What Type and Gauge of steel should I use to repair a seam rusted open in my passenger side floorboard along the edge next to the front and rear passenger side doors?
Can you please consider that a beginning welder will be welding this? Also should i weld from the top or bottom? I haveheard you should weld from the bottom in floorboard work. I get pretty obsessed with strength sometimes. I want to avoid welding 100 pounds of steel and girders into the seam.

I have already removed the passenger side seat. The rusted open seam extends from rear of the front door to rear of the backdoor. Sometimes I (jokingly) worry that one day I will be driving along some bridge and my carpool partner will literally fall out of the car and disappear into the river if I don't fix this seam before it turns into major cancer.

I would use whatever sheet metal I could find. 16 gauge will be harder to work with, but if it works out that the spot needs very few bends or curves, then the added thickness would be easier for a rookie to weld and will take longer to rust through.

Make sure you trim back as much of the cancered floor as possible and get back to something substantial enough to weld to. Make sure the metal where you will weld is COMPLETELY clean using abrasives of some kind.

What kind of welder do you have to work with?

Good luck and have a great day,

If you are a beginner, you are going to have trouble welding sheet metal, use the MIG process. The heavier the gage, the easier it is to weld and the harder it is to shape. One other thing - use cold rolled steel, hot rolled must be seriously cleaned before painting. If you are using scrap sheetmetal anything that is painted will likely be OK.

Stronger steel is used in the roof of many cars. I cut the roof out of an old SAAB from the late 70's and used it to replace the floorboards in an old Ford pickup. That repair lasted through many years of hard use.

Cleanliness will make an easier and longer lasting repair.

After years of using recycled sheet metal to repair things, recently I actually bought some virgin sheet metal at the local hardware store. I quickly overcame the pain and suffering associated with actually PAYING for metal because it was such a treat to work with clean, straight metal. 18 ga is about 1.2mm thick which was about right for the floor spots I repaired.

BTW if you have this extensive of damage to your car, be sure to inspect the rest of the auto for other such bad rust. You defintely don't want to patch up your floor and find out the unibody is shot!

Just wanna be careful....

you may be able to buy the panel new or cut one out from a wrecked vehicle.try to find a dismantler in the south where they maybe rust free

What about buying aftermarket floor pans? I know for like Mustangs you can get them cheap. I think their is a company called K&K maybe that makes MB sheet metal.

At least that way if your a good welder it would be very close to factory.

Mercedes Benz I generally use 18 gauge sheet metal.

It depends upon which gauge matches vehicle panel thickness best, and needed structural support in the area.

The toughest repairs are double or triple layers of sheet metal to reinforce structural points.

pfft diamond plate everything! and put dual stacks on it:D






;)

I have had good success with 16/18 gauge metal and a Hobart 135 (now 140 I think) model MIG welder. Best practice is to weld about an inch or less and let it cool to prevent warping (and fire). All my welding has been from the top, because that's where the metal fit best in terms of the junction seam with the rest of the car.

The driver's side of Cinderella has a new floor pan that I will guess is 18 gauge steel. That's the side where the seat was propped up with a 2x4 wood stick so the driver would not fall out. :) The passenger side is going to get sheet metal patches instead of a new floor pan because it has rusted out only along the areas you describe.

Cinderella's floor rust is mostly the result of blocked hood drains, and so it is from the inside out. Fortunately, this means the rocker panels are still in quite good shape. On the driver's side they were opened up enough when cutting away bad metal that a good POR-15 treatment was possible.

I have given some consideration to having a custom license plate for little Cinderella: "POR 15"

:)

Ken300D

floor repair is normally done with rivit gun rather than welder.

floor repair is normally done with rivit gun rather than welder.

maybe, but Rich seems to take his repair work seriously and wants to do it right.

floor repair is normally done with rivit gun rather than welder.

Rivet joints are not strong at all, especially for a unibody.

Blue Ranger is absolutely CORRECT !
There are other threads on sheetmetal where I go into the reasons for that...

WBain, that is a silly statement and you should do your research quickly, determine that it is a silly statement and delete it as soon as you can... for the sake of your own reputation....:D

A Beginner is ...well a beginner...I think I am fair to middling mechanic now and "OUCH" I wince at all the mistakes I made along the way to even get that far, so I am "OUCH" wincing at what will happen on the path to learning Welding.
If past experiences are representative, I will probably end up welding my driveshaft to new sheet metal by accident, melt my vacuum lines and accidentally weld my doors permanently shut.
So w.r.t. I am diassembling everything near the weld to minimize my chances of doing this.Sure wish i were 20 or 25 because I would be done already.

I'm going to stay away from this one but I won't do large reapirs with pop rivits....


And let me add that I am not an autobody specialist....thats my personal unprofessional opinion.....

I'm going to stay away from this one but I won't do large reapirs with pop tarts....stated by Bonehead Doctor


Are you sure you dont mean the cinnamon pop tarts? The cherry pop tarts are pretty heavy, thats why I put on 5 pounds recently. maybe they would make great floorboard material

Are you sure you dont mean the cinnamon pop tarts? The cherry pop tarts are pretty heavy, thats why I put on 5 pounds recently. maybe they would make great floorboard materialno I mean pop rivits.... even the steel ones...these can also be called blind rivits...


I love the frosted cinnamon pop tarts.....can't buy them becasue I would eat them all....

Again Carrameow, what kind of welder do you have? A stick or a MIG?

Have a great day,

I love the frosted cinnamon pop tarts.....can't buy them becasue I would eat them all....

Damn!...I just woke up and this is what I read...talk about waking up hungry! :D :D

Are you sure you dont mean the cinnamon pop tarts? The cherry pop tarts are pretty heavy, thats why I put on 5 pounds recently. maybe they would make great floorboard material

RASPBERRY pop tarts are the only type you should use. the little seed thingys inside abrade the steel just enough to provide proper adhesion.

Are you sure you don't mean the cinnamon pop tarts? The cherry pop tarts are pretty heavy, thats why I put on 5 pounds recently. maybe they would make great floorboard material
Hmmm, glue the metal together?

PANEL REPLACEMENT - New Technologies Challenge Old Habits
http://www.autobodypro.com/tektips/articles/panel.htm

Bonding: The Adhesive Alternative
http://www.abrn.com/abrn/article/articleDetail.jsp?id=71150

I have no opinion on this new technology.
Have a great day.

Hmmm, glue the metal together?

Hey Mr. Hunter some one has hacked your account and suggested that I glue the metal together! We better notify the Webmaster!

Boy was that guy dumb, he didnt realize we know the real WHunter, our hero and idol, would never suggest glue because he is the shopforum's Weld King, After welding, he would probably make me melt the floorboards down and roll them at a mill again.

To Mr. Bible: I hope to buy a MIG welder soon, next week, as soon as I catch my better half stocking up at the post holiday sales....

I just used a product called Copper Bond (a type of epoxy) on the pipes for the new water softener downstairs. Seems to be holding.

And rivits are for frogs.

Lotus has been using epoxy bonded aluminum frames for years.

Hey Mr. Hunter some one has hacked your account and suggested that I glue the metal together! We better notify the Webmaster!

Boy was that guy dumb, he didn't realize we know the real WHunter, our hero and idol, would never suggest glue because he is the shopforum's Weld King, After welding, he would probably make me melt the floorboards down and roll them at a mill again.
It is a new technology.
I wanted it on record that it exists.
In my opinion, the only flaws that I know of with this system are that surface preparation must be totally perfect, humidity, and temperature are also critical.

Have a great day.

For the new floor board you might contact these people. They have a lot of body parts.
www.mercedes-auto-and-parts.com

Lotus has been using epoxy bonded aluminum frames for years.yes...but they have been designed to work that way.....replacement floorboards typically havent been...

well, if you go to a professional body shop
and pay to have this done then they will buy floor pans
and they will rivit them in....

the reason they rivit them is becasue welding a car with an interior
and carpet and paint is tough... some times they even catch fire.


Secondly, the last time i checked all airplanes are rivited... and they
are pretty strong and some of them are very old...

just pretend like your working on a wonderful old mercedes airplane and
rivit in new floor pans... do an internet search and do them as if your doing
aircraft rivits...

RASPBERRY pop tarts are the only type you should use. the little seed thingys inside abrade the steel just enough to provide proper adhesion.

I was so happy this morning when I walked downstairs and found BOXES of pop tarts...

...was having such a craving after reading this thread...I enjoyed them :)

I replaced the floor on a Jeep Cherokee (one side). I used 16 guage as I remember. I cleaned the area very well and bedded the patch with marine grade bedding material and then used stainless steel rivits to hold it all together. After the bedding material dried I coated the outside with auto under coat and painted the inside.

The car is still on the road with no problems.

want another reason not to buy a new car? The new BMW 5-series sedan has front frame rails that are aluminum, and are glued and riveted to the firewall. If you replace a front rail, you have to use special rivets that cost $5 each and special blue epoxy. You can't do any welding because the heat would destroy the aluminum and you can't very weld aluminum to the steel firewall/floor structure. So much for repairability...

Aeroplanes have been glued together for ages.. They were made of spruce, birch plywood, and balsa-wood,...the De Havilland Mosquito was a case in point.
So...why not a car/truck ?

.

I had a rust hole in my 82 300D right under one of the passenger seat's rear support points and I had a bodyshop do the repair. They chose to rivet in a piece of metal and further secure it with something similar to JB weld. I plan to do the same on my 240D because I have a similar situation there, just a different place. I'll check out Harbor Freight Tools and see if they have any rivet guns. What's a good place to get some sheet metal?

now i am the advocate of riveting but
if you have to weld then what i would do
is go to harbor freight and buy the welder that
is like a big plier and it will spot weld ...

if you just have to weld then go buy that thing...
it will spot weld it as if your riveting...

it looks like the jaws of life....

The only problem with a spot welder for floorboard repair is having one with a deep enough throat to reach to all areas of the floorboard.

The MIG is a good choice for this work, but a little practice and experimenting will be needed. I would suggest a 175 or 180 Amp MIG such as the Hobart Handler 180 or the MillerMatic. Use CO2/Argon and .030 solid wire. You will be much better off with one of these welders and a 220 circuit than using one of the 120V welders that are about 135 or 140 Amps. They will be MUCH more versatile for jobs far beyond welding the floorboard.

TSC now has a great special that includes Handler 180, a cart, a small gas bottle and a self darkening helmet for right at $600. This is a GREAT buy.

Some folks prefer the Miller equivalent but it is much more expensive and the infinitely variable voltage adjustment is very tricky for a rookie welder. Even highly experienced welders have trouble with it. Hobart is now made by Miller and the latest Handler series is a really good unit for the money.

Good luck,

well, if you go to a professional body shop
and pay to have this done then they will buy floor pans
and they will rivit them in....

the reason they rivit them is becasue welding a car with an interior
and carpet and paint is tough... some times they even catch fire.


Secondly, the last time i checked all airplanes are rivited... and they
are pretty strong and some of them are very old...

just pretend like your working on a wonderful old mercedes airplane and
rivit in new floor pans... do an internet search and do them as if your doing
aircraft rivits...airplane were designed to be rivited together....unibody cars weren't.

While airplanes do last quite a good number of years they don't tend to be very crash worthy in general.


My point being using the proper method of attachments in the proper situations.....each has its place and are not universilly interchangible.

I plan to use Rivets and Welding after studying the damaged Seam yesterday; Rivets to secure the metal (vice clamps) while its being welded. Heck I may also put POR on top of the whole thing and all my floorboards so they will last out another couple of years...With my luck and being a Beginner, I cant wait to see what shows up as a end product. I suspect I will weld a screwdriver or ratchet into the frame or do something equally dumb. My learning curve isnt bad though

Comment about composites, epoxies, etc. Well the Boeing 777 is going to be made of Composite Resin (not metal) Yikes!!! That will be cool, sitting in Cross Pacific flight and watching some terrorist hijack the plane with a bottle of Nail Polish remover (" Take me to Hahadinamahia or I will melt a hole in the airplane with this stuff!")Thats the new thing in this industry. The only problem is newer cars are tougher and tougher to repair after collision damage. You can't strengthen composites.....

Have fun with the welding. It may not be a big issue if you choose to rivet it in, then weld it, but its a good idea to weld little tack welds every 6 inches or so first, to hold the piece in place, and prevent it from warping (which the heat will make it want to do). Then lay down your full beads.

Also, if you haven't already, Haynes has a good automotive welding manual. It goes over basic welding techniques, plus a lot of auto-specific tips. I found it a useful read.

And have fun! Learning to weld is like learning to use a screwdriver, it opens up so many repair possibilities. I was laying down functional beads after only about 10 minutes of practice with the MIG process, so it'll come fast.

peace,
sam

TSC now has a great special that includes Handler 180, a cart, a small gas bottle and a self darkening helmet for right at $600. This is a GREAT buy.

Some folks prefer the Miller equivalent but it is much more expensive and the infinitely variable voltage adjustment is very tricky for a rookie welder. Even highly experienced welders have trouble with it. Hobart is now made by Miller and the latest Handler series is a really good unit for the money.

Good luck,

Wow! That is a good deal. I paid that for just a Handler 120, reg, and bottle about 14 years ago. I STILL don't have a cart!:o :( Rich, this setup has your name on it.

I don't think I would use it in the case Richard is talking about, but I have used quite a bit of this stuff to patch smaller floorbard holes. I have a floorboard patch about the size of my fist in the corner where by left foot resides on my '82 240D and it has held up well for 3 years:


http://www.lord.com/Default.aspx?tabid=1190#108B109BT30

No corrosion, no heat, no welder. This stuff is about $25 for 7.5 ounces.

I don't think I would use it in the case Richard is talking about, but I have used quite a bit of this stuff to patch smaller floorbard holes. I have a floorboard patch about the size of my fist in the corner where by left foot resides on my '82 240D and it has held up well for 3 years:


http://www.lord.com/Default.aspx?tabid=1190#108B109BT30

No corrosion, no heat, no welder. This stuff is about $25 for 7.5 ounces.floorbooard patching and floorboard replacement are two different animals...one affects structural integrity the other doesn't.

Gee Whiz Guys....
I have posted this stuff before.... and I realize that many of you don't have a metalworking background and that many of you have never seen a car which was Not unibody.... etc...
But it is in the archives... spelled out in physics and logic both...

Anytime you bring metal to a heat sufficient to weld it you have taken away any special strength which it had to begin with. You do not have a way to cool at the proper rate and method to give it back those characteristics... if you know about metal working then you know that even if you tried... the fact that there is no way to it due to the whole piece not being the same temperature when the process starts and ends...

So butt welding a piece of metal ... even the correct thickness, style and alloy decreases the strength of the metal... which may be important when talking about something you rest your feet on AND which at a certain point in terms of size might even effect the structural integrity of your car during a crash.

It also almost automatically introduces a line of increased suseptibility to corrosion all around your attaching line.

Welding sheet metal always produces distortion in addition to deterioration of the original characteristics... .. sometimes it is controable.. sometimes barely...and at too much extra work...

The metal which you have available to attach TO needs to be carefully conserved with regards to strength also... we are dealing with old cars here...

Everyone needs a copy of the paper catalog from these guys :

http://www.aircraft-tool.com/atscat.aspx

The proper way to attach a floorboard to a unibody car is by using an offset flanger and overlapping the sheetmetal being installed with the sheetmetal in the car. Then you use whatever kind of rivets ( and plug welds if you want ) to attach it. Solid rivets can be used where any ability to put a bucking plate behind ( anvil type device ) And CherryMax rivets can be used where only one side is accessible. However, the Cherrymax are used regularly by themselves to build Experimental Aircraft....
And no one studies sheetmetal methods closer than those guys.... they know their lives are on the line and spare no expense.

And then there IS the fire starting question when dealing with a tight area with bad access from the other and Under side..

Find a good general metal working book... like used to be used in Metal Work courses in High Schools... all this stuff is in there... including how to judge by the thickness of the metals you are putting together the size,material, spacing and length of the rivets you need to buy .

and I realize that many of you don't have a metalworking background and that many of you have never seen a car which was Not unibody.... as stated by Leathermang

You seem to be taking this both emotionally and personally. Are you under some stress or are you angry? Is your health okay? Any issues you would like to discuss..Are you happy here at this Company?

(he he just kidding Greg--last year my supervisor used that line on me after I got a Bloody Nose on the treadmill and he tried to initiate an investigation on it--he's gone now...)

But I am fine now... that pretty much fulfilled my need to share on this subject... LOL

...or you could just plug weld it and seam seal it.

If you attempt to follow the advice in this thread be sure that you understand the difference between structural rivets and the aluminum pop rivets most people are thinking of when they read this. Also understand that the roof and floor of a unibody car provide much of the car's structural strength. Note that the car's structural components are originally welded together and not riveted.

If you weld, don't breath the fumes and understand why.

We have comparisons between aircraft and rusty old cars in this thread and in another thread someone builds-up a rear windshield flange from JB weld.

Be safe and be sure that you are being safe.

In another thread someone builds-up a rear windshield flange from JB weld.
Where is it?
Did they post any pictures?

Where is it?
Did they post any pictures?oh there are pictures...I can't remember what member it was.....I remember the thread...I think it was a gold colored W126.

I think it was PAWOSD and most of it was lost in the crash, IIRC.

I think it was PAWOSD and most of it was lost in the crash, IIRC.I thought the crash only took out 30 days of material......and I thought this predated the crash buy a few months. But you might be right.

Where is it?
Did they post any pictures?

http://www.mercedesshop.com/shopforum/showthread.php?t=129289&highlight=workmanship

http://www.mercedesshop.com/shopforum/showthread.php?t=129289&highlight=workmanship


Yes thats the thread.....its not lost after all.

Carrameow
I just completly fabracated my coupe floors and frame before i sold it. I have some templates and fabracated parts let me know.
I run a full service sheet metal shop

" Note that the car's structural components are originally welded together and not riveted." --TwitchKitty

Note that the original welding is Resistance welding... like you see the robots welding with the big splash of sparks... instant , under pressure with minimal heating except to the two points on the sheet metal being welded....
NOT mig, tig, stick, oxy-acet....very specific and correct application of pressure and heat.
It is Spot welding.....and done Before the application of primers, paints, rustproofing and that sort of stuff....

For plain flat sheet metal steel, I used www.metalsdepot.com and they shipped from Winchester, KY.

I think I got a sheet each of 16, 18, and 20 gauge 2' x 4' and that was shipped by UPS with no problem.

I'm sure there are local sources at reasonable prices where I live, I just didn't have time to track them down. TSC is crazy in their pricing and only have small sheets.

When you refill your MIG gas bottles, is it always a "swap" operation where they give you something that looks like it was from WWII, or will they refill your nice new pretty gas bottle? :)

Ken300D

Wow...

...its come to internet ordering steel and having it delivered.

Wow.

:D

Well, it won't take much longer and the web site URL will end in .cn as in China...... For all I know Kentucky was just an intermediate stop from China anyway. :)

I want to build my own shed building from 2" x 2" square steel tube. Online it looks to be pretty expensive at about $20-25 per 12' section. Anyone ever buy this stuff? What's a reasonable price for small quantities? Diesel Forum relevance - shed will protect diesel Mercedes!

Ken300D

Ken,

There should be an iron and metal distributor in your area where you can buy structural steel with no problem. These distributors typically only sell in full length sections which are usually 20 or 24 feet, but they will usually cut it to any length you want so that you can load it.

For the quantity necessary for building a shed, you would be better served to find someone with a long trailer that you can borrow and get it in the full lengths to minimize the scrap amount as you build.

Such material is priced by the pound. Most distributors have a give away sheet or brochure that will tell you the pounds per feet for any given shape/size. You can then simply go to the table to see the weight per foot, multiply by the number of feet and then by the price per pound.

You can probably do a little surfing and find the weight per foot charts on websites nowdays.

Also there will be several different wall thicknesses for 2" square tubing. I would think that 16 gauge would be plenty strong enough if you can weld material that thin. With practice and proper fit up, welding it should be no trouble. I used to weld 16 gauge material with a 5/64" 6011 rod using my Lincoln Tombstone crackle box, but I now use a MIG welder on the thin stuff. It's a piece of cake to learn to weld thin material with a MIG, but you still need a very good fitup.

Many iron and metal distributors are also in the scrap iron business. You typically can dig through their scrap and buy it really cheap by the pound. I do this all the time for projects that don't need large quantities of material. For building a shed, however, just buy the regular lengths, you would be a long time getting long enough pieces for your project from the scrap pile.

Good luck,

"When you refill your MIG gas bottles, is it always a "swap" operation where they give you something that looks like it was from WWII, or will they refill your nice new pretty gas bottle?"

Depends on the place.. in Austin there are about three places where you swap out.. but if you want your own bottle filled you can go to a place downtown.. but that makes one trip to deliver and one to pick up days later... they send them off so you can't wait...

If you have bought your own bottles... and just swap out then over time you save a tiny amount on a hydrotest which has to be performed every decade or something... swapping out they do that and you always have legit bottles on hand...

Ah... maybe you shoul get a body shop that does this kind of work to fix it. Dont lean to weld on your ride, it could get really messy.

Uhhh I learned how to fix cars on my ride. I learned how to do AC and rebuild engines and trans's on my ride as well as repair from a dash Fire..of course I have made mistakes along the way .nothing would ever be fun to outsource to anyone.

I know you mean well, but half the fun of doing this is the satisfaction of doing it. I know I could set my car on fire again, or really mess it up, but If I paid someone else to do it, it would HURT my spirit. And our spirit is what keeps us going in Life....

by all means do the work yourself. But before you go to town on your car with a new welder, get acquainted with it first with flat, clean plates on a benchtop. Then when you think you've got the hang of it, take a stab at the real thing. You'll be glad you did.

Thanks for the tips on steel supply and gas bottle filling - Thanks!

Some of the welding manufacturers have good welding tutorial pages. One of the good tips for MIG welding is to listen to the sound. If you are getting a good weld it will sound like hissing or frying eggs. If you get a popping sound then most likely the materials you are working on are not clean enough. I read that and it was hard to imagine, but its pretty much true in practice.

The other thing I find if the materials are not clean enough is a string of weld "pellets" instead of a smooth seam.

You know you're on the right level of "beginner" project when the welder cost you more than the car...... :)

Ken300D

Uhhh I learned how to fix cars on my ride. I learned how to do AC and rebuild engines and trans's on my ride as well as repair from a dash Fire..of course I have made mistakes along the way .nothing would ever be fun to outsource to anyone.

I know you mean well, but half the fun of doing this is the satisfaction of doing it. I know I could set my car on fire again, or really mess it up, but If I paid someone else to do it, it would HURT my spirit. And our spirit is what keeps us going in Life....

You are definitely on the right track, and I'm sure that you realize that you should practice on some scraps that are the same thickness as what you will be welding. Shouldn't be hard to find some scrap sheet metal to practice on.

The sound is important with any kind of welding. For me, sound is even more important with stick welding. With MIG the sound is determined by the way your machine is set up. There are two types of MIG welding, short circuit transfer and globular transfer. Short circuit transfer is what you will use on gauge metals and it sounds less like frying eggs and more like a steady frequency square wave with a little of the frying egg sound on the side. Globular transfer is for much more penetration and is a more advanced type of welding.

It will depend on the gas you are using and what you are trying to accomplish. With a MIG welder, if you will follow the charts, you USUALLY can operate with out any adjustments. Get the voltage, wirefeed and gas volume set according to the manual and you will be able to operate.

Good luck,

Google:
plug weld
3m seam sealer
weld through coating (try variations)

The weld through coatings are cold-galvanization sprays that prevent rust in overlapping joints.

At this point I recommend an auto body textbook to sort out conflicting information.