Couple quick answears on bars

[sad_rocc@veedub.com (Dan Smith)]

>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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