Steel or Aluminium

[Jehu]

If getting a tig welded strut bar would you get it steel or aluminum. a difference of 4 lbs. http://cgi.ebay.com/ebaymotors/BMW-E34-535-M5-RACING-FRONT-TOWER-STRUT-BAR-ALUM_W0QQcmdZViewItemQQcategoryZ33591QQihZ017QQite mZ270030806142QQrdZ1QQtcZphoto

[rob101]

yay for welding heat treated aluminium alloy!:(
would you like me to burn my money too?
steel will be stiffer and cheaper. 6063-T6 that has been welded is 6063-O (annealed)
if its been welded (and of course not artificially aged after) that will be no stiffer than steel per unit of weight.
when will people learn, STEEL IS NOT HEAVIER THAN ALUMINIUM FOR THE SAME STRENGTH or stiffness. unless it is heat treated/Aged.
however that bar might not be welded to the strut tower mounts, in which case 6063-T6 is some goooooooood stuff!

[Jehu]

So i think somewhere in your rant you say the Aluminum bar shouldn't be any weaker than their steel bar .I would think the best aimj would be for the highest strength. They state the Al bar is 2.5 lbs and the Steel is 6lbs..IF this AL is as strong as the steel i'd get it Aluminum but if the heavier steel will prove stiffer i would assume it would perform better and four lbs isn't going to slow me down. I gain that much at lunch for Heaven's sake.

[rob101]

aluminium IS NOT STRONGER THAN STEEL, it may be 1/3 the weight but it is only 1/3 as strong. eg a 1kg beam of Al is the same strength and stiffness as 1kg beam of steel
since steel and aluminiums that aren't heat treated (and IF the bar is welded which is looks) have the same strength and stiffness per unit of weight. then it is correct in assuming the steel bar will be stiffer because it is heavier. don't worry about strength. its stiffness you want in a strut bar.

[Jehu]

Got it , thanks. Thats what i thought i thought, i think.

[rob101]

well yeah i can't see i think the bar may be just pressed into the ends
in which case it would be good, but it has been touched by the heat of welding you loose all the T6 spec treatment which i think is artificial aged treatment.

edit: actually just realised the treatment only affects strength not stiffness, so yeah steel bar = stiffer and probably cheaper too.

[Jehu]

Huh, I don't know but it sure looks welded to me.You saying such a weld won't withstand at the site of the welds the stresses when in place on the strut towers?I've heard hinged braces dismissed as ineffective because as the bar bends the pivoting joint allows give when the object of the bar is to defeat that movement. I've seen the UUC bars for other models which are a single steel tube bar with no joints that look like the optimal connection at the towers but can a steel tube provide the stiffness you want from a brace and if not where are the solid steel bars with no welding at the fasteners?

[rob101]

Huh, I don't know but it sure looks welded to me.You saying such a weld won't withstand at the site of the welds the stresses when in place on the strut towers?I've heard hinged braces dismissed as ineffective because as the bar bends the pivoting joint allows give when the object of the bar is to defeat that movement. I've seen the UUC bars for other models which are a single steel tube bar with no joints that look like the optimal connection at the towers but can a steel tube provide the stiffness you want from a brace and if not where are the solid steel bars with no welding at the fasteners?
no i am saying there is no point in gettin a High grade heat treated aluminium and then welding it. after you weld it, the strength goes back to what it was before it was heat treated so you've effectively just wasted whatever money you spent on using heat treated aluminium as opposed to unheat treated aluminium.
this is the same with steel also.

[BillionPa]

too bad they dont make a forged magnesium alloy and carbon fiber bar O_o