Post by: bluelake on May 14, 2009, 07:16:11 PM
What is the reasoning for octagonal barrels on many bp arms? Is there something structural about it, such as withstanding gas pressures, or was it more ornamental?
Post by: Three Hawks on May 14, 2009, 11:28:33 PM
Quote from: "bluelake"
I wasn't exactly sure where to put this, so...
What is the reasoning for octagonal barrels on many bp arms? Is there something structural about it, such as withstanding gas pressures, or was it more ornamental?
Now that is a really good question. It's one of those questions that is so good, it never occurred to me before. I have no idea why so many barrels are octagonal. But I'll bet someone who has will be along pretty quick with a reasonable answer.
Three Hawks
Post by: bluelake on May 15, 2009, 01:27:28 AM
Quote from: "Wyosmith"
It's because squares are easier to forge then rounds. An octagon is a square with the corners "knocked down"
How did they do it? Did they take a solid square bar, knock down the corners and then drill it out? Did they take a sheet, bend, forge, and then take down the corners? Some other way? It's interesting, as it was done like that here in Asia, too (and the sides of the octagon are perfectly straight and flat).
Post by: bluelake on May 15, 2009, 02:34:22 AM
Post by: cb on May 15, 2009, 04:05:37 AM
Solid steel drilled barrels first appeared in the 1830's, but rifle barrels retained the octagon shape until the early 1900's.
Post by: Gambia on May 15, 2009, 08:16:57 AM
Another interesting thing about barrel grinders and also knife grinders when steam driven became the thing the average life span of a grinder was just over 40 years it was a dirty job
Feltwad
A Flint Lock will not secure a chicken house door
Post by: Captchee on May 15, 2009, 09:17:54 AM
As I understand it the octagon does 3 things
1) if provides for a more rigid barrel while at the same time allowing the barrel material to be somewhat soft .
Normally if you measure from a flat to the bore and then from the peak to the bore , you will find about .025 or more in diameter
2) ease of welding . As steve mention , barrels were hammered by hand , around a mandrel somewhat smaller then bore size . As such the barrels are somewhat round as the anvil “ hope that’s the right name “ that is use has half round notches in it . If you get muzzleloader , you will see , if I recall Hershel House forge welding up a barrel using the half round anvels .. The barrel is then hammered , Not ground to a to a given wall thickness .
Rotated , hammered again , so on and so forth . then the flats are draw filed or ground to true them up .
later as feltwad stated , this changed to just making the barrels thicker and grinding the flats , not drawing thiem
3) as steve said again . It provides for a easy way to know the barrel is true .
Now that should not be confused with meaning that the bore is true . We are only speaking of the outside of the barrel
Now with the bore , special reamers are made to bring the bore to a given constant , clean bore size . Then the barrel is placed in a rifling machine.
If you go to the the link for Toad hall , given above , you will see examples of a rifling machine
This is where what feltwad said comes into play ..
Later when steam and water hammers and grinders came into play , the processes changed a lot . But it was not really a whole lot easier to produce a octagon barrel , then a round one. but a minsat had been instilled and people wanted what they had come to know as a proper made barrel
Now I was also once told , long ago by a learned foe, that it was much simpler then that . In his view the octagon was architectural IE #1
Basically people looked for strenght in nature .
Basically a true round was weak , and it was thought that if a tree would bend and sway in the wind , a round barrel would do the same .
Yet a bee’s honey comb is ridged , withstands many times its own weight upon its walls , without deforming as such , this was felt to be the best design for something like a barrel .
Now true or not . I cant say . There sure seems to be a lot of examples of round barrels . However I can see the logic in that explanation as well
Post by: bluelake on May 15, 2009, 09:47:35 AM
Ever since I bought my son a .32 cal. Remington rolling block with octagonal barrel (pre-1898) years ago, I always thought that style barrel looked really sharp. Now I appreciate it even more and like it that much more.
Post by: bluelake on May 18, 2009, 08:11:27 PM
Has anyone seen it?
Post by: Kermit on June 01, 2009, 03:25:46 PM
I've done more than my share of traditional wood boat work, necessarily including sparmaking and oar making. It's pretty easy to get a hunk of stuff--wood in this case--to a square condition using hand tools. Then on the way to getting round stock, you knock the corners off (and there are clever formulas and jigs for marking out the lines for this, even on tapered stock) to get it eight-sided. From there it's pretty simple to eyeball it into a sixteen sided state, and from there to round.
You'll see a lot of stuff--oars and spars--that never get beyond octagonal. Oar looms are a common example in traditional boats.
I'd guess that stopping at octagonal when you are using files to do the work is not much more than a way to save a bunch of really fussy work. Getting wooden spars to the eight sided state is quick and simple. It's from there to round that takes time--and skill--and might have been seen as just guilding a lily. And then folks probably just liked it, thought it was the way it was supposed to be, and never thought about it much after that.
But I've been wrong before...
Post by: Three Hawks on June 01, 2009, 06:06:50 PM
Fortunately, wood suited to masts, booms, and yards is very easily worked by hand, and pleasant work it is, too.
Three Hawks
Post by: Gambia on June 02, 2009, 12:30:21 AM
Post by: Kermit on June 02, 2009, 11:08:16 AM
Post by: Riley/MN on June 02, 2009, 11:30:56 AM
Post by: Gambia on June 02, 2009, 11:46:01 AM
Post by: Gambia on June 02, 2009, 11:53:25 AM