Barrel Fluting simulation using SolidWorks

[ntsqd]

I've read that increased surface area claim for fluted barrels and I've wondered. So I made my life easy and modeled a barrel in SolidWorks and made it tell Me what the different in surface area was rather than trying to calculate it. Since I didn't know any exact dimensions and I don't really care for them myself, so nothing in inventory, I had to guess at flute width, depth and length.
It wasn't a very large increase, maybe 10% at most if I recall correctly. I can do it again if some wants to feed me their fluted barrel's dimensions. Can even post pretty pictures if you want. Ooohhh, I could also run a simple bending strength analysis on the barrel w/ and w/o the flutes........

That doesn't stop me from admiring the tools created to do the work and the artistry that some people put into their fluting.

Pulled out of the Dividing Head thread since it's sort of off-topic. https://www.longrangehunting.com/threads/dividing-head.335921/

Since no one sent me any barrel dims I decided that I was curious enough to look at this on my own. I used a Shilen #3 contour, cut to 20", 7mm (Ø.284", not actual) bore, no chamber & no rifling for the model. Six straight Ø.250" flutes radially arrayed that cut to a minimum diameter of Ø.700" Obviously without real world sample(s) I'm guessing at the depth, starting point, and length of the fluting.

Unfluted barrel "weighs" 2.89 lbs and has a Surface Area of 71.9509 square inches.
Fluted barrel "Weighs" 2.78 lbs and has a Surface Area of 73.5067 square inches.

Assuming that I did the math correctly that is a 3.8% reduction in mass and a 2.2% gain in Surface Area.

A heavier barrel and/or different fluting will affect these results, perhaps dramatically and perhaps not. I can run the simulation again with real numbers if someone wants to provide them.

 

[stiff neck]

As you found out, fluting a #3 sporter barrel is mostly just for looks because the flutes have to be very shallow. If you can even get someone to do it. Flutes are more common on thicker barrels. I think they look good even if they don't do much.

There's a barrel weight calculator somewhere already that allows you to compute flutes vs no flutes. I used it to figure that a 20" light varmint or magnum sporter barrel is pretty much the same weight as a 22" fluted barrel same contour. This turned out to be true with a CBI barrel I ordered. Basically with fluting you save 2" of barrel weight (on a medium-heavy contour barrel).

 

[ntsqd]

I picked the #3 as a place to start. Was/am really hoping someone will post some real barrel dimensions to work from.

 

[Bob Wright]

Solid Works is a great modeling system, among many.

 

[Justice1327]

Spiral fluting reduces more weight and increases surface area more than straight flutes.

 

[ntsqd]

Let's walk before we try to run. Frankly, I'm not looking forward to modeling spiral flutes. Doing it isn't difficult, it's making it still work after various changes to the barrel shape.

Adjusted the barrel dims to a Shilen #5:
Unfluted barrel "weighs" 3.50 lbs and has a Surface Area of 77.2502 square inches.
Fluted barrel "Weighs" 3.16 lbs and has a Surface Area of 82.4180 square inches.

Assuming that I did the math correctly that is a 9.7% reduction in mass and a 6.7% gain in Surface Area.

Length of the fluting was adjusted to what looked more appropriate.

This seat of SW doesn't have the simple analysis tool installed, so having a look at the change in bending strength is going to have to wait until a solution presents itself. Intuitively I expect spiral fluting to be more flexible than straight fluting. I'm hoping to prove that right or wrong, so I'll keep looking for a solution to that.

 

[Bob Wright]

Let's walk before we try to run. Frankly, I'm not looking forward to modeling spiral flutes. Doing it isn't difficult, it's making it still work after various changes to the barrel shape.

Adjusted the barrel dims to a Shilen #5:
Unfluted barrel "weighs" 3.50 lbs and has a Surface Area of 77.2502 square inches.
Fluted barrel "Weighs" 3.16 lbs and has a Surface Area of 82.4180 square inches.

Assuming that I did the math correctly that is a 9.7% reduction in mass and a 6.7% gain in Surface Area.

Length of the fluting was adjusted to what looked more appropriate.

This seat of SW doesn't have the simple analysis tool installed, so having a look at the change in bending strength is going to have to wait until a solution presents itself. Intuitively I expect spiral fluting to be more flexible than straight fluting. I'm hoping to prove that right or wrong, so I'll keep looking for a solution to that.

I agree on the spiral flute bending vs straight "beams". I would think spiral has a unique response to bending or vibration.

 

[stiff neck]

So that #5 20" barrel lost 5.4oz with fluting. I bet that's roughly equivelent to 2.5" of barrel. (Same weight #5 not fluted would be 22.5").

So if a guy wanted to chop a couple inches off to save weight...

Barrel fluting = $150+
Barrel chop & crown = $100
Barrel chop/crown/thread = $150

 

[ntsqd]

That #5 barrel at 28" long "weighs" 4.28 lbs. according to the model, so cutting 8" off reduced it's weight by .78 lbs. or 12.5 oz. Since the barrel is tapered each inch of barrel will weigh slightly differently.

I agree on the spiral flute bending vs straight "beams". I would think spiral has a unique response to bending or vibration.

I think so too, and intuition says it's not favorable.

 

[Aloeus]

Let's walk before we try to run. Frankly, I'm not looking forward to modeling spiral flutes. Doing it isn't difficult, it's making it still work after various changes to the barrel shape.

Adjusted the barrel dims to a Shilen #5:
Unfluted barrel "weighs" 3.50 lbs and has a Surface Area of 77.2502 square inches.
Fluted barrel "Weighs" 3.16 lbs and has a Surface Area of 82.4180 square inches.

Assuming that I did the math correctly that is a 9.7% reduction in mass and a 6.7% gain in Surface Area.

Length of the fluting was adjusted to what looked more appropriate.

This seat of SW doesn't have the simple analysis tool installed, so having a look at the change in bending strength is going to have to wait until a solution presents itself. Intuitively I expect spiral fluting to be more flexible than straight fluting. I'm hoping to prove that right or wrong, so I'll keep looking for a solution to that.

If you can send me the files I might be able to run stress simulations in inventor. I'll try and find the time and patience to measure out and model my tikka barrel too.

Me: "wow, flutes really aren't worth the extra price you tend to pay for them."
Engineer brain: "but they're more efficient."

 

[Bob Wright]

If you can send me the files I might be able to run stress simulations in inventor. I'll try and find the time and patience to measure out and model my tikka barrel too.

Me: "wow, flutes really aren't worth the extra price you tend to pay for them."
Engineer brain: "but they're more efficient."

As far as heat rejection "efficient" with >area?

 

[wasskeet]

As far as heat rejection "efficient" with >area?

Inventor Professional may be able to calculate that also. It used to be an add-on package, but now it may be included. You've made me curious now LOL.

 

[Radman]

I agree on the spiral flute bending vs straight "beams". I would think spiral has a unique response to bending or vibration.

Ditto, what you said, plus you have to wonder what that does as the barrel warms up, more at the breech than the muzzle? Is there a torsional or slight tendency to twist? Does it matter?
For that matter, all barrels experience the same localized heat up. Wouldn't that mean that a barrel actually has an insignificant (?) difference in the twist rate?
For MY target shooting NONE OF THIS will ever be a factor but it is intriguing to think about! I have 2 rifles with spiral flutes, same caliber. One shoots "good" (stainless) & the other "is a laser" (black). Both are heavy barrels.
Higher tech than I but fun to think about. Good topic!

 

[ntsqd]

Generically heat rejection does increase with surface area, but the geometry can have a damping effect on it. If said geometry causes small areas of turbulence in a given region then I'd expect that region to be less efficient at dissipating heat. In the overall picture this may well be so tiny of an effect as to be splitting hairs, I've no idea. Thermo was my second least favorite class (Statistics was my least favorite).

My mind has always pictured the "slow-mo replay" of firing a spiral fluted barrel acting a lot more like a Slinky than one of the same contour w/o any fluting.

I would expect a spiral fluted bolt to act like a compression spring when fired, except that the lugs take all of that load. Heaven help the person who spiral flutes a 788 bolt.....
I'd like to see someone start plunge EDM fluting the ID of bolts instead of external external flutes. Now that would be trick!

In the models the fluting is a configuration. Not sure how well or even if those will translate in a neutral file format. I'm sending out some emails to like minded friends to see if they can do the simple bending strength analysis.