GTA
Airguns by Make and Model => Diana Airguns => Topic started by: Louis Loria II on August 25, 2018, 05:48:49 PM
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I had a "failure" of the O-ring piston seal in my 54. Or maybe it wasn't a failure and its just the nature of O-rings. My rifle was extremely consistant and accurate and then it suddenly lost about 25fps just sitting in the bag in the closet. Having it apart everything looked good, except that the seal seemed to have a bit less grease on it than when I installed it. Do these seals require more grease to work properly? Any information is greatly appreciated.
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Louis
The problem with current "Oring seal adaptors" currently on the market is that they do not provide a rigid, solid gland/backing to the ORing, so the ORing cannot really and fully do its job.
My O'Ring'ed pistons, as well as many others I know, run completely "dry". And use a powder, or mixture of powders to ensure proper slippage (Graphite and MoS2 are just the two most common ones).
Try using dry lubes, or try a better piston/head.
JMHO
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I had a "failure" of the O-ring piston seal in my 54. Or maybe it wasn't a failure and its just the nature of O-rings. My rifle was extremely consistant and accurate and then it suddenly lost about 25fps just sitting in the bag in the closet. Having it apart everything looked good, except that the seal seemed to have a bit less grease on it than when I installed it. Do these seals require more grease to work properly? Any information is greatly appreciated.
I've been successfully using home turned oring sealed piston caps with my HW springers (HW77k, Beeman R9 & HW95) for a couple decades and found that when the oring is fitted correctly the oring will outlast a couple premium springs.
I don't know if your oring piston seal and cap was a "custom fit" like I use of one of those "rubber adapters". I really don't understand how a generic fit oring adapter would work over the long haul because the nature of "sloppy receiver geometry" doesn't allow much oring seal misfit at all. I've also found that while the oring sealed piston caps I've cut work really well with receivers and compression tubes up to about 26mm inside diameter, I also found that there wasn't much (if any) benefit when I oring sealed a couple Webley Kodiacs and RWS54s. LOL...the main benefit for properly fitted oring seals in guns with larger 30ish mm receiver diameters was the fact that the seal was very consistent and cheap to replace with an "over the counter" oring from a parts warehouse.
Here are a couple oring sealed piston caps I made for HW77/97, beeman R9, HW95 and even a cheap Chinese B3. The earlier piston caps were "bare aluminum, however later on (a couple years ago) I started adding a Delrin bearing to the piston cap skirt...............
(https://i.imgur.com/Cgh87Kol.jpg)(https://i.imgur.com/WknqNuVl.jpg)(https://i.imgur.com/GyTMWD7l.jpg)
I'm currently testing out an "all molly filled 6/6 nylon" piston cap to determine if the plastic will hold up to the heat and pressure of the transfer port.......
(https://i.imgur.com/dgFfuqTl.jpg)(https://i.imgur.com/BE8seEGl.jpg)(https://i.imgur.com/e591fUgl.jpg)
So far so good!
I read in Hectors reply that he uses "dry powdered lube" for his oring seal lubing and I also used "powdered graphite" (the stuff you puff into locks, after stripping all petro lubes) for a piston seal lubes to get away from diesel prone molly paste. The graphite worked great and there was absolutely no "piston seal stiction". LOL.....the oring actually looked like it had a "metallic plating" when inspected after shooting for a while. I got away from the "dry lube" when I discovered non-dieseling Dupont Krytox "space station lubes" which I've been using for a few years since.
Anywhoo.....for my setups I use a rather thin size 020 oring to minimize "rubber against metal rubbing".
The first thing I do is to gage the consistency of the HW receiver using a home made gage like this............
(https://i.imgur.com/JjxZu5Wl.jpg)
If the gage slides the length of the receiver all is fine, however if it gets "hung up" on a constriction the home made hone comes out and removes enough of the constriction so the "gage" will pass..........
(https://i.imgur.com/Gsa7pdll.jpg)(https://i.imgur.com/sImpGWkl.jpg)
After verifying the the receiver is "suitable" the piston is fitted with an oversized "puck" to be sized on the lathe after the piston shell is centered in the lathe chuck...........
Next the puck us machined till it's about .005 smaller than the smallest constriction in the receiver. The reason the puck is machined mounted to the piston is that some HW piston seal retainers aren't concentric with the piston shell. Machining the piston cap while mounted to the piston maintains concentricity.........
(https://i.imgur.com/W0IcFJRl.jpg)(https://i.imgur.com/5xp7Mm8l.jpg)
The final step is to cut the oring groove for the orings. The oring groove isn't as wide as the standard groove for a size 020 oring and it's also deeper that the standard dynamic groove giving only "8-10% oring squeeze instead of the normal "15-25% squeeze". This is done to minimize the "rubber to metal" contact which I personally believe affects the consistency of the shot cycle when there are temperature shifts that can change the viscosity of the lube or the durometer of the oring.
Anywhoo.....if this is the type of oring seal you're using, I don't see how it could be better than the factory seal or other "more normal" Vortek seals.........
(https://i.imgur.com/RmUwKtcl.png)
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NCED,
Great post and let us know how the Moly filled 6/6 piston cap works out. ;)
-Y
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I had a "failure" of the O-ring piston seal in my 54. Or maybe it wasn't a failure and its just the nature of O-rings. My rifle was extremely consistant and accurate and then it suddenly lost about 25fps just sitting in the bag in the closet. Having it apart everything looked good, except that the seal seemed to have a bit less grease on it than when I installed it. Do these seals require more grease to work properly? Any information is greatly appreciated.
I've been successfully using home turned oring sealed piston caps with my HW springers (HW77k, Beeman R9 & HW95) for a couple decades and found that when the oring is fitted correctly the oring will outlast a couple premium springs.
I don't know if your oring piston seal and cap was a "custom fit" like I use of one of those "rubber adapters". I really don't understand how a generic fit oring adapter would work over the long haul because the nature of "sloppy receiver geometry" doesn't allow much oring seal misfit at all. I've also found that while the oring sealed piston caps I've cut work really well with receivers and compression tubes up to about 26mm inside diameter, I also found that there wasn't much (if any) benefit when I oring sealed a couple Webley Kodiacs and RWS54s. LOL...the main benefit for properly fitted oring seals in guns with larger 30ish mm receiver diameters was the fact that the seal was very consistent and cheap to replace with an "over the counter" oring from a parts warehouse.
Here are a couple oring sealed piston caps I made for HW77/97, beeman R9, HW95 and even a cheap Chinese B3. The earlier piston caps were "bare aluminum, however later on (a couple years ago) I started adding a Delrin bearing to the piston cap skirt...............
(https://i.imgur.com/Cgh87Kol.jpg)(https://i.imgur.com/WknqNuVl.jpg)(https://i.imgur.com/GyTMWD7l.jpg)
I'm currently testing out an "all molly filled 6/6 nylon" piston cap to determine if the plastic will hold up to the heat and pressure of the transfer port.......
(https://i.imgur.com/dgFfuqTl.jpg)(https://i.imgur.com/BE8seEGl.jpg)(https://i.imgur.com/e591fUgl.jpg)
So far so good!
I read in Hectors reply that he uses "dry powdered lube" for his oring seal lubing and I also used "powdered graphite" (the stuff you puff into locks, after stripping all petro lubes) for a piston seal lubes to get away from diesel prone molly paste. The graphite worked great and there was absolutely no "piston seal stiction". LOL.....the oring actually looked like it had a "metallic plating" when inspected after shooting for a while. I got away from the "dry lube" when I discovered non-dieseling Dupont Krytox "space station lubes" which I've been using for a few years since.
Anywhoo.....for my setups I use a rather thin size 020 oring to minimize "rubber against metal rubbing".
The first thing I do is to gage the consistency of the HW receiver using a home made gage like this............
(https://i.imgur.com/JjxZu5Wl.jpg)
If the gage slides the length of the receiver all is fine, however if it gets "hung up" on a constriction the home made hone comes out and removes enough of the constriction so the "gage" will pass..........
(https://i.imgur.com/Gsa7pdll.jpg)(https://i.imgur.com/sImpGWkl.jpg)
After verifying the the receiver is "suitable" the piston is fitted with an oversized "puck" to be sized on the lathe after the piston shell is centered in the lathe chuck...........
Next the puck us machined till it's about .005 smaller than the smallest constriction in the receiver. The reason the puck is machined mounted to the piston is that some HW piston seal retainers aren't concentric with the piston shell. Machining the piston cap while mounted to the piston maintains concentricity.........
(https://i.imgur.com/W0IcFJRl.jpg)(https://i.imgur.com/5xp7Mm8l.jpg)
The final step is to cut the oring groove for the orings. The oring groove isn't as wide as the standard groove for a size 020 oring and it's also deeper that the standard dynamic groove giving only "8-10% oring squeeze instead of the normal "15-25% squeeze". This is done to minimize the "rubber to metal" contact which I personally believe affects the consistency of the shot cycle when there are temperature shifts that can change the viscosity of the lube or the durometer of the oring.
Anywhoo.....if this is the type of oring seal you're using, I don't see how it could be better than the factory seal or other "more normal" Vortek seals.........
(https://i.imgur.com/RmUwKtcl.png)
This is my o-ring. The retainer seems to be made of the same material as the Vortek MO2 parachute seals. I have some O-rings on order. Going to try a couple of different materials.