Safe or Silly?

[rsterne]

Here is a photo (from the Green Forum) of a gauge fitting soldered to the side of a Benji 39X pumper tube with soft solder....



I think this is a ridiculously dangerous practice.... If the joint is perfect, maybe.... but IMO too many variables....

Bob

[AirGunEric]

Not likely the safest way of doing things- especially, if, as you mention, the joint is not perfect. I don't know what the shear strength of soft solder is/isn't- but when one of it's most common uses is holding <70psi copper pipe together, I think 2000+ psi is a bit of a risk.

Mind you, Sheridan and Benjamin soldered some parts in their older rifles- but I recall this may only have been barrels to tubes and "contained" parts in/on valves- not things with any real potential to blow out.

Other than deformation of the tube, perhaps using a steel gauge fitting and tube and welding would be a better idea- but would also need to be a near-perfect weld to ensure no leaks.

[rsterne]

Good call about the volume, Sean, I missed that....

It turns out that in the final version, there is only a "pinhole" feeding the space under the gauge.... Therefore, on further consideration.... if you have a very small hole feeding the space under the gauge, and that space is small, the "explosion" would be limited to maybe 1 FPE of energy released, depending on the volume and the pressure.... As shown, there is a potential for injury in the result of a failure.... That may not be the case if you keep the volume under the gauge, and the hole pressurizing it, small enough....

I still wouldn't do it, but in terms of safety, it MAY be OK because of the flow limiting "pinhole"....

Bob

[rsterne]

Tensile of lead-tin solder runs 4400-6700 psi depending on the alloy.... If you use 6000 psi, and assuming the solder joint is the same area as the end of the gauge, you would have a 4:1 safety margin at 1500 psi (pretty much the max for a Benji).... However, that assumes a perfect joint, no cracks or voids (which could pressurize), and that the adhesion of the solder to the brass is also 6000 psi.... If the cracks/voids fill with HPA, not only does the area of solder decrease, but he pressurized area increases.... I sure wouldn't trust it....

Bob

[rsterne]

An Apology to Casey on the Green Forum....

I felt very strongly that the soft soldering of a gauge fitting on the outside of a Benji tube was unsafe.... Rather than simply discussing it on the Green Forum, however, I started threads about it on four other airgun forums entitled "Safe or Silly", and while it was not my intention to ridicule Casey, but to question the method, the result was I generated criticism of him, as well as better information and other ways of viewing the safety of the installation.... Once I learned that Casey restricted the flow with a pinhole, it was pointed out to me that the captured volume was small enough to not be dangerous, and I have agreed with that on this and the other Forums.... However, I had no right to take this further than the Green Forum, regardless of what my intentions were, and for that I apologize....

Bob

[Redlock]

Few people these days will admit a mistake, fewer still apologize publicly. I suppose they lack a sense of personal honour.
I respect you for this post Bob.
Red.

An Apology to Casey on the Green Forum....

I felt very strongly that the soft soldering of a gauge fitting on the outside of a Benji tube was unsafe.... Rather than simply discussing it on the Green Forum, however, I started threads about it on four other airgun forums entitled "Safe or Silly", and while it was not my intention to ridicule Casey, but to question the method, the result was I generated criticism of him, as well as better information and other ways of viewing the safety of the installation.... Once I learned that Casey restricted the flow with a pinhole, it was pointed out to me that the captured volume was small enough to not be dangerous, and I have agreed with that on this and the other Forums.... However, I had no right to take this further than the Green Forum, regardless of what my intentions were, and for that I apologize....

Bob

[FRANK]

could it be silver solder? if it is well that is very strong. but how strong? nothing beats my mig or a tig welder.

[rsterne]

Impossible, the Benji's are soft soldered together (eg barrel to main tube)....

Bob

[FRANK]

Silver is a soft welding it's done with a small torch at low to med heat.
but I'm sure it's no what they use on the benji. since it's very expensive.

[rsterne]

I've done silver (ie hard) soldering.... yes, it's "low heat" (as in lower than brazing), but a LOT hotter than what is required for lead/tin solder.... There is no question if he tried to silver solder that nut on he would have melted the solder on the barrel just 1/2" away.... Besides, he stated it was soft solder....

Bob