|
|
|
|
Machinest Handbook lookup request (Pleeeeze)
In article ,
says...
In article , Ned Simmons
says...
I don't see how that's relevant. The question is not what
the optimum solution is, but rather, can pipe threads carry
significant axial loads. Clearly they can.
I will again interject that the real question is, how
close to the line is this widget? Black iron hardware
store pipe with sharp-V NPT threads, 3/4 inch IIRC.
Best way to figure that is to a) use the minimum minor
diameter for that NPT thread and calculate the X-section
area, then divide the ultimate number by about three.
Not knowing all the details of the device, I was reluctant
to make a calculation before. Since it's now built, they
can't blame us for any mishaps, can they? g
I get about .925 dia at the root of the thread at the gage
line of a 3/4 NPT fitting. ID is .824 . Yield on A53B pipe
is 35 ksi min. Ultimate tensile is 60 ksi min.
..138 in^2 x 35000 lb/in^2 = 4830 lb to yield
..138 in^2 x 60000 lb/in^2 = 8280 lb to ultimate tensile
I assume your 3X multiplier is a stress concentration
factor, which sounds reasonable to me, so there will be
some yielding at the root above 4830/3 = 1610 lb., and
failure will occur at 8280/3 = 2760 lb. There's likely a
pretty high uncertainty in the second number depending on
exactly what happens at the root as it yields.
Ned Simmons
|