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Old 01-31-2013, 05:56 PM   #27181
Schlug
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Quote:
Originally Posted by Aurelius View Post
I once asked this very question of a mechanical engineer who had considerable experience in both design and manufacturing. His response was that while it's possible to manufacture steel tubing every bit as light as aluminum, the steel would have to be made so thin that it would be virtually impossible to weld without destroying it. The second reason he gave is that while aluminum tubing can be just as strong as steel tubing of equal weight, aluminum is by nature less prone to bend under stress than steel. Since frame flex is an undesirable trait for a bicycle, the combined virtues of lightness and stiffness of aluminum makes it a better choice than steel.

Aluminum is not nearly as stiff as steel, actually.


Stiffness is quantified by whats called the modulus of elasticity.
The modulus of elasticity of aluminum is 10 million psi (+/-)
The modulus of elasticity for steel is 30 million psi (+/-)

The stiffness of chro-mo steel might go up a little bit. Not really enough to matter.
The stiffness of aluminum doesn't really matter vs. its alloy.
Aluminum's tensile strength is lower than steel, it's yield (bendind) is far less, and it's ability to deform before failing is remarkably less.

But because its density is so low, it's easy to make thicker and larger diametre tubes which weigh less than steel.

Stiffness is desirable in bicycle frames only in certain directions, while undesirable in other. A frame that is too stiff will make for a miserable ride and fatigue the rider unnecessarily. A frame that sways back and forth under load will waste the rider's power on flexing the frame rather than propelling the rider forward.

I don't particularly care for the rider of aluminum, but I have a Columbus Airplane frame. And an Eddy Merckx metal matrix/carbon frame.
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Old 01-31-2013, 06:25 PM   #27182
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Originally Posted by BobbySands View Post
I don't particularly care for the rider of aluminum, but I have a Columbus Airplane frame. And an Eddy Merckx metal matrix/carbon frame.
Last Airplane frame I had rode very nicely thankyouverymuch.

Ask a Euro about AL frames and they think Alan/Vitus = noodle. Ask an American about AL frames and we think of Cannondale = stiff with a capital S.

You can make both steel and AL ride like a noodle (Vitus, ALan, SL 531l) or like a board (Cannondale, Columbus Max, TSX) depending on what you do with the material.

You can do the same thing with CF too. My Full Tilt Boogie is a much softer ride than the TCR I just got. Different layups within the same material affect the ride a significant amount.

AFA bikes go: the geometry hasn't changed a whole lot since about the mid-90s if you're talking about 26" wheels. It has changed a bit in the 29ers since they were introduced, but it seems that they've figured out the geometry in the last little bit and things aren't changing as fast any more.

HTH

M
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Old 01-31-2013, 09:58 PM   #27183
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Gimme the fat!

Hey all, I'm looking for a new tires for my mtn bike. Criteria? They need to have lots of volume so I'm thinking 2.4 - 2.5. Unfortunately most tires in that range are dh tires and are either too heavy, have knobs that are too agressive making them roll like doodoo, or both.

Ideally I'd like something like a Kenda Small block but the biggest they come in is a 2.35 which isn't big enough. FWIW, they're going on a fully rigid bike that I'm building for super techy xc riding (think very trialslike). Suggestions?
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Old 01-31-2013, 10:54 PM   #27184
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Originally Posted by ducnut View Post
Of those two, I'd take the late-model one, every time. Componentry has come a long way, since the 80's.
Actually cycle components are not part of my problem since they can be swapped easily. Ok I'll declare my steel bias. Guess I was more after weight vs strength etc views on the frame only. The frame I'm looking at is a late 80s tange Cr-Mo d/butted hardtail made here [ie yep I know, nothing special] so I wonder what the weight penalty for a 61cm/24" CTT would be over an equivalent ~ 2005 welded aluminum hardtail frame?

Quote:
Originally Posted by Aurelius View Post
I once asked this very question of a mechanical engineer who had considerable experience in both design and manufacturing. His response was that while it's possible to manufacture steel tubing every bit as light as aluminum, the steel would have to be made so thin that it would be virtually impossible to weld without destroying it.
Thanks - but welding? Isn't that why lugs (however unfashionable they are presently) have been around for so long - to provide a means of mechanically attaching very thin walled tubes to other such tubes?
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Old 01-31-2013, 11:02 PM   #27185
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Quote:
Originally Posted by championsound View Post
Ideally I'd like something like a Kenda Small block but the biggest they come in is a 2.35 which isn't big enough. FWIW, they're going on a fully rigid bike that I'm building for super techy xc riding (think very trialslike). Suggestions?
Two tires spring to mind:

Schwalbe Racing Ralph comes in a "2.4", but they're bigger than that labeling suggests. I use a pair of the 2.4s on my rigid Karate Monkey.

WTB WeirWolf LT comes in a nominal "2.55". I'm not sure it's actually that big, but it is a really fat tire; I've got one on the rear of my FS rig. (Don't confuse this with the non-LT WeirWolf; That's got a knobbier tread that doesn't sound like what you want.)

Both have relatively shallow, fast-rolling treads that I think would behave similarly to the small block.
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Old 02-01-2013, 05:41 AM   #27186
Aurelius
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I see the engineering geeks are well represented here.
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Old 02-01-2013, 06:21 AM   #27187
zippy
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cyclocross world championships

Anybody know if this is being televised this weekend ? The world is coming to kentucky , wish I could be there with cowbell in hand.


I heart Marianne Vos
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Old 02-01-2013, 06:28 AM   #27188
Gummee!
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Quote:
Originally Posted by overlandr View Post
The frame I'm looking at is a late 80s tange Cr-Mo d/butted hardtail made here [ie yep I know, nothing special] so I wonder what the weight penalty for a 61cm/24" CTT would be over an equivalent ~ 2005 welded aluminum hardtail frame?
Of the 2, get the newer AL frame. Geometry is going to be better all-round. The late 80s was still the time of the first gen or two of mtn bikes and the geometries weren't 'right.'

Quote:
Thanks - but welding? Isn't that why lugs (however unfashionable they are presently) have been around for so long - to provide a means of mechanically attaching very thin walled tubes to other such tubes?
There's several ways of joining tubes together: screwed and glued (Alan/Vitus), welded (TIG), Fillet Brazed, ...and lugs. With lugs you're limited to the sizes of tubes and the angles that the lugs were built for. IOW if you want a compact frame or frame with Max tubes, you need different lugs than a standard frame. That means different molds. Different castings. Different... well... everything. (read $$)

It took a while for TIG welding to catch on in the road world. Even today, the 'craftsmen' of the industry still use lugs, but they're building 'classically styled' bikes (Richard Sachs et al See Velocipede Salon's 'Friday Night Lights section) Gian was the leader in the compact road scene with the TCR from the ONCE team 'way back when.' Its been downhill ever since.

I still love the look and ride of the small-tubed steel bikes from my early years of riding. All those old Graham Watson coffee table books? However, being built like a gorilla, I fit better on compact frames. Go figure, huh?

M
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Old 02-01-2013, 06:29 AM   #27189
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Quote:
Originally Posted by zippy View Post
Anybody know if this is being televised this weekend ? The world is coming to kentucky , wish I could be there with cowbell in hand.


I heart Marianne Vos
yeah.

Oh, and 'Hi! My name is Gummee! and I'm a wheel whore.' Picked up a D/A Open SUP CD Ceramic wheelset for $150 the other day for a set of dirt road knobbies. That brings me to:

Ritchey WCS Zetas
Ritchey Road Aero
571/2 Reflex Ceramics
571/2 A23s
XTR Escape/Mach2CD2
Hugi Matrix Photon
600/King* Escapes
D/A Open SUP Ceramics

...and misc front and rear wheels. Its gonna be a LONG time before I go 11sp!

M
*the King is coming out and an Ultegra is going in for next cross season. Kings are going to be built into low-profile carbon rims for racing cross.
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Gummee! screwed with this post 02-01-2013 at 06:39 AM
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Old 02-01-2013, 06:46 AM   #27190
zippy
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Thanks Gummee !!

I just moved three or four spare wheelsets into the shed from the house to appease the woman ...

only one of note being a set of aerospokes with a DA 9 speed cassette on the rear.
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Old 02-01-2013, 06:50 AM   #27191
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Originally Posted by zippy View Post
Thanks Gummee !!

I just moved three or four spare wheelsets into the shed from the house to appease the woman ...

only one of note being a set of aerospokes with a DA 9 speed cassette on the rear.
I didn't say anything about 'spare.' No such thing around here (at least the complete sets). They all see action at some point or another.

Intervals? Aero wheels
Sprints and JRA? Reflex Ceramics or A23s (32/32 'cause they're tougher)
Cross? tubulars
Dirt roads? Either the Hugis or the new D/A wheels

etc

The hard part is keeping cassettes on em all!

M
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Old 02-01-2013, 06:55 AM   #27192
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We're 2nd class citizens all over.

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Old 02-01-2013, 07:07 AM   #27193
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Originally Posted by Gummee! View Post
We really don't help our cause sometimes though....
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Old 02-01-2013, 09:13 AM   #27194
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Quote:
Originally Posted by Oznerol View Post
Two tires spring to mind:

Schwalbe Racing Ralph comes in a "2.4", but they're bigger than that labeling suggests. I use a pair of the 2.4s on my rigid Karate Monkey.

WTB WeirWolf LT comes in a nominal "2.55". I'm not sure it's actually that big, but it is a really fat tire; I've got one on the rear of my FS rig. (Don't confuse this with the non-LT WeirWolf; That's got a knobbier tread that doesn't sound like what you want.)

Both have relatively shallow, fast-rolling treads that I think would behave similarly to the small block.
Thanks for the suggestions! Looking really quick at what's available... neither of my usual "go to" mail order companies have them and I know for sure that none of my lbs' are gonna have them either.
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Old 02-01-2013, 09:54 AM   #27195
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Originally Posted by championsound View Post
Thanks for the suggestions! Looking really quick at what's available... neither of my usual "go to" mail order companies have them and I know for sure that none of my lbs' are gonna have them either.
I've read good things about the Maxxis Ardent 2.4, but don't have any personal experience with it.
http://www.cambriabike.com/Maxxis-Ar...Tire-Black.asp
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