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My '71 cutlass is equipped with a rear swaybar, but unboxed lower control arms.
Anyone know where I can find the reinforcing sleeves that are supposed to be installed inside the unboxed arms, through which the swaybar mounting bolts pass?
My '71 cutlass is equipped with a rear swaybar, but unboxed lower control arms.
Anyone know where I can find the reinforcing sleeves that are supposed to be installed inside the unboxed arms, through which the swaybar mounting bolts pass?
Many thanks in advance!
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Search "boxed control arm insert" on eBay. It has to be stitch welded in place but can be done while the arms are still on the car
Yes, it's not just preventing crush of the locality where the the bolts pass thru but also forming an enclosed box for most of the length of the control arm that provides the extra sturgidity and strength required to transfer loads by means of a stabilizer bar.
Thanks guys. Yes, I am familiar with the advantages of boxed control arms. However I am looking for the correct reinforcement sleeves to use until I am ready to rebuild the rear suspension.
Thanks guys. Yes, I am familiar with the advantages of boxed control arms. However I am looking for the correct reinforcement sleeves to use until I am ready to rebuild the rear suspension.
Thanks guys. Yes, I am familiar with the advantages of boxed control arms. However I am looking for the correct reinforcement sleeves to use until I am ready to rebuild the rear suspension.
What about two nuts on the end of the bolt going into the rear control arms to fill the void of the lower control arms so that they won't be crushed?
To clarify, there are no stock "sleeves". The factory used the boxing plates that both stiffened the lower control arms to maximize effectivity of the rear bar and reinforced the LCAs against crushing. For a quick and dirty solution, I simply cut four sections of iron pipe that fit into the LCAs at the bolt locations.
To clarify, there are no stock "sleeves". The factory used the boxing plates that both stiffened the lower control arms to maximize effectivity of the rear bar and reinforced the LCAs against crushing. For a quick and dirty solution, I simply cut four sections of iron pipe that fit into the LCAs at the bolt locations.
The cut pipe are exactly the same idea I was thinking. Good idea!
"cut four sections of iron pipe that fit into the LCAs at the bolt locations."
That gets you the bar bolted in place, but zero boxing for torsional stiffness and bending stiffness... Hell, why not save some more hassle and just bolt to the inboard side of each bar...
I vote for buy the $40 in pcs set forth above, do the welding, and have it all done and all right.
"cut four sections of iron pipe that fit into the LCAs at the bolt locations."
That gets you the bar bolted in place, but zero boxing for torsional stiffness and bending stiffness... Hell, why not save some more hassle and just bolt to the inboard side of each bar...
I vote for buy the $40 in pcs set forth above, do the welding, and have it all done and all right.
and that's exactly what I am doing......thanks guys!
"cut four sections of iron pipe that fit into the LCAs at the bolt locations."
That gets you the bar bolted in place, but zero boxing for torsional stiffness and bending stiffness... Hell, why not save some more hassle and just bolt to the inboard side of each bar...
I vote for buy the $40 in pcs set forth above, do the welding, and have it all done and all right.
While I can't dispute the preference to have boxed rear arms, the reality is that even the factory stopped doing that after the 1972 model year. The 1973-77 cars used that ridiculous U-shaped piece that slipped into the arm (OK, the bar bolted to the bottom, not the inside in that case). The G-body cars returned to the A-body style bar position and used these spacers on the inside of the LCAs. Looks like four pieces of steel tube to me. The plate between them just positions the tubes for easy assembly.
While I can't dispute the preference to have boxed rear arms, the reality is that even the factory stopped doing that after the 1972 model year. The 1973-77 cars used that ridiculous U-shaped piece that slipped into the arm (OK, the bar bolted to the bottom, not the inside in that case). The G-body cars returned to the A-body style bar position and used these spacers on the inside of the LCAs. Looks like four pieces of steel tube to me. The plate between them just positions the tubes for easy assembly.
"cut four sections of iron pipe that fit into the LCAs at the bolt locations."
That gets you the bar bolted in place, but zero boxing for torsional stiffness and bending stiffness... Hell, why not save some more hassle and just bolt to the inboard side of each bar...
I vote for buy the $40 in pcs set forth above, do the welding, and have it all done and all right.
Do you really think the extra "rigidity" is worth the hassle? The extra stiffness, I would bet, can't even be measured.
Aren't the sway bars bolted to the inboard side anyway?
I'm not picking a fight, please don't take it that way.
Do you really think the extra "rigidity" is worth the hassle? The extra stiffness, I would bet, can't even be measured.
As an aerospace structures engineer, I'll DEFINITELY take that bet!
Not only can you measure the difference, but the added compliance you get by twisting the LCAs partially negates the stiffness of the rear sway bar, reducing the effectiveness of the bar. Also, this twisting eventually leads to fatigue failure. And yes, this is EXACTLY due to the bar being mounted on the inboard side of the LCA. The 73-77 cars bolted the bar to the bottom of the LCA, so the twisting of the arm was dramatically reduced.
Again, installing spacers is far preferred to doing nothing and simply crushing the LCA, and the proper boxed design is much better than that. I understand that not everyone has access to a MIG and want's to do the best job that they can practically, even if it isn't the ideal solution.
Joe certainly has a valid argument in post #14 in that the factory unit shown is essentially 4 tubes with some structurally inconsequential convenience metal between each pair.
That is one viable solution.
Do you really think the extra "rigidity" is worth the hassle? The extra stiffness, I would bet, can't even be measured.
===
Yes. Appearance too. The torsional stiffness would be greatly increased by the amount of boxing that the weld-on kit above provides. The bending resistance probably moderately increased. I have not done the math, fresh out of Solid Works at home.
Aren't the sway bars bolted to the inboard side anyway?
===
Sorry, I meant why not cheap out and bolt ONLY to the inboard side of the LCA's. No tubes needed, shorter bolts. Faster road to metal fatigue and a broken LCA. Whereas the weld-in kit appears to offer the best and strongest possible solution to changing the LCA's from simple tension-compression struts with some twisting allowed, to a force-carrying, less twisty [along its axis], subject- to- bending member. Two very different loading scenarios.
As an aerospace structures engineer, I'll DEFINITELY take that bet!
Not only can you measure the difference, but the added compliance you get by twisting the LCAs partially negates the stiffness of the rear sway bar, reducing the effectiveness of the bar. Also, this twisting eventually leads to fatigue failure. And yes, this is EXACTLY due to the bar being mounted on the inboard side of the LCA. The 73-77 cars bolted the bar to the bottom of the LCA, so the twisting of the arm was dramatically reduced.
Again, installing spacers is far preferred to doing nothing and simply crushing the LCA, and the proper boxed design is much better than that. I understand that not everyone has access to a MIG and want's to do the best job that they can practically, even if it isn't the ideal solution.
As a mechanical engineer, I should have spoke better. Agreed, that not having a spacer in there would increase the deflection of the LCA and result in negating a lot of the gain with the sway bar. But the difference between spacers/bolts in the rear arm vs boxes arms, negligible, assuming, of course the spacers are properly sized and fit snuggle between the lca's. The only difference would be the the distribution of force over the entire boxed LCA, but unless you are taking corners at 200+mph, you're not going to compromise that control arm. Unless is rotted out beyond recognition.
Originally Posted by Octania
Joe certainly has a valid argument in post #14 in that the factory unit shown is essentially 4 tubes with some structurally inconsequential convenience metal between each pair.
That is one viable solution.
Do you really think the extra "rigidity" is worth the hassle? The extra stiffness, I would bet, can't even be measured.
===
Yes. Appearance too. The torsional stiffness would be greatly increased by the amount of boxing that the weld-on kit above provides. The bending resistance probably moderately increased. I have not done the math, fresh out of Solid Works at home.
Aren't the sway bars bolted to the inboard side anyway?
===
Sorry, I meant why not cheap out and bolt ONLY to the inboard side of the LCA's. No tubes needed, shorter bolts. Faster road to metal fatigue and a broken LCA. Whereas the weld-in kit appears to offer the best and strongest possible solution to changing the LCA's from simple tension-compression struts with some twisting allowed, to a force-carrying, less twisty [along its axis], subject- to- bending member. Two very different loading scenarios.
Want a bootleg copy of solidworks? ha. It works well.
Agreed, not having even a spacer in there would lead to all of those things. I thought that went without saying. I was talking only about a properly fitting spacer and the boxed arms. But as it translates to actual handling, no way. We could test out deflection in solidworks, sure. OVer 500 years of everyday use, could the non boxed arms fatique? Ehh. Most you'll do is put marks in the inside where the spacers fit. These cars handle like dog shi* anyway, that welded bar vs a a spacer bar, not worth the extra time/money, and aggravation to weld them in.
As a mechanical engineer, I should have spoke better. Agreed, that not having a spacer in there would increase the deflection of the LCA and result in negating a lot of the gain with the sway bar. But the difference between spacers/bolts in the rear arm vs boxes arms, negligible, assuming, of course the spacers are properly sized and fit snuggle between the lca's. The only difference would be the the distribution of force over the entire boxed LCA, but unless you are taking corners at 200+mph, you're not going to compromise that control arm. Unless is rotted out beyond recognition.
I still disagree. I'm not talking about the crushing of the arm due to not having spacers. I'm talking about the torsional deflection in the LCA caused by the offset loading from the sway bar bolted to the inside of the arm. Do the math. A closed box has significantly more torsional stiffness than an open section. Any torsional deflection in the LCA reduces the deflection of the end of the sway bar, which reduces the effective stiffness of the sway bar. As for compromising the LCA, I'm talking about fatigue loading, not quasi-static loads.
I still disagree. I'm not talking about the crushing of the arm due to not having spacers. I'm talking about the torsional deflection in the LCA caused by the offset loading from the sway bar bolted to the inside of the arm. Do the math. A closed box has significantly more torsional stiffness than an open section. Any torsional deflection in the LCA reduces the deflection of the end of the sway bar, which reduces the effective stiffness of the sway bar. As for compromising the LCA, I'm talking about fatigue loading, not quasi-static loads.
But with the spacers the torsional deflection isn't a closed vs an open box. The difference between the boxed arm, and an arm with a piece of pipe properly fitted effectively makes it a boxed arm. The pipe prevents the same torsion that the box does. Now sure, if you put an open arm with spacer into a torsion tester and the boxed, the box will resist more before breaking, but you don't see that much torsion when hitting an on ramp, especially not at the speeds our cars can effectively take corners.
Plain and simple, if you took the same car, the same driver, the same test circuit, one with boxed arms, one with open arms and a spacer(properly sized), the effects on handling would not be measurable.
But with the spacers the torsional deflection isn't a closed vs an open box. The difference between the boxed arm, and an arm with a piece of pipe properly fitted effectively makes it a boxed arm. The pipe prevents the same torsion that the box does. Now sure, if you put an open arm with spacer into a torsion tester and the boxed, the box will resist more before breaking, but you don't see that much torsion when hitting an on ramp, especially not at the speeds our cars can effectively take corners.
Sorry, but not even close. First, I am not talking about strength "breaking" the arms, I'm talking about torsional stiffness. That's degrees per ft-lb, or similar units. The bolted spacers do virtually nothing to increase torsional stiffness. At best you've built a four-bar linkage, and even that is only at the two discrete points where the bolts are.
Remember I just left a site where they completely ignored and squandered all my engineering expertise. And mechanical aptitude. And tools savvy. And shopping skills... etc.
It is nice to discuss such matters and gain a better understanding of the why and wherefore.
and yes I so do want some Solid Works
Maybe I can use it to make a Solid Main Web 403?!?!
Last edited by Octania; March 10th, 2016 at 12:13 PM.
There's a very simple experiment you can do to demonstrate why this is important. Take an empty soda can. Grab the top and the bottom and try to twist the can about the long axis. Pretty stiff, no? Now cut a longitudinal slot in the can from top to bottom to simulate the unboxed arm. Repeat the twisting experiment. We're talking orders of magnitude difference here.
There's a very simple experiment you can do to demonstrate why this is important. Take an empty soda can. Grab the top and the bottom and try to twist the can about the long axis. Pretty stiff, no? Now cut a longitudinal slot in the can from top to bottom to simulate the unboxed arm. Repeat the twisting experiment. We're talking orders of magnitude difference here.
That's not the same thing! With spacers/or in your case the tubes, it is effectively not a slit down the middle anymore. The arms are reinforced by the tubes. Also, the can is being twisted in opposing directions, from top and bottom, the LCA's are not being.
But really, if you think it matters, why didn't you box yours in?
That's not the same thing! With spacers/or in your case the tubes, it is effectively not a slit down the middle anymore. The arms are reinforced by the tubes. Also, the can is being twisted in opposing directions, from top and bottom, the LCA's are not being.
I would suggest that you go back and review basic structural mechanics. First, the can experiment was simply an example of the differences in torsional stiffness between an open section and a closed section. Second, loading the arm in the middle with the sway bar is equivalent to loading an arm half the lenght at one end. We often simplify analyses by taking cuts at lines of symmetry (yes, the LCA loading from the sway bar isn't truly symmetric, but this is a simplification for illustrative purposes). Third, simply wedging tubes inside the arm and bolting it together at two doesn't even come close to equaling the torsional stiffness of a closed section. Feel free to run some FEA in SolidWorks.
But really, if you think it matters, why didn't you box yours in?
Because it was 1974, I was young and stupid (and a high school student), I didn't own a welder, and had just inherited the family 1968 Vista Cruiser. One of the first things I did was go to the local wrecking yard and pull a rear bar off a 442. I didn't even know the stock LCAs were boxed at that time.
I would suggest that you go back and review basic structural mechanics. First, the can experiment was simply an example of the differences in torsional stiffness between an open section and a closed section. Second, loading the arm in the middle with the sway bar is equivalent to loading an arm half the lenght at one end. We often simplify analyses by taking cuts at lines of symmetry (yes, the LCA loading from the sway bar isn't truly symmetric, but this is a simplification for illustrative purposes). Third, simply wedging tubes inside the arm and bolting it together at two doesn't even come close to equaling the torsional stiffness of a closed section. Feel free to run some FEA in SolidWorks.
I appreciate what you're saying. But I think you're missing my point. An in another application, I would agree. In the LCA example, the added torsional stiffness is irrelevant. The tubes are more than adequate for a sway bar to prevent the deflection the LCA will see. There is no way, even on a race track, you'd even approach the plasticity limit of the bars and compromise them. The difference, if any, would in no way affect the handling of these car. Certainly not in any A-body Cutlass/442. They aren't race cars, they never will be, and they never will corner well.
It's only $40 in parts, and whatever in labor to have a shop do it. For most of you guys, that's acceptable, I've only got a base cutlass s with a stock 350. It's not worth the extra $100 plus to have it done. Especially not if they have to be taken out to weld the plates in. The benefit isn't there. The handling difference is non-existant. And thats what the rear sway bar is all about. If you can prove otherwise, great. If it was an issue, the later cars wouldn't have done something similar, they'd have continued to use the full boxed arms.
Originally Posted by joe_padavano
Because it was 1974, I was young and stupid (and a high school student), I didn't own a welder, and had just inherited the family 1968 Vista Cruiser. One of the first things I did was go to the local wrecking yard and pull a rear bar off a 442. I didn't even know the stock LCAs were boxed at that time.
There is no way, even on a race track, you'd even approach the plasticity limit of the bars and compromise them.
One more time. I'm NOT talking about plastic deformation. I'm talking about purely elastic deformation of the LCA in tortion. The stock rear sway bar relies on the up/down motion of the LCA to impart twist into the bar (which is really just a torsion bar mounted laterally). Compliance in the LCA reduces the amount of deflection of the sway bar end flange for a given LCA motion, which effectively reduces the stiffness of the bar.
Can the layman feel this? Probably not, but it is a real effect. And like it or not, the LCA DOES deflect in torsion more than it would if boxed, which DOES put you further down the S-N Curve towards a fatigue failure. Again, will you see this in your lifetime? Likely not, but still.
One more time. I'm NOT talking about plastic deformation. I'm talking about purely elastic deformation of the LCA in tortion. The stock rear sway bar relies on the up/down motion of the LCA to impart twist into the bar (which is really just a torsion bar mounted laterally). Compliance in the LCA reduces the amount of deflection of the sway bar end flange for a given LCA motion, which effectively reduces the stiffness of the bar.
Can the layman feel this? Probably not, but it is a real effect. And like it or not, the LCA DOES deflect in torsion more than it would if boxed, which DOES put you further down the S-N Curve towards a fatigue failure. Again, will you see this in your lifetime? Likely not, but still.
Been digging through old threads looking for something else and I came across your response.
My point on this went back to a direct correlation of boxed control arms to handling which is negligible.
I wasn't trying to argue about the theoretical calculations of if the LCA will twist, etc.
My point was, the boxed control arms are not easy for everyone to install, and for the money and time, it's not worth it. Especially the time, if they have to be removed to be welded. That's a lot of hassle. The minute reduced stiffness of the bar from the LCA flexing is, in this case irrelevant. Now if your bushing were bad, and you were removing them anyway, and you had a welder, sure, what the he**, for $40, why not. But for the hours to remove good LCA's, to box them in, to re-install. No thanks.
These aren't space ships, they aren't taking corners at 150mph, and they aren't being thrown back and forth on the S curves, we're not driving Indy cars. Boxing in the arms is just overkill. Unless, of course, you want to be able to say you have "Boxed Lower Control Arms".
Not that anyone is going to take an antiquated A-body cutlass around Leguna-Seca, but if they did, maybe the fatigue would be an issue. After a couple dozen full out races. Under normal, even spirited driving, It's not worth the trouble to box them in to install a sway bar. These cars will long be off the road due before the metal will fatigue in the LCA is enough to be a problem.
But for the hours to remove good LCA's, to box them in, to re-install. No thanks.
They can be boxed right on the car, no need to remove them. I boxed the rear lower control arms on my 67 Cutlass while they were mounted on the car, no problem.
Why the big argument over what Joe is saying? He's correct.
Boxing that arm has a huge effect on rigidity, strength, torsional flex, fatigue, etc.
I didn't think it was an argument. Just discussion whether or not boxing the arms is actually worth the trouble.
Originally Posted by texxas
They can be boxed right on the car, no need to remove them. I boxed the rear lower control arms on my 67 Cutlass while they were mounted on the car, no problem.
Are 67's different? I looked at mine and didn't think it'd be able to weld them in place.
March 8th, 2016, 04:33 PM
