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  #16  
Old 01-15-2013, 03:27 PM
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Quote:
Originally Posted by JamesDean View Post
My main concern for welding new metal in there is strength...

1) Can my welder weld at suitably high enough amps/volts to ensure that the metal can endure the forces/duty cycles?

2) Whats the condition of the other bolt's metal surrounding area? It might be weak? Fine?

Ideally what I would like to do is replace:
-the arm with a rust-free arm with new bearing and rubber bits.
-A new swaw bar link
-new springs and spring pads.
Make parts like diesel911 has suggested. You can't just weld on new tabs.

I welded mine (flat strap across the arm, dropping the shock 2") with a lincon 115V unit that constantly tripped the garage's circuit. It held up around 10k (When I finally scrapped the ol' girl)

Clean everything before welding, and use gas. Run it on the hot side of the dial, but be sure to test it on the broken flange first to see if you will be burning through.

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  #17  
Old 01-15-2013, 04:02 PM
Flawless
 
Join Date: Jul 2009
Location: Buffalo, New York
Posts: 142
I created the same situation on mine two years ago.

I replace the rear shocks, and managed to lose 1 bolt. Went to Ace Hardware and bought a nice shiny silver one and installed it.

2 month later I became alarmed by the loud thumping in my rear end (car, not my arse). Took a look and the Ace bolt was still shiny, but now headless. Unfortunately the stress created from only 1 point of attachment resulted in the remaining bold, A Arm, and shock breaking free.

I took stock and determined to replace the A Arm, until I discovered the price, and how incredibly difficult it would be to actually remove two old ones to replace mine.

Finally, I took my car to a farm implement dealer, who dropped the wheel end of the A arm, and welded a beautiful cradle into the formerly messed up A arm, creating a secure attachment for this and any new shocks I want to install. Cost me $45 for the work, and most likely kept my car from the pick and pull.

I heartily recommend that you consider adding to the current A arm, instead of replacing the existing A arm.

Just my opinion!
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  #18  
Old 01-17-2013, 08:14 AM
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Location: NE Ohio
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Here are some pictures I meant to post a few days ago. I finally got to upload them.

I took some close up shots of the broken piece.

1982 Mercedes 300SD Rear Lower Control Arm - Imgur
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82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
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  #19  
Old 01-17-2013, 09:54 AM
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If this were mine, I'd go to my local bolt shop and buy 2 washers (recently purchased some 3" OD and they had larger on hand) with the OD of the indented flat area. Most likely the ID would have to the be drilled out larger to match the current opening for the shock. The idea would be to sandwich the flat area with the broken bolt tab between the 2 washers. Clamp the washers together and drill the 2 bolt holes for the shock mount. Weld 2 nuts to the top washer. Clean the broken flange really well. If I couldn't access the top of the arm to position the top washer I'd cut a slot in the bottom flange opposite the torn spot and slide the washer in from below. Drill a few hole in the bottom washer and arm flange to allow spot welds up to the top washer. Bolt the washers in place without the shock and spot weld it all together. Coat to prevent rust. Install shock and call it good.

Good luck!
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  #20  
Old 01-17-2013, 10:30 AM
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Quote:
Originally Posted by Walkenvol View Post
If this were mine, I'd go to my local bolt shop and buy 2 washers (recently purchased some 3" OD and they had larger on hand) with the OD of the indented flat area. Most likely the ID would have to the be drilled out larger to match the current opening for the shock. The idea would be to sandwich the flat area with the broken bolt tab between the 2 washers. Clamp the washers together and drill the 2 bolt holes for the shock mount. Weld 2 nuts to the top washer. Clean the broken flange really well. If I couldn't access the top of the arm to position the top washer I'd cut a slot in the bottom flange opposite the torn spot and slide the washer in from below. Drill a few hole in the bottom washer and arm flange to allow spot welds up to the top washer. Bolt the washers in place without the shock and spot weld it all together. Coat to prevent rust. Install shock and call it good.

Good luck!
Just what I was thinking, although I thought a person could make it work without welding.
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  #21  
Old 01-17-2013, 10:41 AM
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Quote:
Originally Posted by Walkenvol View Post
If this were mine, I'd go to my local bolt shop and buy 2 washers (recently purchased some 3" OD and they had larger on hand) with the OD of the indented flat area. Most likely the ID would have to the be drilled out larger to match the current opening for the shock. The idea would be to sandwich the flat area with the broken bolt tab between the 2 washers. Clamp the washers together and drill the 2 bolt holes for the shock mount. Weld 2 nuts to the top washer. Clean the broken flange really well. If I couldn't access the top of the arm to position the top washer I'd cut a slot in the bottom flange opposite the torn spot and slide the washer in from below. Drill a few hole in the bottom washer and arm flange to allow spot welds up to the top washer. Bolt the washers in place without the shock and spot weld it all together. Coat to prevent rust. Install shock and call it good.

Good luck!
This is not a bad idea at all. I think I could probably make it work out well. I don't mind the welding. I am just not sure where to get the big washer! I dont think I've ever seen one locally that size.

BUT WAIT. There is always McMaster-Carr.




So basically, two of those. Drill press two holes in them for the bolts, welt appropriate size nuts on top plate...grind out inner diameter so shock fits... Sammich them to the existing control arm. Tack weld them to each other? Tack weld them to the arm--or no? And call it a day?
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
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(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #22  
Old 01-17-2013, 10:50 AM
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...like a shield of steel
 
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I can understand the desire to fix things and I know this is "only" a SD and doesn't go too fast - so we're not talking about super cars - but a shock letting go at an inconvenient moment could cause an inconvenient twitch couldn't it?

You've done some lovelly work on your other trailing arms why not replace this broken one with a good one?

I know I'm a bit of a fuss pot with this kind of stuff but safety first!

Seeing what bad trailing arms look like I'd hazard a guess that there's more weakness in that trailing arm than just the bit that has gone. Why risk it?
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  #23  
Old 01-17-2013, 10:54 AM
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Oh and as for the welder question - I think you might be at a thickness of steel that would require edge preparation to ensure that you got adequate penetration. "How to weld" books say to file a V shape profile at the joint and lay several beads on top of each other (cleaning before each bead).
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #24  
Old 01-17-2013, 11:03 AM
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Check your local bolt supply house as I bought 16 of those exact washers locally last week for a project of mine.

I would clean the area to be samiched between the 2 washers and drill it out to match the bottom washer so that the spot weld merged all 3 pieces of metal. Personally, I think this repair would be stronger than original. You could also weld the bottom washer around the perimeter but I think it would probably be overkill myself.

Army is one of the most knowledgeable posters to this forum and I would always give strong consideration to his positions.

To me, a broken shock on the rear isn't a catastrophic failure such as a broken ball joint. I think you state the car has been driving with the shock loose. I wouldn't think if it broke loose again after your repair that the result would be any different from the current driveablity or level of safety. If you're comfortable with that then go for it. If not, get a replacement arm.
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  #25  
Old 01-17-2013, 11:09 AM
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Quote:
Originally Posted by Stretch View Post
Oh and as for the welder question - I think you might be at a thickness of steel that would require edge preparation to ensure that you got adequate penetration. "How to weld" books say to file a V shape profile at the joint and lay several beads on top of each other (cleaning before each bead).
My experience with this type of spot weld is the thicker the steel the larger the hole should be. This allows you to melt the undrilled metal piece before the hole fills up. The drilled piece always gets the sides melted for me, its just the bottom doesn't get hot enough if the hole is too small. I would do a 3/8" hole and test it on some scrap before putting it on the car. Adjust to a larger hole if everything doesn't flow before the hole fills up.
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  #26  
Old 01-17-2013, 11:10 AM
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Quote:
Originally Posted by Walkenvol View Post
Check your local bolt supply house as I bought 16 of those exact washers locally last week for a project of mine.

I would clean the area to be samiched between the 2 washers and drill it out to match the bottom washer so that the spot weld merged all 3 pieces of metal. Personally, I think this repair would be stronger than original. You could also weld the bottom washer around the perimeter but I think it would probably be overkill myself.

Army is one of the most knowledgeable posters to this forum and I would always give strong consideration to his positions.

To me, a broken shock on the rear isn't a catastrophic failure such as a broken ball joint. I think you state the car has been driving with the shock loose. I wouldn't think if it broke loose again after your repair that the result would be any different from the current driveablity or level of safety. If you're comfortable with that then go for it. If not, get a replacement arm.
Last time I worked on the car the arm looked solid to me, there was no rust holes on it like my other 300SD. So I coated the bottom side of it with some rust encapsulator product.

What I think I'll do is take the spring out and assess the condition of the upper portion of the arm. Tap it here and there looking for weaknesses. If I don't find any and it just seems that the shock mount area failed due to stress and some minor rusting--which from the pictures seems that it might have been the case... MAYBE.

If the arm looks out and seems OK I'll go ahead with the washer repair if not, i'll be getting an arm off someone on here or locally if possible.
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #27  
Old 01-17-2013, 12:35 PM
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...like a shield of steel
 
Join Date: Sep 2009
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Quote:
Originally Posted by Walkenvol View Post
...

To me, a broken shock on the rear isn't a catastrophic failure such as a broken ball joint. I think you state the car has been driving with the shock loose. I wouldn't think if it broke loose again after your repair that the result would be any different from the current driveablity or level of safety. If you're comfortable with that then go for it. If not, get a replacement arm.
I agree it isn't like watching your rear wheel passing your side window - in most cases cars behind might think oh wow a cool spark making chicano W126!

I just don't want to hear that someone has ended up in a ditch like his (user)name sake. After all there's the well being of a real car at stake here - not some crappy little Porsche speedster!

I am a self confessed fuss pot for this sort of stuff but it still remains to be a possible stability problem that might occur at an inconvenient moment.
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #28  
Old 01-17-2013, 12:38 PM
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...like a shield of steel
 
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Quote:
Originally Posted by Walkenvol View Post
My experience with this type of spot weld is the thicker the steel the larger the hole should be. This allows you to melt the undrilled metal piece before the hole fills up. The drilled piece always gets the sides melted for me, its just the bottom doesn't get hot enough if the hole is too small. I would do a 3/8" hole and test it on some scrap before putting it on the car. Adjust to a larger hole if everything doesn't flow before the hole fills up.
It sounds like you are plug welding - replicating a spot weld with a MIG torch - working from one side of the metal; or have I missed the boat on this one?
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #29  
Old 01-17-2013, 01:31 PM
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As usual you are on deck and I stand corrected in my termonalogy - plug weld.
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  #30  
Old 01-18-2013, 09:09 AM
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My, my, my! Stretch you have certainly come a long way in your welding abilities. It seems as though it was only yesterday you were learning how to braze sheet metal. Sigh, brings a tear to my eye when I realize how quickly you've grown.

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