Billet Aluminum front spring crossmember and steering arm

[wasted wages]

one can only dream to aspire to this level of fabrication......

http://128.83.80.193/scarysteering/scarysteering.html

 

[troutbum_mt]

one can only dream to aspire to this level of fabrication......

http://128.83.80.193/scarysteering/scarysteering.html

tff!

That was very educational AND entertaining!

 

[loafer]

A cast aluminum part is completely different than a billet aluminum part.

Though it is true that the endurance limit of aluminum is generally significantly lower than steel (as already mentioned) which is the only thing you can really take away from that paper with respect to this thread.

Addressing other comments in this thread:
It's also impotent to understand that using 7075 over 6061 would have little impact on the fatigue life of the part. Though 7075 is stronger, it has about the same endurance limit as 6061. Additionally, many engineers will argue that aluminum has no "real" endurance limit.

http://www.mime.eng.utoledo.edu/people/faculty/afatemi/papers/2004SAEZoroufiFatemi2004-01-0628.pdf

Page 10- has some interesting conclusions, although the materials are technically not the same as discussed here.

 

[BGKYK5]

Don't get me wrong, Blazr77400 does some nifty stuff with a CNC mill, and I hope he never has an issue with his aluminum parts, but I'll never be comfortable with aluminum parts in those applications. Aluminum does not have an endurance limit, so at some point it will fail in cyclic loading applications. But depending on the stresses that could be 10 cycles or 10^10 cycles. I personally wouldn't risk it.

 

[troutbum_mt]

Don't get me wrong, Blazr77400 does some nifty stuff with a CNC mill <snipped>

I think he does some pretty amazing work. I mean there is no doubt he has some really good skills. I am not an engineer and I don't play one on the internet so won't touch the other issue with a 10' pole. I do admire his work though and can appreciate that as one craftsman admiring anothers work. I'll leave the design issues up to those more qualified.

As a consumer though, I'd be a little iffy given the reasons that have been raised here and me not knowing any better one way or the other. Hey, if it works give the guy kudos. Seeing as how this thread was brought back from the dead, I am sure we will get some more info a year from now on how it works.

 

[wasted wages]

It's also impotent to understand that using 7075 over 6061 would have little impact on the fatigue life of the part. Though 7075 is stronger, it has about the same endurance limit as 6061. Additionally, many engineers will argue that aluminum has no "real" endurance limit.

Freudian slip ??????


impotent

Main Entry:im·po·tent Pronunciation: \ˈim-pə-tənt\ Function:adjective Etymology:Middle English, from Anglo-French & Latin; Anglo-French, from Latin impotent-, impotens, from in- + potent-, potens potentDate:14th century 1 a: not potent : lacking in power, strength, or vigor : helpless b: unable to engage in sexual intercourse because of inability to have and maintain an erection ;





.

 

[MaxPF]

Aluminum does not have an endurance limit,

Wrong. I just looked it up - the endurance limit for 6061T6 is 14ksi. That is presumably measured using a standard R.R. Moore 10 million cycle test, so while it may not be a 'true' infinite endurance, 10 million cycles is a LOT.

 

[BGKYK5]

I agree that 10M is a lot of cycles. I would also say that there are probably several different definitions of "endurance limit" floating around. I think we can all agree that steel is a better material for cyclic loading than aluminium. Again, depending on the loading aluminum may fail after 10 cycles or 10^7 (10 million) or 10^10, but it will fail. Loading steel above it's endurance limit will also cause it to fail. I still prefer steel.

 

[wasted wages]

I'm sorry,,but aluminum just does not belong on steering components,
or any load bearing part of a vehicle where there is a POSSIBILITY of failure causing an accident and possibly killing someone. Period.

Our sport already get enough bad press,,ask any lift kit manufacturer,,

WHY would you take a chance, be it one in a million that if something could go wrong it will go wrong...

Do you think car companies employ the best of the best engineers to design and destructive test parts to failure for the hell of it ? No,,it's because they have a responsibility to the public that the hunk of steel they send down the highway at 80 MPH is safe!!

And I'm sure they don't ask the guy running the mill or lathe to design the the parts and then try them out on the general public....

here's another thing to chew on,,,,aluminum connecting rods,,
at least twice the cross section of a steel rod and half the life cycle.
Great for a fast reving race engine,,but suck for long term endurance.
why ? aluminum work hardens with use,,stresses and fails way before a steel rod would.


just a few random thoughts.....

 

[Hogback Fabrication]

Wrong. I just looked it up - the endurance limit for 6061T6 is 14ksi. That is presumably measured using a standard R.R. Moore 10 million cycle test, so while it may not be a 'true' infinite endurance, 10 million cycles is a LOT.

That is actually how the endurance limit is defined for all of the materials, 10 million cycles is the line for when something will have an "infinite life". If its loaded below the EL (14ksi apparently for 60601T6) then its considered to have an infinite life and not fail in fatigue.

Most aluminums don't have an endurance limit, apparently 6061T6 does.

For comparison, 1020 steel (what most of the steel arms are probably made of) has an endurance limit at 22 ksi or so.



Here is a chart showing steel vs. aluminum (5xxx grade), this is how the two normally behave (but NOT in this case). As long as the loading is below a certain limit (3xx MPa or 20ksi for steel) it will last forever. Aluminum usually has no endurance limit.

I went and measured my steering arm to make some quick hand calculations, my arm was 4.5" from the draglink hole to the front of the knuckle mount surface, 3.5" wide and 1.25" tall.

stress = (6*1000lbs*4.5in)/[(1.25in*(3.5in)^2] = 1763 psi = 1.763 ksi

1000 lbs. of steering force is probably pretty generous.


That puts the regular steering force well under the endurance limit and WAY under the 35 ksi that the material would yield at.



So there ya go, IMO, this steering arm looks perfectly fine in my eyes.

Its pretty easy to surmise that the arm won't inherently fail, and now that we know that 6061T6 has an endurance limit, I'm not the least bit surprised it all looks good.

I'm pretty surprised that I didn't know that 6061T6 had an endurance limit unlike most aluminum, its a really common aluminum alloy.


That's a pretty surprising post at the end of this thread, I think

 

[wasted wages]

That is actually how the endurance limit is defined for all of the materials, 10 million cycles is the line for when something will have an "infinite life". If its loaded below the EL (14ksi apparently for 60601T6) then its considered to have an infinite life and not fail in fatigue.

Most aluminums don't have an endurance limit, apparently 6061T6 does.

For comparison, 1020 steel (what most of the steel arms are probably made of) has an endurance limit at 22 ksi or so.



Here is a chart showing steel vs. aluminum (5xxx grade), this is how the two normally behave (but NOT in this case). As long as the loading is below a certain limit (3xx MPa or 20ksi for steel) it will last forever. Aluminum usually has no endurance limit.

I went and measured my steering arm to make some quick hand calculations, my arm was 4.5" from the draglink hole to the front of the knuckle mount surface, 3.5" wide and 1.25" tall.

stress = (6*1000lbs*4.5in)/[(1.25in*(3.5in)^2] = 1763 psi = 1.763 ksi

1000 lbs. of steering force is probably pretty generous.


That puts the regular steering force well under the endurance limit and WAY under the 35 ksi that the material would yield at.



So there ya go, IMO, this steering arm looks perfectly fine in my eyes.

Its pretty easy to surmise that the arm won't inherently fail, and now that we know that 6061T6 has an endurance limit, I'm not the least bit surprised it all looks good.

I'm pretty surprised that I didn't know that 6061T6 had an endurance limit unlike most aluminum, its a really common aluminum alloy.


That's a pretty surprising post at the end of this thread, I think

Nice,,,


Still wouldn't use it for steering components....

 

[roadnotca]

Durability should be a part of this discussion. The OEMs design this stuff to be cheap to build, and usually easy to service. Tapered joints in aluminum do not fit that description.
I'm not dissing the craftwork, but it seems out of place for hard working trucks.

 

[Hogback Fabrication]

Durability should be a part of this discussion. The OEMs design this stuff to be cheap to build, and usually easy to service. Tapered joints in aluminum do not fit that description.
I'm not dissing the craftwork, but it seems out of place for hard working trucks.

That's another good point (that I apparently argued in this thread way back).

You'd have to model that one I think, the hand calculations might be a bit rough.

Remember that the point of the taper is to guarantee no lateral movement so that there is no play in the connection; this is the best way to mount joints in single shear.

The aluminum could collapse and move (and steel could too) and screw up the taper but in this case I really doubt it. The applied stress in that case is probably around 1ksi (assuming 1 in^2 of contact area on half of the TRE taper, which is probably pretty close), that's so far from the yield stress that I don't think it will ever happen (you're looking at a factor of safety of 35 or so, no way that's going to fail).

The one thing that I'm assuming through out all of this is 1000 lbs. of steering force. The stock steering is probably less than that, full hydro with a 2.5" ram is probably 3000 lbs.

The worst case (that I could reasonably see) is sliding in the snow at high speed and hitting a curb or something, that would surely put more than 1000 lbs of force into the steering components. How much, tough to tell.

The bottom line is this: A 1020 steel arm is ~57% stronger than a 6061T6 arm. Both are WAY overdesigned. You're talking about a static factor of safety of 31.2 and 19.85 respectively.


As for the "hitting a curb at high speed" example, I can practically guarantee that a steel or 6061 arm will not be the first thing to fail. Draglink ends, draglink buckling, pitman shaft shearing, and frame failure will probably all occur before the steering arm even thinks about yielding.


A little different than arguments I made in the past, I know

 

[wasted wages]

Hitting a curb at high speed example - may result in something bending
with steel and I'm OK with a bent component in an accident etc.

steel will yield and bend,,,aluminum goes snap..I'm not OK with that...

 

[supersize75k5]

the only thing im concerned about is the use of the zip ties to retain the brake line to the shock body,

the deflection front the bushing and frame flex could over time cause slight movement and stress the plastic/nylon, thus failing and the brake line could float in the breeze..just like the factory allowed.

scary thought, just keep an eye on those zip ties

 

[twoslo4five0]

the only thing im concerned about is the use of the zip ties to retain the brake line to the shock body,

the deflection front the bushing and frame flex could over time cause slight movement and stress the plastic/nylon, thus failing and the brake line could float in the breeze..just like the factory allowed.

scary thought, just keep an eye on those zip ties

 

[dremu]

the only thing im concerned about is the use of the zip ties to retain the brake line to the shock body,

the deflection front the bushing and frame flex could over time cause slight movement and stress the plastic/nylon, thus failing and the brake line could float in the breeze..just like the factory allowed.

scary thought, just keep an eye on those zip ties

Well, this depends on whether they're the UV-resistant zip ties, or the ZBX-1234 neon green ones, because the torque breaking point of the green ties is twice that of the UV-resistant ones, until the green ones have been exposed to the sun, on prime-numbered Tuesdays.

-- A

 

[Blazr77400]

That is actually how the endurance limit is defined for all of the materials, 10 million cycles is the line for when something will have an "infinite life". If its loaded below the EL (14ksi apparently for 60601T6) then its considered to have an infinite life and not fail in fatigue.

Most aluminums don't have an endurance limit, apparently 6061T6 does.

For comparison, 1020 steel (what most of the steel arms are probably made of) has an endurance limit at 22 ksi or so.



Here is a chart showing steel vs. aluminum (5xxx grade), this is how the two normally behave (but NOT in this case). As long as the loading is below a certain limit (3xx MPa or 20ksi for steel) it will last forever. Aluminum usually has no endurance limit.

I went and measured my steering arm to make some quick hand calculations, my arm was 4.5" from the draglink hole to the front of the knuckle mount surface, 3.5" wide and 1.25" tall.

stress = (6*1000lbs*4.5in)/[(1.25in*(3.5in)^2] = 1763 psi = 1.763 ksi

1000 lbs. of steering force is probably pretty generous.


That puts the regular steering force well under the endurance limit and WAY under the 35 ksi that the material would yield at.



So there ya go, IMO, this steering arm looks perfectly fine in my eyes.

Its pretty easy to surmise that the arm won't inherently fail, and now that we know that 6061T6 has an endurance limit, I'm not the least bit surprised it all looks good.

I'm pretty surprised that I didn't know that 6061T6 had an endurance limit unlike most aluminum, its a really common aluminum alloy.


That's a pretty surprising post at the end of this thread, I think

This is by far the best post in this thread. Even if it would not have went my way, I would have used this information. None of the "I think", or "rule of thumb" or "manufacture this".

I am glad it went my way because I could not have argued this post.

Now how about some calculations on the shackles?

 

[Blazr77400]

As far as the zip ties holding the brake lines on, I planned on making some 300M clamps. Heat treating and Cryogenically(sp?) freezing them.

 

[supersize75k5]

what about the zip ties? We need an annaylisis on them, I would park it for now till we can figure this out