The Stovebolt Site Forums The Parking Lot Big Bolts Making mods to a '46 frame questions

Howdy All --- Looks like I need to relocate a major frame crossmember on my 1-1/2 ton and wanted to poll some opinions. I have always been told to keep welding to a minimum on these older frames due to their metallurgy & design. With the need for a new main crossmember I have not come up with a viable alternative to attach it so I wanted to hear from some others hopefully more knowledgeable in this area.

My frame is already missing the front engine mount crossmember so I really need to make this replacement strong & secure. Hot bucked rivets are out of the question given my toolbox and skills, so I am looking at partially boxing the section in question via a welded plate attached to the upper & lower rails, then adding the new crossmember with large, grade 8 bolts to that plate. The crossmember itself will be 2" square x 1/8" thick tube in a slight arch to clear the driveshaft and the plates probably 1/4" plate.

Any thoughts? Warnings? Experience from you "serious" chassis builders?

Thanks in advance.

I'd be concerned about missing the front engine mount crossmember. Does the radiator also bolt to that, and does it help tie the frame together at the front of the front springs?

Have you considered installing any new crossmember in similar fashon/design to the originals? Skip the welding and use flanged head grade 8 frame bolts where you can instead of the rivets.

Grigg

Howdy Grigg --- the front member and the brace that carries the rad are both in place but apparently the one under the engine got whacked out some time ago. The center (3rd from the front) crossmember is the one I have to relocate in order to accommodate the tranny & park brake.

I looked into fabbing a "C" channel that would fit over and bolt onto the frame for the crossmember to attach to pretty much as you described but frankly, drilling all those holes had me as concerned as welding. Hot buck rivets "fill" any hole they are in by compression and almost become part of the frame, but no matter how precisely you drill, bolts will always have some slop. Which I took to be a potentially bad thing, especially smack in the middle of the flexing moment. Plus...getting a drill into some of those spots is a monumental bear with the body on...and it ain't coming off.

On the other side, the story I got (from an old school rodder) was that the pre-war frames were designed to flex...a lot...and welding could lead to fracturing unless properly annealed with a lot of pre & post welding heating and slow cooling. Of course I have also talked to other builders who don't hesitate to weld all over them and even fully box them using mig welders(?).

Just trying to achieve some balance that won't jeopardize the remaining integrity of the frame.

Can you slide the existing crossmember back a few inches, perhaps even reuse some of the rivet holes.

Some pictures would help further the discussion.

In my opinion if the frame wasn't welded when new then do all you can to avoid welding on it now.
Welding may be the easy way out but fully understanding the stresses and compromises involved is above my pay grade. Therefore I'll trust the engineers that designed that frame and so many after it, general rule is don't weld on a riveted or bolted frame, I'm sure they have good reasons.

I have welded on frames before though... To repair them where no other option sort of replacement existed. One was a 1928 Hudson car that some time long long ago was wrecked and two frames pieced together front to back but welded very poorly. They even laid an old carriage bolt in the bottom flange to fill a gap and welded right over top of it. That one I cut out the bad/questionable areas and slipped new pieces of frame in with proper clean welds. When done it looked as if nothing ever happened. Another was a 60's Chevy truck someone had cut and welded on the bottom flange of the frame just behind the front crossmember, probably trying to fit some exhaust. This modification caused it to crack and it traveled well up the web of the frame and in a short time the frame would have folded up, would have been the end of the truck.

What you're looking at I think could still be done without welding and may avoid some of the risk that welding brings to a frame. Not to say that drilling and bolting doesn't bring it's own risk but they seem easier to understand.

Welding doesn't hurt the metal because it was very mild steel. However, welds don't flex. Rivets and flange bolts do. These are the type flange bolts we use.
http://www.imperialsupplies.com/item/0191980?service=/browse/

I have been making frame modifications on heavy trucks for many years and this all I use. I use 3/4 and 5/8, but 3/8 or 1/2 is big enough for a 2 ton.

Thanks guys --- After laying underneath it for a few hours and staring at it today...I may have a plan. Everything is tight but my sheetmetal shop should be able to make a couple of "C" channel inserts that I can slide into the frame and bolt up that will carry the new crossmember. And Roger the flange bolts. I use them profusely throughout my build.