400 rivets & sheet metal - PeachParts Mercedes-Benz Forum

MunichTaxi · #1 09-24-2007, 09:07 PM

Rust repair= 40+ hours

First time I did a job like this. It became easier after I started using paper templates. I fiber-glassed all sheet metal pieces and seams. messy O/H job
All 4 corners needed treatment, about 12 different-shaped 20 gauge metal pieces: cut, bent and riveted. The largest pieces were the 2 front ends of the rockers, 18" & 26" long. The jacking supports are 'covered', so I will have to carry a different jack in the trunk.

I'll probly use truck bed liner next, with some POR-15 for other areas.

I AM GLAD THIS IS FINALLY FINISHED!

t walgamuth · #2 09-24-2007, 11:20 PM

Did you take pictures?

Sounds like you did a yeoman's job.

Tom W

cth350 · #3 09-25-2007, 06:10 PM

rivets? The rockers are structural and rivets won't serve, will they? On an aircraft, rivets hold down a stressed skin on a frame. The design is rather different.

Is there a mechanical engineer in the house?

-CTH

t walgamuth · #4 09-25-2007, 07:41 PM

Rivets hold large bridges together. He also mentioned epoxy so the combination of epoxy and rivits should be pretty good if done correctly.

Tom W

MunichTaxi · #5 09-25-2007, 11:38 PM

the rockers are structural

Never thought of that. Fortunatly, only short sections in front were replaced.

I tried MIG welding, but the metal is too thin. The original rocker panels were spot welded every 2", so it wasn't a continuous weld, anyhow.

Coating the rocker panels with Truck bed liner should hide most irregularites.

alabbasi · #6 09-26-2007, 01:25 AM

MunichTaxi, your style in unorthodox... but if it keeps one of these old cars on the road, then more power to you.

cth350 · #7 09-26-2007, 03:28 PM

I was just walking through an inner passage of my building (50 story sky scraper in manhattan) and was admiring the 2" rivets holding the beams together. The difference there is nature of the materials, the seam and the load.

The rockers, especially in the corners will be subject to some flexing that you won't see where two I beams are joined (I think).

That it's not the whole rocker being done likely means it's a non-issue. Though do react to any cracks you see in the filler material that covers the work.

-CTH

Dee8go · #8 09-26-2007, 03:39 PM

Bridges and buildings flex too, don't they? I'm pretty sure they do.

t walgamuth · #9 09-26-2007, 10:24 PM

Absolutely.

My late uncle, the Manufacturing engineer, used to say that according to his professor at Purdue, if you drop a feather on an anvil it will deflect. It would be a little tough to measure but it will deflect.

In my experience, I once was in a 20 story steel framed building when a storm knocked out the power. Folks started evacuating by the fire stair because the power was out and the elevator did not work. The radio was predicting a tornado or some such thing.

I headed out my office which was on an intermediate floor. As I neared the fire stair the sound was like a locomotive....folks stomping down the stair like a herd of buffalo. I thought about it and decided it would be pretty easy to get trampled if some folks happened to lose their footing, so I went back to my office and sat under a desk as far away from the glass windows as I could get.

While I was sitting there with no other ambient noise from AC or anything and a heavy wind outside I could hear the steel structure creaking pretty loudly. At first I got kindof panicy but I decided it must be normal and waited til the thundering stopped in the stairwell and sauntered out to my car and went home.

Oh yeah, a building will deflect.

Try driving with your fingers resting on the crack between the door and roof and go over a big dip in the road....you will feel the crack opening change width as the car flexes.

Tom W

Tom W

Dee8go · #10 09-26-2007, 10:46 PM

Ever looked out the window of an airplane at the wing tips? They go up and down all the time.

Stoney · #11 09-26-2007, 10:51 PM

All buildings are designed to tolerate and absorb stress and deflection is a form of release of the built up tension.

I am presently 37 stories into a 45 storyhigh rise framed entirely of high strength concrete. There are 60 tons of rebar per floor (columns, shear walls and slab) wrapped in 12,000 PSI concrete (180 Cubic Yards per floor @ 160 lbs per cubic foot).

Yet the superstructure still moves.

I've been on top of the Empire State, outside the 102nd floor level and in the Chrysler building at the very top (where there is only 1 triangular window per side) and you can feel them move up to 6 inches or more on a very windy day.

I have sat and watched my boss, Prof. Ysrael Seinuk of Cooper Union and one of the most respected Structural Engineers in the business, explain it to his students. Telling them that a building or bridge is a living breathing thing and the forces and tensions contained within must be recognised and respected and allowed to be released in a controlled manner. This understanding is the difference between chaos and engineering.

MunichTaxi · #12 09-26-2007, 10:56 PM

I work in the WSDOT Bridge Preservation offife. I used to inspect bridges. When a truck started at B.O.B., the vibration and 'ripple' in the deck could be felt at the E.O.B. easily on a Steel Truss. We have a Tied Arch bridge over the Toutle River (below Mt. Saint Helens) that has measured up to 3" of deflection at mid-span.

P.S. I maintain Washington's Steel Bridge Fatique List. The longest crack in a Primary member was 68". That Bridge was removed.
The longest crack in a Secondary member was 14", and repaired with a 'Sister' Plate. An effective method to stop the progression of a crack is to drill a hole at the end, and torque a bolt. The radius of the hole usually stops any further crack progression.

cth350 · #13 09-27-2007, 07:36 AM

One of metal's great virtues is its ability to flex. However, there's a difference between the joint flexing and the structure as a whole flexing. The Tacoma Narrow Bridge was a wonderful example of how much flexing is possible and what happens when it it's a bit too much.

I'm by no stretch of the imagination a structural engineer. But since you are, you have an idea of what I'm talking about and what to look for. Just keep your eyes open and let us know how it ages.

Thx -CTH

Jordan G · #14 09-27-2007, 08:26 AM

I am also a structural engineer....mostly for small bridges....and I totally agree, everything moves, even just from temperature changes.

But to stay on point....POP rivets are totally different than rivets found in high strength structural applications (and typically not used anymore....bolts or welds are much more common for new construction). Granted, the loads in his rocker panel are magnitudes different...but it would be interesting to know how much shear a little rivet can handle. Never really looked before. I suppose it's just a function of how many he used per panel.

I'm curious to see the how repairs look (as an owner of a rusting W123 - not an engineer). Have any pictures?

Blue 72 250 · #15 09-27-2007, 09:10 AM

Quote:

Originally Posted by Jordan G

...but it would be interesting to know how much shear a little rivet can handle. Never really looked before. I suppose it's just a function of how many he used per panel.

If you are talking the aluminium - not much. They do make stainless steel that are much stronger hold.

I saw this show on the iron workers that worked with the hot rivets. What a cool art that was. There is film of them tossing a bright red rivet 3+ stories from the forge to be caught in a metal can.... Talent

Blue