Pedro
٩(͡๏̯͡๏)۶
that may not be a good setup for you.
How much camber is too much?
- Thread starter Shorty
- Start date
that may not be a good setup for you.
Redline
Member
What does a hollow SB offer for advantage/disadvantage? Is it just weight?
Redline
Member
but don't you want it to be stiffer? what am I missing here?
ruggedman
New member
Solid is better than hollow. A sway bar is a torsional member. If you're familiar with torsion in round members the further you get from the surface the less torsion force you experiance and the less material you really "need". A 25mm hollow bar is probably about the equivalent of a 23mm solid but at less weight. The idea being that since the surface does most of the work, hollow it out and make it lighter.
However, where ulimate stiffness is concerned solid is best by far. Personally I like to have a comfortable daily driver so the bigger the bar you can run the smaller spring ratio you can get away with (in the idea of comfort). If you're running something sort of comfy like the prodrives huge solid bars are what I'd run 1" or 1 1/8" at least. With that said running huge bars especially on the back with stock or close to stock spring rates is also a very bad idea, 3 wheeling in a scoob is not good.
akinaspeedstar
New member
prodrives =/ to comfy
ruggedman
New member
No sir, that is 100% incorrect. You need a bigger hollow bar to be as stiff as a smaller solid bar. The material in the middle may not do much, but it still does something. Think about it a bit What is harder to twist a straw or a solid plastic rod?
The largest sway I can imagine fitting in the front of my car is the 27/29 that's up there now. If that same bar were offered and hollow it would be less rigid. You'd need something like a 32mm or so to make up for the missing material in the middle and you'll never fit one up there. Solid > Hollow....straight from the mouth of a BSME...you can take that to the bank.
ruggedman
New member
Think about the polar moment for both a solid and tube member:
Solid:
J = pi/2 * r^4
Tube:
J = pi/2 * (ro^4-ri^4)
The two r's in the tube are the inner and outer diameter. If the outers could potentially be the same but with the pipe you still have to subtract the radius of the hole and put it to the fourth power. There's no way to get that back.
The highest shear stress in a torsional member is on the surface because in the equation tau = T * r / J the radius is the little r so you can see the highest shear stress will be at the furthest point out (it's in the numerator). The middle portions however due still experiance some shear stress.
You could perhaps use a different material in a hollow bar that had a higher shear modulus but I'm pretty sure most cost effective bars will be made from similar steels. Another interesting thing is that the smoothness of the bar surface is of the utmost importantance in a shear stress situation, dimples, imperfections and whatnot lead to stress concentrations at those areas and could lead to failures down the road.
Ah, that makes a lot more sense :
Like I said, I'm not a scientist (apparently you are) What the hell is a BSME?
Now I remember. I thought a solid bar is better when it comes to twisting, but a tube is better when it comes to torsion. Hmmmm?
I'm not being a smart-ass, just curious.
Like I said, I'm not a scientist (apparently you are) What the hell is a BSME?
Now I remember. I thought a solid bar is better when it comes to twisting, but a tube is better when it comes to torsion. Hmmmm?
I'm not being a smart-ass, just curious.
<-----not an engineer, not even close.
But to play devil's advocate, and hijack this a bit.
Roll cages are made with hollow tubing. They don't deal with torsional stress. However, tubing is used rather than solid bar stock. Wonder why that decision was made ages ago. Ditto with bike frames etc.
As far as I understood it. The hollow sway bars were created for their light weight relative to their strength.
A hollow bar needs to have a larger diameter to be as strong as a solid one. Yet at equal strength, the hollow ones are lighter.
But to play devil's advocate, and hijack this a bit.
Roll cages are made with hollow tubing. They don't deal with torsional stress. However, tubing is used rather than solid bar stock. Wonder why that decision was made ages ago. Ditto with bike frames etc.
As far as I understood it. The hollow sway bars were created for their light weight relative to their strength.
A hollow bar needs to have a larger diameter to be as strong as a solid one. Yet at equal strength, the hollow ones are lighter.
akinaspeedstar
New member
andy what do you think this is? the cmc fourm?
LOVING enginers....... :
LOVING enginers....... :
ruggedman
New member
Cages are hollow because the cage would weigh more than the car if they were solid steel
Plus tubing can be manufactured relatively cheaply in sizes like that compared to solid bars. Tubing is better than flat bar because it is torsionally rigid and more resistant to torque than flat bar. And that last sentence you said nailed it.If you're in bending the larger outer diameter is beneficial (think supported on both ends with a force applied in the middle). You can bend rebar if you're really rugged, but you cant bend a 2" diameter thin walled tube. 8)
ruggedman
New member
At equal diameters the solid bar is stronger for everything. A BSME is a Bachelor Science in Mechanical Engineering. I've taken some advanced strength of materials classes and it was one of my favorite topicsAh, that makes a lot more sense :
Like I said, I'm not a scientist (apparently you are) What the hell is a BSME?
Now I remember. I thought a solid bar is better when it comes to twisting, but a tube is better when it comes to torsion. Hmmmm?
I'm not being a smart-ass, just curious.
The benefits of tubing in general manufacturing is lighter weight and supremely less costs (due to the cost of steel in material weight).
johnny6speed
New member
+1 ;Dandy what do you think this is? the cmc fourm?
LOVING enginers....... :
ruggedman
New member
Hey no prob ;D When i ordered the big solid 27/29 from you it wasn't by mistake. I knew what i was doing.
And sorry for trying to add something to the forum. I'll be sure to post more about personal problems in my life and less about actual knowledge to keep with the forum guidelines
akinaspeedstar
New member
that's more like it ;D