Why cylinder flutes?

[mike100]

I'm going to go with the indexing/quality cosmetic feature item from way back argument. Funny now how unfluted is a trend, even a premium item...just because it is different. It certainly is easier to not cut and machine the fluting.

[Parag]

Clearly, the solution is *fins*. Lots and lots of fins. It should look like a hedgehog!

-- Parag

[bobfried]

Fluting also strengthen the cylinder up considerably. It's the same reason you see fullers on swords, people will almost mistaken them as som comic-relief "blood grooves" but they're there only to strength the structure.

In a round cylinder the stresses that push outward on the surface really has nothing to counteract against it. Adding flutes create two leading edge where the cylinder meet the bore and significantly improves the structural stiffness of the area. Especially on a cylinder that has been bored through, flutes gives added structural rigidity loss when the rear was opnened up.

[drclark]

I'm not a mechanical engineer. It sure is counter-intuitive to think that removing material from the cylinder actually increases its strength/rigidity. Any chance you could post a picture to better visualize the effect you are describing?

I had heard that a fuller on a sword is there to allow easier extraction from a stabbed victim as it prevents the wound from closing completely around the blade and forming a vaccum. I have no idea if thats true though.

drc

[rivviepop]

I'm not a mechanical engineer. It sure is counter-intuitive to think that removing material from the cylinder actually increases its strength/rigidity. Any chance you could post a picture to better visualize the effect you are describing?

I learned something similar in my (long past) years I was working in theatre tech - basically take some thin plywood and cut a circle out. That circle of wood, while containing more surface area, is actually less strong that if you took it and made a triangle out of the middle of the circle. The triangle by it's shapely nature has a greater ability to keep things together (in our case the flats for scenery) than a round object. I can see how the fluting would apply in the same way, it creates a stronger set of tension points whereas a purely round cylinder has nothing to really keep it from expanding outwards under pressure.

(I'm not mechanical engineer either, just going off life experience )

[tunder]

bobfried-
You're right about the fuller in the sword blade. It increases strength/rigidity in the bladewhile decreasing the overall weight in the sword.

But I don't think the cylinder flutes strenghten it any.
The first revolver I purchased with an unfluted cylinder was a Ruger Super Blackhawk.
The reason given at the time was that the unfluted cylinder was stronger.
The same reason is given for the cylinder stop cuts being between the chambers on the cylinder.

Since flutes were present before modern metallurgy, and non destructive testing methods were limited, I have to think that the flutes were for a better grip on the cylinder when reloading.

[Knauga]

There is fluting and then there is removing metal to reduce weight. I would guess that removing the metal on a cylinder is about reducing unnecessary weight from the mechanism.

Traditional fluting is about stiffening otherwise flat metal to strategically strengthen it like in the example below.

[Crazyhorse]

I think we are mistaking strengthen with stiffen. A same weight fluted barrel is stiffer than a same weight non-fluted barrel but not as able to take the same pressures a non-fluted barrel would. Failure would always be at your weakest points and the fluting creates those.

[bobfried]

I made a super long post but realized it was all too archaic an argument for anyone else to understand. I will keep my thinking that it is there for rigidity, but will have to accept that it was probably an afterthought behind cosmetics.

Sometimes function just happens to follow form.

[Scarecrow Repair]

Fluting and surface area

Surface area depends on the radius of the surface, since more of the complete circle is present. All other things being equal, the sharper the radius, the more surface area.

If the before and after radii are the same, there will be no change in that aspect of the surface area.

If the fluted section does not extend all the way to the ends of the cylinder, ie, if one or both ends of the cylinder retain their original shape, that will add surface area at the end of the fluted section. But if the fluting extends all the way to the end, it will decrease surface area because the end used to have surface and now has nothing. I suspect this makes more difference than having a sharper fluted radius, or to put it another way, I think the radius change necessary to make up for the loss of end material would be too sharp and thus too deep to be practical. I doubt it's a very tricky math problem.

[M. Sage]

I'm not a mechanical engineer. It sure is counter-intuitive to think that removing material from the cylinder actually increases its strength/rigidity. Any chance you could post a picture to better visualize the effect you are describing?

I had heard that a fuller on a sword is there to allow easier extraction from a stabbed victim as it prevents the wound from closing completely around the blade and forming a vaccum. I have no idea if thats true though.

drc

Simpler way for you to see it:

Take a sheet of paper out of your printer, holding it flat, bend it mid-way down. Now with the same sheet of paper, roll it into a U-shape. Try bending it mid-way down again. The U-shape resists flex, but only if it's fairly perpendicular to it.

A pipe is more rigid than a solid bar, too.

[Parag]

A pipe is more rigid than a solid bar, too.

I think this is only true if they are the same *weight* but not if they are the same *size*.

Damn - I vaguely remember how to figure this stuff out from physics classes long ago - but my brain has rebelled and wants scotch instead.


-- Parag