Is there a rule of thumb for the proper way to lengthen/splice a frame?

I'm looking at lengthening a frame approximately 2 ft. The frame is your standard C type frame of about 0.20" thick metal.

I know vert welds are a no-no.

My "plan" is to cut a 45 degree cut and weld in the metal I need. Should the 45 degree be angled a certain way(ie top of the 45 toward the front of the rig)

I was thinking of using some 0.25" thick flat bar to make the splice on the inside of the C(approximately 3.5" tall and 1.75" wide inside) because I haven't found any tubing with the right dimentions:( I intend to have about 1ft of the flat bar inside the frame away from the splice.

Strength is obviously IMPORTANT:D

Thanks for any input,
John

What we do when cutting the frames of our lowboy tilt trailers is to cut (we cut a notch to make the back angled) , then reweld the section (inside and out) and then cut a diamond shapped gusset to cover the original joint area so the tips of the diamond extend 5 or 6" beyond the original cut, this provides alot of surface to weld to and strengthens the joint considerably - I would also box the frame for 8 - 10" on the inside overlaping the joint with a single plate to really make it bomb-proof, just my 2ct's

Matt http://home.off-road.com/~wanderingwillys/xjpics/eek13.gif

Matt,
That describes shortening very well... but my concern is with adding in a 2 foot section to the frame and what type(square tube, flat bar, etc) of metal to use:(

Any recommendations from the weekday day crew? :p

Thanks in advance,
John

International Travellers came with a lengthen Scout II frame from the factory and they ran a larger diameter square tube over the cut section. The lengthening tube was about 3 feet long for a 18 inch gap. The welded the tubing all the way around. If I recall the ends were just cut square.

FJ45 Long wheelbase pickups have a factory lengthened frame, and use a 12" section of frame rail with 45* cuts added and welded. then there is a ~3/16" c-channel about 24" also with 45* ends(looks like it was made on a big metal brake) clamshelled over the outside with a flat plate on the inner side of the framerail...

I used to work on limos and almost all of the ones I saw used a fishmouth style cut in the side fo the C-channel and then the added material was rectangular tube that snugly fit inside the channel. Some had gusset plates over the splice some did not, it depended on the manufacutre.

Sorry but I couldn;t find any pics of one.