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PostPosted: Sun Apr 21, 2019 10:48 am 
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TBI Slant 6
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The LCA's also absorb braking forces via the strut rods that are increased with larger brakes and stickier tires. If you are building your car for handling, I can see doing this. If you are not, I wouldn't bother.

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PostPosted: Sun Apr 21, 2019 11:10 am 
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A subframe connector is a generally accepted, and PROVEN, way to stiffen up the car*. An LCA mod is not.

The aftermarket offers upper arms that are stiffer than OEM? Again, show me the proof of that. But let's suppose they are stiffer, and let's suppose that is a good thing. It's far easier to make that argument since the UCA lends itself to being stiffer, by design. It's two 'arms' are quite far apart and not that large. The LCA, by design, is far tougher to stiffen. It's two main pieces are already very close together, very well riveted, and are heavier steel.

The stiffening parts that are welded in serve to 'strengthen' the arm in all the directions it doesn't need it (if it needs it).

*Many drag cars show improvements in 60 foot times and, more importantly, don't twist the body thanks to subframe connectors. The connectors pay for themselves by keeping the car from becoming a car that has doors that don't open/close properly and/or wrinkles in the sheetmetal.


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PostPosted: Sun Apr 21, 2019 12:40 pm 
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afastcuda1970 wrote:
The LCA's also absorb braking forces via the strut rods that are increased with larger brakes and stickier tires. If you are building your car for handling, I can see doing this. If you are not, I wouldn't bother.




The geometry of the Strut rod makes it control, I suspect by a factor 5-10, more brake forces then the LCA controls, and hence my earlier comment on other unmentioned forces, "everything else is minor".

And We should be careful attributing larger braking forces due to larger brakes.

Brakes stop the wheels, tires stop the car.

If your current brakes can lock your wheels, larger brakes do not not add larger forces.


Last edited by jcc on Sun Apr 21, 2019 1:11 pm, edited 1 time in total.

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PostPosted: Sun Apr 21, 2019 1:01 pm 
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DadTruck wrote:
Quote:
LCA is compressing or stretching


go back and look at the initial video that was posted,
there you will see what holds the two halfs of the LCA together.
The 1/8 thick plate of steel, that is added (if it is that much) would not do much to
affect compression or stretching, but allows one to align the two halfs to minimize
the play around the torsion bar mount and to certainly allow the two half to stay
where they were set and not pry open from the bottom side or from around the torsion bar mount.
Again, strengthening the LCA adds robustness, for those that run sticky tires, large sway bars
and expect to explore some limits of cornering. No one said that you need to do it.

You have not made the case IMO that: containing the halves with a gusset is necessary or needed in real world application. I get that it might make something more robust, but applies to almost anything added to a loaded item, nor that sticky tires or whatever is justification

This would be very similar to welding up a K frame
and reinforcing the steering box mount. Another item that for me checks all three of the boxes
1) it is affordable ,, yes check
2) it is with the realm of something I can do ,, yes check
3) directionally it is the right thing to do,, yes check

Except no case has been made the benefits are the same



and my comment concerning the general strength of A body structure and component robustness
as designed is valid.
Designs for families of components, designed about the same point in time to be used in the same family
(the uni body chassis is the 'family' in this discussion) will be subject to the same general loading and durability requirements
that were written when the design was developed - tested - released for production.

if some individual component ends up being really strong when compared to the other parts that surround it, that is possible only because
1) the part is a shared design with something that needs higher strength, and there is some savings available due to volume production to share the design across platforms,
2) a mistake was made in the design review process and a potential cost savings opportunity to take money out was missed

and your 1/4 inch vs 1/2 ratchet is a perfect analogy, assuming the 1/2 inch ratchet has a longer lever, the 1/2 inch ratchet adds robustness and allows the proper torque to be attained
with less effort. Assuming that more torque is needed,, ie sticker tires, larger torsion bars, super shocks,,,, the 1/4 ratchet would no longer be appropriate and the additional robustness
as provided by the 1/2 ratchet would be needed.

Most would assume a 1/2" ratchet has a longer lever arm. I am unclear how its thought or why its a desired goal to be easier using a long 1/2" ratchet to tighten a rather torque limited 1/4" bolt, which was the point of my analogy. Still don't understand the significant of stickier tires, etc. nobody is breaking LCA with 10 TW trtires i am am aware of.

As written your analogy only makes sense as a counter point if you had used the word 'socket', as a 1/2 in drive socket adds nothing to the process that a 1/4 inch socket would provide if standard 1/4 drive torque is the goal.
If more than 1/4inch drive torque is desired, the use of a 3/8 inch drive socket would be recommended or 1/2 if the torque level requires it

Well we still disagree, my analogy is only logical to me if talking about a bolt much smaller then any larger ratchet needed to supply the necessary torque, kinda like the LCA always is more robust then any TB conceptt..


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PostPosted: Sun Apr 21, 2019 4:29 pm 
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Quote:
real world application.

My car went from 9" drum brakes with 13" wheels to 11.75 disc brakes with almost twice as wide tread pattern 15" wheels.
That's "Real World" enough for me.(IMO)

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PostPosted: Sun Apr 21, 2019 7:35 pm 
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Ironic isn't it. Mopar in the real world used the same LCA's in almost every drivetrain configuration, Slant to a hemi, on the same platform.

Must have been a management design shortcoming, to no one in particular? :lol:


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PostPosted: Sun Apr 21, 2019 7:44 pm 
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Greg Ondayko wrote:
https://www.speedwaymotors.com/QA1-52307-Tubular-Control-Arm-Front-Lower-Mopar-A-Body,258467.html?sku=72152307&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=EAIaIQobChMImeLd56Hf4QIVB0sNCh2qiwpqEAQYAiABEgJmuPD_BwE

Lower arms. I would not buy these however.

Greg


Comparing "bending" robustness of the OEM LCA, effectively two back to back 3"? tall x 1/8" steel channels to a 1.75"? OD tube made of any material, is IMO, no comparison, except maybe lighter. Only explanation I can fathom, the OEM LCA are so over designed, putting them on a diet has no downside, which of course would then make a fairly strong case about the merits of needing an end user added stiffening gusset, ie there are none from a structural standpoint.


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PostPosted: Sat May 04, 2019 9:41 pm 
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https://www.musclecardiy.com/performance/drag-racing-traction-front-suspension-torsion-bars/
Image
Boxing stamped-steel control arms is a good idea. Here’s a boxed Mopar lower front control arm, which shows that everyone understands the importance of minimizing flex and adding strength to these suspension components.

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PostPosted: Tue May 07, 2019 3:27 pm 
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It's a good idea? That's not enough. Why is it a good idea? Prove it's a good idea.

Minimizing flex, presumably, is great. Show me that the arms flex any less after the mod.

Until then...all I see is an arm that weighs more and is a dirt-trap.


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PostPosted: Tue May 07, 2019 5:22 pm 
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Quote:
weighs more
:lol:
If you've never done it, you'll never know.

The original title is
Quote:
repair-strengthening lower control arms
, both of which it does.

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PostPosted: Thu May 09, 2019 7:56 am 
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Danarchy wrote:
Quote:
weighs more
:lol:
If you've never done it, you'll never know.

The original title is
Quote:
repair-strengthening lower control arms
, both of which it does.


And welding on a 1/2" thick steel donut onto your steering wheel could be said to do the same, and is, as long as no one requests a reason for this modification, its sounds like a "great" idea, line of thinking. :D

If one is not certain that adding material to anything does not increase its weight, I have nothing for you.

And let me be clear, this is intentional sarcasm, for both modifications, (gusset and steel donut) that could be easily discounted IF anyone could answer the clearly question recently succinctly asked, "Why?"


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PostPosted: Thu May 09, 2019 8:16 am 
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Watching one of the videos it was clear that some separation between the two halves of the control arm had occurred resulting in the torsion bar anchor being less positively located. A small strap welded across the control arm at that end would remedy that and add minimal weight. I have searched for some info on the factory SCCA Trans Am effort from the 1970s to see if they did such mods but can't find any pictures of the front suspension. If those lower control arms needed reinforcing then they would be on those Trans Am racers.

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PostPosted: Thu May 09, 2019 10:58 am 
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Hmmmm, after reading 3 pages of the dink pulling contest I seem to get that the idea is if you want to box your control arms go ahead and do it. It may or may not help anything, but it won't hurt it either........ :mrgreen:

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PostPosted: Thu May 09, 2019 11:07 am 
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slantzilla wrote:
Hmmmm, after reading 3 pages of the dink pulling contest I seem to get that the idea is if you want to box your control arms go ahead and do it. It may or may not help anything, but it won't hurt it either........ :mrgreen:

I like a man with a good attitude!

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PostPosted: Thu May 09, 2019 2:08 pm 
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Well said, Zilla...

Lou

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