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  #1  
Old 05-08-2012, 01:58 AM
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Fun with Floorboards!

So I got this cute little 1980 240D for a reasonable price cause I knew the floorboards needed fixing.
It has the typical rust through in the corner between the floorboards and the sides, making for lowspeed seatbelts and potential ejector seats.
I fixed one of these before using sheet metal lot's o' steel pop rivets and seam filler. It made a strong fix, not welding it's true, but strong.
I ground away as much rust as I could reach, treated everything with a German rust converter, primed it and then did the fix.

Anyway my question is..the evil undercoating.
Should I get rid of it below the area I'm fixing ,then clean it ,rust treat it, and paint it. That's my inclination

I've looked at those cool panels they have for fixing all the rust problem areas and I was tempted but I have all this nice old galvanized sheet metal .(it's free)

240Ds are cute..it's an auto, but I like a slow car, everybody drives way too fast, it's inefficient , dangerous, expensive and tickets are very costly!!

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  #2  
Old 05-08-2012, 02:36 AM
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Answer

http://www.peachparts.com/shopforum/bodywork/

The undercoat must be removed for welding, or are you planning to use alternative mounting?

http://www.peachparts.com/shopforum/bodywork/

.
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  #3  
Old 05-08-2012, 02:42 AM
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Welding galvanised metal can be dangerous

http://www.peachparts.com/shopforum/tools-tricks-supplies/261041-welding-fumes-galvanized-metal-can-kill-you.html
__________________
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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  #4  
Old 05-08-2012, 02:46 AM
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I'm pop rivetting , with seam filler
Perhaps I should've made that clearer
The sheet metal is vintage organ chassis, I have a fair bit of varying thickness. adequate for the job
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  #5  
Old 05-08-2012, 03:01 AM
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Good point

Here is plenty of study material to help you..


Paint Codes/leather codes
http://www.peachparts.com/shopforum/tools-tricks-supplies/145136-paint-codes-leather-codes.html

POR-15 Rust Preventative Paint
http://www.peachparts.com/shopforum/tools-tricks-supplies/145164-por-15-rust-preventative-paint.html



"Sandblasting and Restoration" Going to bare metal
http://www.peachparts.com/shopforum/tools-tricks-supplies/145168-sandblasting-restoration-going-bare-metal.html


Beginner welder: What type of steel should I use to repair Floorboards?
http://www.peachparts.com/shopforum/tools-tricks-supplies/142064-beginner-welder-what-type-steel-should-i-use-repair-floorboards.html




Pop Rivets
http://www.peachparts.com/shopforum/tools-tricks-supplies/275658-pop-rivets.html



Braze ,Weld or epoxy ???
http://www.peachparts.com/shopforum/tools-tricks-supplies/159628-braze-weld-epoxy.html

Mig welder joy and frustration
http://www.peachparts.com/shopforum/tools-tricks-supplies/309257-mig-welder-joy-frustration.html

The Safe Use and Handling of OXY FUEL Cutting, Welding, and Heating equipment
Cutting Torch Safety

Welding Video threads, auto body
http://www.peachparts.com/shopforum/tools-tricks-supplies/272893-welding-video-threads-auto-body.html

Beginner welder: What type of steel should I use to repair Floorboards?
http://www.peachparts.com/shopforum/tools-tricks-supplies/142064-beginner-welder-what-type-steel-should-i-use-repair-floorboards.html

Technical issues associated with welding floorboards..
http://www.peachparts.com/shopforum/tools-tricks-supplies/143078-technical-issues-associated-welding-floorboards.html

#!! I am finally going to learn to Weld.. need recommendation for a used Welder..
http://www.peachparts.com/shopforum/tools-tricks-supplies/139241-i-am-finally-going-learn-weld-need-recommendation-used-welder.html

best way to bridge a gapping hole?
http://www.peachparts.com/shopforum/tools-tricks-supplies/148070-best-way-bridge-gapping-hole.html

Danger: Painters Lung
http://www.peachparts.com/shopforum/tools-tricks-supplies/251775-danger-painters-lung.html




Dealing with Rust Repair on your Camaro
How to Paint Your Own Car, Auto Body Discussion Forum and Videos | Learning how to paint your own car and general automotive restoration
.
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  #6  
Old 05-08-2012, 03:07 AM
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Hmm

Quote:
Originally Posted by Toxophilite View Post
I'm pop riveting , with seam filler
Perhaps I should've made that clearer
The sheet metal is vintage organ chassis, I have a fair bit of varying thickness. adequate for the job
I suggest you use stainless steel rivets and 14 gauge steel for the repair.

Pop Rivets
http://www.peachparts.com/shopforum/tools-tricks-supplies/275658-pop-rivets.html

.
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  #7  
Old 05-08-2012, 01:16 PM
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Location: West Quebec
Posts: 4,025
What about rivnuts?

What about rivnuts?

I know that welding is the preferred way to go for most people on this list, but in some situations rivets are what is available.

I can tell you that here in Quebec -- where in addition to chronic floor rot problems from road salt used in winters, we have a very strict safety inspection prior to plating a used car purchased outside of the province, or if you manage to really p*ss off a cop who has pulled you over -- a few years back a guy took the government to court for not accepting riveted repairs on vehicle floors.

The government conceded that it could not demonstrate that rivets should be rejected out of hand for floor work, if properly done. Screws were disallowed, however.

The rule is that if you use rivets you have to deliver the car with the rivet work in clear view for the inspection. If you try to disguise how the repair was done the car will fail.

But from what I have read about rivnuts, aren't they more secure?
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2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22
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  #8  
Old 05-08-2012, 02:45 PM
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Answer

Quote:
Originally Posted by Zacharias View Post
What about rivnuts?

I know that welding is the preferred way to go for most people on this list, but in some situations rivets are what is available.

I can tell you that here in Quebec -- where in addition to chronic floor rot problems from road salt used in winters, we have a very strict safety inspection prior to plating a used car purchased outside of the province, or if you manage to really p*ss off a cop who has pulled you over -- a few years back a guy took the government to court for not accepting riveted repairs on vehicle floors.

The government conceded that it could not demonstrate that rivets should be rejected out of hand for floor work, if properly done. Screws were disallowed, however.

The rule is that if you use rivets you have to deliver the car with the rivet work in clear view for the inspection. If you try to disguise how the repair was done the car will fail.

But from what I have read about rivnuts, aren't they more secure?
Yes and NO.

IMO; they are more difficult, time consuming, and costly than rivets.
If they are steel to steel, and installed to aircraft specification they can be acceptable.

Aluminum to steel will corrode and/or extrude, quickly becoming unsafe.
Some steel rivets have the wrong metallurgy for safe use in this application.


FYI: The floor pan is a MAJOR STRUCTURAL component of the Mercedes unibody construction. By design the floor pan must accept - distribute serious load stress, and is in constant motion, flexing - twisting.

Here is some educational material on the unibody.


Monocoque - Wikipedia, the free encyclopedia

http://www.fkm.utm.my/~arahim/Lecture%201%20smc4133.pdf

Rusted Out Unibody - Exposing and Checking the Car Floor Pans And Subframe
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  #9  
Old 05-08-2012, 04:53 PM
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Quote:
Originally Posted by Toxophilite View Post
So I got this cute little 1980 240D for a reasonable price cause I knew the floorboards needed fixing.
It has the typical rust through in the corner between the floorboards and the sides, making for lowspeed seatbelts and potential ejector seats.
I fixed one of these before using sheet metal lot's o' steel pop rivets and seam filler. It made a strong fix, not welding it's true, but strong.
I ground away as much rust as I could reach, treated everything with a German rust converter, primed it and then did the fix.

Anyway my question is..the evil undercoating.
Should I get rid of it below the area I'm fixing ,then clean it ,rust treat it, and paint it. That's my inclination

I've looked at those cool panels they have for fixing all the rust problem areas and I was tempted but I have all this nice old galvanized sheet metal .(it's free)

240Ds are cute..it's an auto, but I like a slow car, everybody drives way too fast, it's inefficient , dangerous, expensive and tickets are very costly!!
you REALLY need to understand how dangerous welding galvanized is.
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  #10  
Old 05-08-2012, 05:37 PM
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Join Date: Feb 2012
Posts: 79
I appreciate your concern
and I am already aware the danger
However
At no point in my post does it say I'm going to be welding the galvanized metal, and when there was a misunderstanding about it I then put up a reply clarifying that I'm planning on riveting rather than welding
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  #11  
Old 05-08-2012, 06:46 PM
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I appreciate the responses that are concerned with safety, and they are correct. But being in America, where freedoms are eroded daily, I'd say go for the riveting, it's your car. If you ever sell it, caveat emptor! But you should probably mention it.
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  #12  
Old 05-08-2012, 07:31 PM
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Answer

Quote:
Originally Posted by wildest View Post
I appreciate the responses that are concerned with safety, and they are correct. But being in America, where freedoms are eroded daily, I'd say go for the riveting, it's your car. If you ever sell it, caveat emptor! But you should probably mention it.
I am not objecting to rivets, and done properly they are safe + fast + cheap.

I am concerned that he use rivets that won't fail and KILL him..

FYI: Galvanized is typically too thin, I use double layers when riveting body metal.

.
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  #13  
Old 05-08-2012, 08:23 PM
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Location: Alexandria, Virginia
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I've had my share of 'Swiss-Cheese' Mercedes, and probably won't buy another with major rust. For small holes in the footwells or floor, I've used pop-rivets. However for the typical major W123 rot that I've found in the inner-sill/floor/seat-mount area, I've been using a 7-foot long piece of very heavy guage galvanised steel donated by a neighbor. It's about the thickness of the stuff used in galvanised steel electrical boxes.

For the worst rust I encountered on an '81 240D, (where I discovered one end of the front passenger seatbelt was only attached to carpet!), I cut a 3-foot long by 10-inch wide section of the galvanised. Then I rigged up a jig on the workbench to bend it to make a 3-foot long repair-panel, with an approx 100 degree "L" cross section, which was then bolted to the remaining inner-sill and floor, using many 1/4 fine-thread bolts & nuts. I used plates and bars, with 1/4 inch threaded holes, pre-riveted to the upper part of the 'L' panel that went up behind the inner-sill, where I wouldn't have been able to reach it with a wrench.

It was certainly much stronger than typical pop-rivets, but we'll never know how well it might have fared in a crash. I sold that 240D to the same neigbor who gave me the galvanised steel, and some dirtbag later stole the car and torched it! (See my thread 'The Sad Demise of Beirut Taxi')

Happy Motoring, Mark
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Last edited by Mark DiSilvestro; 05-08-2012 at 08:55 PM.
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  #14  
Old 05-08-2012, 09:05 PM
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The sheet metal I have is from a 1950s organ chassis
I have a large sheet that's at least as thick if not thicker than the current floor board material. and a a couple of long 8" wide pieces that are twice as thick if not thicker . I plan to have a piece from the rocker arm to the floorboard (perhaps on the outside)and then a piece from the side to the floorboard as well(on the inside). I'll use the heavier guage material to re-enforce the seatbelt area and any place I think needs more strength
I plan to use a lot of SS rivets with seam filler in between and over top
I found that a wire wheel on an angle grinder works great fro removing undercoating
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  #15  
Old 05-08-2012, 09:14 PM
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Quote:
Originally Posted by whunter View Post
I am not objecting to rivets, and done properly they are safe + fast + cheap.

I am concerned that he use rivets that won't fail and KILL him..
Okay but I am still not clear on which rivets those are. And what percentage of the floor pan would be feasible to replace with a riveted patch....

I read the riveting (no pun int) thread you had as a link, in another post, and was confused as heck when I was finished. Seems to me that everyone is saying "no argument with that" after each statement -- then suggesting a different type of rivet than in the previous statement.

I have an interest in this thing as I have an awful rusty Coupe floor staring back at me from on top of jackstands in the driveway. Not pretty at all, on the passenger side. Damn depressing actually.....

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2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22
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