Got some .30 cal mags in from Lloyd at Airgun Lab. Slick! Does anyone smell something cooking?I promised this would be a fun winter!
Oh, and Rod... there comes a time when it's best to shoot the engineers, and go into production".(J/K)
Yup.If a 60 is cut to take an MRod .25 mag, it can be used for .22 (wheel change), .25, and with Lloyds' mags, .30 cal. With the impending single shot tray, we can keep going up, until the barrels are too thin to mount.johninthecamper has .30 BTs that work well. I don't know the specifics, though.
With a scope as low it will go, there's plenty of room.
Rod, you know the rules out West... just keep banging out the Ragtime, and you can ignore the gunfire...
At Eric's request, I have run the numbers for the safety of the Fill Plug and Retaining Nut at 3000 psi.... Bear in mind I am NOT an engineer, but here is my take on it, complete with the math I used.... First of all, I assumed that the tube and nut are mild steel, with a tensile strength of 53K and a yield strength in tension and compression of 44K.... I used 6061-T6 aluminum for the end plug, with a tensile of 45K, a yield of 40K in tension, and a compressive strength of 56K.... If brass is used instead, the strengths are similar, depending on the grade selected.... I used the standard of 60% of yield strength for the shear strength....The tube on the FD-PCP is 0.875" OD x 0.065" wall, giving an ID of 0.745" (the XS-60C has a 22 mm x 1.5 mm tube) and the threads are external, 22 mm x 1 mm pitch, with a minor diameter of 20.8 mm (0.819"), and a pitch diameter of 21.3 mm (0.838"), using standard Metric thread dimensions.... The end cap (retaining nut) has an ID of 21mm (0.827") and a hole through the end flange that measures 18.75 mm (0.738").... The flange on the end of the cap is 2.3 mm (0.090") thick.... I used a flange of 0.100" on the end plug to mate with that (I did not have that actual dimension).... The O-ring is positioned inboard of the threaded portion of the tube.... Here are the numbers:Area of end plug: PI x (0.745^2) / 4 = 0.4357 sq.in.... End force at 3000 psi: 3000 x 0.4357= 1307 lbs....Thickness of tube wall below the threads: (0.819 - 0.745) / 2 = 0.037".... Area of tube wall below the threads in tension: PI x (0.745 + 0.819) x 0.037 / 2 = 0.0909 sq.in.... Yield point: 44,000 x 0.0909 = 3998 lbs.... Safety margin: 3998 / 1307 = 3.1:1Shear area of threads for 1/4" engagement: PI x 0.838 x 0.25 / 2 = 0.329 sq.in.... Yield point: 44,000 x 0.6 x 0.329 = 8683 lbs.... Safety margin: 8683 / 1307 = 6.6:1Shear area of plug flange: PI x 0.738 x 0.100 = 0.232 sq.in.... Yield point: 40,000 x 0.6 x 0.232 = 5568 lbs..... Safety margin: 5568 / 1307 = 4.3:1Shear area of nut flange: PI x 0.827 x 0.090 = 0.234 sq.in.... Yield point: 44,000 x 0.6 x 0.234 = 6170 lbs.... Safety margin: 6170 / 1307 = 4.7:1Width of flanges in compression: (0.827 - 0.738) / 2 = 0.044"....Area of flanges in compression: PI x (0.827 + 0.738) x 0.044 / 2 = 0.108 sq.in.... Bearing limit: 44,000 x 0.108 = 4557 lbs.... Safety margin: 4557 / 1307 = 3.6:1I have asked QVTom to double-check my math, and to do a Finite Element Analysis of the strength of the retaining nut in case the simple shear calculation I did is not complete enough.... I will ask Tom to add his comment to this thread when he has had the time to run the FEA.... However, based on the above, it would appear to me that the weak point is the remaining tubing wall below the threads in the tube itself.... It just barely makes the recommended 3:1 safety margin at 3000 psi, and this assumes that the threads are not cut deeper than spec.... If they are, the safety margin drops even more.... Bob
The tube on the FD-PCP is 0.875" OD x 0.065" wall, giving an ID of 0.745" ........Thickness of tube wall below the threads: (0.819 - 0.745) / 2 = 0.037".... Area of tube wall below the threads in tension: PI x (0.745 + 0.819) x 0.037 / 2 = 0.0909 sq.in.... Yield point: 44,000 x 0.0909 = 3998 lbs.... Safety margin: 3998 / 1307 = 3.1:1Bob
I purposely did NOT address the strength of the threaded portion of the tube, as I got my knuckles rapped for doing so previously.... I asked repeatedly for the material the tube was made from and was told that information was proprietary.... I did the calculations assuming mild steel, as above, and got a pressure to yield of the threaded portion of 4370 psi and to burst of 5264 psi, which works out to a safety margin at 1500 psi of 2.9:1 to yield.... Using normalized 4130 CrMoly, with a tensile of 97K and a yield of 68K, and bumping the pressure to 2000 psi, I got 6258 psi to yield (3.1:1).... The threads in the receiver do not really concern me (assuming they are machined properly) as the thread depth is such that the shear area is huge.... It is to address the issue of pressurizing the threaded portion that Eric is looking at doing a "through tube" installation without threading to weaken the tube....Bob
Thank you, Bob.Guys, if we can use this arrangement, it will not only allow someone to use their custom cap when upgrading to 3k... but, it will allow the side port(s) to be turned to any angle.Just trying to make this design as adaptable as possible, as well as keeping the amount of part #s as low as I can.
I therefore used 22 - (0.6 x 2) = 20.8 mm = 0.819" as the diameter at the bottom of the threads...Bob
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