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Author Topic: .257 cal Monocoque PCP  (Read 54059 times))

Offline sixshootertexan

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Re: .257 cal Monocoque PCP
« Reply #160 on: December 31, 2015, 11:41:08 AM »
As usual great work Bob. I'm not seeing how the breech is secured in the tube. I know you have it somewhere so when you put the barrel in tension with the bellville washers.
  • Magnolia,TX
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Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #161 on: December 31, 2015, 01:16:33 PM »
There are two 10-32 screws, top and bottom, behind the loading port.... to keep it aligned.... Once all the other screws are in place (scope rail, the screws that fasten the upper and lower tubes together, etc. it isn't going anywhere.... Even just the mount for the cheekpiece on the back is probably enough to hold it (two 8-32 screws in tension)....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline Michael Loar

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Re: .257 cal Monocoque PCP
« Reply #162 on: January 01, 2016, 01:20:20 AM »
My range will clear of snow about April.... *LOL*.... and then the Motel will get busy by Mid-May.... so my shooting time will be VERY limited.... With luck I will get time to bust some Ground Squirrels with it in June....

bob

I am glad you are apparently a patient person since I could not put the time and effort into such a project like your gun and have to wait till then to really see what it will do. You don't have any indoor ranges in the area that you can shoot it just to work any bugs out before the snow breaks so its ready to have fun with or will you just start a new project to stay busy till its time to shoot all the toys.

Mike
  • Oxford, Alabama
Benjamin Marauder 177 in Boyds blaster stock 
Benjamin Marauder25 Wicked Air rifles bottled
Hatsan 22 AT 44S10 long
FWB 124 177 Tuned
FWB 300s Match L 177 Tuned
FWB 300s Match Junior 177 Tuned
Diana 48 177 Vortek Tuned
Xisisco 60C PCP Tuned 22
Xisisco 60C PCP 177 tuned LW barrel
Benjamin Titan NP 22 Tuned GRT trigger
Crosman Titan GP 22 Tuned GRT trigger
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Taipan Mutant Standard 22, BSA FFP 4x14x44 scope
TX200 , TL 22mm kit 177
B-40, TL 22mm kit 177
B50 in 51 stock Tuned .177
CH2009 challenger 177
1720T carbine regulated 177
Prod carbine with AR butt stock 22
CZ200 regulated 177
C9 silver streak 20 rocker safety
Crosman 1400 X 2 177 and 22
B28 Mike Melick tuned 25
Hatsan flash 25
Daisy 853 X 5 177
B3-2 177
Benji Maximus 177 Mrod trigger
QB 78/79 177 and 22 HPA bottled
HW Blue Laminate 97 .22cal tuned
1966 Diana model 60 Tyro resealed and tuned




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Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #163 on: January 01, 2016, 01:29:46 AM »
Yeah, I have a staggering 20 feet available in my garage/shop.... but that is good enough for testing and development.... Generally my guns are fully sorted before they ever get shot outdoors....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline Michael Loar

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Re: .257 cal Monocoque PCP
« Reply #164 on: January 01, 2016, 01:36:26 AM »
I should have figured as much with the expertise you bring to the table that you have the bugs fixed before they get a chance to develop and 20 feet is still enough to shoot with a proper backstop for your cannons. LOL

Mike
  • Oxford, Alabama
Benjamin Marauder 177 in Boyds blaster stock 
Benjamin Marauder25 Wicked Air rifles bottled
Hatsan 22 AT 44S10 long
FWB 124 177 Tuned
FWB 300s Match L 177 Tuned
FWB 300s Match Junior 177 Tuned
Diana 48 177 Vortek Tuned
Xisisco 60C PCP Tuned 22
Xisisco 60C PCP 177 tuned LW barrel
Benjamin Titan NP 22 Tuned GRT trigger
Crosman Titan GP 22 Tuned GRT trigger
Crosman Venom 177 Tuned GRT trigger
Taipan Mutant Standard 22, BSA FFP 4x14x44 scope
TX200 , TL 22mm kit 177
B-40, TL 22mm kit 177
B50 in 51 stock Tuned .177
CH2009 challenger 177
1720T carbine regulated 177
Prod carbine with AR butt stock 22
CZ200 regulated 177
C9 silver streak 20 rocker safety
Crosman 1400 X 2 177 and 22
B28 Mike Melick tuned 25
Hatsan flash 25
Daisy 853 X 5 177
B3-2 177
Benji Maximus 177 Mrod trigger
QB 78/79 177 and 22 HPA bottled
HW Blue Laminate 97 .22cal tuned
1966 Diana model 60 Tyro resealed and tuned




Bikes, Guns and Family is all I need for a good day

Offline OleTomCat

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Re: .257 cal Monocoque PCP
« Reply #165 on: January 01, 2016, 03:46:44 AM »
My range will clear of snow about April.... *LOL*.... and then the Motel will get busy by Mid-May.... so my shooting time will be VERY limited.... With luck I will get time to bust some Ground Squirrels with it in June....

bob

Bob,

Put it in a Box and send it to me, we have 70f and sunny here, I will be shooting at my outdoor range, up to 200 yards, this Saturday...

Al
  • Cross, SC
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Offline lloyd-ss

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Re: .257 cal Monocoque PCP
« Reply #166 on: January 01, 2016, 11:29:57 AM »
Hi Bob,
I was just going to skim through this long thread but instead got hooked and read it all.  This is certainly a well thought out single purpose gun and I would be shocked if it didn't live up to the expectations.  I understand how everything has to be custom made, because what you can normally buy is close, but never quite right. I like the barrel tensioning with the belvilles. I might have missed it, but are the only attachment points for the barrel at the breech and the muzzle? I will be curious to see if you need to add any centering rings along the length of the barrel, or if the 2 attachment points get the job done.  With the belvilles, you can certainly put plenty of tension on the barrel and hopefully get the performance of a solid barrel.
Doing your milling with one hand behind your back is an understatement! I don't know how you get all the milling done with your set-up, but you obviously do.
It looks like like you are getting close on this one and we are all anxious to hear about the first shots.
Very nice project!
Lloyd
  • Central Virginia
An engineer by nature. The affliction is knowing that everything can be made better. It is easy to make one that works, but it is difficult to make on that works WELL.
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Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #167 on: January 01, 2016, 12:10:07 PM »
Lloyd, thanks for the kind words.... I've tried the Bellevilles before, and the concept works but my biggest problem is time to test at longer ranges as the Motel is always busy in the summer.... QVTom who builds the Slayer uses a tensioned barrel without the Bellevilles (they get in the way of using the shroud as an LDC), I think he torques the tensioner.... My idea (since we can't make guns quieter in Canada anyway) is to virtually eliminate temperature change as a problem by using the Belleviles to compensate, and to turn their compression distance into a tuning tool.... I don't have any intermediate supports at the moment, they can always be added later.... Tom found he was getting a nice musical note without them on firing, and added one.... My guess is now only dogs can hear the barrel on his gun singing to them.... *LOL*.... I figure if I need one, I will try it at 3/7ths of the distance between the supports to avoid a resonance point....

Some days I certainly feel like I am milling with one hand tied behind my back.... but somehow my stubbornness pays off in the end.... I really don't have a choice, do I?.... I'm certainly looking forward to getting the moulds from NOE, casting some bullets (in itself quite a development project), cutting the chamber, and the first test firing....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline Bill G

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Re: .257 cal Monocoque PCP
« Reply #168 on: January 01, 2016, 03:43:01 PM »
Oh yea, I forgot about you still needing to cut the chamber.  Duh, that's why you are anxious to get the molds.   Job best done with a slug on hand.  The more I review this project the more I like your lines on this rig.  For me the simplistic look and straight forward function of design just hit the spot.  I've never been one who gets wrapped around beautiful wood and so on.  Its nice no doubt but its best left to fine furniture IMO.  In fact the design makes me think about what if's.  What if you were to use the tensioning shroud as a reservoir?  Do you think that it could or would have an adverse effect on the barrel dynamics?  since you have all the wasted volume that can't be used for hushing, why not use it to increase shot count?  That is, as long as it doesn't affect accuracy. :-\
  • Nicholasville KY
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Offline Bill G

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Re: .257 cal Monocoque PCP
« Reply #169 on: January 01, 2016, 03:45:58 PM »
never mind..... that would make it not floating duh.
  • Nicholasville KY
Engineering is the art of modeling materials we don't wholly understand, into shapes we can't precisely analyze, so as to withstand forces we can't properly asses, in such a way that the public has no reason to suspect the extent of our ignorance.

Offline lloyd-ss

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Re: .257 cal Monocoque PCP
« Reply #170 on: January 01, 2016, 04:34:32 PM »
Bob,
BTW, very nice Christmas gift from your wife.  It is good when we get to the point in life where we can exchange gift "hints" and they work out 100%.
I am sure, being the gentleman you are, that she received something very special also.  But you don't have to tell us, LOL.
Lloyd
  • Central Virginia
An engineer by nature. The affliction is knowing that everything can be made better. It is easy to make one that works, but it is difficult to make on that works WELL.
My YouTube channel is    Airgun Lab

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #171 on: January 01, 2016, 04:57:39 PM »
Using the shroud for a reservoir, while possible, would either make the gun even heavier (the upper tube is only 0.065" wall instead of 0.095").... and, as you say, I would likely fasten the tubes together full length.... I'm not so sure that would be a bad idea anyway, as the barrel being tensioned the way it is, isn't exactly floated anyway.... My guess is that changing the pressure in the reservoir would change the length of the reservoir enough to change the tension, even with the Bellevilles, however.... or at the very LEAST change the POI.... I'm  hoping by using the Monocoque tube idea, with the barrel, scope, and breechblock all inside it, will provide the maximum rigidity and least POI shift possible.... At one point I contemplated using aluminum or carbon fibre for the shroud Monocoque tube, and also using a carbon sleeve glued on the barrel, but was advised against it by michaelthomas (builder of the Thomas BR), to keep all the thermal coefficients the same between the scope and muzzle.... His guns are built not only to shoot amazing groups, but not have any POI change day to day, week to week, or under hugely varying conditions.... I took his advice....

Lloyd, that scope is MASSIVE, but it doesn't look at all out of place on this gun.... and yeah, she did OK.... *grin*.... We're at the stage in life Christmas and Birthday gifts are seldom a surprise any more, and often occur before the event.... "You want that, no problem, it's your Christmas present".... *LOL*....

Bob
« Last Edit: January 01, 2016, 04:59:35 PM by rsterne »
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline match

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Re: .257 cal Monocoque PCP
« Reply #172 on: January 02, 2016, 05:10:47 PM »
Note that using the shroud as a reservoir will put multiple stress effects on the tube so you would have a much lower burst/yield pressure and the force to buckling will also be reduced.

take a look at petrowiki.org/Strength_of_casing_and_tubing to see the details.

john
  • Colorado, Littleton
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Offline Michael Loar

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Re: .257 cal Monocoque PCP
« Reply #173 on: January 03, 2016, 09:08:29 PM »
Lloyd, that scope is MASSIVE, but it doesn't look at all out of place on this gun.... and yeah, she did OK.... *grin*.... We're at the stage in life Christmas and Birthday gifts are seldom a surprise any more, and often occur before the event.... "You want that, no problem, it's your Christmas present".... *LOL*....

Bob
[/quote]

Bob
Same here with the better half as we ask/tell each other what we want/need for Bdays and Christmas since there are no secrets in a good marriage/partenership that last any amount of time. Besides I usually by what I want before she get the chance so have to save something for her to buy. Hehe

Mike
  • Oxford, Alabama
Benjamin Marauder 177 in Boyds blaster stock 
Benjamin Marauder25 Wicked Air rifles bottled
Hatsan 22 AT 44S10 long
FWB 124 177 Tuned
FWB 300s Match L 177 Tuned
FWB 300s Match Junior 177 Tuned
Diana 48 177 Vortek Tuned
Xisisco 60C PCP Tuned 22
Xisisco 60C PCP 177 tuned LW barrel
Benjamin Titan NP 22 Tuned GRT trigger
Crosman Titan GP 22 Tuned GRT trigger
Crosman Venom 177 Tuned GRT trigger
Taipan Mutant Standard 22, BSA FFP 4x14x44 scope
TX200 , TL 22mm kit 177
B-40, TL 22mm kit 177
B50 in 51 stock Tuned .177
CH2009 challenger 177
1720T carbine regulated 177
Prod carbine with AR butt stock 22
CZ200 regulated 177
C9 silver streak 20 rocker safety
Crosman 1400 X 2 177 and 22
B28 Mike Melick tuned 25
Hatsan flash 25
Daisy 853 X 5 177
B3-2 177
Benji Maximus 177 Mrod trigger
QB 78/79 177 and 22 HPA bottled
HW Blue Laminate 97 .22cal tuned
1966 Diana model 60 Tyro resealed and tuned




Bikes, Guns and Family is all I need for a good day

Offline lloyd-ss

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Re: .257 cal Monocoque PCP
« Reply #174 on: January 06, 2016, 08:56:21 AM »
.................................................
Same here with the better half as we ask/tell each other what we want/need for Bdays and Christmas since there are no secrets in a good marriage/partenership that last any amount of time. Besides I usually by what I want before she get the chance so have to save something for her to buy. Hehe

Mike

My wife is happy for any suggestions so long as she can find it on line, LOL. I guess I am lucky that we are both pretty level headed about the money. But we each have our own weaknesses and respect that.
Lloyd
  • Central Virginia
An engineer by nature. The affliction is knowing that everything can be made better. It is easy to make one that works, but it is difficult to make on that works WELL.
My YouTube channel is    Airgun Lab

Offline Bill G

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Re: .257 cal Monocoque PCP
« Reply #175 on: January 09, 2016, 12:05:03 PM »
Note that using the shroud as a reservoir will put multiple stress effects on the tube so you would have a much lower burst/yield pressure and the force to buckling will also be reduced.

take a look at petrowiki.org/Strength_of_casing_and_tubing to see the details.

john

Seals would likely be the weakest link.  but not reason to consider if repeatable accuracy is the goal.  the dynamics of a design of such would simply add variables and we don't need any more than that.
  • Nicholasville KY
Engineering is the art of modeling materials we don't wholly understand, into shapes we can't precisely analyze, so as to withstand forces we can't properly asses, in such a way that the public has no reason to suspect the extent of our ignorance.

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #176 on: January 13, 2016, 03:39:18 PM »
Finally got my valve screws, so I got to assemble the reservoir today and pressure test it.... Filled it 1K at a time, checking for leaks (none) and it's currently sitting at 3500 psi.... I'm topping off my Great White tank with the ShoeBox to complete the fill....

I slid the hammer down the tube, with it angled about 20*, and was rewarded with a nice loud POP and the valve sealed up again 100%, so things are looking good so far....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline lloyd-ss

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Re: .257 cal Monocoque PCP
« Reply #177 on: January 13, 2016, 04:18:03 PM »
Note that using the shroud as a reservoir will put multiple stress effects on the tube so you would have a much lower burst/yield pressure and the force to buckling will also be reduced.

take a look at petrowiki.org/Strength_of_casing_and_tubing to see the details.

john
John, Good information to think about if the tensioning tube was going to be used used as a reservoir, with the barrel as the hollow inside of the reservoir.  But if I read the info correctly, with the normal D/t diameter to wall ratio of gun barrels being 10 to 1 or lower, that puts them well within the 16 to 1 safe zone for likelihood of any yield (changing shape) from the reservoir pressure.  But just running some numbers, it looks like a .62" tube with .065 wall with a 70ksi yield is safe to over 14000 psi before deformation is likely to start. 
With the small  L/D ratio of the shroud, and the fairly light end compression loading of maybe 1000 pounds max, it looks like buckling is not a concern, either.  Still, it is good to be aware of all relevant failure modes.
Lloyd
  • Central Virginia
An engineer by nature. The affliction is knowing that everything can be made better. It is easy to make one that works, but it is difficult to make on that works WELL.
My YouTube channel is    Airgun Lab

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #178 on: January 13, 2016, 04:27:19 PM »
Lloyd, if you pressurized the Monocoque tube, to use it as a reservoir (and of course it would need the same 0.095" wall thickness as the main reservoir).... would that not remove any compression load from it completely, and instead put it in tension?.... Instead of about 1000 lbs. of compression, I see it as having over 3300 lbs. of tension at my 3800 psi working pressure.... If you loaded the barrel to 1000 lbs. of tension, relative to the outer tube, the outer tube couldn't have any bucklng because it would still be in about 2300 lbs. of tension.... You are just transferring some of the load on the end cap to the barrel instead of the tube....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline rsterne

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Re: .257 cal Monocoque PCP
« Reply #179 on: January 13, 2016, 05:47:18 PM »
It's now sitting at 4500 psi, no leaks I can find, so I'll leave it for a week and see what happens....

Bob
  • Coalmont, BC, Canada
🇺🇦 Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦

Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).