Alternative idea for S14 long-stud ball joints?

[djsilver]

Turns out BMW front control arms use a ball joint with a 41mm OD and a long stud that is designed to bolt through the chassis. I haven't put my hands on one for verify the dimensions but I'll be hitting the Cash-n-Carry soon to source a used control arm for measurements. It's not a straight up home run but we have some free thinkers around here........, :D

They can be purchased from $15-40 each, depending on the source and brand.

http://www.fcpgroton.com/images/products/large/31121126253L.JPG

[Bubba]

Nice. I'll be keeping track if this thread.

[Sleepy_Steve]

Nice. I'll be keeping track if this thread.

+1

Where are our resident engineers late on a Saturday night in the off season?

[Bubba]

They start drinking earlier in the days now...

[Sleepy_Steve]

http://www.temperancetantrum.com/Site%20Graphics/temperance%20tom%20sans%20enter.gif

[AdamR]

I was under the impression that the length didn't matter, only the pivot point did.

[Matt93SE]

the location of the pivot is what's important. the length of the stud gives you the ability to place the pivot where you want.

in engrish, it's all about the length of your shaft... :P

[Tidge]

Good find, are we talking any particular model of the BMW?

[BeerBringer]

See this thread please:

http://nissanroadracing.com/showthread.php?t=1615&highlight=beerbringer

The balljoint in my sketch is a E30 one iirc.

[djsilver]

http://contentinfo.autozone.com/znetcs/product-info/en/US/ksm/FA2049/image/4/

I just ordered a couple of these E30 ball-joints for experimentation. The first issue I see with them is that the stem has been necked down and the threads are a larger OD than the stem. That will make it difficult to properly fit a spacer onto the stem but below the spindle. I have a couple of ideas but I'll wait until I get them and take measurements before bragging! You'l notice that they don't have the groove for a circlip either. I noticed on the Nissan ball-joints that the circlip doesn't rest tight against the LCA so it's just there as a back-up safety device. You could do the same with these by machining a groove, or just tack them onto the LCA in a way that could be ground off later (or just not worry about it!)

[BeerBringer]

I just ordered a couple of these E30 ball-joints for experimentation. The first issue I see with them is that the stem has been necked down and the threads are a larger OD than the stem. That will make it difficult to properly fit a spacer onto the stem but below the spindle. I have a couple of ideas but I'll wait until I get them and take measurements before bragging! You'l notice that they don't have the groove for a circlip either. I noticed on the Nissan ball-joints that the circlip doesn't rest tight against the LCA so it's just there as a back-up safety device. You could do the same with these by machining a groove, or just tack them onto the LCA in a way that could be ground off later (or just not worry about it!)

You are correct. I had actually missed this when I made my fast sketch.
The thread on my joint measures 13.8 mm and the stem 13.1

[djsilver]

You are correct. I had actually missed this when I made my fast sketch.
The thread on my joint measures 13.8 mm and the stem 13.1

That's actually still good info. That means the threaded part is an M14 but it could be re-threaded to M13 and allow the use of a 13mm ID spacer.

I'm not an engineer but this is my take on it; You could make a tapered adapter and have a tight joint, but with a long stem like this one that's (OMG!) in single shear you'll have the bending load at the tapered joint, which is now a lot farther from the ball socket than it was. I'm thinking I'd rather have a spacer that's resting on the lip you see near the bottom of the stem. The OD of the spacer would be equal to the flat area around the bottom of the knuckle where the stem enters and use a nut on top to pull it all tight. That way the nut pulls tension against the lip at the bottom of the spacer and allows the larger OD of the spacer to sit flat on the knuckle and handle the bending load.

[Matt93SE]

Just FYI.. you DO NOT want to press this thing in without a backup plan. circlip or weld or something, but make damn sure you have something.
I replaced the press-in ball joints on the wife's altima a few years ago. about 5k miles later, I heard a popping sound. guess what came loose. the circlip saved us there by not destroying the ball joint. it's sitll a captive design and you wouldn't lose the control arm, but you wouldn't want it to come loose and destroy the boot and possibly damage other parts as well.

When I put it back together, I just tack welded the balljoint to the control arm in about 4 places. never had a problem again.

[BeerBringer]

That's actually still good info. That means the threaded part is an M14 but it could be re-threaded to M13 and allow the use of a 13mm ID spacer.

I'm not an engineer but this is my take on it; You could make a tapered adapter and have a tight joint, but with a long stem like this one that's (OMG!) in single shear you'll have the bending load at the tapered joint, which is now a lot farther from the ball socket than it was. I'm thinking I'd rather have a spacer that's resting on the lip you see near the bottom of the stem. The OD of the spacer would be equal to the flat area around the bottom of the knuckle where the stem enters and use a nut on top to pull it all tight. That way the nut pulls tension against the lip at the bottom of the spacer and allows the larger OD of the spacer to sit flat on the knuckle and handle the bending load.

M13 is a odd metric size. Don't even know if I could get a M13 nut in Sweden.
I guess 1/2" might work and be easier to find, even for me in Sweden.
But at this point I see this whole design starting to be to complicated to bother. When I went to the car parts store and looked for long balljoint my Idea was a cheap bolt in rollcenter solution. You might aswell weld a bearing cup in and use a long bolt at this point.

[djsilver]

M13 is a odd metric size. Don't even know if I could get a M13 nut in Sweden.
I guess 1/2" might work and be easier to find, even for me in Sweden.
But at this point I see this whole design starting to be to complicated to bother. When I went to the car parts store and looked for long balljoint my Idea was a cheap bolt in rollcenter solution. You might aswell weld a bearing cup in and use a long bolt at this point.

I received a couple of Meyle ball joints today from FCPGroton but they were mis-matched. I called them up and told them I'm a shade-tree mechanic but I don't like my stuff to look like it! The guy said he'd send me two more and an RMA/return shipping label and I can send back whichever two I don't want, so that was nice.

To your point, I can get M13x1.5 but doing that does add a step. The other alternative I've considered is threading the spacer's ID to M14x1.5 so it can be threaded on until it passes the threads then comes to rest on the lip below. I can make them out of 4130 tubing without getting too fancy with the tooling. It can also be heat-treated after machining.

The more complicated part of this is actually the bump steer adjustment for the tie-rod ends. The 240sx tie rod ends are M12x1.5 but commercially available metric rod-ends that I've found are only made in M12x1.25 or M12x1.75

[Matt93SE]

Errrr, the tie rod ends on my S14 are M14x1.5, not M12.
just saying.. :)

[djsilver]

Errrr, the tie rod ends on my S14 are M14x1.5, not M12.
just saying.. :)

Yup, that's the difference between the S13 and S14. I keep forgettin' about all the mixed up parts I'm using..., You can see the difference by looking at the inner tie-rod end threads. M12 rod ends come in 1.25 or 1.75. M14 rod ends come as M14x2.0

Here's the S13 part; http://images.oreillyauto.com/parts/img/large/moo/ev169_top.jpg

Here's the S14 part; http://images.oreillyauto.com/parts/img/large/moo/ev347_top.jpg

[Matt93SE]

2.0? I thought it was 1.5... oh well. that's by memory. back to creeping on FB..

[djsilver]

2.0? I thought it was 1.5... oh well. that's by memory. back to creeping on FB..

Sorry, I wasn't being clear. The S14 tie rod is threaded M14x1.5. What I was saying is that if you just wanted to screw the stock outer tie rod off and screw on a female rod end with a spherical bearing it's not that simple. I did find that Aurora makes them but they're not long enough to just replace the outer tie rod ends. The other bolt-together option would be to use a male rod-end and a barrel adjuster. You could use a LH rod end and a Left/Right barrel adjuster or use a RH rod end and use a RH coupler and make alignment ajustments by turning the inner tie-rod, just like factory.

The only way to make it bolt-on for an S13 is to swap out the 12mm inner tie-rod ends with the 14mm units from the S14. My memory is that the inner tie-rods will swap between the models.

[Matt93SE]

I did option 2 on mine. 9/16" rod end on the outside with a 14mm to 9/16" coupler in the middle.

You can do just the same with 12mm on the inside just as easy.

[djsilver]

I hate to leave this hanging but tolerances are killing me! BeerBringer measured the stem on his ball joints at 13.1mm. The one odd one I have matches his, but the other three are 12.7mm. I bought a foot of 1"ODx.250" wall 4130 from Online Metals. You'd think the ID would be 1/2" (12.7mm) but it's actually 13.2mm. The ledge where I'd have the spacer sitting (where the taper starts) is not very wide and I'd want the ID fit to be as tight as possible and this setup is giving up 0.5mm. I'm going to find out the source of the ball-joints with the 13.1mm stem before moving ahead. :(

[Def]

You have to finish machine DOM tubing, the ID tolerance is pretty large on them. but + 0.020"ish sounds large.

[djsilver]

You have to finish machine DOM tubing, the ID tolerance is pretty large on them. but + 0.020"ish sounds large.

Yep, I think I've gotta re-think my thinking!

I've been googling the f**k out of "ball joint taper", "tie rod taper", "automotive taper reamer", etc..., and have only positively identified 3 different tapers in automotive use. We've been discussing them in (nominal) degrees but they're actually made as a function of run/rise ratio;

- 10:1 works out to 1.2"/ft or 5.71 degrees (6 degree taper)
- 8:1 works out to 1.5"/ft or 7.14 degrees (7 degree taper)
- 6:1 works out to 2"/ft or 9.56 degrees (10 degree taper)

Best I can tell, the S14 ball-joints are 10:1 and the BMW ball joints are 8:1. I'm going to visit a local machine shop to measure and back up these numbers and start over again. I'll also take an S13 ball joint and a tie-rod end. I suspect the final product will be a spacer with an inside taper on one end and an outside taper on the other end. Isn't this fun?

[djsilver]

Never mind. This isn't going anywhere......,