Making My Own Control Arms

[lambertius]

Lambertius, have you sectioned an arm through the ball joint yet? It looks to me like the arms are forged around the joint capsule. The forging line down the arm is a clue. I work for a company that fabs doodads from nonmetallic materials (ceramics mostly) and am used to machining with diamond and ceramic cutters. Machining out the old ball joint would not be a problem, however there is not much aluminum around the capsule to support a replacement if a suitable replacement could be found. I am following your progress with interest.

I was thinking about it. I might head down to a work shop and see if they will split one open for me. Just need to get the time!

 

[lambertius]

So I went around to a workshop yesterday to get the ball joint cut open (they have it at the moment) and they had a XRF gun! I don't know a lot about them as they aren't a particularly common item, but the gist is that you point and click and some lasers do fancy things and it tells you with a fairly high degree of accuracy what alloy you're working with. If the alloy isn't proprietary then it is usually bang on. As I've already paid for the lab tests, and I suspect it is probably some fiat group proprietary allow it is still worth it anyway. That said, the XRF gun results were:

6063 Aluminium with Manganese, Titanium and Iron doping. If the chemistry tests verity it that would be very good news, 6063 is pretty much butter. You can make a replacement very easily and cheaply as almost any material will exceed the strength and yield properties of 6063.

 

[Trev Latter]

Thanks for the update. Interesting stuff.

 

[philw696]

Very interesting indeed and totally agree the joint will be out of the Fiat Group.
My guess something like a Ducato.

 

[lambertius]

So I have my ball joint back. I'll explain what we're looking at:

-Left is the cup of the ball joint. Typically the cup is a part of the ball joint and is pressed with an interference fit into the arm, however on our arms this is not the case. The cup is machined into the arm itself, this is why the joints cannot be replaced or serviced - there is no ball joint to remove!

-Centre is the lower half of the ball joint lubrication and is a simple PTFE (Teflon) plastic part. Teflon is self-lubricating but extremely soft, just rubbing on the polished ball would be enough to wear it out let alone any dirt. There is a corresponding cup on the upper half of the ball (impossible to photograph) and was originally shrink wrapped over the ball.

- Right are the golden retention rings. Assembly would've been:

1. Machine out the socket
2. Insert the ball (with the shrink wrapped PTFE inserts)
3. Place the larger golden retention ring over the ball and press the arm to fold a metal lip over the ring to hold it in place. You can see a thin metal ring under the ball in the photos. This ball was the lip of pressed metal that retained the larger golden ring.
4. The smaller golden ring would've been pressed onto the rod of the ball joint allowing the dust cover to be installed.

So what do we learn from this?

Well I'm still waiting on my lab test results from SGS (just got my cleared invoice today so I may even get the results before the end of the week!), but if it confirms 6063 or some variation of, combined with the weird manufacturing you can be certain that it was done this way to be cheap. Double wishbone suspension despite its benefits is known as a poor choice for heavy cars due to the significant change in camber and toe that it causes during cornering. On a car like an MX-5 this loading isn't a problem but on a 1700kg many angry horse V8 durability is a serious issue. Maserati would've known this when designing the car and chose to do it anyway knowing the arms would have a short life expectancy. The implementation is arguably one of the cheapest ways they could've done it and isn't serviceable so ensures repeat sales. If you want to buy into the conspiracy that the cars are made to last 5 years or owned by collectors and not driven, this is one of the many bits of evidence you can collect.

Going forward however it shows me a few things, the first is that it points towards a high-probability of success for the injection. There is nothing fancy going on inside the ball joint at all. Injection should just fill in the wear with more PTFE. With the ball joint apart I'll be able to do a practice run where I can see what is going on.

It also highlights the possibility of replacing the ball joint with a conventional ball joint. I'll have a look in some catalogues and see if there is anything the right size that socket could be machined out and a conventional design ball joint pressed in. This is more a luck outcome than anything, I'll have to find a part that is exactly the right size so that I only machine out the minimum to allow it to press in. However, if this were to be possible then I would be an almost ideal outcome. Sure, we'd still be stuck with overpriced bushings from Fiat group but you would be able to fully refurbish the arms without having to manufacture new ones. This would make costs for new ball joints around $200-$400 AUD (including the machining time) and if you wanted to fully refurbish them it would be that plus two bushings per arm. So in today's money, that would be 200-400GBP per arm to be refurbished and have a serviceable joint so that the issue is gone for good.

I've also sent off for a quote to have the OEM part machined out of 6063 billet just to see what it would cost to have an exact copy of the arm made. If it comes back as something reasonable, I'll pick a ball joint and bushing size from a catalogue and resize it to fully escape the Fiat group. This option is obviously cost dependent, but if it is cheap enough this would be the perfect outcome. I would try and pick something from a common sports car so that people have the choice to run harder or softer bushings in the future.

 

[philw696]

Some excellent work going on there and I commend your commitment in doing this.

 

[lozcb]

I do like an intelligent dog with a bone , let's hope you achieve the marrow you seek soon as ,spot on sir

 

[GTVGEOFF]

This is excellent work, I raise my cap to you sir.

 

[Paulrv2]

Thanks for that! Throw up a couple of pictures of those new shiny boys!

After a bit of faffing about, I'm going to model up the hub and simulate the loads in situ as well. Mostly out of interest.

Afraid I don’t have them at home to take pictures - they went straight to the workshop who are fitting them for me. Work on the car is unfortunately stalled at present waiting for a replacement power unit to fix a problem engaging reverse gear; hoping it will arrive today so work can be done next week

 

[lambertius]

Thanks for all the support guys!

I got my lab results back last night, and this is why you do things properly or not at all. The actual grade is 4343 Aluminium, I suspect the high Silicon content is what messed with the portable XRF, but like I said I'm not super familiar with the tool and would need to read the manual to properly understand what is going on. The test that was run on the sample I provided was a destructive test - that means the material was consumed in the process and is the gold standard for material identification. The details below are the unequivocal details of the alloy, and would indicate that it is with certainty a 4XXX series alloy, probably with a propietary blend which is why there is a notable titanium component.




From this I can look up the material properties on any number of catalogues. Here is a nice easy to read link for anyone who is curious https://www.makeitfrom.com/material-properties/4343-BAlSi-2-AlSi7.5-Aluminum

Reading up on the 4343 alloy shows that the primary goal is stiffness - which makes sense, you don't want the arm flexing or work-hardening under the car. It is also a cast able alloy which is good for manufacturing costs. The blend is likely proprietary, but the addition of things like titanium would just be to enhance that stiffness and would be negligible for the purpose of analysis, but it is important to be aware. I could do one further test and directly measure the material yield properties, but I've already spent enough money identifying the alloy and looking up the known properties in a table is good enough. I'll be making my own arms and it just doesn't matter if the titanium doping makes it 10% stiffer or not as it is just my point of reference for the properties of whatever I use. The good news is again, it is a low strength alloy which improves the number of alternative materials I can use. One thing a lot of people don't realise, is that per unit weight most aluminium and steel alloys are the same strength. That is to say, a kilo of steel is as strong as a kilo of aluminium (very broad generalisation, shape and application make differences). What this means is that depending on costs I could make the part out of steel and still get the same weight strength but drive the material costs down.

The surface hardness is a bit more ambiguous and I'll need to get some clarification from the lab. The arm is either die cast or cold worked, but which one exactly I can't say without a bit further clarification.

So now I'm waiting for a quote back on the 'as is' model to give me a point of reference for costs, which I'm expecting to be unreasonable but will give me an idea of the material vs machining costs.

I also tried chasing up some ball joint suppliers, but like almost everyone else in Australia I try to deal with I hope their businesses go bankrupt. Honestly, it is like squeezing blood from a stone. I'll have to get in contact with a manufacturer directly in china, or go to a retailer with some calipers and see if I can find a suitable joint that way. Knowing that the 4343 grade is weldable makes a big impact to the potential or refurbing them.

I also contacted a business in Sydney that makes and sells aftermarket parts for BMW about either manufacturing the arms I designed, or coming up with a regular service to refurbish them. It will make Con happy to know they have all the business liability stuff in place since they're a business that is already doing this sort of thing. I'll be trying the injection repair in a few weeks when I'm home, and if it works I'll probably end the journey there for myself. I'd be happy to continue on however if there is a legitimate interest in developing another solution so I'm just getting the pieces in place. Is this something anyone wants?

 

[Oishi]

Lambertius, if you could post some dimensions of 1. the Id of the socket (the larger counter bore). 2. the depth of the socket. 3. the diameter of the actual ball, I would be happy to search here in the US for a possible replacement. The maintenance dept. at the plant where I work has access to lots of machinery parts, there may be something off the shelf we could use. Also, it occurs to me that the pocket could be machined slightly deeper (just a few thou) a replacement PTFE cup installed and the gold steel top pressed/ swaged back in, to rebuild the arms. Or an Oilite bronze insert machined to fit and pressed in. Otherwise, machine the cup all the way thru, thread it and screw in a replacement joint from the back side. Thanks, Ed

 

[3200_Josh]

So I have my ball joint back. I'll explain what we're looking at:

-Left is the cup of the ball joint. Typically the cup is a part of the ball joint and is pressed with an interference fit into the arm, however on our arms this is not the case. The cup is machined into the arm itself, this is why the joints cannot be replaced or serviced - there is no ball joint to remove!

-Centre is the lower half of the ball joint lubrication and is a simple PTFE (Teflon) plastic part. Teflon is self-lubricating but extremely soft, just rubbing on the polished ball would be enough to wear it out let alone any dirt. There is a corresponding cup on the upper half of the ball (impossible to photograph) and was originally shrink wrapped over the ball.

- Right are the golden retention rings. Assembly would've been:

1. Machine out the socket
2. Insert the ball (with the shrink wrapped PTFE inserts)
3. Place the larger golden retention ring over the ball and press the arm to fold a metal lip over the ring to hold it in place. You can see a thin metal ring under the ball in the photos. This ball was the lip of pressed metal that retained the larger golden ring.
4. The smaller golden ring would've been pressed onto the rod of the ball joint allowing the dust cover to be installed.

View attachment 69192
View attachment 69193

So what do we learn from this?

Well I'm still waiting on my lab test results from SGS (just got my cleared invoice today so I may even get the results before the end of the week!), but if it confirms 6063 or some variation of, combined with the weird manufacturing you can be certain that it was done this way to be cheap. Double wishbone suspension despite its benefits is known as a poor choice for heavy cars due to the significant change in camber and toe that it causes during cornering. On a car like an MX-5 this loading isn't a problem but on a 1700kg many angry horse V8 durability is a serious issue. Maserati would've known this when designing the car and chose to do it anyway knowing the arms would have a short life expectancy. The implementation is arguably one of the cheapest ways they could've done it and isn't serviceable so ensures repeat sales. If you want to buy into the conspiracy that the cars are made to last 5 years or owned by collectors and not driven, this is one of the many bits of evidence you can collect.

Going forward however it shows me a few things, the first is that it points towards a high-probability of success for the injection. There is nothing fancy going on inside the ball joint at all. Injection should just fill in the wear with more PTFE. With the ball joint apart I'll be able to do a practice run where I can see what is going on.

It also highlights the possibility of replacing the ball joint with a conventional ball joint. I'll have a look in some catalogues and see if there is anything the right size that socket could be machined out and a conventional design ball joint pressed in. This is more a luck outcome than anything, I'll have to find a part that is exactly the right size so that I only machine out the minimum to allow it to press in. However, if this were to be possible then I would be an almost ideal outcome. Sure, we'd still be stuck with overpriced bushings from Fiat group but you would be able to fully refurbish the arms without having to manufacture new ones. This would make costs for new ball joints around $200-$400 AUD (including the machining time) and if you wanted to fully refurbish them it would be that plus two bushings per arm. So in today's money, that would be 200-400GBP per arm to be refurbished and have a serviceable joint so that the issue is gone for good.

I've also sent off for a quote to have the OEM part machined out of 6063 billet just to see what it would cost to have an exact copy of the arm made. If it comes back as something reasonable, I'll pick a ball joint and bushing size from a catalogue and resize it to fully escape the Fiat group. This option is obviously cost dependent, but if it is cheap enough this would be the perfect outcome. I would try and pick something from a common sports car so that people have the choice to run harder or softer bushings in the future.

Seriously impressive work with this! Thank you.

 

[rockits]

Great work and really interesting to see the results so far. Keep up the good work

 

[rs48635]

I am watching with genuine interest and congratulate you in diligent research. Chapeau!
My own 3200 lies dormant with at least one defective wishbone replaced. The potential is for another seven to be replaced.

 

[3200_Josh]

Thanks for all the support guys!

I got my lab results back last night, and this is why you do things properly or not at all. The actual grade is 4343 Aluminium, I suspect the high Silicon content is what messed with the portable XRF, but like I said I'm not super familiar with the tool and would need to read the manual to properly understand what is going on. The test that was run on the sample I provided was a destructive test - that means the material was consumed in the process and is the gold standard for material identification. The details below are the unequivocal details of the alloy, and would indicate that it is with certainty a 4XXX series alloy, probably with a propietary blend which is why there is a notable titanium component.

View attachment 69358
View attachment 69359

From this I can look up the material properties on any number of catalogues. Here is a nice easy to read link for anyone who is curious https://www.makeitfrom.com/material-properties/4343-BAlSi-2-AlSi7.5-Aluminum

Reading up on the 4343 alloy shows that the primary goal is stiffness - which makes sense, you don't want the arm flexing or work-hardening under the car. It is also a cast able alloy which is good for manufacturing costs. The blend is likely proprietary, but the addition of things like titanium would just be to enhance that stiffness and would be negligible for the purpose of analysis, but it is important to be aware. I could do one further test and directly measure the material yield properties, but I've already spent enough money identifying the alloy and looking up the known properties in a table is good enough. I'll be making my own arms and it just doesn't matter if the titanium doping makes it 10% stiffer or not as it is just my point of reference for the properties of whatever I use. The good news is again, it is a low strength alloy which improves the number of alternative materials I can use. One thing a lot of people don't realise, is that per unit weight most aluminium and steel alloys are the same strength. That is to say, a kilo of steel is as strong as a kilo of aluminium (very broad generalisation, shape and application make differences). What this means is that depending on costs I could make the part out of steel and still get the same weight strength but drive the material costs down.

The surface hardness is a bit more ambiguous and I'll need to get some clarification from the lab. The arm is either die cast or cold worked, but which one exactly I can't say without a bit further clarification.

So now I'm waiting for a quote back on the 'as is' model to give me a point of reference for costs, which I'm expecting to be unreasonable but will give me an idea of the material vs machining costs.

I also tried chasing up some ball joint suppliers, but like almost everyone else in Australia I try to deal with I hope their businesses go bankrupt. Honestly, it is like squeezing blood from a stone. I'll have to get in contact with a manufacturer directly in china, or go to a retailer with some calipers and see if I can find a suitable joint that way. Knowing that the 4343 grade is weldable makes a big impact to the potential or refurbing them.

I also contacted a business in Sydney that makes and sells aftermarket parts for BMW about either manufacturing the arms I designed, or coming up with a regular service to refurbish them. It will make Con happy to know they have all the business liability stuff in place since they're a business that is already doing this sort of thing. I'll be trying the injection repair in a few weeks when I'm home, and if it works I'll probably end the journey there for myself. I'd be happy to continue on however if there is a legitimate interest in developing another solution so I'm just getting the pieces in place. Is this something anyone wants?

I’d be very interested in these depending on how long they’d take to produce. Ideally I’d like my 3200 back on the road by the end of summer....challenge set

 

[conaero]

Thanks for all the support guys!

I got my lab results back last night, and this is why you do things properly or not at all. The actual grade is 4343 Aluminium, I suspect the high Silicon content is what messed with the portable XRF, but like I said I'm not super familiar with the tool and would need to read the manual to properly understand what is going on. The test that was run on the sample I provided was a destructive test - that means the material was consumed in the process and is the gold standard for material identification. The details below are the unequivocal details of the alloy, and would indicate that it is with certainty a 4XXX series alloy, probably with a propietary blend which is why there is a notable titanium component.

View attachment 69358
View attachment 69359

From this I can look up the material properties on any number of catalogues. Here is a nice easy to read link for anyone who is curious https://www.makeitfrom.com/material-properties/4343-BAlSi-2-AlSi7.5-Aluminum

Reading up on the 4343 alloy shows that the primary goal is stiffness - which makes sense, you don't want the arm flexing or work-hardening under the car. It is also a cast able alloy which is good for manufacturing costs. The blend is likely proprietary, but the addition of things like titanium would just be to enhance that stiffness and would be negligible for the purpose of analysis, but it is important to be aware. I could do one further test and directly measure the material yield properties, but I've already spent enough money identifying the alloy and looking up the known properties in a table is good enough. I'll be making my own arms and it just doesn't matter if the titanium doping makes it 10% stiffer or not as it is just my point of reference for the properties of whatever I use. The good news is again, it is a low strength alloy which improves the number of alternative materials I can use. One thing a lot of people don't realise, is that per unit weight most aluminium and steel alloys are the same strength. That is to say, a kilo of steel is as strong as a kilo of aluminium (very broad generalisation, shape and application make differences). What this means is that depending on costs I could make the part out of steel and still get the same weight strength but drive the material costs down.

The surface hardness is a bit more ambiguous and I'll need to get some clarification from the lab. The arm is either die cast or cold worked, but which one exactly I can't say without a bit further clarification.

So now I'm waiting for a quote back on the 'as is' model to give me a point of reference for costs, which I'm expecting to be unreasonable but will give me an idea of the material vs machining costs.

I also tried chasing up some ball joint suppliers, but like almost everyone else in Australia I try to deal with I hope their businesses go bankrupt. Honestly, it is like squeezing blood from a stone. I'll have to get in contact with a manufacturer directly in china, or go to a retailer with some calipers and see if I can find a suitable joint that way. Knowing that the 4343 grade is weldable makes a big impact to the potential or refurbing them.

I also contacted a business in Sydney that makes and sells aftermarket parts for BMW about either manufacturing the arms I designed, or coming up with a regular service to refurbish them. It will make Con happy to know they have all the business liability stuff in place since they're a business that is already doing this sort of thing. I'll be trying the injection repair in a few weeks when I'm home, and if it works I'll probably end the journey there for myself. I'd be happy to continue on however if there is a legitimate interest in developing another solution so I'm just getting the pieces in place. Is this something anyone wants?

If the items are covered by indemnity then yes, I will be happy if they are safe.

nobody wants to push on and worry about the arms, it defeats the object of our cars.

 

[Paulrv2]

I make no claim to be an engineer but do understand the basics. Looking at what you’ve been able to establish does suggest the wishbones could be fitted with new and much more durable ball joints at economic cost if somebody wants to take on the task. For me its disappointing that a premium price performance car has such a short-lived component in a critical area of the car! Certainly appears that Maserati designed the control arms with an eye to boosting replacement part revenue.

 

[conaero]

I make no claim to be an engineer but do understand the basics. Looking at what you’ve been able to establish does suggest the wishbones could be fitted with new and much more durable ball joints at economic cost if somebody wants to take on the task. For me its disappointing that a premium price performance car has such a short-lived component in a critical area of the car! Certainly appears that Maserati designed the control arms with an eye to boosting replacement part revenue.

They make a stack on parts. Think the issues are more with supplying companies rather than Maserati not stocking. Several went bust at one point, inc the wishbone supplier.

 

[philw696]

From my experiences working in Dealerships it's the brand manufacturers that make the money on parts not the dealer.
The Workshop makes the money that a lot of the time carries sales and parts.

 

[lambertius]

Lambertius, if you could post some dimensions of 1. the Id of the socket (the larger counter bore). 2. the depth of the socket. 3. the diameter of the actual ball, I would be happy to search here in the US for a possible replacement. The maintenance dept. at the plant where I work has access to lots of machinery parts, there may be something off the shelf we could use. Also, it occurs to me that the pocket could be machined slightly deeper (just a few thou) a replacement PTFE cup installed and the gold steel top pressed/ swaged back in, to rebuild the arms. Or an Oilite bronze insert machined to fit and pressed in. Otherwise, machine the cup all the way thru, thread it and screw in a replacement joint from the back side. Thanks, Ed

I meant to measure it up today but didn't get a chance, hopefully I'll get to it tomorrow. I'll modify the CAD to show how I propose making the arms servicable as well as some dimensions. It'll make a lot more sense with some pictures but the idea is to press in and weld a retention ring, then machine it out to accommodate a more standard fitment front-press ball joint. For various reasons replacing the PTFE insert or trying to service the existing ball joint is a bad idea, I would be significantly more confident with the ball joint injection than trying to reassemble the original joint. The OEM arm is very brittle, and I have no confidence that you could peen the original joint back in place. There will be pretty pictures with dimensions for you soon!

If the items are covered by indemnity then yes, I will be happy if they are safe.

nobody wants to push on and worry about the arms, it defeats the object of our cars.

It would all be covered properly regardless of who manufactures them if it gets to a point where other people want them. I'm not looking too deeply into manufacturing yet. Once I get a quote back it will give me a much more solid idea of what is viable and what isn't but it doesn't hurt to sound it out. I'm pretty confident that the ball joint injection will suit my needs, so anything after that I'll only be pursuing for forum members' benefit.

I make no claim to be an engineer but do understand the basics. Looking at what you’ve been able to establish does suggest the wishbones could be fitted with new and much more durable ball joints at economic cost if somebody wants to take on the task. For me its disappointing that a premium price performance car has such a short-lived component in a critical area of the car! Certainly appears that Maserati designed the control arms with an eye to boosting replacement part revenue.

Double-wishbone suspension does have a lot of benefits, one is that it is really cheap to design for. I suspect the ball joint was probably implemented to generate parts sales, but realistically I think the real reason such a heavy car uses double-wishbone is that is unreasonably difficult to design multi-link suspension. Its one of the 80:20 rule type things. With double-wishbone you get 80% of the performance for 20% of the effort.

To all the 3200 guys - are your rear control arms different geometry or are they a direct swap? If someone wants to donate some scrap arms and cover the measurement costs I can validate it and see if this solution applies there as well. If there is a difference I'd be happy to follow through the design and CAD work there as well.