OK guys what say you is the best way to stretch or lengthen a frame? Butt it together, fish plate it, overlap one another or what? I am opened to all suggestions. Thanks for your opinions and yes I know opinions are like A$$HOLES, everybody has one.... Just want to make sure it is strong when I'm done....
I have done it multiple ways, but the way that has felt the strongest was to slip some box tubing that barely fits in , and then rosette weld a few holes and fishplate it. I hope this makes sense, but I don't think it does...
It depends on the frame. Some Chev frames telescope together, you can grind off a weld, slip them together or apart, and lengthen or shorten several inches with 1 weld on each side. A butt weld can be quite strong especially if you make the cut at an angle for a longer weld, and don't grind it down too much. But some boxing or reinforcement is a good idea. I have seen old chassis from the twenties and thirties that were bolted together. The frame was cut in 2, pulled apart, and a piece of suitable steel channel overlapped a foot and a half or 2 feet at each end and bolted together with multiple bolts. This was a factory or coach built stretch to build a hearse, limousine or similar long wheelbase car. I was told at that time, a welded frame was not considered strong enough. You have to use your own judgement but remember when you lengthen a frame the rails will be under more stress than before due to the law of leverage so it pays to make sure it is plenty strong.
Thanks Rusty, this frame is not the telescope type so I would have to do the angle cut like you suggested. Longer weld does sound better along with the boxing for reinforcement.....
If it were mine, I would "Z" cut it, add filler pieces, then back it up with a long fishplate rosette welded and fillet welded. May be overkill, but strong makes for good sleep.
You do not state how much you want to lengthen the frame or for what purpose. I have also seen pictures of cars converted to stretch limos in the thirties and forties. The frame was lengthened 4 feet or more. In that case they bolted on a length of channel iron then added an extra reinforcement underneath. Sometimes this took the form of a strut or a series of struts with a rod in a long flat V shape stretching from front to back. Or in some cases they added a piece of channel that was 2 inches deeper than the stock frame. On new built limousines today they add as much reinforcement to the body particularly the rocker panel area as they do to the frame.
Thanks VoodooTwin but I'm not sure I follow you on the "Z" cut. Could you explain that a bit please? Thanks....
Thanks Rusty, this is a 1947 Ford COE frame that I want to lengthen by about 2 feet. I want the engine in back of the cab and the stock frame would be to short. I know a lot of guys use late model frames and I am doing that on another one I am building. I just wanted to see if I could use the stock frame and stretch it and change out the front end....
Cut the frame vertically from the top flange down to the midpoint, then horizontally (parallel with the frame rail), then vertically down through the bottom flange. For a 2 foot stretch, I'd probably make the horizontal cut at least 12" or so, to maximize the weld lengths.
The best way is to have a competent welder weld the joint. Angle cuts and step joints are for guys that don't understand welding done by a professional. A properly executed weld will be just as strong as the original metal and does not need special joints to make them safe. Slanted and steped joints are for gluing wood where you need a lot surface area for the glue. Welds should not need scabs to reinforce them. To pass a certified welding test The weld is machined flat to the original surface of the parent metal and bent into a complete U shape with a hydraulic press with out it opening up or showing up at all. If a crack shows up you will not pass. I could have gotten certified but I did not want to spend 8 hrs a day under a shield.
X2 and i was certified for many years and spent many hours a day under a shield in different discusting places. Fishplates is for those that can not weld
COE truck is usually a heavy truck. Have some channel bent to fit inside your frame. Figure your overlap at about a foot. You can bolt it together, as it was done in the old days (tradtional), or weld it up and run a boxing plate past each weld. Second option would be the best by todays standards, but non- traditional. Big trucks were usually bolted together in the 50's, when changing frame length.
Here's GM's recommended procedures.......... http://www.gmupfitter.com/publicat/chassis.pdf HTH James
One thing to remember is that the lengthened part of the frame, if done in the middle must be stronger than the exising frame becauce of the forces mutliply with the length. Quoted from another post, "The best way is to have a competent welder weld the joint. Angle cuts and step joints are for guys that don't understand welding done by a professional." Good information, but you forget this is not a site that is formed of competent welders.
If the frame is made of straight rails, which most of them were back then, you can simply weld a piece of channel on the back of the frame and redrill the mounting holes for the rear springs etc. Frames were pretty standardized and did not change for many years. There is a good chance you can find a junkyard truck or bus frame made of the same steel, same size and thickness, and cut off what you need. That way you only have one joint to worry about and the frame is stronger. Not sure what you are driving at, do you want to move the front axle forward and move the engine back behind the cab????
Don't put anything inside the frame, it will be strong but will cause fatigue at the ends of where ever the piece thats inside finishes, haut stagger the welds as mentioned above and use a tapered fish plate do there's no edge for it to flex off of.
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