Perminent Attachment of Compensaters

M

mongrel66

New member
There was a string in art of the rifle that dealt with this about ten days back...It confused me a bit..so i've posted this message here and on an engineering post...can anyone help.

"Okay heres the dilema ...two pieces of pipe
one is a gun barrel..the other a compensator that goes over the end of the
barrel
Usually the compensator(female) is threaded ,as is the end of the
barrel(male), they screw together like a bolt(barrel) and nut (compensator)
My question is...lacking threading..or pinning the compensator in
place...can the compensator be machined to a close tolerance, heated, then
slipped over the barrel , and cooled to a room temp,to hold in place?
I was under the impression that expansion would be inward as well as
outward, I realize I hadnt mentioned expansion along the outer circumference
because that wouldn't be a concern in the actual fitting of the peice.
I assumed the compensator...with it's inner diameter being slightly smaller
at the start, than the barrel outer diameter, could not, by the application
of heat, be made fit ..because the heat would further reduce the inner
diameter of the compensator.
Someone mentioned to me how bushings are applied to solid rod with heat
then cooled to a snug fit...how can this occur?
Can it occur at all...What is physically happening when the bushing is
heated that allows it to slip over a solid rod"
 
Mongrel, I don't know all the physics involved but it does work. Personally I would drill through the compensator and into the barrel and weld it after the heat fitting. It might not be needed but if you didn't do that the ATF might not consider it permanent. George
 
The metal will expand in all directions, and will get thicker, however, the majority of the expansion will take place around the circle making the whole circle and thus the inside diameter bigger. As an easy illustration, make a circle out of say, a dozen dimes. This represents the molecules in a cross-section of the bushing. Now make a circle of a dozen quarters representing the heated expanded molecules. They have expanded in all directions, including inward (from the center of each molecule toward the center of the circle) but the cumulative "growth" of each molecule, due to their alignment in a circle, has caused the circumference to expand more than the inward expansion, thus the inside diameter has gotten larger.
Hope this helps
Bergie
 
I've been doing a lot of oven burning this evening,figuring this out.next question..

Does this hold for thick walled objects as well , would there be a ratio of circumference to wall thickness that once crossed would change the dynamic whereas the circumferential expansion wasnt as great as the expansion of the wall..say for instance..a bull barrel

[This message has been edited by mongrel66 (edited March 13, 2000).]
 
Conventional wisdom is to drill and pin the compensator. Welding and high temp solder (law says the solder's melting point must be higher than 2000F) will warp the barrel and destroy accuracy. It will also burn off the Parkerizing. Plus installing a pin is just so dang easy, inexpensive, verifiable, and reversible. -- Kernel
 
let me explain..I dont want to do this..I want know how it works..i wanted to know the physics involved..I'm imagining it would be perminent as any attempt to heat the compensator again would also heat the barrel, causing IT to expand along its outer circumference..
 
I'm not sure if there could ever be a ratio of diameter to thickness that would cause a lessening of the i.d. The energy levels of the molecular structure would always try to create an equal expansion and a decrease in i.d. would try to "force" the molecules closer together.
All metals expand at different rates/temperatures. Mercury switches and some other switches use a bi-metal spring made of two layers of different metals, even a temperature change of a degree or two causes diferrential expanson of the two metals. If the barrel and comp were both of the same steel they might expand at about the same rate making it a more or less permanent installation, but if they were of different alloys, they could possibly be made so that the comp could be removed by the application of heat (It would expand at a faster rate and/or lower temp than the barrel), or so that heat would actually lock them tighter (the barrel expands faster/ cooler).
Bergie
 
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