300D (W123) Weld repair of rusted chassis & floorpans - Page 5 - PeachParts Mercedes-Benz Forum

barry12345 · #61 11-29-2012, 11:20 PM

Here were rust is king nobody wants to really work on it. Fundementally you do it yourself or it does not get done.

Silber Adler · #62 11-29-2012, 11:28 PM

seeing those repairs makes me want to get a plasma cutter.

birkhoff · #63 11-30-2012, 12:20 AM

A zip wheel on a small die grinder, a set of left and right snips for the rough out and a conical stone on a 4 inch angle grinder to smooth and fine-tune the edges and corners is all the kit you need. Make a neat hole and the rest is easy. Fit the patch to the hole. You need the zip wheel to knock down the weld beads anyway. This will handle 99% of small patch work and you can get into really tight spots with it.

Very occasionally, for large sectioning of pre-made patch panels, for example, you trim the patch and cut the hole at the same time. That's a whole other deal where plasma may have its place, but you will have to have really tight fit up to ensure that the gap between the hole and the patch ends up being reasonable. Again, zip wheel does this almost automatically, at least on straight cuts.

What is most impressive about Graham's job (for me anyway) is the large amount of fabrication going into it. Its not the cutout and welding that takes time, and one can learn that relatively quickly. Fabrication and finishing is the real art and generally where the time and $$ end up going.

Quote:

Originally Posted by Silber Adler

seeing those repairs makes me want to get a plasma cutter.

Zacharias · #64 11-30-2012, 01:01 AM

Quote:

Originally Posted by barry12345

Here were rust is king nobody wants to really work on it. Fundementally you do it yourself or it does not get done.

That's about it. The shops that tackle involved work in these parts have a bad rep for greed. They get the car half done and then jack the price way above the original estimate. What choice do most people have then? If the owner says no or tries to argue, the half-done car is thrown outside, not even covered by a tarp, to rot. Yes I have seen it.

Always stories of the odd guy here and there who works out of his garage at home: takes the car from you in October, you get it back done in March for a decent price. Finding the actual person is like nailing Jello to a wall.

So far I have been lucky in tripping over an honest guy when I needed one. Over the long term I am going to have to learn how to weld....

Codifex Maximus · #65 11-30-2012, 01:29 AM

Quote:

Originally Posted by barry12345

I wish we lived closer together so I could spend part of a day with you showing all the advantages mig presents for amateurs like ourselves. I certainly by no stretch of the imagination am a proffessional welder.

It is an amazing type approach when working as intended. The beauty for amateurs like ourselves as well is that penatration is far easier to achieve in my opinion than other forms of welding. Warpage where important can also be better controlled. Brazing introduces the dissimular metal issue. Where you are filling over it make sure to apply a coat of short hair fibreglass body filler before using your normal body filler. It is waterproof where the normal filler is not. Stronger too as well.

I do not get the time as much anymore to get to a lot of things I enjoy doing. My practice is to almost use a coat of "glass bodyfiller" over repairs prior to the easier worked body fillers. Sometimes since I have very agressive finishing equipment I will make the better body filler most if not all of the repair over welded patch panels etc. It is much harder to sand until you get enough skill to only put about the right amount on. If you do not use this approach over brazed points you may get a bubble or expansion in normal fill after awhile coming up through your paint. Brazing is fairly strong but is still basically a very hard soldering method versus welding that is instead the fusion of metals.

If working in the suspension areas of more modern cars make sure to check if weld repairs are allowed. Some cars use high stress steel in those areas and your heat will remove the temper or designed hardness from the parent metal.

Right, I wouldn't dream of depending on a braze on a structural steel part. I also agree with the dissimilar metal issue. Tends to detract from the utility of brazing when the metals fight each other especially in the presence of a water containing medium. Good advice about the filler - was not aware of this issue.

Graham · #66 11-30-2012, 08:26 AM

Quote:

Originally Posted by Zacharias

You are fortunate to have him local. I would as a guesstimate say that around here what I see in those pics would cost upwards of $5k at any shop willing to do it (not many).

The fact that he posts such detailed pics for public view is really something.

You are right! I was fortunate to find this shop!

Last Chance has a location in a rural area with low overhead. His rates are low. The work you see in pics consumed 42 hrs, but total bill (incl tax) is half of your estimate. Not that far from Ottawa actually and because his communications are good, worth looking into for those up there with cars in need of rust repair or restoration.

Just about to go pick the car up.

Air&Road · #67 11-30-2012, 08:40 AM

Quote:

Originally Posted by barry12345

Very small rods as described are not common here. I had to special order a package of smaller rods every time I ran out at one time. . They are still far heavier than 1.6 mm I believe. I do agree that for the occassional use you could get by fairly well with very small rods. I just had a look. 3/32 7018 rods are the smallest I have for my stick welder on hand. This was the size I used as well but was less than happy with them for sheet metal. Even 1/16 would be a step up in ease of use my opinion. Even smaller than that if available. No sense buying a mig for just really sporatic use if you have a stick welder. I think I have a gentle touch but blew holes through thin metal with the 3/32 rods.

If you say reduce a rod from 1/8 to 1/16 you reduce the rods surface area by a signifigant factor of 3-4 times if I remember but not going to look it up at this time. Formula is diameter squared X 3.14 or pi if you wish for the surface area of circle Unless it is the radius squared. I do not use this formula often enough to be absolutly sure.

Just looked it up and it is radius squared. So a 1/8 rod has a surface area of .050 square inches and a 1/16 rod a surface area of only .014 sqaure inches. Oviously you can get by with a lot less heat appilication with the smaller rod. You still have to reach fusion temperature but far more localised so less blow through etc. I do not want to especially convert a 1.6 mm rod to imperial measure.

I personally have never tried small 7018 on sheet metal. It's hard enough to weld thin material with thin 6011 and the added strength doesn't seem to be necessary. You might want to try small 6011 and see if it's easier for you. Small 6011 is extremely easy to find in this neck of the woods.

I am a fan of 7018 for heavy material. It's a little harder to learn to weld with and requires good surface preparation, but I use it on almost anything heavy where I want lots of strength.

I know lots of guys who insist on using nothing but 6011 because they never do any surface prep. They weld over rust paint, or whatever is there. If you keep a few different grinders handy, it only takes a minute to clean something up so it will take 7018. I have added two more grinders to the cart since that picture. Keep them handy and use them. It will improve your welding the same as proper preparation will improve a paint job.

barry12345 · #68 11-30-2012, 10:04 AM

Once again just from my experience. Instead of attempting to basically form patch panels. Cutting the sections from a donar car for where they are needed on your project usually makes a lot better and hopefully faster repair. Since there are so many portable generators out there now. Even if there is no power near a donar vehicle you can cut your required patch panels off.

I have had one of the parts suppliers in our forum send me the lower portion of front fenders for example to weld in. Even though I have acess to metal stretchers and shrinkers and a brake this gives me a better fit and is much easier to finish up. Some profiles are very hard to get right when attempting to hand fabricate them.

Since I consider myself an amateur when doing body work I designed a very useful tool. This one may make someone break out laughing but it works. I was faced with a six foot section of 250c quarter panel that was sound but rippled from the car sliding backwards off a race track in germany I believe.

Got it back into reasonable shape first. Then I was faced with the issue of truing it up. Impossible with my limited skill level. At least I felt I could not pull it off with 18 inch sanding boards.

So I took some ash boards and ran them through a planer to reduce them to about 1/4-5/16 inch thickness. They are at least five feet long. Made a handle on each end. Purchased some really good belts for belt sanders. Opened them up and using contact cement glued them to the boards. Then called an aquaintance of mine to operate one end of the very long sanding boards. Worked as slick as I had hoped it would. The length of the board replacing the skill required.

My good friend who unfortunatly passed away was a very good body repair person. I seldom wanted to take advantage of him but when I needed information he was always there. He would have done many things I needed done on car bodies gratis.

Since I considered that a form of abuse to a friend I was more than happy just to use his information. When visiting later he asked me If I had changed the quarter out. When I told him what was done he laughed and wanted to see the sanding boards.

The point being if you know that you do not have the skill. Think about ways to circumvent that. It is truly amazing at times what you can pull off as a substitute.

Air&Road · #69 11-30-2012, 10:08 AM

barry,

You're definitely correct when it comes to exterior panels. It cuts down the filler work which not everyone is good at, myself included. For floor boards, inner fender panels, trunk floors and other places that don't show, IMHO, a patch cut out of an old discarded hood or something is the best approach.

barry12345 · #70 11-30-2012, 10:15 AM

Quote:

Originally Posted by Air&Road

barry,

You're definitely correct when it comes to exterior panels. It cuts down the filler work which not everyone is good at, myself included. For floor boards, inner fender panels, trunk floors and other places that don't show, IMHO, a patch cut out of an old discarded hood or something is the best approach.

Old oil furnace enclosures have proved both easily available and a cheap and a decent gauge of metal for patching cars. Some paint has to be ground off usually. Or I use my sandblaster to clean it down in the areas my welds will be present. That seems a pretty tough finish on it locally.

Stretch · #71 11-30-2012, 10:42 AM

Generally speaking I've been very impressed with MMA. It seems to be ideal for welding outside - where a shielded gas method would suffer from wind (and not just from me!) - and on the whole cleanliness isn't that much of an issue. Using a heat sink is a real plus on thin metal. The comments about slag made above though (by Larry and Barry - hee hee you two should be a double act!) are very true; you need a whole lot more heat to re-melt slag than you do to melt metal; so clean it off before you start welding over tacks.

One day I plan to upgrade to an oxy kit. I think it is far far more versatile than any other method of welding. I've already got an AXA X11 torch kit; I just need the rest of the stuff so I can start learning a real art.

I must say, however, I'll still be keeping my hand in with the MMA - it seems to help with my seasonal adjustment disorder - it is the best light therapy I've found yet...

Air&Road · #72 11-30-2012, 12:07 PM

Yes Army, the first welding of any sort that I ever did about 50 years ago was using an oxacetylene torch and bailing wire. I got pretty good at it LONG before I could carry a decent bead with a stick.

Because of my brazing abilities, I've always wanted to try TIG welding. I can't justify buying the equipment, but maybe someday, somewhere I'll get the chance.

I currently have an oxyacetylene rig, but never use it for anything but cutting or heating.

Stretch · #73 11-30-2012, 01:41 PM

Quote:

Originally Posted by Air&Road

Yes Army, the first welding of any sort that I ever did about 50 years ago was using an oxacetylene torch and bailing wire. I got pretty good at it LONG before I could carry a decent bead with a stick.

Because of my brazing abilities, I've always wanted to try TIG welding. I can't justify buying the equipment, but maybe someday, somewhere I'll get the chance.

I currently have an oxyacetylene rig, but never use it for anything but cutting or heating.

If you look at the cost of MIG welders (that won't be give you any trouble) they are just as expensive as TIG machines now.

I picked up a really cheap TIG amplifier on ebay (German) - brand new one - that does really well just with the MMA settings. The "anti-stick" functionality means you reduce the chance of just buzzing and swearing at it. I looked at the cost of a decent argon valve and some gas; but at the moment I reckon I'll be spending my money on an oxy set up.

There's a chap called David Gardenier Our Online Shop who has made a really nice DVD (for a reasonable price) showing some impressive gas welding skills. That's one of the reasons why I want a gas set up. I wanna do that.

Here's a youtube link showing what he gets up to

http://www.youtube.com/watch?v=IGElSHzm0q8

(welding starts at 2:18)

Graham · #74 03-27-2013, 10:56 AM

Quote:

Originally Posted by Graham

Update.
Quite a bit of the rust repair welding has been done. There are pictures on shop's site:

1985 Mercedes 300D - Last Chance Auto Restore

Comments welcomed!

I wanted to correct the link in the above post, but it seems it is not possible to edit old posts?

Anyway, this is the current link:

1985 Mercedes 300D - Last Chance Auto Restore

Stretch · #75 03-27-2013, 11:00 AM

Is it all done then?

Have you got it back yet?

I must say that I'm not looking forward to this tricky bit to fix =>