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Gents;
I have decided to let the local Vocational School welding shop TIG fill all the rivet holes used to hold the belly pan in place while the epoxy sets up.
Is there a softer metal available for the fill to promote ease in grinding/filing/sanding: e.g., brass?
V/r
Iverson
Rick, I assume that they will need to weld the rivet holes from the bottom (ie through the floor pan) ? If so, what material is the floor pan? If so you will need a material that is compatible with both the floor pan and the chassis tubes.
Thanks, Tom
Tom;
The pan has been removed, and the chassis stripped exposing the holes.
The chassis tubing is 4130 tube, heat number 37590 Pacific SMLS, condition N.
Factory brazing rod is Nickel Bronze 2mm Sifbronze 101.
V/r
Iverson
I'm a little confused as to what you are envisioning. How will they weld on it without destroying the epoxy?Quote:
Originally Posted by Rick Iverson
Or, are you envisioning that you remove the floor. Weld all the holes shut. And then re-install the floor (drilling new holes in the process)?
I TIG welded over quite a few rivet holes in my frame. It's slow, but rather easy to do. If done properly, there is very little (if any) grinding after. I would use a standard TIG steel filler like ER70S-2. If you want to be fancy, you can use ER312, which is a high chromium stainless filler. High strength, crack resistant, easy to weld and makes attractive looking and very corrosion resistant beads. Much more expensive than the ER70S-2, however.
Jon
Don't think about filling the holes.Quote:
Originally Posted by Rick Iverson
This is the best prescription to ruin a frame I can think of. The process of filling the holes will wrap the bottom of the frame to the point where you will not be able to attach a belly pan securely to the frame or if you grind the bottom flat you will remove enough metal to compromise the structure.
You have two options, maybe three. If your line of holes are down the center of the tube, you can add a second pattern by staggering the holes 1/4 to 3/8 inch either side of the center of the tube. If your holes are already staggered, place the new holes in between the existing holes.
The next option is to use over sized rivets or go up one size in rivets. Oversized rivets are an aircraft product. They are smaller than the next step up in rivet size.
You can use a rivet hole duplicator to get the holes aligned with the existing holes. The rivet duplicators are available from Wicks or Aircraft Spruce, as are the oversized rivets.
Why is it "the best prescription to ruin a frame I can think of."?
I can think of lots worse things to do to a frame, including leaving the holes in and drilling new holes that overlap and create stress risers that crack... Tig welding is pretty non-invasive as welding techniques go, and I have brazed up holes in the past. Ideally you do match the holes when you install the new floor, a PITA but not impossible, of course.
Brian
Quote:
Originally Posted by Brian
My recommendation comes from decades of building frames myself. I weld stuff all the time. I have mounted belly pans on hundreds of cars.
The welding process heats the metal up in a flat surface. You then add the filler metal. When every thing cools down you have a little mound where you had a hole. Do that several hundred times down a frame rail and you have a first class mess.
The existing holes will not weaken the frame if you get a good bond between the belly pan and the surface of the lower frame rails.
I think there are pros and cons to welding over and not welding over existing holes. When presented with the question, I decided to weld over as I thought that was preferable to leaving the holes.
If you have a modern inverter TIG machine with a pulse feature, and are pretty good with the torch (I'm not sure the guys at the vocational school fit the bill here), you can put remarkably little heat into the frame when patching over a hole.
I probably patched over 30 or so holes in my frame, and it was quite easy. Very sharp electrode, DC negative, 110 amps on the pedal, and with the pulse feature set to 100 Hz with 25% background amps 75% of the time. The pulser is key, as it really cuts down on the heat input. ER312 filler.
I never blew out a hole, and the powdercoat that was within 1.5 inches of the patch didn't blister or go soft - meaning the heat affected zone was quite small. I'll take a little residual stress rather than the hole.
YMMV.
Regards,
Jon
I am with Steve. You already have a perfectly good set of holes, most likely well placed in the chassis bottom. I would build a new pan, match the existing holes, then bond and rivet.
Best, Tom
I use the old pan as a template, carefully drilling holes at each end to register the pattern. I drill the new pan slightly undersize, align the thing up with clecos on the frame, and then drill to the oversize rivets. done two on the same car this way and no problems with either.