How Do I Shorten an Antique Truck Frame?

I have a 1941 WWII Dodge pickup truck. I found a perfect ambulance frame for it, identical but 7" longerin the center section. I have been told I can cut it at a 45 dgree angle and mig weld it back together. This would be done about center of theframe, between the axles. I want to keep it "original" so don't want to add gussets. It's built in two layers of steel, about 3/16" and 1/8". I don't think these old frames were hardened. Will this hold okay? Should I have a certified weldor do it?

Also, is there any way to replace the large factory rivets to replace cross a memeber? Again, I want to keep it as close to original as possible.

I would appreciate any expert advice,
Maurice

 

[MikeMilburn]

Not being an expert by any stretch this would be my approach.
Cut the frame at a 45 deg angle, as much as you don't want to I would definetly consider using a doubler (fishplate)if it's a single frame. If looks are a concern, can't you put it on the inside of the channel, this would work if it was a single frame.
You said yours is a double,if you can cut both frames so the cuts are not in line, you could probably do away with the doubler. It shouldn't be hard to cut the frames in a different spot as the rust accumulated between the rails should prevent any inadvertant damage to the rail you're not cutting.
As far as rivets go, if you can't find rivets with the appearance you want, how 'bout carriage bolts, not an ideal solution but....
If you're not used to welding, I would consider getting someone that knows what he's doing, after all, if the frame breaks, think of the consequences...Mike

 

[TheBlacksmith]

In theory, the weld should be stronger than the base material. In practice, this requires knowledge of the base material, and its metalurgy may not be as well controlled as today, selection of proper filler and considerable skill. Preheating the base metal may be required, as well as limiting the maximum temperature and/or slowly cooling, to prevent brittleness. Finally, as great as Mig is for sheet metal, a lot of the home/hobby machines don't have the power - they are limited to 1/4 or 5/16 inch thick, to do a great structural weld. I'd rather use SMAW (stick) for this. Mike may be right - see a professional for this. You can purchase rivet heading tools from blacksmithing suppliers (look on the internet), heat the appropriate steel grade up with an oxyacetylene torch and make new rivets. I'd practice on scrap before doing the frame.

Blacksmith

 

[evelrod]

All above are pretty much 'spot on' so far. MIG, TIG , stick, if it gets hot enough I can weld it. The man doing the welding is MORE important than the method. Over the years I have lengthened and shortened many frames and have had NO failures (knock wood) so far. Definately use some form of doubler (fish, flitch, fich---whatever) as it increases the strength of the connection . Use great care and proper heat treating ,pre and post, as these old frames are subject to embrittlement problems.

Blacksmith---I have even welded one section (MANY years ago) with gas and it worked ok, not great, but ok! Never brazed one--- A lot of tubing frames on race cars have been brazed together for about a hundred years, though.


Rod

 

[jstanczyk]

If you have access to TNN (The National Network) on cable tv, they have shows such as "Trucks" that do that sort of thing on Saturday mornings. They might even have a Q&A on their website.


75 & beautiful Thank you West Coast, look out East Coast because Chicago is ____________
today!!

 

Thanks for the help. Looks like a fishplate, heat treating and an experinced weldor.
Maurice