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4130 Chromoly vs. Reynolds 853 Steel



 
 
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  #11  
Old August 6th 03, 11:19 PM
Mark Stonich
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Default 4130 Chromoly vs. Reynolds 853 Steel

(Jim Plaia) wrote in
If I'm correct about that, frame stiffness is again a function of
modulus and does not include tensile strength at all.


The desirable types of stiffness in a bike frame come from
increasing rigidity in bending and torsion. These increase rapidly
with increases in diameter. Higher tensile strength steels allow
higher diameter to wall thickness ratios. OX Platinum is available in
1.375" diameter that is only 0.016" thick between the butts. In 4130
such a tube would dent or buckle too easily to be practical.

there isn't a steel in existence that matches aluminum or titanium in
modulus to weight ratio.


Steel and Aluminum have almost identical modulus to weight ratios.
Steel's is pretty constant. Aluminums have some variation but the
average is about the same as steel. Titanium lags well behind at
about 87% of steel. Aluminum will build a stiffer frame for a given
weight, only because you can use larger diameters.

Example; If an aluminum tube has a 20% larger OD can have walls twice
as thick as a steel one, for dent and buckling resistance, and still
be 11% stiffer yet weigh only 82% as much.

If OD is constrained, steel wins, as the extra bulk of the aluminum
is closer to the middle of the tube where it is less effective.

Don't get me wrong, I've no desire to move into exotic steels, Al, CF
or Ti. I built a 4130 frame with a 60" wb that weighs 4.5lbs. and is
stiff as granite against pedalling forces, yet nicely compliant
vertically. An Al frame with this much vertical flex would fail rather
soon IMHO.

BTW True Temper has found that their non-air hardening, heat treated
steels retained a higher percentage of their strength after welding
than their non-HT tubes.
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  #12  
Old August 7th 03, 01:34 AM
R2D2
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Default 4130 Chromoly vs. Reynolds 853 Steel

Mark Stonich wrote:
Don't get me wrong, I've no desire to move into exotic steels, Al, CF or
Ti. I built a 4130 frame with a 60" wb that weighs 4.5lbs. and is stiff
as granite against pedalling forces, yet nicely compliant vertically. An
Al frame with this much vertical flex would fail rather soon IMHO.


Kudos Mark on the great frame!

My attempt at a 66" LWB weighed in at a full 6 lbs. I have nowhere near
enough experience to start pushing wall thicknesses or shaping. I guess
I'll just keep being conservative until I can find a Mentor.

I agree, vertical compliance is a pretty high priority with these
babies. R2






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  #13  
Old August 7th 03, 02:59 AM
Mark Stonich
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Default 4130 Chromoly vs. Reynolds 853 Steel

R2D2 wrote in message news

This unique
air hardening property of Reynolds 853 provides additional stiffness
through reduced micro yielding at the joints, allowing stiffer frames
with excellent fatigue strength (when compared to standard chrome
molybdenum) and excellent ride quality."


Well that settles it then. Alloying and heat treatment CAN alter the
modulous of elasticity of steel. This sentence, written by some
advertizing flack, ovbiously disproves the results of more than 200
years of metallurgical science and many, many thousands of tests. Just
think of all the textbooks that will have to be re-written. The
implications for spring design alone are enormous.
  #14  
Old August 7th 03, 02:04 PM
R2D2
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Default 4130 Chromoly vs. Reynolds 853 Steel

Point well made guys. Thanks for persevering (darn advertising hacks!)

R2



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