22mm Skirtless Conversion



Author Topic: 22mm Skirtless Conversion  (Read 3120 times - 2 votes) 
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Offline Gear_Junkie

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Re: 22mm Skirtless Conversion
« Reply #40 on: December 06, 2018, 02:14:02 PM »
I ordered the parts last night from Tony.  He was super helpful in answering all of my questions, and has already shipped the parts :o  I can't wait to give them a shot.  Of course, there is that small issue that I don't yet own a TX200.  I hope to get one soon.  In the meantime, another member has offered to let me shoot the holy grail of TX200/22mm conversions, and I hope to take him up on that!  That should let me know what perfection feels like, and will give me something to work towards as I tune my rifle.
  • Nevada City, CA
.177 Daystate Regal XL & Hawke Airmax 30 SF 6-24x50
.177 Air Arms TX200 HC & Hawke Airmax 30 SF 6-24x50
.177 HW50S & Compact UTG 3-12x44

Offline TonyL

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Re: 22mm Skirtless Conversion
« Reply #41 on: December 06, 2018, 02:43:03 PM »
I ordered the parts last night from Tony.  He was super helpful in answering all of my questions, and has already shipped the parts :o  I can't wait to give them a shot.  Of course, there is that small issue that I don't yet own a TX200.  I hope to get one soon.  In the meantime, another member has offered to let me shoot the holy grail of TX200/22mm conversions, and I hope to take him up on that!  That should let me know what perfection feels like, and will give me something to work towards as I tune my rifle.

Now thats dedication, orders a conversion and does not even own the rifle ;)

get on to PA and get an order in, make sure they check the barrel for rust first though ;)
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Offline Yogi

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Re: 22mm Skirtless Conversion
« Reply #42 on: December 07, 2018, 02:18:42 PM »


Yes, Tony reduces TP length on his conversions.  He machines them down by 3mm.  This increases velocity by 40fps with the same swept volume on JSB Express 7.9.

By reducing the TP by 3mm does he not increase the stroke? :-\  Or does the new piston nose reduce the stroke by 6mm?

-Y
  • San Francisco, CA
Hatsan 95 Vortex, .22
RWS 6G, .177
RWS LP8 Magnum, .177
Diana 340 N-Tec, .22 Compact Lexus
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Offline Nitrocrushr

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Re: 22mm Skirtless Conversion
« Reply #43 on: December 07, 2018, 08:05:09 PM »


Yes, Tony reduces TP length on his conversions.  He machines them down by 3mm.  This increases velocity by 40fps with the same swept volume on JSB Express 7.9.

By reducing the TP by 3mm does he not increase the stroke? :-\  Or does the new piston nose reduce the stroke by 6mm?

-Y

The 3mm reduction in Transfer Port length does not affect the stroke, it just improves the efficiency with the 22mm set-up.  The reduction in stroke length comes from the total length from front of main seal to the end of the piston rod.  The shorter this length is, the longer the stroke, the longer this length...the shorter the stroke ;)

Steve

Steve
  • Lancaster, Pennsylvania
Air Arms TX200 .177 Rifle - 22mm skirtless dual seal conversion from Tony Leach

HW98 .177 - Vortek 12fpe


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Offline TonyL

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Re: 22mm Skirtless Conversion
« Reply #44 on: December 11, 2018, 09:25:54 AM »


Yes, Tony reduces TP length on his conversions.  He machines them down by 3mm.  This increases velocity by 40fps with the same swept volume on JSB Express 7.9.

By reducing the TP by 3mm does he not increase the stroke? :-\  Or does the new piston nose reduce the stroke by 6mm?

-Y


The piston nose sits on the rod 4mm further out, the seal then sits a further 3mm past this so effectively now the stroke is reduced by 7 to 8mm.
The TP length is reduced by 3mm so this adds 3mm stroke back on.

so lets call it 5mm off the stoke, which means the conversion runs 93mm stroke.

All depends on that piston nose to rod fit...most come out between 4 to 5mm.

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Offline DanT

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Re: 22mm Skirtless Conversion
« Reply #45 on: December 20, 2018, 10:28:20 PM »
This conversion is awesome and glad to see Tony on GTA. Once you get your TX you will not be disappointed.

Merry Christmas air gunners!

Cheers!

Dan
  • Shawnee, KS

Offline Gear_Junkie

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Re: 22mm Skirtless Conversion
« Reply #46 on: January 11, 2019, 12:27:50 PM »
Have any of you tested this kit at different temperatures and elevations?  I'm just curious how much it is affected by these variables.  It will be another month before I have a chance to check these things out, so I thought I'd throw the question out there...

Thanks!
  • Nevada City, CA
.177 Daystate Regal XL & Hawke Airmax 30 SF 6-24x50
.177 Air Arms TX200 HC & Hawke Airmax 30 SF 6-24x50
.177 HW50S & Compact UTG 3-12x44

Offline Gear_Junkie

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Re: 22mm Skirtless Conversion
« Reply #47 on: January 11, 2019, 07:25:31 PM »
One more question...  Is anyone else noticing that their barrel is fouling quickly?  Attached is an image of some cleaning patches that I pulled through the barrel after only 25 shots with FTT's going at 770 fps.  I'd like to know if the barrel is fouling so quickly since a brushed it so heavily with a brass brush and J-B Bore paste (to remove the rust) or if this is just a result of the higher pressure that the 22mm piston kit creates.  No exaggeration - the barrel was aggressively brushed for probably 5 - 10 minutes a session 3 different times.  It does get clean after only 4 patches, but my other rifles would need to be shot at least 100 times in order to produce the first patch that is this dirty.

Thanks!
  • Nevada City, CA
.177 Daystate Regal XL & Hawke Airmax 30 SF 6-24x50
.177 Air Arms TX200 HC & Hawke Airmax 30 SF 6-24x50
.177 HW50S & Compact UTG 3-12x44

Offline Nitrocrushr

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Re: 22mm Skirtless Conversion
« Reply #48 on: January 13, 2019, 04:48:27 PM »
Have any of you tested this kit at different temperatures and elevations?  I'm just curious how much it is affected by these variables.  It will be another month before I have a chance to check these things out, so I thought I'd throw the question out there...

Thanks!

Zack, I ran a test on my 22mm dual seal conversion today.   Outdoor temperature was 27 degrees with a light breeze.  I ran about 5 shots over the chronograph straight off the rack at room temperature, which was about 70 degrees.  I then set the rifle outside on a sandbag in the fresh snow - 27 degrees for 1 hour.




After the rifle sat outside for an hour, I quickly ran 5-6 shots over the chronograph straight from the outside.

TX200 Rifle - .177 caliber - Tony Leach 22mm conversion kit (dual seal)
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.86 grains - 806 fps - 11.34 fpe

Outdoors - 27 degrees for 1 hour
JSB 7.87
Pellet weighed at 7.88 grains - 816 fps - 11.65 fpe

2.7% increase in energy

Next, I swapped power plants and ran the exact same test using my standard sub-12 fpe tune with the Maccari Tesla MK2 seal

TX200 Rifle - .177 caliber - with factory piston, JM Ultra XLD, Maccari Tesla MK2 main seal
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.90 grains - 810 fps - 11.51 fpe

Outdoors - 27 degrees for 1 hour
Pellet weighed at 7.86 grains - 835 fps - 12.17 fpe

5.5% increase in energy


While the dual seal design helps to reduce the variation due to temperature changes, as with any springer there is still some variation.  In a spring piston air rifle I think you will always see variation with temperature change.

On the positive side, the amount of variation was 51% less than the hand fitted JM Tesla MK2 seal 8)

This summer I can do some comparisons in the summer heat.

Steve
« Last Edit: January 13, 2019, 04:59:50 PM by Nitrocrushr »
  • Lancaster, Pennsylvania
Air Arms TX200 .177 Rifle - 22mm skirtless dual seal conversion from Tony Leach

HW98 .177 - Vortek 12fpe


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Offline nced

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Re: 22mm Skirtless Conversion
« Reply #49 on: January 13, 2019, 05:03:53 PM »
Have any of you tested this kit at different temperatures and elevations?  I'm just curious how much it is affected by these variables.  It will be another month before I have a chance to check these things out, so I thought I'd throw the question out there...

Thanks!

Zack, I ran a test on my 22mm dual seal conversion today.   Outdoor temperature was 27 degrees with a light breeze.  I ran about 5 shots over the chronograph straight off the rack at room temperature, which was about 70 degrees.  I then set the rifle outside on a sandbag in the fresh snow - 27 degrees for 1 hour.




After sitting outside for an hour, I grabbed the rifle and quickly ran 5-6 shots over the chronograph straight from the outside.

TX200 Rifle - .177 caliber - Tony Leach 22mm conversion kit (dual seal)
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.86 grains - 806 fps - 11.34 fpe

Outdoors - 27 degrees for 1 hour
JSB 7.87
Pellet weighed at 7.88 grains - 816 fps - 11.65 fpe

2.7% increase in energy

Next, I swapped power plants and ran the exact same test using my standard sub-12 fpe tune with the Maccari Tesla MK2 seal

TX200 Rifle - .177 caliber - with factory piston, JM Ultra XLD, Maccari Tesla MK2 main seal
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.90 grains - 810 fps - 11.51 fpe

Outdoors - 27 degrees for 1 hour
Pellet weighed at 7.86 grains - 835 fps - 12.17 fpe

5.5% increase in energy


While the dual seal design helps to reduce the variation due to temperature changes, as with any springer there is still some variation.  In a spring piston air rifle I think you will always see variation with temperature change.

On the positive side, the amount of variation was 50% less than the hand fitted JM Tesla MK2 seal 8)

This summer I can do some comparisons in the summer heat.

Steve

When I moved to North Carolina a decade ago I did a similar test using my .177 R9, oring sealed piston cap, and Krytox GPL205 lube. I left the R9 in my sunroom over night when the temp dropped to the 20s and shot a few CPLs over the chrony. A couple days later I left the gun indoors and chronied the gun in temps of mid 60s. I don't remember the exact velocity (I wasn't shooting sup 12fpe) but the velocity only varied 10fps between the two temps. I was surprised to find that the higher velocity was shot in the lower temp rather than the higher temp. While 10fps is such a minor variation that it could have simply been due to "atmospheric conditions" like humidity, or maybe even pellet weight variations. Anywhoo......I do think that perhaps denser cooler air being compressed affects the velocity.

Offline Gear_Junkie

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Re: 22mm Skirtless Conversion
« Reply #50 on: January 13, 2019, 05:12:15 PM »
Have any of you tested this kit at different temperatures and elevations?  I'm just curious how much it is affected by these variables.  It will be another month before I have a chance to check these things out, so I thought I'd throw the question out there...

Thanks!

Zack, I ran a test on my 22mm dual seal conversion today.   Outdoor temperature was 27 degrees with a light breeze.  I ran about 5 shots over the chronograph straight off the rack at room temperature, which was about 70 degrees.  I then set the rifle outside on a sandbag in the fresh snow - 27 degrees for 1 hour.




After the rifle sat outside for an hour, I quickly ran 5-6 shots over the chronograph straight from the outside.

TX200 Rifle - .177 caliber - Tony Leach 22mm conversion kit (dual seal)
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.86 grains - 806 fps - 11.34 fpe

Outdoors - 27 degrees for 1 hour
JSB 7.87
Pellet weighed at 7.88 grains - 816 fps - 11.65 fpe

2.7% increase in energy

Next, I swapped power plants and ran the exact same test using my standard sub-12 fpe tune with the Maccari Tesla MK2 seal

TX200 Rifle - .177 caliber - with factory piston, JM Ultra XLD, Maccari Tesla MK2 main seal
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.90 grains - 810 fps - 11.51 fpe

Outdoors - 27 degrees for 1 hour
Pellet weighed at 7.86 grains - 835 fps - 12.17 fpe

5.5% increase in energy


While the dual seal design helps to reduce the variation due to temperature changes, as with any springer there is still some variation.  In a spring piston air rifle I think you will always see variation with temperature change.

On the positive side, the amount of variation was 51% less than the hand fitted JM Tesla MK2 seal 8)

This summer I can do some comparisons in the summer heat.

Steve

Great info, thanks for doing this test Steve!!!  That's quite impressive that there is such a small difference in energy for such a large temp difference.  Even with the Maccari kit, that's not as bad as what I thought it would be.

Nice job Steve!
  • Nevada City, CA
.177 Daystate Regal XL & Hawke Airmax 30 SF 6-24x50
.177 Air Arms TX200 HC & Hawke Airmax 30 SF 6-24x50
.177 HW50S & Compact UTG 3-12x44

Offline Nitrocrushr

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Re: 22mm Skirtless Conversion
« Reply #51 on: January 13, 2019, 05:20:20 PM »
Have any of you tested this kit at different temperatures and elevations?  I'm just curious how much it is affected by these variables.  It will be another month before I have a chance to check these things out, so I thought I'd throw the question out there...

Thanks!

Zack, I ran a test on my 22mm dual seal conversion today.   Outdoor temperature was 27 degrees with a light breeze.  I ran about 5 shots over the chronograph straight off the rack at room temperature, which was about 70 degrees.  I then set the rifle outside on a sandbag in the fresh snow - 27 degrees for 1 hour.




After sitting outside for an hour, I grabbed the rifle and quickly ran 5-6 shots over the chronograph straight from the outside.

TX200 Rifle - .177 caliber - Tony Leach 22mm conversion kit (dual seal)
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.86 grains - 806 fps - 11.34 fpe

Outdoors - 27 degrees for 1 hour
JSB 7.87
Pellet weighed at 7.88 grains - 816 fps - 11.65 fpe

2.7% increase in energy

Next, I swapped power plants and ran the exact same test using my standard sub-12 fpe tune with the Maccari Tesla MK2 seal

TX200 Rifle - .177 caliber - with factory piston, JM Ultra XLD, Maccari Tesla MK2 main seal
Indoors - 70 degrees
JSB 7.87
Pellet weighed at 7.90 grains - 810 fps - 11.51 fpe

Outdoors - 27 degrees for 1 hour
Pellet weighed at 7.86 grains - 835 fps - 12.17 fpe

5.5% increase in energy


While the dual seal design helps to reduce the variation due to temperature changes, as with any springer there is still some variation.  In a spring piston air rifle I think you will always see variation with temperature change.

On the positive side, the amount of variation was 50% less than the hand fitted JM Tesla MK2 seal 8)

This summer I can do some comparisons in the summer heat.

Steve

I was surprised to find that the higher velocity was shot in the lower temp rather than the higher temp. While 10fps is such a minor variation that it could have simply been due to "atmospheric conditions" like humidity, or maybe even pellet weight variations. Anywhoo......I do think that perhaps denser cooler air being compressed affects the velocity.

Hi Ed, No doubt that the cooler, denser air has an affect ;) In fact, I stepped outside when cocking the rifle during the cold temp testing to make sure it was pulling in the cool outside air.  So many things can affect our springers over the course of a day’s shooting.  Temp, humidity, clouds, direct sunlight. 

While there are things that can help to minimize the effects, it will never eliminate them.

Steve

  • Lancaster, Pennsylvania
Air Arms TX200 .177 Rifle - 22mm skirtless dual seal conversion from Tony Leach

HW98 .177 - Vortek 12fpe


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Offline Nitrocrushr

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Re: 22mm Skirtless Conversion
« Reply #52 on: January 13, 2019, 05:36:59 PM »

Great info, thanks for doing this test Steve!!!  That's quite impressive that there is such a small difference in energy for such a large temp difference.  Even with the Maccari kit, that's not as bad as what I thought it would be.

Nice job Steve!

No problem Zack, It was info I wanted to know as well ;)  There are so many things that could come into play that might have an effect on the temperature/condition related variation you would see;

Seal type
Seal material
Seal fit
Lube being used
Tar on the main spring - how much tar is on the spring

I'm sure that is just scratching the surface.  Some of the folks who have far more knowledge than I do could probably elaborate even more on this subject ;)

Steve
  • Lancaster, Pennsylvania
Air Arms TX200 .177 Rifle - 22mm skirtless dual seal conversion from Tony Leach

HW98 .177 - Vortek 12fpe


N.U.A.H. Club - Master

Offline TonyL

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Re: 22mm Skirtless Conversion
« Reply #53 on: January 13, 2019, 06:13:43 PM »

When I moved to North Carolina a decade ago I did a similar test using my .177 R9, oring sealed piston cap, and Krytox GPL205 lube. I left the R9 in my sunroom over night when the temp dropped to the 20s and shot a few CPLs over the chrony. A couple days later I left the gun indoors and chronied the gun in temps of mid 60s. I don't remember the exact velocity (I wasn't shooting sup 12fpe) but the velocity only varied 10fps between the two temps. I was surprised to find that the higher velocity was shot in the lower temp rather than the higher temp. While 10fps is such a minor variation that it could have simply been due to "atmospheric conditions" like humidity, or maybe even pellet weight variations. Anywhoo......I do think that perhaps denser cooler air being compressed affects the velocity.

Its nothing to do with the lube, its to do with the expansion and contraction of the material used for the seal and the effect on friction it has, get your seal, measure it at 68f accurately for OD, then freeze it at 25f or so and measure it again, then heat it in an oven to 110f or more and measure it again...you will then see why the velocity goes up and down.

lets talk in mm as thats what im used too.

A seal at 25.4mm on the lip will shrink when cold, effectively sizing in better, it may shrink to 25.1mm, in an AA comp tube this is perfect sizing, the power will shoot up, smaller the seal will fail and the set up will go slammy.
The same seal when hot will grow in size, friction will increase, efficiency will decrease and power will go down, this was seen by all competitors in Poland for the FT worlds this last year, it was well over 30C so guns were running 40C+ so well over 110f
At 68f or 20C the seal is within the normal working temperature and power will be what you have set when you built the gun, no one sets the gun up seriously cold or seriously hot ;)

i run a front seal on the 22mm set up with a lip around 22.1mm or just under, when cold it will fail, BUT the O ring takes over and the shot feel remains soft as the poly seal cushions the piston, when hot the lip diameter will grow to around 22.25mm and the seal will do all the work. The O ring runs zero crush, the groove is 18mm OD it sits in and the O ring is 2mm cross section so 22mm OD,it takes pressure to blow the O ring out to form a seal.

We will never cure temperature shift, its akin so chasing your tail....you will only reduce the effects.

« Last Edit: January 13, 2019, 06:16:15 PM by TonyL »
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Offline Gear_Junkie

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Re: 22mm Skirtless Conversion
« Reply #54 on: January 13, 2019, 06:32:02 PM »

When I moved to North Carolina a decade ago I did a similar test using my .177 R9, oring sealed piston cap, and Krytox GPL205 lube. I left the R9 in my sunroom over night when the temp dropped to the 20s and shot a few CPLs over the chrony. A couple days later I left the gun indoors and chronied the gun in temps of mid 60s. I don't remember the exact velocity (I wasn't shooting sup 12fpe) but the velocity only varied 10fps between the two temps. I was surprised to find that the higher velocity was shot in the lower temp rather than the higher temp. While 10fps is such a minor variation that it could have simply been due to "atmospheric conditions" like humidity, or maybe even pellet weight variations. Anywhoo......I do think that perhaps denser cooler air being compressed affects the velocity.

Its nothing to do with the lube, its to do with the expansion and contraction of the material used for the seal and the effect on friction it has, get your seal, measure it at 68f accurately for OD, then freeze it at 25f or so and measure it again, then heat it in an oven to 110f or more and measure it again...you will then see why the velocity goes up and down.

lets talk in mm as thats what im used too.

A seal at 25.4mm on the lip will shrink when cold, effectively sizing in better, it may shrink to 25.1mm, in an AA comp tube this is perfect sizing, the power will shoot up, smaller the seal will fail and the set up will go slammy.
The same seal when hot will grow in size, friction will increase, efficiency will decrease and power will go down, this was seen by all competitors in Poland for the FT worlds this last year, it was well over 30C so guns were running 40C+ so well over 110f
At 68f or 20C the seal is within the normal working temperature and power will be what you have set when you built the gun, no one sets the gun up seriously cold or seriously hot ;)

i run a front seal on the 22mm set up with a lip around 22.1mm or just under, when cold it will fail, BUT the O ring takes over and the shot feel remains soft as the poly seal cushions the piston, when hot the lip diameter will grow to around 22.25mm and the seal will do all the work. The O ring runs zero crush, the groove is 18mm OD it sits in and the O ring is 2mm cross section so 22mm OD,it takes pressure to blow the O ring out to form a seal.

We will never cure temperature shift, its akin so chasing your tail....you will only reduce the effects.

Well, you did a darn good job at minimizing the effects as much as possible - WELL DONE!!!
  • Nevada City, CA
.177 Daystate Regal XL & Hawke Airmax 30 SF 6-24x50
.177 Air Arms TX200 HC & Hawke Airmax 30 SF 6-24x50
.177 HW50S & Compact UTG 3-12x44

Offline nced

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Re: 22mm Skirtless Conversion
« Reply #55 on: January 13, 2019, 09:48:02 PM »

When I moved to North Carolina a decade ago I did a similar test using my .177 R9, oring sealed piston cap, and Krytox GPL205 lube. I left the R9 in my sunroom over night when the temp dropped to the 20s and shot a few CPLs over the chrony. A couple days later I left the gun indoors and chronied the gun in temps of mid 60s. I don't remember the exact velocity (I wasn't shooting sup 12fpe) but the velocity only varied 10fps between the two temps. I was surprised to find that the higher velocity was shot in the lower temp rather than the higher temp. While 10fps is such a minor variation that it could have simply been due to "atmospheric conditions" like humidity, or maybe even pellet weight variations. Anywhoo......I do think that perhaps denser cooler air being compressed affects the velocity.

Its nothing to do with the lube, its to do with the expansion and contraction of the material used for the seal and the effect on friction it has, get your seal, measure it at 68f accurately for OD, then freeze it at 25f or so and measure it again, then heat it in an oven to 110f or more and measure it again...you will then see why the velocity goes up and down.

lets talk in mm as thats what im used too.

A seal at 25.4mm on the lip will shrink when cold, effectively sizing in better, it may shrink to 25.1mm, in an AA comp tube this is perfect sizing, the power will shoot up, smaller the seal will fail and the set up will go slammy.
The same seal when hot will grow in size, friction will increase, efficiency will decrease and power will go down, this was seen by all competitors in Poland for the FT worlds this last year, it was well over 30C so guns were running 40C+ so well over 110f
At 68f or 20C the seal is within the normal working temperature and power will be what you have set when you built the gun, no one sets the gun up seriously cold or seriously hot ;)

i run a front seal on the 22mm set up with a lip around 22.1mm or just under, when cold it will fail, BUT the O ring takes over and the shot feel remains soft as the poly seal cushions the piston, when hot the lip diameter will grow to around 22.25mm and the seal will do all the work. The O ring runs zero crush, the groove is 18mm OD it sits in and the O ring is 2mm cross section so 22mm OD,it takes pressure to blow the O ring out to form a seal.

We will never cure temperature shift, its akin so chasing your tail....you will only reduce the effects.


"nothing to do with the lube, its to do with the expansion and contraction of the material used for the seal and the effect on friction it has, get your seal, measure it at 68f accurately for OD, then freeze it at 25f or so and measure it again, then heat it in an oven to 110f or more and measure it again...you will then see why the velocity goes up and down."

Hummmm.......My experience with "tar", molly paste & factory HW piston seals a couple decades ago suggest otherwise! After I stopped using "tar" on my R9 spring (replacing it with molly paste) and replacing the old design HW factory seal a home made oring sealed piston cap my "temperature related poi shifting" was greatly reduced! I personally believe that changes in lube viscosity and piston seal durometer was due to a 30+ degree temperature differential which affected the functioning of the piston, especially since my changes in lube and piston sealing worked well. Back then (a couple decades ago) I was content simply to solve my "poi shifting issues" and never chronied the R9 while cold and warm to see if there was any velocity changes. After moving to NC I was simply wondering if my oring sealed/Krytox lubed .177 R9 would have a marked velocity difference when shot cold or warm so I took th etime to do what I never did in WV (checked velocity wamm/cold). The velocities were so similar that if there is any "temperature induced poi shifting" it's due to atmospheric conditions the pellet is flying through....not variations in velocity.
Here is my piston seal that you're suggesting I measure..........

A later version cut from molly filled 6/6 nylon (currently testing)...

LOL....the oring used only has a .070nominal cross section so I don't think the diameter or amount of rubber rubbing against the receiver would be effected much by temp changes.....
 

Offline Yogi

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Re: 22mm Skirtless Conversion
« Reply #56 on: January 13, 2019, 11:00:42 PM »
Love the idea of a double seal, one for hot weather and one for cold.  Like of like DoubleMint gum! ;D 8)

Could you achieve something similar with 2 o-rings?  Different cross sections and different grove depths, maybe even different rubber compositions. :-[

Either really stupid or real great idea? :-[ :-\ >:( :(

-Y
  • San Francisco, CA
Hatsan 95 Vortex, .22
RWS 6G, .177
RWS LP8 Magnum, .177
Diana 340 N-Tec, .22 Compact Lexus
HW 50S, .177 and/or .22

Offline nced

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Re: 22mm Skirtless Conversion
« Reply #57 on: January 14, 2019, 11:30:47 AM »
Love the idea of a double seal, one for hot weather and one for cold.  Like of like DoubleMint gum! ;D 8)

Could you achieve something similar with 2 o-rings?  Different cross sections and different grove depths, maybe even different rubber compositions. :-[

Either really stupid or real great idea? :-[ :-\ >:( :(

-Y

"Love the idea of a double seal, one for hot weather and one for cold"
The pic is showing a "Quad seal" cross section oring as opposed to a round cross section design......

Funny that you should mention "hot & cold" because I oring sealed a couple springers for a west coast shooter. His issue was that he would get poi shifting when shooting in comfortable "morning temps" but before the "daytime temps" got to 90+ degrees the poi would shift when using factory seals. The oring sealed piston cap also reduced his "high temp" poi shifting which is why several of his springers were "oring sealed".


"Could you achieve something similar with 2 o-rings?"

As far as the quad seals vs "normal" round section orings I never saw enough difference to matter. LOL. a size 020 quad seal however does take some care to make sure the seal doesn't twist in the groove when installing. I've been using standard orings for a while and they work just fine lubed with Krytox.

There are a couple issues with a double oring setup on a HW95 piston. 1st, the oring groove would need to be so wide that the piston cap would need to be made a lot thicker to keep the oring groove from cutting into the c-bore that gets pressed over the piston seal retaining "button" and the thicker cap would reduce the "swept volume" of the compression area. 2nd, double orings would also double the amount of "rubber" compressed against the receiver wall. This would increase "piston drag" and the amount of lube as the durometer of the "rubber" and the viscosity of the lube changes with the temperature defeating the reason I went with an oring sealed piston cap in the first place.

"different grove depths"
I already use modified oring groove dimensions since the HW95 receiver isn't anything close to a pneumatic clyinder that would be actuated with "mist lubricated air" and expected to work for 100s of thousands of cycles at a few thousand psi. LOL, if a factory spring in a modern springer lasts just 10,000 shots it's exceptional (Beeman R10 springs would break with less than 5,000 shots) and the compression is perhaps 1,500-2000 psi (unless the gun diesels with petroleum lubes). For my size 020 oring grooves the width is about .080 (standard dynamic groove width is .093 to .098) and I use only 10% compression (standard oring compression is 15% to 25%).

"maybe even different rubber compositions"   
I currently use 75 durometer spec Viton orings because they have relatively high heat tolerance of 400 degrees F. (nitrile about 250 degrees F). While polyurethane is a very tough wear resistant rubber, it also has a low heat tolerance of about 180 degrees F......


Anywhoo......I've tried several different oring compounds, durometer ratings and cross sections and quite frankly, all will work as long as they last. :o Decades ago I tried to use the really tough polyurethane orings and they didn't hold up to the "heat of compression" very long! There are other compounds that would seem to be perfect for use in an oring sealed piston cap like Kalrez, however $20-$40 EACH for an 020 size is too pricey!! LOL.....I can buy a 25 count bag of military spec size 020 75duro Viton orings for under $10. The 4 cent each Viton orings I use will last longer than a good aftermarket spring so there is no need to use the "more expensive than gold" stuff. LOL.....I generally break down my springers yearly during the winter months for a "dustin' & cleanin" so I roll in a new 4 cent oring at that time if needed or not.




How do you word it... "Air Guns" or "AirGuns"?