Heartbreak-broken rear shock mount

Stevehose

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The post mortem

Here are some pics of the damage, in prep for the welder I have removed all the trunk panels, elephant skin wheel well covers, the parcel shelf and speakers (so he can weld by reaching through the speaker hole), and the rear seats.

Here are the blown out pieces shown from top and bottom:
IMG_1365.JPG

IMG_1366.JPG

IMG_1362.JPG


Looking through the speaker hole:
IMG_1372.JPG


The other in tact tower:
IMG_1371.JPG



So guys, seeing the damage to the tower, how would you recommend I go about repairing these? I am thinking Sven's technique for the damaged one, do I tell the welder to cut the other top off the same amount the bad one is trimmed back to so they are level?

Should I have him add welds all over the curved top area down to the sides for added strength? Seems like the curved tops are the fatigued areas.

What do you all think?
 

Sven

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Wow. That was quite a blow-out.

I am not sure if adding any welds down the sides would help. You could bend the perimeter edges of the washer downwards since it looks like the tower top has broken partially down the curve. That would make the top the same elevation as the left one. The trick is going to be welding the backside section.

Replace the entire tower?

Do you have a bump stop inside your rear spring?
 

Stevehose

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Where does one get replacement towers? I only see entire wheelhousings with the tower.

I do have the bump stops.

I am going to repair the left one also so maybe just cut the tops off both and fabricate a replacement? What about cutting off 1/4" inch off each tower and replacing with a 1/4" steel disk?

This is getting more complex...


Wow. That was quite a blow-out.

I am not sure if adding any welds down the sides would help. You could bend the perimeter edges of the washer downwards since it looks like the tower top has broken partially down the curve. That would make the top the same elevation as the left one. The trick is going to be welding the backside section.

Replace the entire tower?

Do you have a bump stop inside your rear spring?
 
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Peter Coomaraswamy

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Steve, might be a cray idea but if you could find some 1/8 pipe the same diameter as the tower you could fabricate everything outside the car and slip them over the existing towers and weld them at the base. Not sure where you would get that pipe though?

I wonder how the club car racer towers were built?
 

Keshav

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Shock mount

Hi Steve, just saw on German Ebay, 191473596806, for €38. Brand new. Check it out. Keshav
 

Sven

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It looks like the broken tower has a hole that is fairly close to the 3" diameter. Maybe a bit larger in places. You could grind the opening to a cleaner round shape and then just make the washer a bit larger at the jagged parts of the opening to fit. You might have to hammer those bits that are outside of the 3" line to bend them down a bit. I still think this is your best option.

Alternatively, replacing the whole tower with a custom built tower out of new steel tube could work. I am not sure it the elephant skin would fit over the top since it would have a square and not a round corner at the top. In the parlance of the steel industry you want "tube" and not "pipe". There are some 1/8" thick tube sizes in the 4, 4.5 and 5" diameter that may work. Speedymetals.com is a good source for small pieces.
 

decoupe

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deQuincey

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i assume that the top of the tower has been suffering fatigue from perpendicular forces exerted by the strut,

this leaves you with a very well defined damaged area, i may assume that the cylindric part of the tower is intact, but i would prefer not only replacing the top

my vote is for building a inner tower, that includes a new top, just inside the actual one, and weld it to the cylinder in which you should convert your old tower

so, cut your actual tower top part, place the new tower inside, now from inside the trunk weld a circular ring on top, and from inisde the wheel arch weld another ring almost flush with the wheel cavity

i am assuiming the the new tower leaves enough free space for the movement of the strut rod

thoughts ?
 

Nicad

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That is kinda what I was thinking too. Seems there might be a market for these sleeves.
 

Stevehose

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Interesting, is it posisble to get a welder tip up into the tower from below? How would one build an inner tower???


i assume that the top of the tower has been suffering fatigue from perpendicular forces exerted by the strut,

this leaves you with a very well defined damaged area, i may assume that the cylindric part of the tower is intact, but i would prefer not only replacing the top

my vote is for building a inner tower, that includes a new top, just inside the actual one, and weld it to the cylinder in which you should convert your old tower

so, cut your actual tower top part, place the new tower inside, now from inside the trunk weld a circular ring on top, and from inisde the wheel arch weld another ring almost flush with the wheel cavity

i am assuiming the the new tower leaves enough free space for the movement of the strut rod

thoughts ?
 
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deQuincey

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my concept:



not an expert in welding but mechanically i think this will work pretty well to substitute the original design through the repair

i think that there is enough Access for both the bottom and to add some lateral holes to tighthen there too
 

Stevehose

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How would you fabricate the insert piece?

At this point I am considering cutting off the top curved part (which is the fatigued area anyway and would prefer to eliminate all of that weakness instead of keeping some in the new repair) and replacing it with a CNC'd steel disk of the same height as the removed curve (say 3/8" or so). This keeps the geometry intact. Weld it to the tower in the same manner as the bottom part of the tower is welded to the wheel well panel. That should be plenty strong? Clean and simple too. Opinions?


my concept:



not an expert in welding but mechanically i think this will work pretty well to substitute the original design through the repair

i think that there is enough Access for both the bottom and to add some lateral holes to tighthen there too
 
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Arde

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Print a new shock tower with a 3D printer?

If that sounds naive you should hear other ideas I discarded:

1) Attach the shock to the rear speaker, you can hear the bumps in stereo.
2) Move Luis to the rear right seat and have him hold the top of the shock absorber. A human self leveling suspension!

Good luck!
 

Stevehose

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I for one am happy to see this thread go from problem to resolution.

This looks to be an excellent solution but I don't know who locally could do a job like this for me given it's complexity to manufacture and install and level correctly.

I am still leaning towards cutting off the fatigued curved metal top and capping the tower with a thick steel disk welded on top and innner sides (if accessible) unless someone tells me this would not hold up better than the orginal design. It seems the spring supports a significant amount of the weight of the car, if not most of it.



This thread is getting hijacked (sort of) so we can start a new one about the strut housing repair if you want. Here's my thoughts... The load needs to be transferred to the walls of the can and bottom edge as much as possible. It seems like the only solution should come from the bottom and I think it would be better to do it without any welding. A support "sleeve" could be bonded to the inside of the strut can and provide plenty of additional support. The trick is the shape being close enough to the original to slide in and bond, but it only needs to hold it in place since the strength comes from bottom edge and thicker top surface.
 

Luis A.

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The inner sleeve designs seem sturdy and relatively easy to install but precise measuring of the existing tower and accurate fabrication may be very challenging.

Steve, I'm not near my coupe to be able to measure but you're saying the thickness of the disc would only have to be around 3/8" if you were to completely cut off the radiused top section of the tower? Including some overlap to be able to securely weld it in place? With sufficient overlap, it may not matter if the cut isn't exact to the millimeter.

If this is a CNC'd part and therefore easy to replicate, maybe some of us would be interested in such a part, amortizing the set up costs. I know I would be.
 

Stevehose

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I have not taken exact measurements yet so the 3/8" is only an estimate. I will take some measurements tomorrow and report back.

I was planning on drawing a line around the tower on which the cut will be made, the difference being made up by the new disk. If it's off a mm or 2 height-wise I don't think would be a big deal as would not affect ride height much if at all. I want to cut off the fatigued metal foremost.

Yes, I was thinking of the possibility of a CNC'd part that once the dimensions were determined could be mass-produced, or at least the specs could be published so each owner could take them to their machinist after I guinea-pig the process.

The inner sleeve designs seem sturdy and relatively easy to install but precise measuring of the existing tower and accurate fabrication may be very challenging.

Steve, I'm not near my coupe to be able to measure but you're saying the thickness of the disc would only have to be around 3/8" if you were to completely cut off the radiused top section of the tower? Including some overlap to be able to securely weld it in place? With sufficient overlap, it may not matter if the cut isn't exact to the millimeter.

If this is a CNC'd part and therefore easy to replicate, maybe some of us would be interested in such a part, amortizing the set up costs. I know I would be.
 

Nicad

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If someone had an old and intact mount you could cut out of a wreck, making a mold might be the first step to getting an accurate sleeve made out suitably robust steel. It only has to last as long as the original one.
I think it would need to be welded in though as the shock puts stress on the metal both going up and down.
 

Stevehose

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Proposed design

What do you all think of this:

Cut the tower to the point where it starts to curve thus removing any fatigued metal.

Measure the diameter of the tower.

Measure the height of the removed damaged section so the new geometry can be matched relatively closely to the old. To be determined.

CNC a disk to match the thickness and tower width of the removed curve piece plus the width of the cut.

Cut a hole in the disk to match the existing hole in the tower for the shock bushing, I think it is 1" ?

Dish out/bevel the inside of the disk to to make up the difference between the new disk thickness and the thickness needed for the shock bushing to fit. Maybe a little thicker than original for added strength and trim the bushing to fit in the middle if needed (I have new rubber bushings on the way and will inspect if they can accept a thicker piece of metal). To be determined.

Optional: Bevel/round off the topside of the new disk to give it a slight curvature to mimic the original and perhaps aid the fitting of the elephant skin piece.

Here is a crude drawing of the above points, it offers a fairly simple and cost effective solution without constructing an inner sleeve etc and the complications that would create. It would use similar welds to those that hold on the base of the tower to the wheel housing. Opinions?

IMG_1376.JPG
 

Luis A.

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Steve, that looks good. I know you didn't draw it to scale but my guess is that the disc will be pretty thick, maybe 1/2 to 3/4" thick. Not sure if that impacts anything. I always envisioned the disk as fitting inside the diameter of the tower. The resulting overlap weld would be easier (stronger?) than a butt weld to the edge of the cut tower and prevent the possibility of damaging/burning out the relatively (to the disk) thin edge of the tower. Thoughts?
 
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