OK

Just curious as to why no one uses stainless steel for a frame...

-- too expensive (by what - a factor of 3 or 5?
-- too hard to "work"
-- too "weak" in a crash
-- too heavy?

 

I don't think it's as strong, materially. DOM mild steel is incredibly strong.

 

Depends on the alloy, or grade of stainless, for workability/flexibilty/hardness. Some is not conducive to welding.

The price seems to be 5x or more.

The weight should be about the same.

http://en.wikipedia.org/wiki/Stainless_steel

 

Carbon steel currently is about $0.65/lb SA-516-70/SA-36

Stainless steel is currently about $3.15/lb SA-240-304

Stainless weighs MORE than carbon steel as it is denser.

For the sake of argument, say you make your frame out of 3/16" thick material and that the carbon steel weight of the frame is 500 lbs.
The same frame in stainless would weigh 60+ lbs more. That is more than a 10% increase in weight.

Carbon has higher tensile and ultimate strengths while stainless has better corrosive and heat allowance properties. It just really depends on the grade of steel you are talking about to compare carbon to stainless.

 

Titanium frame....

 

Found a good link about the subject.Titled "Stainless Steel Properties For Structural Automotive Applications". Very interesting stuff.
http://www.euro-inox.org/pdf/auto/St...tiveApp_EN.pdf

Table 1 Materials Sorted By Category Then Density
Category/ Material/ Density (g/cm3)
Metal/ Steel, tool/ 7.715
Metal/ Wrought Iron/ 7.75
Metal/ Carbon Tool Steel/ 7.82
Metal/ Steel, cold-drawn/ 7.83
Metal/ Carbon Steel/ 7.84
Metal/ Steel, C1020, HR/ 7.85
Metal/ Pure Iron/ 7.86
Metal/ Soft Steel (0.06% C)/ 7.87
Metal/ Stainless Steel, 304/ 8.03
Metal/ Stainless 18Cr-8Ni/ 8.03


I know the wabbit meant per ft, not lb. I just wanted to show how much heavier it is relative to other steels. Not alot, really, .1-.2 grams per cubic centimeter.

Info from http://hypertextbook.com/facts/2004/...therland.shtml

 

ahhh, as if this thought doesn't come up at work enough (bicycle shop)..

Wanna really see prices soar, check out Reynolds 925 chromo!!
IE: Independent Fabrications...mmm nice and expensive!!

FYI: Chromoly Steel, and the components needed to mix the steel are going way up in price right now due to limited mineral availability.

Ask Wabbit, he deals with the stuff, $3.15/lb for the SA-240-304's a decent price, I've seen the other rated steel's up to around $7-9 for bicycle applications, then include in the milling, welding needs, etc-etc, and it's no wonder a frame goes for around $1500-2300.00 for a nice set-up.

Cripes, imagine if you used the stuff rated for a vehicle frame, you'd approach $20k really easily!!

 

Brian, do you know that joke about what weights more, if a kg of straw or a kg of lead?

I suppose you meant "SS it's more dense, weights more per cubic feet than carbon steel" hehehe

David

 

Well David, I think Wabbit is just talking about the variety of different pulls of gravity he experiences in a day. You know, mostly it's 9.8m/s^2 but who knows, on a good day it could be as much as 20 m/s^2 and then the same amount of mass weighs twice as much!

Pretty funny that you point that out heh heh

 

The weight difference can be quite a bit as the density difference depends on the grades of carbon and stainless and the thickness of the material. With a frame, maybe not a big deal, but with something large and a lot of material, it makes a big difference.

A lb of straw weighs more. SI units suck.

Density...relative to the steels and my brain.

 

OK - so by mass the approximate cost difference is a factor of FIVE.

As far as property differences between ss and carbon steel - those can be worked around in terms of "design" of the frame.
I was not implying that a SS frame had to LOOK exactly like a carbon steel frame.

Given that the goal was corrosion resistance - it almost seems as if a "plastic" (i.e. carbon fiber / fiberglass / composite) would be lighter and cheaper and easier to work in a low scale production environment.

One huge advantage of metals is that they can be "stamped" in a high production environment.

As mentioned - welding to a SS frame (or CF) an be an issue - but not impossible to work around - they make airplanes out of composities

 

i've got a question for y'all metallurgist. can stainless be treated into spring steel?

and, brushed stainless bumpers would be cool.

 

To the higher material cost of s/s, you need to figure about that much more in terms of fabrication cost. It is a lot harder to machine than carbon steel and for welding, usually need to use TIG plus it is a lot more likely to warp, so that also adds to the complexity.

Might consider having the existing frame sandblasted and hot dip galvanized. Have heard of folks doing that before. The time consuming hart of that is plugging all the holes that you don't want to get coated, but it'll get inside the frame as well as outside.

 

Given that a different thread pegs a BudBuilt frame at $3-4K at 5x we are looking at ... hmm $15-$20K for a FRAME...

Oh well - it was a nice "benchtop" dream....

 

I've heard that galvanizing a frame runs less than $1000.

 

yes some types can be.

 

A gerallium tube with honeycomb internal reinforcing would be the go,
they make helicopter blades out of it, must be strong and lightweight

 

Helo blades spin in air.

Toyota Truck frames get bashed on rocks...
Different strenght needs.

That being said a "plastic" frame (aka fiberglass and carbon fiber and kevlar weave) might be strong enough as well as bashable...

If I win PowerBall tonite I'll try that as a project...

 

Hey if CF is good enough for McClaren F1 frame, why not a Toyota Pickup.

 

Deloreans were all stainless.