powdered Graphite.
The factory replacement Piston Seals appear to only be tinted to the various colors they come in, not really impregnated with Graphite or any other elements and it's those factory Seals that have generally given me the highest velocities. The Australian aftermarket Piston Seals gave me slightly slower velocities than any of the factory replacement Seals I've ever used and it's those aftermarket Piston Seals that were said to impregnated with Powdered Graphite. It will be interesting to see if adding that Powdered Graphite effects velocities at all. In my opinion, I think it has more to do with the geometry and fit of the finished Piston Seal rather than the inclusion or exclusion of Powered Graphite or any other additive to promote lubricity.
The eight Home Made Piston Seals I've successfully cast represent about one-hundred dollars worth of replacement Piston Seals; that's if you include shipping from an online vendor. The aftermarket Piston Seals actually cost a bit more. Strangely enough, One hundred dollars is about the amount I've spent on replacement Piston Seals over the years I've owned my Umarex Octane break barrel air rifles.
I have a few more closeup pics of my latest home made Piston Seals that I'll be posting as soon as I can get them shrunk down for uploading to the few online blogs I'm working with.
At this point I want to remind the members of our Umarex Octane Users Group (AFTER I've Tested Them) that if you need a Piston Seal replacement please contact me and I'll send out one of these prototype home made Piston Seals. You will have to pay for postage but the Seal Is on me. The postage, when I send out trigger components is about two dollars and fifty cents worth of stamps and envelopes so I'm thinking that the postage for one of these little Seals will be about the same. ALSO; If you own a 3D printer and you'd like to try making your own Piston Seals as well, just contact me and I'll email you the STL files at NO COST.
Please understand that you will have to process the STL file in your slicer software of choice to be printed on your particular 3D printer. The resolution on my printer was such that I had to lightly sand the surfaces of my prints to get a semi-smooth surface and then I opted to quickly pour and then allow to quickly drip off and dry some acetone on the surfaces of my mold-halves which gave me an even smoother surface in the areas of the mold cavities where the Piston Seals are actually formed.
Your 3D printer may be a far better printer than mine and not need this kind of post-print work to get smooth surfaces. My printer isn't all that great but it's good enough to generally give me what I'm looking for, with a bit of work after the print.
I'll be back with those photos later.
HollowPoint