Matching Spot Welds on Trunk Floor Panel Replacement

[rbouch8828]

I have a shop that is looking into replacing the floor panels on my 280SL. They are looking for a way to reproduce the factory spot welds that are most especially visible on the lip of the center panel, where it turns up to join the shock absorber tower.

Joe Alexander has told me that he uses a "Pick Hammer" procedure to replicate the spot welds, after he has welded the panels into place and grounded the welds flat. However, I am hoping to find some kind of photo of this kind of procedure, if anyone has gone through it, or something similar.

Kind regards,

Roland

[ja17]

Roland, I modify the end of a "pick Hammer" or "welding hammer" to be flat and approximately the size of the factory spot welds.  I put the weld marks in the new panel before installation. I use a hard rubber backing and strike the modified hammer on the panel with the hard rubber back up behind it. A hockey puck can be used for you hard rubber back-up. Most often I place the modified hammer where I want the spot weld then strike it with a heavy hammer or mallet, forming the simulated weld marks. Also before installation I use an air tool to punch holes around the edge of the panel for the new plug welds. The plug welds are ground smooth, the hammer formed simulated spot welds are left so as to resemble the original welds.  During installation, I use self drilling screws to hold and position the new panel before and during the plug welding process.  Pay close attention to the original welds, and seams to get it right. Take pictures. Seam sealer is only used on some of the seams from the factory. Make notes or pictures of this also. Pay attention to the locations of padding and the square patches holding wires in place. Also be aware of the square pads on the bottom of the trunk floor between the tank and the trunk floor. Watch for pictures to be added to this thread as time permits.


Installation of a new trunk floor is a long and tedious task. Removal of the fuel tank is required, hours of cutting and clean up is needed. In some cases the entire rear diff. may need removed to get at all the areas to make a factory correct repair. 30 to 40 hours of labor for a factory correct installation may be required. The trunk floor is made with three panels; center, right and left sides.

Find a nice original example of photos to guide you ........

[ja17]

More original factory details........................

[ja17]

Grind a welding hammer or pick hammer to match factory spot welds.

[rbouch8828]

Hi Joe,

Many thanks! This is really appreciated! Great to have for the club too!

Thank you so much!

Roland

[ja17]

I am not doing a trunk floor at the moment, so I have pictures of some scrap metal pieces to show my process. I am sure there are other techniques others have used. Feel free to add or comment.

I use an inexpensive pneumatic hole punch to punch holes around the edges of the metal for the plug welds. You can also use a drill. After the holes are drilled for the welds, I add the simulated spot weld marks with the modified hammer. As mentioned it is easiest to place the end of the hammer on the metal then strike it with another hammer or mallet to make the weld marks. Remember the plug welds will be ground smooth so they disappear and only the pick hammer marks end up visible after painting. Use a softer material for back-up while making the simulated spot weld marks. Experiment with some scrap metal first, hard rubber or hard wood for back-up should work. Slightly and gently straighten the metal after punching holes and making spot weld marks with a body hammer. This will allow the metal to fit flat.

[RobSirg]

Hi Joe,

I'm hijacking this past post as I have a question about the rubber/bitumen sheets on the trunk floor (in the rectangular depressions). Looking at Joe's photos the rubber/bitumen sheets are clearly diamond patterned - similar to the firewall padding (but thinner I presume)

However, when I look at my original trunk (and a few other original ones - RHD) the sheets are not textured. Can anyone explain this?

Did they use 2 different products? Perhaps a USA thing vs RHD?

Could it be that mine was originally diamond patterned also, that simply "flattened out" over time? (hard to imagine as there is no hint of texture).

There is no doubt that mine is original - as is Joe's. (also another one I saw this weekend that matched mine).

Thanks

Rob

[ja17]

Hello Rob,
I am not really sure if they used two types?  I will try to look at some more original cars and comment later.

[ja17]

Once the holes are punched in the new metal and the simulated spot welds are made the new floor panel can be fitted and trimmed. I like to use self drilling sheet metal screws to temporarily hold everything in place until most of the plug welding is finished. Then the screws are removed and the holes are also plug welded shut.  All plug welds are ground smooth and disappear leaving only  the simulated spot welds to show. Carefully position panels to match the gap of the original seams.  Sealer is mostly used underneath but a few seams have some light sealer brushed on the topside.

[rbouch8828]

Very nicely presented for all to see. Beautiful job Joe!

[Benz Dr.]

I agree but I have a question. Since all of this is mostly covered by the trunk rubber floor mat and it is in the trunk, why? I can see this being a good idea in the engine bay for attaching the front fenders and other places where these spot welds are visible but in the trunk? I guess if someone is willing to pay for it............

[114015]

Perfectly done, Joe.

Thanks a lot, much appreciated.

Achim

I agree but I have a question. Since all of this is mostly covered by the trunk rubber floor mat and it is in the trunk, why? I can see this being a good idea in the engine bay for attaching the front fenders and other places where these spot welds are visible but in the trunk? I guess if someone is willing to pay for it............

Well, Dan....,
Good question. Why? Why do you want to do so?

Basically everybody knows that welding/filling punch holes is qualitatively as good as the proper "spot welding" done at the factory. The latter was only done because of automatism and rational manufacture.

Well, why copy that? Why using old-style hose clamps instead of the newer worm-type style clamps? And there are many other things like this - details.

The reason is - because owners, possible buyers, brokers, auctionators, judges during car shows on the green (and so on) increasingly look for these little details. 
And the more a particular car looks like "factory original" or has been brought back to that appearance, the better it is, or to be honest - the car is supposingly claimed to be so.

On the one side the knowledge on classic or older cars in general and Pagodas in particular has dramatically increased throughout the last three decades (which I have observed ...),
on the other side, it is always also providing the "illusion" that this particular car of interest is an "untouched factory original survivor" although in reality it had undergone heavy modification.

It's all about impressing or somehow humbug a potential buyer - in order to achieve a better trade.
Or, today also in order to fake or to calm down possible fellow owners during an Event or get-together.
It's quite annoying to every car owner to hear from fellow owners: "Hey mate, this is not correct or original on your car, this has been poorly repaired on your car..."
That's why this "faking" spot welds have come up. 

Don't take this too serious, just enjoy.


Best,

Achim
(with former rust traces in the trunk)

[Peter h]

We fix it this way

Achim du musst ins Bett
Peter