I have been curious for sometime as to why high end aluminum (or steel) bike frames arn't fluted. A fluted tube of metal is stiffer and lighter. Just curious if it had ever been tried or if there is a reason why it won't work.

Brazos

Those fluted tube frames, such as Columbus SLX, TSX, SPX, were only marginally stiffer, but heavier, than the non fluted versions of the same tubeset. I'm pretty sure the manufacturing expense of making the flutes is non recoverable for the manufacturers so they discontinued the style.

Nessism lists examples of internally "fluted' tubesets. The original SLX frame briefly offered by Colnago some thirty years ago was externally fluted or pinched. More prevelent by the '80s 'till the earlier in the '90s was Gilco; offered by Colnago, Tommasini & a few others. All these stated were Cyclex alloy, Columbus' first and only mat. for some sixty years. Nivachrome, a supererior type of chrmly. from a metalurgical standpoint came to supplant Cyclex starting in the late '80s and beyond. Nivachrome and subsequently others were found to respond better to being drawn thinnner but at a larger OD. the point is that "flutting" was tried for a spell but the oversize approach proved to be better.

Ok then I guess at least I know it was tried out. I had a feeling it was too obvious. Thanks for some history behind fluted frames. I guess the industry has been there and done that.

Brazos

Good point here! Going OS was a much better evolutionary step than adding the flutes which didn't do all that much. That said, a nice SLX/TSX frame was a wonderful thing! A little heavier than later tubesets but ride quality was excellent.

SLX & TSX .. HIGHest quality, true traditional

I`d heard of Miyata fluted tubes, but had no idea so many others had dabbled in it as well.

Miyata called theirs Splined.....as there were internal splines in the tube. My miyata is splinde triple butted.

I there was a bias at the time to retaining the tube dimensions, to fit certain lugs, or whatever, then flutes would make sense, but if you can apply that weight to increased tube dimensions better still. Stiffness increases to the cube of diameter, so flutes increase weight in the wrong direction (below surface of the tube), unless the flute was pushed above tube dimensions. This is a negative threefer. One, more weight; two, weight in wrong place; three, tube surface that could have been at max diameter is pushed under surface so less working tube at max diameter.

Flutes make most sense in solid bars or at least really thick walled structures, particularly if there is an advantage to added surface area like heat dissipation. Think bull barrels on rifles.

It was from gun experience that I wondered about flutes. Obviously heat dispertion is no real advantage for bike frame but the other 2 attributes (stiffness & weight reduction) would be good. I guess it just doesn't pan out in bike applications.

Yours was a good question ... the concept it frames did pan - out for a number of years but like so many other things, it just got trumped ... BTW ,, Bianchi & Miyata were both gun makers .. how's that ?

Oh yeah- SPLINED Miyata tubes. Are fluted and splined the same when it comes to bike tubes? I know that gun barrels were what I thought of when I first heard "splined tubes" and fluted barrels always looked splined to me, so I thought it was the same thing.

As an aside, the next thing that might be considered fluted on a bike would be open ended tubes that whistle with the wind, like an uncapped handlebar sometimes. I REALLY don`t think that`s the case, but flat bars can sometimes get a pretty good flute howl going

"but the other 2 attributes (stiffness & weight reduction) would be good."

Stiffness is a relative thing with barrels. Fluting them reduces the stiffness over the bull barrel itself, but the hope is that it will be stiffer than the smaller bull barrel you could make out of a the metal remaining in a fluted barrel.

Same thing with heat. A heavier barrel will absorb more heat, but at some point it becomes important to cool the barrel so flutes will do that, but to what degree I don't know.

One thing about flutes is that they are relatively easy to cut and faster to cut than profiling barrels (though in the current CNC world probably not a big deal). So it was a relatively cheap way of making a cool looking barrel. Another thing is the rifling changes shape relative to any contouring done to the outside of the barrel, at least with cut barrels. So the effect on a barrel with flutes must be interesting if not crtitical.

Some bike parts like stems actually employ these strategies, so it does have some relevance.

Two different kinds of stiffness to consider -- bending and torsion (twisting). Fluted might be stiffer in bending but is less stiff in twisting. A lot of what strain a bike experiences is twisting and a round section works better for that.

SLX, SPX had reenforcement inside the tubing something like rifling. I think the poster is asking about frames like a Colnago or Rossin that are crimped or corregated.

Oh, thanks for the pictures! I pretty much gathered that from the posts (eventually), but if I`ve ever seen a bike made with that kind of tubing I didn`t notice it.

Were these flutes "rolled" into the tubing? Or were they machine cut? If they were rolled then I could see some strength increase. If they were cut, like on a gun barrel, there would be no strength added. A fluted gun barrel is not made stronger by the flutes, but it would be stronger than a barrel of the same weight, which would be smaller in diameter.

Hi I think the fluting is done hydraulicly similar to how the manderls that do the butting is used. there are certainly not machined.

yw rodar. not many comapnies made fromes this way. I guess the cost v benifit was not worth it. my Cornelo is the only frame other than a Colnago or Rossin I remember seeing like this.

Not fluted exactly, but have you seen the hexagonal frames by Caminade?

Just a note here. As far as I know "Flutes" are in reference to the outside profile of a cylindrical object like say a drill bit or end mill or somewhat like the Cornello pic in Bianchigirll's post. "Rifling" or "splines" refer to the inside profile of a cylindrical shape.

I remember cutting into some very thin steel tubing that was on an English-style 3-speed as a kid and found interior ridges running lengthwise. The cross section cut looked kinda like a wheel with thick spokes running short of the hub. Figured the tubing was extruded like that for stiffness. Anyone ever seen such tubing before?

Ferrite is correct when he describes rifling. The tubing I described above had greatly enhanced lands that were .200 to .250 tall, not .003 to .004 like firearm rifling. (and no twist, of course)

Are any of you fellers referring to the Prestige externally fluted tubes? I've got a big box overflowing with those tubes.