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Couple quick answears on bars



I think I agree! :)

One thing mentioned is the heat-treat of the aluminum.
I am not a Materials Engineer, but I did do some
reading to find out that 4130 cromo will keep it's
heat treatment reasonably well during the welding
process.

Neal

--- Dan Smith <sad_rocc@veedub.com> wrote:
> From working in a bike shop, here's the difference
> between chromoly and aluminum. Chromoly has thick,
> but small diameter tubes, where aluminum has the
> opposite. Aluminum dents a lot easier, but is
> considerably stiffer. Chromoly absorbs vibrations
> better, it is not necessarily more flexible. The
> aluminum they use on bikes gets heat tempered to
> make it stronger and stiffer. As for steel in bikes,
> they use a ton of it. BMX bikes are the only ones
> made out of steel so you can basically toss them off
> a cliff without anything happening. If you want a
> big, comprensive analysis between steel and aluminum
> for strut bars, go to tmtuning, they make a
> convincing argument for using aluminum. From bike
> experience, I think chromoloy or aluminum would work
> well, chromoly would absorb some of the force,
> acting like a reinforcement piece and a dampener.
> Aluminum is stiffer, lighter and doesn't rust but
> has zero give. Just my $0.02.
> 
> Dan
> 
> --- Neal Tovsen <nealtovsen@yahoo.com> wrote:
> >> Aluminum really wouldn't be a good choice for
> this
> >> part.
> >> Aluminum is ~1/3 the weight of steel, but it's
> also
> >> <1/3 as stiff as
> >> steel. So, the weight to stiffness ratio is
> roughly
> >> the same and you'd
> >> have to really bulk up the aluminum part to make
> it
> >> stiff enough to make
> >> it worthwhile.
> >
> >Ahhh...the same sorts of things could be said about
> >advanced composites. Yet F1 cars use aluminum and
> >composites more than steel, because that logic
> doesn't
> >take design into account. Comparatively oversized,
> >thin-wall aluminum tubing can be both stiffer and
> >lighter than steel. Autotech does this with their
> >strut tower bars. The concept was pioneered in the
> >bicycle industry by people like Cannondale.
> >Cannondale, Trek, and similar bikes are STIFF and
> very
> >lightweight. Conversely, I've seen (and ridden)
> some
> >cheap aluminum bikes that had steel-like tubing
> >diameters with thicker walls to compensate. As you
> >suspect, they weren't any lighter than a decent
> steel
> >bike.
> >
> >I think the stiffness of a well-built aluminum bar
> >would actually work better than steel for this
> >purpose, in addition to being lighter. Chromoly
> bikes
> >can be made to be almost as light as aluminum, but
> >they tend to have much more compliant (some would
> say
> >"spongy" or "springy", others would say "lively")
> >characteristics. Aluminum bicycles are often
> >characterized as being too stiff. Well, that't good
> >for us. We want a bar that is RIGID.
> >
> >If I only had a TIG welder...
> >
> >Neal
> >
> >--- Dan Bubb <jdbubb@ix.netcom.com> wrote:
> >> Aluminum really wouldn't be a good choice for
> this
> >> part.
> >> Aluminum is ~1/3 the weight of steel, but it's
> also
> >> <1/3 as stiff as
> >> steel. So, the weight to stiffness ratio is
> roughly
> >> the same and you'd
> >> have to really bulk up the aluminum part to make
> it
> >> stiff enough to make
> >> it worthwhile.
> >> Dan
> >> 
> >> Bob wrote:
> >> > 
> >> > Stock  is 3/4''with .125 walls this can be
> changed
> >> if people want to cut
> >> > weight, haven't got a weight yet
> >> > Kicking around the thought of a handfull of tig
> >> welded aluminum ones.
> >> > Price still haven't got that figured yet
> >> > Mounting to the same place as Kevins with a
> plate
> >> on top to spread  presure,
> >> > will come with all bolts.
> >> > Hope to have all things figured out tomorrow
> >> > Bob
> >> > 
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