Material Selection
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Do some looking around on this site for information... its a good read
http://www.key-to-steel.com/Articles.htm
http://www.key-to-steel.com/Articles.htm
Glad to see this type of reading. Many folks do misunderstand material properties and miss-quote advantages/disadvantages. Unfortunately as you stated, not all suspension designers are engineers. Modulus of elasticity, stress and strain etc may not be in their vocabulary.
Overall deflection in tubes is directly related to materials used, shape and load. Material choice does makes a difference in deflection characteristics of the component. Modulus of E. is a very important constant …certainly if the material has a similar M.O.E. deflection will be very similar between like shapes and mil thickness.
When a company states that a material has less deflection using thinner 4130 material and same shape over mild steel i.e. 1020…this certainly is not correct. You can build stronger and lighter designs but geometry and mil thickness must be taken into consideration.
Companies may also play on weight savings using more expensive alloy materials. Using 4130, companies shouldn’t state that the product is better or lighter…density is the same if similar material geometry as well as wall thickness is used….there is NO weight savings whatsoever. The ONLY additional cost in the product should solely be due to material cost, manufacturing process i.e. 4130 must be tig welded…it is harder to cut etc. Material cost is minimal when considering small items like a panhard rod.
Overall deflection in tubes is directly related to materials used, shape and load. Material choice does makes a difference in deflection characteristics of the component. Modulus of E. is a very important constant …certainly if the material has a similar M.O.E. deflection will be very similar between like shapes and mil thickness.
When a company states that a material has less deflection using thinner 4130 material and same shape over mild steel i.e. 1020…this certainly is not correct. You can build stronger and lighter designs but geometry and mil thickness must be taken into consideration.
Companies may also play on weight savings using more expensive alloy materials. Using 4130, companies shouldn’t state that the product is better or lighter…density is the same if similar material geometry as well as wall thickness is used….there is NO weight savings whatsoever. The ONLY additional cost in the product should solely be due to material cost, manufacturing process i.e. 4130 must be tig welded…it is harder to cut etc. Material cost is minimal when considering small items like a panhard rod.
Originally Posted by DanO
on my race team during college
Originally Posted by Old SStroker
The late (and sorely missed) Carroll Smith's "Engineer To Win" does a fairly good job in about .6 inches. I highly recommed it. He writes much like you do, DanO. Should that be "Book 'em, Dano"? 
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Originally Posted by DanO
Modulus of Elasticity
This is a very important property that all metals have, basically its how much the metal "stretches" or es per unit of force (pressure). For example, a rubber band. You can have 2 rubber bands made from the same material but the thicker one will not strech as far with the same load on it. The thicker one has less force per area but the same "modulus of elasticity"
This is a very important property that all metals have, basically its how much the metal "stretches" or es per unit of force (pressure). For example, a rubber band. You can have 2 rubber bands made from the same material but the thicker one will not strech as far with the same load on it. The thicker one has less force per area but the same "modulus of elasticity"
All Carbon and alloy steels, 4130, 1018, etc HAVE THE SAME MODULUS OF ELASTICITY!!!!!
This means that if you have a mild steel tube and a 4130 tube of the same dimensions, any force you place on it will result in equal deflection. Anyone who tells you 4130 is stiffer doesnt know much about metal.
This means that if you have a mild steel tube and a 4130 tube of the same dimensions, any force you place on it will result in equal deflection. Anyone who tells you 4130 is stiffer doesnt know much about metal.
Strength
The strength of the material is where the difference comes in. Again with the rubberband analogy. If you have two identically sized rubber bands with the same "Modulus of Elasticity" they will stretch equal distances with the same force, HOWEVER, the strength of one of the materials is greater allowing it to stretch further before it breaks.
The strength of the material is where the difference comes in. Again with the rubberband analogy. If you have two identically sized rubber bands with the same "Modulus of Elasticity" they will stretch equal distances with the same force, HOWEVER, the strength of one of the materials is greater allowing it to stretch further before it breaks.
This means that if you progressively increase the load on the equal sized Mild steel and 4130 tubes, the mild steel will fail before the 4130.
Example
There is a quote on BMR's website that i brought to their attension on more than one occasion. The Strut tower brace.
From BMR's site
If you would notice, the 4130 tube is a smaller wall thickness (i.e. smaller rubber band) and is less stiff than the larger wall Mild Steel version. Material properties show that the 4130 "more expensive" STB is actually not adding as much stiffness as the cheaper mild steel version.
Obviously, if i were to purchase one, i would choose the mild steel version. the increase in STRENGTH is not an issue due to the low loading in that location.
There are many designs for aftermarket components that have design flaws (materials, sizes, shapes, etc.) because the engineering knowledge to design these components is usually not had by the company. For one.. engineers are expensive, and two.. the parts are almost always better than "stock" but they are not Optimized which means, in most cases(disclaimer), you will not hurt anything by buying one of these, but you wont be getting exactly what you think you are and in some cases... will be spending more for a worse design.
Example
There is a quote on BMR's website that i brought to their attension on more than one occasion. The Strut tower brace.
From BMR's site
If you would notice, the 4130 tube is a smaller wall thickness (i.e. smaller rubber band) and is less stiff than the larger wall Mild Steel version. Material properties show that the 4130 "more expensive" STB is actually not adding as much stiffness as the cheaper mild steel version.
Obviously, if i were to purchase one, i would choose the mild steel version. the increase in STRENGTH is not an issue due to the low loading in that location.
There are many designs for aftermarket components that have design flaws (materials, sizes, shapes, etc.) because the engineering knowledge to design these components is usually not had by the company. For one.. engineers are expensive, and two.. the parts are almost always better than "stock" but they are not Optimized which means, in most cases(disclaimer), you will not hurt anything by buying one of these, but you wont be getting exactly what you think you are and in some cases... will be spending more for a worse design.
Some great applications for this are:
Roll cages where strength is a concern for saftey. Also works great to reduce weight if more deflection is acceptable over the thicker mild steel design while maintaining the same overall strength.
Control Arms because the parts see high cyclic loading and fatigue is an issue. And once again, can be made lighter if more deflection is acceptable over the similar but thicker walled mild steel design
Many other applications benefit from using this material but make sure it is used for the right reason... if not, your wasting your money!
Roll cages where strength is a concern for saftey. Also works great to reduce weight if more deflection is acceptable over the thicker mild steel design while maintaining the same overall strength.
Control Arms because the parts see high cyclic loading and fatigue is an issue. And once again, can be made lighter if more deflection is acceptable over the similar but thicker walled mild steel design
Many other applications benefit from using this material but make sure it is used for the right reason... if not, your wasting your money!
edit: crap. there are 3 pages. prob been covered
Last edited by treyZ28; Nov 4, 2005 at 07:26 AM.
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Originally Posted by DanO
Yes Chromoloy will be much harder to bend, the reason being is that the strength is much greater. To bend metal you have to bring the stress levels above the yeild strength point for it to deform. mild steel will be easier to bend because it will "yeild" alot quicker than the chromoloy counterpart. That being said, it will still deflect the same (given same geometry) its just that it takes less deflection to bend the mild steel.
Also, when i build racecar chassis i only had 2 bent pieces in the whole thing. Straight tubing is much better for load carrying.
It wasnt too difficult to obtain 4130, there are quite a few places that have it. If you need a list, i'll be more than happy to let you know who.
By the way... what is your industry?
Also, when i build racecar chassis i only had 2 bent pieces in the whole thing. Straight tubing is much better for load carrying.
It wasnt too difficult to obtain 4130, there are quite a few places that have it. If you need a list, i'll be more than happy to let you know who.
By the way... what is your industry?
How did you pull this off! Thats pretty impressive, unless you had 90* joints and stuff.
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Originally Posted by Old SStroker
Memory? Virtually all metals remember every stress that was ever applied to them. In that way they are much like women. If the stresses are below their yield point, they will return to their original state when the stress is removed. The cumulative amount of stress is also remembered, and if the total ever exceeds the fatigue limit, things go boom. Again, much like women.
What did you mean by memory, AFD?
What did you mean by memory, AFD?
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Originally Posted by treyZ28
How did you pull this off! Thats pretty impressive, unless you had 90* joints and stuff.
You design it using "Nodes" (i.e. points of force concentration) You distribue the load directly from one node to the next. for example, you take the force from one suspension point and connect it directly to the front roll hoop (by steering wheel) so bascially all the points you load have multiple tubes comeing off of it to distribute load in the proper direction.
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Originally Posted by treyZ28
How did you pull this off! Thats pretty impressive, unless you had 90* joints and stuff.
You design it using "Nodes" (i.e. points of force concentration) You distribue the load directly from one node to the next. for example, you take the force from one suspension point and connect it directly to the front roll hoop (by steering wheel) so bascially all the points you load have multiple tubes coming off of it to distribute load in the proper direction.
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Originally Posted by treyZ28
This is technically incomplete. This modulus only applies to a very small area where stress/strain are almost a linear relationship. More importantly, it is the area where the deformation is recoverable, meaning that it will return to its original shape.
Originally Posted by treyZ28
Im not sure about the accuracy of this statement, can anyone verify it? I cant.
Originally Posted by treyZ28
Unless i'm readin it wrong, that is ductility. The strain a material can undergo before failure is ductility and it usually decreases as strength increases. strong = brittle.
Originally Posted by treyZ28
personal opinion. When aftermarket companies dont have engineers, they almost always **** it up and make it worse. you just dont know it.
always.
edit: crap. there are 3 pages. prob been covered
always.
edit: crap. there are 3 pages. prob been covered
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Originally Posted by Fandango
Look at a Ducati's steel trellis frame. Probably made the same way.
http://fsae.eng.wayne.edu/documents/...tter_10_03.pdf
the LTU 2002 car is in the pictures at the bottom of page 1... you can barely see but you might get the idea
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ok so whenever ive looked into getting a rollcage ive always seen that using 4130 results in a lighter structure that is 'just as strong' as a mild steel one(due to sfi spec of thinner walls on 4130), but that a mild steel cage lasts longer because its less brittle, but its heavier because sfi requires that they be thicker walls. any comments on that? is sfi correct in requiring thicker wall ms than 4130?
also ive made my own rear suspension links on my chevelle. they are mild steel 1"od x .188 wall that i drilled/tapped for 3/4 16 heim joints. most comercially available 4 link bars are typicly 4130 1.25-1.375 od with .095 walls and they use a 'tube end' that necks down to a 3/4-16 thread. what would be 'stronger' or better for a rear suspension? if you arent sure on that what would be the different compression/extension properties of the 2 designs?
also ive made my own rear suspension links on my chevelle. they are mild steel 1"od x .188 wall that i drilled/tapped for 3/4 16 heim joints. most comercially available 4 link bars are typicly 4130 1.25-1.375 od with .095 walls and they use a 'tube end' that necks down to a 3/4-16 thread. what would be 'stronger' or better for a rear suspension? if you arent sure on that what would be the different compression/extension properties of the 2 designs?
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Originally Posted by DanO
Ductility deals with the strain in the region of plastic deformation between the yeild and ultimate strength , modulus of elasticity deals with the elastic region under yeild strength.
will stretch equal distances with the same force, HOWEVER, the strength of one of the materials is greater allowing it to stretch further before it breaks.
what am i missing here.
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Originally Posted by treyZ28
[/b]
what am i missing here.
what am i missing here.
Nothing.. you are correct... i should have worded it... the material will take a higher load before it breaks "OR" the material will strecth further before it Yeilds
If you want to get technical... Given a higher ultimate strength and the same poission ratio... the material will stretch further before it breaks.
http://www.key-to-steel.com/Articles/Art43.htm another good read
Last edited by DanO; Nov 4, 2005 at 01:52 PM.
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Originally Posted by TrendSetter
ok so whenever ive looked into getting a rollcage ive always seen that using 4130 results in a lighter structure that is 'just as strong' as a mild steel one(due to sfi spec of thinner walls on 4130), but that a mild steel cage lasts longer because its less brittle, but its heavier because sfi requires that they be thicker walls. any comments on that? is sfi correct in requiring thicker wall ms than 4130?
also ive made my own rear suspension links on my chevelle. they are mild steel 1"od x .188 wall that i drilled/tapped for 3/4 16 heim joints. most comercially available 4 link bars are typicly 4130 1.25-1.375 od with .095 walls and they use a 'tube end' that necks down to a 3/4-16 thread. what would be 'stronger' or better for a rear suspension? if you arent sure on that what would be the different compression/extension properties of the 2 designs?
also ive made my own rear suspension links on my chevelle. they are mild steel 1"od x .188 wall that i drilled/tapped for 3/4 16 heim joints. most comercially available 4 link bars are typicly 4130 1.25-1.375 od with .095 walls and they use a 'tube end' that necks down to a 3/4-16 thread. what would be 'stronger' or better for a rear suspension? if you arent sure on that what would be the different compression/extension properties of the 2 designs?
It depends what you are looking for, stiffness or strenght. Given equal strength, the 4130 cage will be lighter. Given equal stiffness they will be of equal weight. The equal strength 4130 frame will deflect more (i.e. lower stiffness) but will withstand fatigue better.
