|steel x steel||colker|
Feb 6, 2003 7:47 AM
|read< in the torelli site, a comparison btween new foco mondonico and an "old" el os torelli nitro saying he (chairman bill) can feel a good difference in the ride... just as when he went from slx to el os. |
i always thought that steel was steel and the builder/ geometry/ tube diameter made the only difference.
..what do u think?
will different steel tubes make for different rides?
have good roads under your wheels!
|re: steel x steel||MR_GRUMPY|
Feb 6, 2003 8:59 AM
|Steels aren't created equal. Lets say you could build a frame out of Columbus SL tubes with butts of .7/.4/.7 . Then lets say you build the same size frame out of Reynolds 853 or True Temper OX Platinum with the same size butts.
There would be a world of difference in how the bikes ride. The Columbus frame would be OK for a rider that weighed 140 Lbs, but the Reynolds frame would be stiff enough for a 200 Lb rider.
Foco is a "stronger" steel than El. If both bikes weigh the same, the foco would be stiffer. Likewise, the foco frame could be made with thinner tubes than the EL frame.(It would then be lighter, but have the same stiffness as the EL frame)
|Strength Does Not Equal Stiffness||Heron Todd|
Feb 6, 2003 9:05 AM
|In your example, the Columbus SL frame would have exactly the same stiffness as the 853 or OX Platinum frame. However, the air-hardened frames would be stronger.
If you want stiffness, you need to either increase wall thickness or tube diameter. Changing to a stronger alloy won't make any difference.
LaSalle, IL 815-223-1776
|Homework to do.||MR_GRUMPY|
Feb 6, 2003 9:37 AM
|Looks like I've got homework to do.|
Feb 6, 2003 9:39 AM
|Didn't we just go over all this stiffness stuff in the Foco thread?
The stiffness of a steel alloy is independent of the strength. Given the same tube diameter and thickness, a high strength alloy tube will be the same stiffness as a low strength alloy one. The difference is that the high strength tube will take more deformation before taking a set - plastic deformation. The high strength tube will also be more dent resistant.
Regarding the new Torelli frame, I also read this and found it interesting. The Foco tubes have shorter butts than ELOS so the ride quality is likely to be smoother. The part I don't understand is about the "increased drivetrain stiffness" with the Foco frame. Maybe the tall oval chainstays make a difference? This is a little surprising to me: tall oval stays are good regarding torsional loading at the bottom bracket but not so good when it comes to resisting lateral flex. At any rate, Chairman Bill is reasonably credible in my opinion so I don't doubt that he can notice a difference.
|Yes, agree!||Heron Todd|
Feb 6, 2003 10:42 AM
|>This is a little surprising to me: tall oval stays are good regarding torsional loading at the bottom bracket but not so good when it comes to resisting lateral flex.
A round tube will be torsionally stiffer than any other shape. Lateral stiffness is not nearly as important at the bottom bracket since the load there is primarily torsional.
With chainstays, tire clearance is an issue. By using oval stays, designers can often get a greater effective diameter than with a round stay. So, torsional stiffness will still be good. Another approach, which we use on Herons, is the round-oval-round stay which is ovalized only at the tire to give adequate clearance.
LaSalle, IL 815-223-1776
|Follow up question||bigrider|
Feb 6, 2003 9:48 AM
|Does this mean that if two steel bikes are designed from different alloys and have the same geometry(same tube dia.) and you want them to have the same strength, the only advantage in using a stronger alloy would be weight(stronger alloy could be thinner walled tubing?|
|Follow up question||Heron Todd|
Feb 6, 2003 10:37 AM
|Yes. You could go with a thinner wall with the stronger alloy and get the same strength. This would make the frame lighter. However, it would not be as stiff.
LaSalle, IL 815-223-1776
|Unless you increase the tube diameter but then...||joekm|
Feb 6, 2003 7:11 PM
|you put back weight and, of course, there is the potential for denting and "oil canning" if you push it too far (this is where a "hard" alloy can be of some help).
None the less, it may be possible to make a lighter frame with a stronger alloy while retaining stiffness, it's just not clear cut.
OTOH - as my understanding of frame design improves, I'm beginning to develop the opinion that a super hard alloy may not be the best choice for the rear triangle.
|Yea, stiffness to density ratio is about the same...||joekm|
Feb 6, 2003 7:02 PM
|This means, like he said, it will boil down to geometry. I wish I had data on the more exotic stuff like Dedacci 16.5. Perhaps a boron alloy has a higher specific stiffness.
The strength and yield behavior of the stronger (and harder) metals allow you to get away with thinner walls. To keep your stiffness however, you have to increase the tube diameter so the cross-sectional inertia stays the same. It's a bit of a balancing act.