Billet arm problem- Metallurgist, ethicists please respond
05-20-2004, 01:04 AM
#61
I've read this with a certain amazement.
First, the choice of 2024 is something very odd. There is stronger, better suited material than 2024. 7075 would be a way better choice. but if you do make them out of 2024, I would suggest that you control all aspects of the manufacture. If you feel they should be anodised, then know what could happen if the anodising is not done properely. Anodise them yourself. There definitetly is a wrong here.
Now, if you buy these arms and get told to anodise them, and are told they are made of 2024, but don't tell the anodioser this, they will fry them, guaranteed. It is absolutely guaranteed that the parts would get fried! No question. Anodising 2024 is very different from more common aluminum, and not many know how to do it. Most won't. Typically, anodizers will not take any responsibility for this process. I think a wrong was done here also. Not by the anodizer, but by the customer, not telling him what the material was.
So which wrong should pay. In my opinion, the customer. The seller told him the material and that they should be anodised. What other information should have been given. Well, maybe be careful, 2024 is difficult to anodize. Maybe, but in most law, ignorance is not an accepted excuse. The customer did not tell the anodizer the material and the anodizer did not ask. Why should he. He's not required to. If you give him some special material, then be sure he knows. The actions of the customer caused the problem, not the seller, and not the Anodizer.
Its hard to take, but stand up to your own actions and say to yourself, I screwed up.
First, the choice of 2024 is something very odd. There is stronger, better suited material than 2024. 7075 would be a way better choice. but if you do make them out of 2024, I would suggest that you control all aspects of the manufacture. If you feel they should be anodised, then know what could happen if the anodising is not done properely. Anodise them yourself. There definitetly is a wrong here.
Now, if you buy these arms and get told to anodise them, and are told they are made of 2024, but don't tell the anodioser this, they will fry them, guaranteed. It is absolutely guaranteed that the parts would get fried! No question. Anodising 2024 is very different from more common aluminum, and not many know how to do it. Most won't. Typically, anodizers will not take any responsibility for this process. I think a wrong was done here also. Not by the anodizer, but by the customer, not telling him what the material was.
So which wrong should pay. In my opinion, the customer. The seller told him the material and that they should be anodised. What other information should have been given. Well, maybe be careful, 2024 is difficult to anodize. Maybe, but in most law, ignorance is not an accepted excuse. The customer did not tell the anodizer the material and the anodizer did not ask. Why should he. He's not required to. If you give him some special material, then be sure he knows. The actions of the customer caused the problem, not the seller, and not the Anodizer.
Its hard to take, but stand up to your own actions and say to yourself, I screwed up.
05-20-2004, 01:16 AM
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Skip, could you please elaborate on "surface variables". I can't think of anything that you could be referring to, except maybe old coolant/lubricant leftover from the maching process (which I'm sure an experience plater would look out for). I'm not trying to take sides at all, but you sure are leaning toward the machinist or the alloy itself. I know you trust this plater, but the best people make mistakes too. I am very good at what I do. I am a perfectionist. Even so, I still make mistakes on very expensive aircraft parts at work. It's called the human factor and it is unavoidable. This doesn't mean that I am saying the plater did it, but that you could narrow it down with a simple test. My two cents again, so I'm up to 4 cents now, so I'll shutup. Kary
05-20-2004, 01:36 AM
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m42racer, just a heads up on the 7075. It is extremely hard and corrodes even worse than 2024. With a part that wants to flex, 7075 will have a tendency to want to stress fatique and fail. On Boeing 747's for example, exterior fuselage skins have to be made from 2024 and not 7075, why?, because of the pressurization cycles the aircraft goes through multiple times a day (expansion and contraction from sea level to altitude to sea level again). A lower control arm will also "cycle" many times in a day (up and down, fwd and aft). I think the 2024 was a good choice for the control arm. I think that leaving it unplated is an extremely bad choice even if it was for a show car only, and was never going to see the track or street. Condensation will corrode unprotected 2024. To combat this, engineer's will use 2024 Allclad for exterior skins. Allclad is a .005 thick coating of almost pure aluminum on both sides of the alloy sheet. This is how American Airlines is able to go paintless and polish their birds to a mirror finish. There is a downside, .063" thick allclad sheet is weaker than .063" bare sheet. This is because the Allclad sheet is actually .053" thick (remember the .010" of pure aluminum). You may have already known this, but it's still educational for those out there that may put some aluminum pieces on their cars and don't work with the stuff on a regular basis. Kary
05-20-2004, 03:35 AM
#64
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I was at Bills house as well. They were the best looking legs ahhh. I mean arms
I have ever seen ........ :-)
Ed
I have ever seen ........ :-)
Ed
05-20-2004, 04:23 AM
#65
Race Director
krutschman1, you're right on about the fatigue resistance of 2024. While 7075 might have better yield and ultimate strengths than any aluminium alloy, it doesn't handle repeated stresses as well. One of the concerns with A-arms, comes from the alloy ones cracking after repeated use and abuse. The traditional way to attack this problem has been to use steel A-arms, which has no fatigue limit. You can stress them right up to their yield points repeatedly and they'd last forever.
Design is a big factor as well and Mumzer's is as good as it gets. Undoubtedly some lessons were learned from Grigg's experience between the street vs. heavy-duty track arms.
"I was at Bills house as well. They were the best looking legs ahhh. I mean arms
I have ever seen ........ :-)"
Ya know... Bill's Mumzer arms were about the 1st auto-parts that's ever given me wood. Besides a big round turbo of course....
Design is a big factor as well and Mumzer's is as good as it gets. Undoubtedly some lessons were learned from Grigg's experience between the street vs. heavy-duty track arms.
"I was at Bills house as well. They were the best looking legs ahhh. I mean arms
I have ever seen ........ :-)"
Ya know... Bill's Mumzer arms were about the 1st auto-parts that's ever given me wood. Besides a big round turbo of course....
05-20-2004, 01:08 PM
#66
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As promised here are pictures of my Mumser Arms. Hard anodized black.
The arms come with a replacable ball joint and teflon bushings.
Close up of the arm. The arms did not come with the holes in the webs. My car is street only and I was concerned about water ponding in the webs. I discussed with Mumser and he said it would be ok, if the hole was no larger than 3/8", the work was done by a mill and was dressed. I did this prior to hard anodizing as the anodizer said that after the process, it would take a diamond drill to scratch through the surface.
Final shot is the joint. Several nice features. The washers are used to raise or lower the spindle, so the arm on a lowered car can be set to the original geometry. This solves the big problem on lowered cars, where the ball joint does not have the proper travel and binds. Eventually breaking the end of the arm off. Another nice feature is the bearing. To replace them, it will cost you $25. The only draw back, like the Charlie arms, the joint bearing does not have a dust cover or grease fitting.
The arms come with a replacable ball joint and teflon bushings.
Close up of the arm. The arms did not come with the holes in the webs. My car is street only and I was concerned about water ponding in the webs. I discussed with Mumser and he said it would be ok, if the hole was no larger than 3/8", the work was done by a mill and was dressed. I did this prior to hard anodizing as the anodizer said that after the process, it would take a diamond drill to scratch through the surface.
Final shot is the joint. Several nice features. The washers are used to raise or lower the spindle, so the arm on a lowered car can be set to the original geometry. This solves the big problem on lowered cars, where the ball joint does not have the proper travel and binds. Eventually breaking the end of the arm off. Another nice feature is the bearing. To replace them, it will cost you $25. The only draw back, like the Charlie arms, the joint bearing does not have a dust cover or grease fitting.
05-20-2004, 04:53 PM
#67
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"The washers are used to raise or lower the spindle,"
Actually it lowers the ball-joint. Moving the balljoint lower restores the pivot point to the same location as stock relative to the inner pivot. This puts balljoint at a lower spot than the inner pivot, which gives a much better camber-gain curve than having the balljoint higher than the inner pivot.
"The only draw back, like the Charlie arms, the joint bearing does not have a dust cover or grease fitting."
You can make a dust cover that works very well from some old bicycle inner tubes... Won't look pretty, but will work very well...
Actually it lowers the ball-joint. Moving the balljoint lower restores the pivot point to the same location as stock relative to the inner pivot. This puts balljoint at a lower spot than the inner pivot, which gives a much better camber-gain curve than having the balljoint higher than the inner pivot.
"The only draw back, like the Charlie arms, the joint bearing does not have a dust cover or grease fitting."
You can make a dust cover that works very well from some old bicycle inner tubes... Won't look pretty, but will work very well...
05-20-2004, 06:54 PM
#68
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Danno,
You have keen eyes!
I stand corrected, yes it allows you to raise or lower the ball joint/control arm. The spindle will remain constant (defined by the wheels), no matter what length spring/adj spring perch you use.
The main point, the Mumser arms have an adjustment that no other arm allows for.
BICYCLE TUBES! spoken like a true racer. Duct tape, bailing wire and back on the track.
Not on my car.
You have keen eyes!
I stand corrected, yes it allows you to raise or lower the ball joint/control arm. The spindle will remain constant (defined by the wheels), no matter what length spring/adj spring perch you use.
The main point, the Mumser arms have an adjustment that no other arm allows for.
BICYCLE TUBES! spoken like a true racer. Duct tape, bailing wire and back on the track.
Not on my car.
05-20-2004, 07:24 PM
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not to hijack my own thread, but there is a little device called a Seals-it for weatherproofing heim joints like this one...they are typically used in commercial applications, and dont respond well to heat (ie the 600*c temps of the brake rotor).
They comprise a steel washer with a skirt of butyl rubber bonded to it in such a way that it forms a flexible gasket around the shaft as it passes through the bearing.
They work for a while. So does greasing...for a while, but both tend to trap dust and grit and brake pad material (which is not suprisingly VERY abrasive) up against the ball of the ball joint...or worse become an emulsion of grease and abrasive with properties an awful lot like valve lapping compound. Unless the boot can be made truly weatherproof, i think you are better off leaving the ball joint dry, or using a dry film lubricant (like you see on off-road motorcycle chains) than grease. The lack of zerk was deliberate.
danno has the right idea on the control arm angularity issue. the goal is to restore a normal roll-center height in front. Lowering a stock car reduces camber gain, increases weight transfer to the outside front tire in a corner, and generally tends to contribute to understeer at turn in on a car with limited caster.
They comprise a steel washer with a skirt of butyl rubber bonded to it in such a way that it forms a flexible gasket around the shaft as it passes through the bearing.
They work for a while. So does greasing...for a while, but both tend to trap dust and grit and brake pad material (which is not suprisingly VERY abrasive) up against the ball of the ball joint...or worse become an emulsion of grease and abrasive with properties an awful lot like valve lapping compound. Unless the boot can be made truly weatherproof, i think you are better off leaving the ball joint dry, or using a dry film lubricant (like you see on off-road motorcycle chains) than grease. The lack of zerk was deliberate.
danno has the right idea on the control arm angularity issue. the goal is to restore a normal roll-center height in front. Lowering a stock car reduces camber gain, increases weight transfer to the outside front tire in a corner, and generally tends to contribute to understeer at turn in on a car with limited caster.
05-21-2004, 02:53 PM
#71
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Wow, this is a long post. It looks like everyone wants to jump on the plater. I have a hard time understanding that. From everything I have read on the internet it looks like 2024 requires a desmut bath before plating. Unlike other alloys that do not unless previously coated.
So, if it is actually required for plating, then why would we think that this was a bad thing.
Yes 2024 has a higher cu content then most other alloys and this will be attacked by a desmut bath, but only in raw form. Once alloyed in al it would not be susceptible to this. (or as susceptible) Unless, the cu has come out of solution. This would indicate an issue with the original material. If the 2024 was improperly solution treated or aged, then this would cause the cu the clump and then be attacked by the bath.
Were there certifications with this material. Has anyone done a look at this material. Has anyone looked at the grain structure of the material to see if there are any problems. If the cu has created stringers in the material, which it sounds like it has, then it is a good thing that this was found out when it did. We would be talking about a much higher liability if the part was on the car and failed.
Another thought is that this could also be caused by high temperatures during the machining process. If the material gets too hot for an extended period of time, it can act as a secondary aging operation, changing the temper. This could cause excess copper to come out of solution, or allow existing copper to combine into larger globules.
Why was 2024 chosen for this application. 2024 is an excellent choice for brake calipers. This is because 2024 has better strength characteristics under higher temperatures, but I would think that there are stronger/cheaper choices than the 2024.
Ed
So, if it is actually required for plating, then why would we think that this was a bad thing.
Yes 2024 has a higher cu content then most other alloys and this will be attacked by a desmut bath, but only in raw form. Once alloyed in al it would not be susceptible to this. (or as susceptible) Unless, the cu has come out of solution. This would indicate an issue with the original material. If the 2024 was improperly solution treated or aged, then this would cause the cu the clump and then be attacked by the bath.
Were there certifications with this material. Has anyone done a look at this material. Has anyone looked at the grain structure of the material to see if there are any problems. If the cu has created stringers in the material, which it sounds like it has, then it is a good thing that this was found out when it did. We would be talking about a much higher liability if the part was on the car and failed.
Another thought is that this could also be caused by high temperatures during the machining process. If the material gets too hot for an extended period of time, it can act as a secondary aging operation, changing the temper. This could cause excess copper to come out of solution, or allow existing copper to combine into larger globules.
Why was 2024 chosen for this application. 2024 is an excellent choice for brake calipers. This is because 2024 has better strength characteristics under higher temperatures, but I would think that there are stronger/cheaper choices than the 2024.
Ed
05-21-2004, 03:59 PM
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Originally posted by 911racer
[B]Wow, this is a long post. It looks like everyone wants to jump on the plater. I have a hard time understanding that. From everything I have read on the internet it looks like 2024 requires a desmut bath before plating. Unlike other alloys that do not unless previously coated.
[B]Wow, this is a long post. It looks like everyone wants to jump on the plater. I have a hard time understanding that. From everything I have read on the internet it looks like 2024 requires a desmut bath before plating. Unlike other alloys that do not unless previously coated.
So, if it is actually required for plating, then why would we think that this was a bad thing.
Yes 2024 has a higher cu content then most other alloys and this will be attacked by a desmut bath, but only in raw form. Once alloyed in al it would not be susceptible to this. (or as susceptible) Unless, the cu has come out of solution. This would indicate an issue with the original material. If the 2024 was improperly solution treated or aged, then this would cause the cu the clump and then be attacked by the bath.
Were there certifications with this material. Has anyone done a look at this material. Has anyone looked at the grain structure of the material to see if there are any problems. If the cu has created stringers in the material, which it sounds like it has, then it is a good thing that this was found out when it did. We would be talking about a much higher liability if the part was on the car and failed.
Another thought is that this could also be caused by high temperatures during the machining process. If the material gets too hot for an extended period of time, it can act as a secondary aging operation, changing the temper. This could cause excess copper to come out of solution, or allow existing copper to combine into larger globules.
this would be localized in areas of high tool speed, and not apparently randomly distributed on the part. Nor would they be present on the bottom surface of the arm which is in its original Mill finish, or on the vertical surface of the arm that was water-jet cut. Not to mention the fact that any hack who burned up a part with that much tool speed would have a hard time getting the surface finish everywhere else uniform. Affecting the temper? By heating and what...re-annealing? what temps and for what duration...this just isnt realistic.
Speeds and feeds in the machining process are controlled by the program, no arbitrarily modifed by the machinist. As noted elsewhere, this is one arm from a run of 10 pair that has had a problem.
Why was 2024 chosen for this application. 2024 is an excellent choice for brake calipers. This is because 2024 has better strength characteristics under higher temperatures, but I would think that there are stronger/cheaper choices than the 2024.
2024 is second in strength only to similary heat treated 70XX aluminums that tend towards the brittle end of things....cheaper...sure...there are cheaper alloys, but that doesnt make them better. Stronger....yep...there are stronger alloys also...all 70xx series and all stronger at the expense of increased brittleness at the same level of heat treat.
Until recently most brake calipers were cast...from alloys of 356 or proprietary alloys. Until the monobloc technlogy was developed anyway.
2024 IS a good choice for elevated temps, and temp heat cycles, (go look at the proximity of the rotor of your car to the ball joint bung) and has better 'toughness' than 60xx and 70xx when subjected to fully reversed stresses.
We are going to have to agree to disagree on the rest of what you have to say here. This is probably all academic...the reality of the part is that even the 60xx series billet will be so much more uniform at the granular level than even Porsches extraordinarly good castings, that its just not a relevant point. 944 arms arent breaking mid-span guys....they ball joints fall out, snap, or are pried out by excessive lowering, inadequate spring rate, excessive travel, and or lack of replacement at the end of service life.
Last edited by mumzer; 05-21-2004 at 04:25 PM.
05-21-2004, 04:22 PM
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Perhaps I've missed it, mumzer, but have you looked at why one of the arms and not both appears to have had a problem? Did the plater re-plate both arms or just the problem piece? I know little more about metallurgy than I've learned in this thread, but thought it might be worth pointing out. Perhaps apply krutschman1's materials test to samples from each arm.
However it works out, I'm taking notes - this is a good lesson in how to give good customer service and how to be a good customer. I have been agreeing with the sentiment that it's no-win for everyone involved but perhaps that can be mitigated if all of the possibilities are run to ground and then you both submit to some kind of arbitration. In the end both parties may not be fully satisfied but a well informed arbitration should be fairest to all involved.
However it works out, I'm taking notes - this is a good lesson in how to give good customer service and how to be a good customer. I have been agreeing with the sentiment that it's no-win for everyone involved but perhaps that can be mitigated if all of the possibilities are run to ground and then you both submit to some kind of arbitration. In the end both parties may not be fully satisfied but a well informed arbitration should be fairest to all involved.
05-21-2004, 04:42 PM
#74
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Ed,
You bored? just happen to be browsing the 944 Turbo board today?
(Seeing with your 29 posts you must be on rennlist a lot)
You just happen to be from Skip's home town?
I know little about metallurgy, but I do know a stretched theory and biased opinion when I hear one.
If you really believe there's something better than 2024, Lets hear it.
Otherwise it just seems like your slinging mud.
You bored? just happen to be browsing the 944 Turbo board today?
(Seeing with your 29 posts you must be on rennlist a lot)
You just happen to be from Skip's home town?
I know little about metallurgy, but I do know a stretched theory and biased opinion when I hear one.
If you really believe there's something better than 2024, Lets hear it.
Otherwise it just seems like your slinging mud.
05-21-2004, 04:52 PM
#75
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OK, boy did we just get defensive. I thought that you wanted to get everyone?s input. I did not see you jumping up with replies when people were pointing at the plater. Are you just getting excited because I am pointing up stream.
The desmut bath. Can we find out exactly what is in the bath. I am sure that the in house Castrol rep for our company can find out about 2024 with whatever was used. SKIP ARE YOU OUT THERE. Can you find out what was used.
Also, I would be happy to send out a piece of 2024 that I use for caliper adapters to put though the same bath and see how it fairs.
_________________
sure theoretically true...but this would be localized in areas of high tool speed, and not apparently randomly distributed on the part. Nor would they be present on the bottom surface of the arm which is in its original Mill finish, or on the vertical surface of the arm that was water-jet cut.
_________________
So, what you are saying is that the pitting is uniform over the surface of the part. I would agree if this is true. I have not seen the part. SKIP do you have a pic we could see to verify this.
So if it is not uniform, would you agree that the machining process would be suspect.
_________________
Speeds and feeds in the machining process are controlled by the program, no arbitrarily modifed by the machinist. As noted elsewhere, this is one arm from a run of 10 pair that has had a problem.
_________________
Evidentaly you had asked your customer to do the anodizing himself, so if you are sending out unplated arms, how do you know that the other 9 pairs did not have a problem too.
__________________
We are going to have to agree to disagree on the rest of what you have to say here.that this does not exist in all of your product.
__________________
What are we disagreeing on. I am just offering something different than the easy point at the plater view. Lets find out what he did wrong if he did something wrong. Like Travis says. I get 2024 plated too.
Ed
The desmut bath. Can we find out exactly what is in the bath. I am sure that the in house Castrol rep for our company can find out about 2024 with whatever was used. SKIP ARE YOU OUT THERE. Can you find out what was used.
Also, I would be happy to send out a piece of 2024 that I use for caliper adapters to put though the same bath and see how it fairs.
_________________
sure theoretically true...but this would be localized in areas of high tool speed, and not apparently randomly distributed on the part. Nor would they be present on the bottom surface of the arm which is in its original Mill finish, or on the vertical surface of the arm that was water-jet cut.
_________________
So, what you are saying is that the pitting is uniform over the surface of the part. I would agree if this is true. I have not seen the part. SKIP do you have a pic we could see to verify this.
So if it is not uniform, would you agree that the machining process would be suspect.
_________________
Speeds and feeds in the machining process are controlled by the program, no arbitrarily modifed by the machinist. As noted elsewhere, this is one arm from a run of 10 pair that has had a problem.
_________________
Evidentaly you had asked your customer to do the anodizing himself, so if you are sending out unplated arms, how do you know that the other 9 pairs did not have a problem too.
__________________
We are going to have to agree to disagree on the rest of what you have to say here.that this does not exist in all of your product.
__________________
What are we disagreeing on. I am just offering something different than the easy point at the plater view. Lets find out what he did wrong if he did something wrong. Like Travis says. I get 2024 plated too.
Ed