Donation

All Springer/NP/PCP Air Gun Discussion General > PCP/CO2/HPA Air Gun Gates "The Darkside"

2260MB Tubes with Ground Finish - DO NOT USE FOR HPA

<< < (3/13) > >>

avator:
Sorry for the confusion, I thought I had posted the link in this thread.... here is the link to the build.
https://www.gatewaytoairguns.org/GTA/index.php?topic=152894.msg155681743#msg155681743

Magnum Airpower:
 The description of a hard transition the o-ring doesn't pass over easily, this would only exist if the tube got thicker than the thread major. The tube would have to be the same outer diameter, not smaller, for there to be threads large enough to fit a fill adapter or piercing cap. So the wall thickness at the threaded section to the thread major would have to be around .049" for the adapter to fit a hold over 4000 PSI before blowing out. That means the inner diameter would have to be larger to have a .049" wall in the non-threaded tube section. That would eliminate the hard transition some tubes have. I plan to order a 2260 tube Monday but will be out of state for two weeks before I will be back to check it out. In the meantime some photos with caliper readings of the back of that tube would be helpful. Also the serial number of the tube so the date it was made can be determined. Most of the tubes I've come across were made in 2015 - 2017 and those, like I said earlier were .0625" wall thickness. My custom adapters have the threads machined over-sized to fit Crosman tubes tighter. As far as I know I'm the only one who does this. I'm aware of fill adapters made by others that blow out at much lower pressures but dare not mention their names here to avoid all the drama that would result. Discovery adapters generally fit well and have stronger threads than the Marauder Pistol version. I usually suggest those as a cheaper option.

Bill

rsterne:
I don't understand what you mean that the tube would have to be larger OD, not smaller to fit the fill adapter.... I looked up the thread dimensions for 13/16"-28, and the minimum minor diameter of the female thread is 0.774".... A standard Disco/22XX tube is nominally 0.875" OD x 0.065" wall, which means it is 0.745" ID, and has to be bored out nearly 0.030" to be threaded.... The dimensions that TKO22 has from his 2260MB tube is 0.863"OD x 0.049" wall, which is 0.765" ID.... That means it still needs to be bored out to be threaded, just not as much.... If the tube was 0.875" OD x 0.049" wall, the ID would be 0.777", which means it would not have to be bored out at all to be threaded, but would still be within the tolerance for 13/16"-28 threads, which can have a maximum minor diameter as large as 0.780" for class 3A threads, or 0.782" for class 2A threads....

I'm not arguing that your 2260MB tubes aren't the same as a Disco/old 22XX/Maximus tube, I'm confident they are, you are a reputable machinist.... I have several 2260 tubes here, and they are all the same 0.745" ID and 0.065" wall thickness as a Disco tube.... What concerns me is that we have a report that there is a new, thinner 2260MB tube, with a 0.049" wall, that has had the fill adapter blow out at 4100-4600 psi.... I have no reason to disbelieve that such a tube exists, and assuming it does indeed exist, then we need to investigate it, and make sure that nobody gets hurt because they believe that all 2260 tubes are created equal....

I will make an unfounded guess here that if the new tube is indeed 0.020" larger ID, and if somebody puts an existing Disco fill fitting into it, (which is about 0.740" OD at the O-ring) then the O-ring (under 4000+ psi pressure) extrudes into the gap, leaks, and the threads become pressurized.... Since the OD of the threads is 0.813", if the OD of the tube is indeed 0.863", then the remaining wall thickness of the threaded portion is only 0.025".... That would yield at 4100 psi, the tube would stretch in diameter, and the fill fitting would blast out the end.... In other words, there would be two contributing factors combining to cause the failure at such low pressure.... The tube being a thinner wall, creates a larger gap, which allows the O-ring to fail, and then when the threaded area is pressurized, the tube expands and the plug blows out the end.... It would be a perfectly logical fit for the failure mentioned....

Please, let's just combine our efforts to insure that if this is happening, nobody gets hurt because of it....

Bob

BigBird:
Thanks for the post and information on this Bob.  Are the part numbers for the 2260 "WC" tube and the 2260MB tube both 2260-004?  I just purchased a 2260-004 two days ago before finding this discussion.
If they are using a thinner walls for the 2260 the 2240 and 2250 tubes should be checked as well before HPA use.
Speculation: as a cost savings measure they may have calculated it driving production sales vs DIY.  A $9.00 pressure tube helps keep project costs lower than some production guns.

rsterne:
I have no idea if they changed the part numbers.... What is the wall thickness on your tube, measured at the back?.... ID and OD?....

Bob

Navigation

[0] Message Index

[#] Next page

[*] Previous page