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Old 09-19-06, 12:17 PM   #1
Eli_Damon
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frame for hauling

I read somewhere that if you plan to use a bicycle for hauling heavy loads, it should have a steel frame because other materials are not strong enough. Is there any truth to this? Does it matter whether the weight is on the bike itself or on a trailer?
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Old 09-19-06, 12:26 PM   #2
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How heavy?
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Old 09-19-06, 12:50 PM   #3
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not quite true. yes, a piece of steel is generally much stronger than a piece of, say, aluminum of the same dimensions, but steel and aluminum bicycles are built differently, with more or less material in various places to produce a reasonably strong result. aluminum bikes can be stronger than steel by just using much more material. if an aluminum bike is well designed and made, it can be both stronger and lighter than many steel bikes.

the argument for steel is more subtle. because less of it is required for a given strength, and the tubes can be of smallish diameter and still be stiff enough, steel bikes tend to have more clearance for things like fat tires, narrow cranks, fenders, etc. steel structures can be visually lighter than aluminum, which i prefer aesthetically. but the biggest argument for steel in cargo applications is failure mode. any material will break under enough stress. with steel, you tend to get some warning. cracks propagate slowly, often after bending or buckling noticeably. aluminum and especially carbon fiber, when they break, break suddenly and completely. so i think steel is safer in applications where breakage is a real possibility.
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Old 09-19-06, 10:11 PM   #4
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Thank you. This was very helpful.
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Old 09-20-06, 08:56 AM   #5
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There's a metallurgical term that escapes me but it boils down to this. take samples of 2 different metals and apply a stress to them (weight, impact, whatev) the 2 samples might have the same maximum load (that is to say, load at which they break) but one metal can take 90% of that load 100 times whereas the other metal can take 90% of that load only once or twice before breaking. I'd call it the ability to withstand repeated strain, and afaik steel is much better at this than aluminum.

Also, +1 for everything tfahrner said, +5 for steel bike structures just having a better aesthetic. They may be heavy, but they look lighter don't they?
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Old 09-20-06, 10:57 AM   #6
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Ask yourself how many machines that are made for HEAVY work or torsinal loading
are made of anything but steel. Are cars? Are road construction equipment? Are trucks?
etc. to start getting a picture of the correct material to build ANY load bearing equipment
from......be they bicycles or semi-trucks.

Steel is real. Everything else wants to be steel.
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Originally Posted by krazygluon
Steel: nearly a thousand years of metallurgical development
Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?
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Old 09-20-06, 03:29 PM   #7
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semi-trucks.
not the body of it which nowdays is made out of mostly fiberglass
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Old 09-24-06, 03:18 PM   #8
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not the body of [a semi truck] which nowdays is made out of mostly fiberglass
Load-bearing parts such as the frames, wheels and driveshafts of semi trucks are steel. The body-panels, which cover stuff up just for rain protection/aerodynamic/visual reasons, are a different story.
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Old 09-24-06, 03:27 PM   #9
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Are cars [made of steel]? Are road construction equipment? Are trucks?
etc. to start getting a picture of the correct material to build ANY load bearing equipment
from......be they bicycles or semi-trucks.
Non-racing cars, trucks, and road construction equipment are made of steel. The reason, though, is partly that engine power is plentiful. Since cars require a lot of metal and designers can add horsepower more cheaply than they can reduce weight (by switching to rare materials like aluminum) cars are made of steel.

Bicycles can't easily add horsepower and the cost of a few pounds of aluminum is nothing like the cost of a car frame's worth of aluminum, so it makes more sense for bikes to use aluminum. Crazy-expensive race cars have engines built mainly out of aluminum and bodies made out of carbon fiber because that way they can maintain strength while reducing weight.
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