Spherical "Bushings"

[erlrich]

Originally posted by ddewhurst@Jan 4 2006, 04:30 PM
The key is the words MINIMAL FRICTION in the GCR glossary with the definition of bearing.

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David, you're absolutely corrrect if you are debating whether a spherical bearing is in fact a bearing. However, I think the debate here is whether a spherical bearing can be used as (or a component of) a bushing. The GCR definition of a bushing is "A sleeve or tubular insert, whose purpose is to reduce the dimension(s) of an existing hole" (didn't someone already post that... sorry). There is nothing in that definition that says a bushing cannot pivot freely. Looking at the pictures I posted above, doesn't the pic of the spherical bushing accomplish the task of reducing the dimension of an existing hole? Note that I used the word bushing, as the bearing is only one component of the bushing.

Wow, this thread has all the markings of a 5-pager

[Andy Bettencourt]

Originally posted by handfulz28@Jan 4 2006, 03:25 PM
Katman, interesting point of view. No agreeing or disagreeing, but it still serves as an example where a rule change required a significant change.

Andy-I guess that's where part of the disagreement with the use of SBs stems from. If you accept that at least part of an OEM suspension bushing's purpose is to limit suspension movement, then you'll have a hard time with SBs.

I think you have to reasonably accept that's not their purpose, but instead a result of material dexterity, or lack thereof.

I'll try to use an example from my car (ITA 240SX): front lower ctrl arm. The inboard mounting point (MP) is a bolt/bushing running in the longitudinal axis of the car, plus or minus some fudge for caster/camber/toe, providing for a nearly vertical single axis of movement. Connected (by fixed bolts) to the ctrl arm near the outboard end is a tie rod, fixed at an approx angle of 45 degrees, said rod being connected to a forward MP using a bolt/bushing, aligned such that the tie rod also rotates through an approx vertical single axis.

Now it's been awhile since I've practiced my analytical geometry, but would you agree that at a static point, the OEM rubber bushings are not deflected in any way? But as the connected suspension pieces move throughout a range of motion, said pieces are limited in their movement by the compliance of the rubber, not by their design or geometry. In fact, wouldn't you agree that the very design and geometry REQUIRES movement outside of the single axis plane, and therefore compliance at the MP/bolt/bushing of multiple planes/axis'?

In this installation, a spherical bushing simply allows a bit more compliance for the suspension assembly to move throughout its designed range. No MPs have been relocated, nothing moves that didn't move before, nothing is fixed that wasn't fixed prior.

Thanks,
Michael

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We would just disagree on 'designed range' then. If a factory setup allows 10 inches of travel and a SB-equipped bushing allows 11 inches of travel (or travel on an axis not possible with the fatcory stuff in there), then I believe it to outside the parameters. Poly or solid bushings would actually limit range of motion even more than compliant rubberized ones with no compression...but that is picking nits and a possible result.

There is nothing in the rules that say you can change the DESIGN of a bushing. If that was the case, the rules would read; "Suspension bushings are free provided they fit in the unmodified and original location" - or something like that...not "Bushing material, including that used to mount a suspension subframe to the chassis, is unrestricted."

I don't see how we can get away from that.

AB

[Matt Rowe]

Originally posted by Andy Bettencourt@Jan 4 2006, 04:09 PM
There is nothing in the rules that say you can change the DESIGN of a bushing.

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So, wouldn't the use of a strictly traditional bushing change the design of a stock suspension bushing that relies on angular as well as axial movement. In that case a spherical bearing is truer to the original design and therefore "more legal" than just a change in bushing material that results in no angular motion. IMHO using the idea of the design or functionality of the stock piece only strengthens the idea that spherical's are allowed, at least in cases where the stock bushing acts as a cheap spherical.

[handfulz28]

Yeah Andy, but I think we are picking nits here, those nits being the strained use of GCR defined "bushing" in a suspension application, and the GCR defined "bearing" as it applies to the use of sphericals in the suspension.

I don't see how you can disagree that a suspension "bushing" isn't inherently also a "bearing". I think Matt points it out more eloquently than I.

You have a point about not changing the design, I'll grant you that. But you're still relying on the OEM material to define your suspension and its relative movement. By pointing out that poly or solid bushings would FURTHER restrict movement, you're actually making the case there needs to be an allowance for different materials to affect suspension movement to varying degrees, solely on the difference between the materials' properties.

[Andy Bettencourt]

Originally posted by handfulz28@Jan 4 2006, 04:43 PM
Yeah Andy, but I think we are picking nits here, those nits being the strained use of GCR defined "bushing" in a suspension application, and the GCR defined "bearing" as it applies to the use of sphericals in the suspension.

I don't see how you can disagree that a suspension "bushing" isn't inherently also a "bearing". I think Matt points it out more eloquently than I.

You have a point about not changing the design, I'll grant you that. But you're still relying on the OEM material to define your suspension and its relative movement. By pointing out that poly or solid bushings would FURTHER restrict movement, you're actually making the case there needs to be an allowance for different materials to affect suspension movement to varying degrees, solely on the difference between the materials' properties.

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Let me write this using another car part:

"Hoods: Hoods may be replaced with those of alternate material."

Does this allow you to design in fuctionality that didn't exist on the stock unit? Of course not.

The rules say you MAY replace. You don't have to if you don't think there is an advantage. If the allowance restricts performance in some way and improves it in some other way, you have to weigh the plusses and minuses and make a choice. You can't go outside the rules to have the cake and eat it to.

Bushing material is unrestricted. Bushing design is restricted because is doesn't say it isn't!

AB

[Bill Miller]

Sorry Andy, but I think you've out-smarted yourself on this one. IF bushing design isn't allowed to be changed, that means you can't replace a compliant stock bushing w/ one that is not compliant. In other words, you can't replace the stock rubber one, that's all squooshy, w/ a metal one that allows for no out-of-axis motion. THAT is a design change. If you're going to use the 'bushing material is free' arguement, the counter to that is 'no allowed modification shall perform a prohibited function'. So, while you can use a metal bushing, if it changes the design from a compliant to a non-compliant configuration, that's a prohibited function.

[Andy Bettencourt]

Originally posted by Bill Miller@Jan 4 2006, 05:14 PM
Sorry Andy, but I think you've out-smarted yourself on this one. IF bushing design isn't allowed to be changed, that means you can't replace a compliant stock bushing w/ one that is not compliant. In other words, you can't replace the stock rubber one, that's all squooshy, w/ a metal one that allows for no out-of-axis motion. THAT is a design change. If you're going to use the 'bushing material is free' arguement, the counter to that is 'no allowed modification shall perform a prohibited function'. So, while you can use a metal bushing, if it changes the design from a compliant to a non-compliant configuration, that's a prohibited function.

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I disagree. That is sooo tortured IMHO.

A change in material is allowed - and it's associated results. A change in design is not. Sorry - not buying. No way, no how.

AB

[Matt Rowe]

Originally posted by Andy Bettencourt@Jan 4 2006, 05:00 PM
Bushing material is unrestricted. Bushing design is restricted because is doesn't say it isn't!

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Okay, but if the original design depends on angular and radial motion then the use of metallic spherical bearing has changed only the material, not the design. Unless you are trying to base design on strict dimensional standards in which case you are going to effectively make most replacement bushings as illegal as the sphericals as many stock suspension bushings have multi piece designs with cast in air gaps and so on that are not replicated in replacement bushings. I doubt that National is going to go for that strict an interpretation. Whether any of us think it meets the letter or the rule or not.

[JeffYoung]

Bill, not to pick a fight, but focus on Andy's example. I think his concept is correct.

"Hoods may be replaced with hoods of an alternate material."

Take that statement within the context of the remaining IT ruleset as it stands.

1. Would you consider a stiffer, but identical in all other dimensional respects, legal? I think we would.

2. Would you consider a hood that was made of a different material and formed with a scoop in the middle for cold air induction legal? I think we would not.

I agree that it a spherical bearing's ability to control and modulate the movement of the suspension and the loading on various suspension pieces via the fact that the sphere rotates with little friction is less clear of a "design change" than the scoop, but I think the principle is correct.

Full disclosure -- this is coming from someone with an IT car that doesn' thave them, and would have to spend a boatload of dollars to get them. So in some respects, Katman is right about the reasoning behind the reasoning for those of us who think this is a gray area that should be kicked over to the black.

[Andy Bettencourt]

Originally posted by JeffYoung@Jan 4 2006, 05:26 PM
Bill, not to pick a fight, but focus on Andy's example. I think his concept is correct.

"Hoods may be replaced with hoods of an alternate material."

Take that statement within the context of the remaining IT ruleset as it stands.

1. Would you consider a stiffer, but identical in all other dimensional respects, legal? I think we would.

2. Would you consider a hood that was made of a different material and formed with a scoop in the middle for cold air induction legal? I think we would not.

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Thanks for the help Jeff but lets use an example that fits the rules. Cold Air Induction is specifically called out as prohibited so we can refer back to an 'authorized mod may not perform a prohibited funtion'.

What if the hood had to reverse NACA ducts that allowed heat to escape out the back side of the hood? Nothing specifically called out on that as illegal but yet a modification where it says 'replacement of alternate material' as the only allowable change. I see this as the same thing.

AB

[Andy Bettencourt]

Originally posted by Matt Rowe@Jan 4 2006, 05:23 PM
Okay, but if the original design depends on angular and radial motion then the use of metallic spherical bearing has changed only the material, not the design. Unless you are trying to base design on strict dimensional standards in which case you are going to effectively make most replacement bushings as illegal as the sphericals as many stock suspension bushings have multi piece designs with cast in air gaps and so on that are not replicated in replacement bushings. I doubt that National is going to go for that strict an interpretation. Whether any of us think it meets the letter or the rule or not.

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I have made my point and don't need to reiterate it over and over. Frankly, you guys are getting way too technical for me now.

A spherical bearing as a bushing (where one did not exist prior) is not simply a 'change in material'. I can't see how anyone could argue that.

AB

[JeffYoung]

Hmm...how about this one:

Brake pad material is free. Does this mean you can fit a bigger pad (assuming it fits in the caliper)?

[dickita15]

Originally posted by ddewhurst@Jan 4 2006, 04:30 PM
***By the way my sperical cartridge allows the same or less pivoting that the foam bushing i use.***

Dick, most times when we talk about foam it has to do with beer. If you are refering to the foam bushings in the rear of 1st gen RX-7 the rule that allows foam bushings is rule 14.1.4.D.5.c.1. Any anti-roll bar(s), traction bar(s), panhard rod or watts linkage may be added or substituted, bla bla bla. The word ANY being key. Kind of the same as the word alternate.

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actually david I disagree. i am refering to the upper link. the rule you sight allows me to put in the tri link and panhard and toss the watts link but the upper control arms do not fall under that, the stock bushings are replaced with foam as a alternate bushing material. if these parts fell under you cited rule i could just throw the links away.

[DavidM]

It seems everyone agrees that a stock rubber bushing allows some flexing. Is the arguement that spherical bearings are a design change because they allow greater "flexing" than the stock bushing or beause they allow easier flexing (i.e. less friction)? I'm having a hard time seeing how easier flexing is considered a design change. Using that argument you'd have to outlaw any bushings other than stock because the type of material used would almost always change the amount of flexing possible. I can almost see the allows greater flexing argument, but see how you could argue against it as well.

David

[erlrich]

I think Andy and Jeff have a good point. If you interpret the rule about bushing material strictly, and on its own, that would imply to me that only the material the bushings are made from may be altered. In all other aspects the bushings would have to be identical to the OEM units, including design, dimensions, range of motion, etc. That interpretation, IMO, would render illegal almost all alternate bushings on the market, including spherical, poly, and even some of the high-durometer rubber pieces, if they were not identical to the OEM units in every other way.

If, that is, you interpret this rule all on its own. But what happens when you take 17.1.4.D.5.d.1., 2., or 3. into account? For instance, d.2. says "On other forms of suspension, camber adjustment may be achieved by the use of shims and/or eccentric bushings". Now, I am willing to bet not all car makers offer OEM eccentric bushings, and yet the rule says nothing about the bushings having to be OEM, so I would take that to imply any type of eccentric bushing is legal, as long as it meets the general definition of a bushing. Or did I miss something? That then begs the question, why would the writers of the GCR allow us to use any type of eccentric bushing, yet restrict us to exactly equivalent (except for material) non-eccentric bushings?

[Andy Bettencourt]

Originally posted by DavidM@Jan 4 2006, 06:29 PM
It seems everyone agrees that a stock rubber bushing allows some flexing. Is the arguement that spherical bearings are a design change because they allow greater "flexing" than the stock bushing or beause they allow easier flexing (i.e. less friction)? I'm having a hard time seeing how easier flexing is considered a design change. Using that argument you'd have to outlaw any bushings other than stock because the type of material used would almost always change the amount of flexing possible. I can almost see the allows greater flexing argument, but see how you could argue against it as well.

David

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Because a SB as a bushing does not flex. It allows the bolt that passes through it a range of motion that was not available stock - or in a stock replacement of alternate material. A change in DESIGN.

AB

[Andy Bettencourt]

Originally posted by erlrich@Jan 4 2006, 06:29 PM
I think Andy and Jeff have a good point. If you interpret the rule about bushing material strictly, and on its own, that would imply to me that only the material the bushings are made from may be altered. In all other aspects the bushings would have to be identical to the OEM units, including design, dimensions, range of motion, etc. That interpretation, IMO, would render illegal almost all alternate bushings on the market, including spherical, poly, and even some of the high-durometer rubber pieces, if they were not identical to the OEM units in every other way.

If, that is, you interpret this rule all on its own. But what happens when you take 17.1.4.D.5.d.1., 2., or 3. into account? For instance, d.2. says "On other forms of suspension, camber adjustment may be achieved by the use of shims and/or eccentric bushings". Now, I am willing to bet not all car makers offer OEM eccentric bushings, and yet the rule says nothing about the bushings having to be OEM, so I would take that to imply any type of eccentric bushing is legal, as long as it meets the general definition of a bushing. Or did I miss something? That then begs the question, why would the writers of the GCR allow us to use any type of eccentric bushing, yet restrict us to exactly equivalent (except for material) non-eccentric bushings?

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The same rule on material applies to this design - it isn't specific to strut-type cars. Actually, I think you make my point...material is free for all types of designs, yet on non-strut cars, a non-stock DESIGN change is specifically mentioned.

You write:

In all other aspects the bushings would have to be identical to the OEM units, including design, dimensions, range of motion, etc.

Replacement poly bushing from an 'off the shelf' supplier should fit your requirements. The OD would have to be the same in order to fit the given hole, the ID of the tube should be the same to utilize the OEM bolt, and the design should be the same - placement in the bushing material so that there is no static bind, and the range of motion - what range of motion? There is a big difference between material COMPLIANCE and full-blown range of motion designed into the product.

Where-the-F is Greg?

AB

[gsbaker]

Originally posted by erlrich@Jan 4 2006, 07:29 PM
I think Andy and Jeff have a good point. If you interpret the rule about bushing material strictly, and on its own, that would imply to me that only the material the bushings are made from may be altered....

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That's my read, also.

YMMV.

[erlrich]

Originally posted by Andy Bettencourt@Jan 4 2006, 07:46 PM
You can't use this as a comparison. This rule is for non-strut-type cars that can not adjust camber through camber-plates.

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But Andy, that's just d.2; d.1 allows MacPherson strut type cars to alter camber by use of eccentric bushings at the control arm pivot points, the strut-to-bearing-carier point, or with camber plates. Rule d.3 allows all cars to adjust caster with eccentric bushings. I apologize, I should have been more clear, but the point was that the GCR allows any car with any type of suspension to use eccentric bushings to adjust camber or caster. And as I think we would all agree not all car makers offer eccentric bushings (or do we?), that would tell me that any eccentric bushing is legal. So, as long as they were eccentric wouldn't spherical bushings be legal under this rule.

I think we would probably agree on the intent of the bushing rules, however I firmly believe the way the section on suspension mounting points is written leaves the bushing design wide open. JMHO.

[Andy Bettencourt]

Originally posted by erlrich@Jan 4 2006, 07:04 PM
But Andy, that's just d.2; d.1 allows MacPherson strut type cars to alter camber by use of eccentric bushings at the control arm pivot points, the strut-to-bearing-carier point, or with camber plates. Rule d.3 allows all cars to adjust caster with eccentric bushings. I apologize, I should have been more clear, but the point was that the GCR allows any car with any type of suspension to use eccentric bushings to adjust camber or caster. And as I think we would all agree not all car makers offer eccentric bushings (or do we?), that would tell me that any eccentric bushing is legal. So, as long as they were eccentric wouldn't spherical bushings be legal under this rule.

I think we would probably agree on the intent of the bushing rules, however I firmly believe the way the section on suspension mounting points is written leaves the bushing design wide open. JMHO.

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You are correct on the strut-stuff, my error. Dang!

I do still believe that the allowance for a SPECIFIC design of bushing is testiment to what IS legal. I understand the thought process you are going through but a eccentric bushing is an offset tube, not an offset spherical bearing!

We will agree to disagree. It has been a healthy debate. Thanks.

AB