I know there are a ton of posts kicking around regarding stepping frames, but there's been nothing that I can see that outlines why one method would be better than another. I have a model A frame that has a really poorly done kickup in the rear - like 8". I don't think I need that much, and so I've cut out the section and intend to re-do it. I think I only need about 4" or so of kick, from what I can see, mocking parts up. I'm going to channel the body the height of the frame rails, and I like the way Jaypee built his RPU. He mentioned that he only used 4" of "z". I guess my question is: which method do y'all prefer from the 2 choices in the image below? Just overlapping the tubing, or actually cutting on 22.5 deg and making a 45 deg addl piece that fits in?
Speaking as an experienced rod builder who has done it both ways, here's the scoop-----Either way will work. If you only want to Z the frame the depth of the framerail, then the method where you lay one section directly over the other and weld them together will be adequate. (keep in mind that the overlap should be at least twice as long as the depth of the frame rail) If you want to Z the frame any deeper than the depth of the frame rail, then you are pretty well forced to use a third peice to make it work. Be sure that you grind a bevel on the end of all the sections being joined, so as to get full weld penetration, Use a welder that has a high enough amperage range to thoroughly fuse the weld metal and the parent metal, and measure twice, cut once. The method using the third peice is actually stronger then the method of laying one peice over top of the other.
So if I'm using 2x3 tubing, I should overlap the joint 6" or more? What's the reason for that? I've seen (not that it's right) people overlap it basically the height of the rail and cap the open ends of the cuts so that it looks like a 45deg "jog" in the tubing. Is that bad to do? No kidding? What's the reason for that - do you know? I would think that you've got 2 potential points of failure with smaller weld area rather than one large weld area. Interesting. I'm not disputing you - just wondering. I find this stuff fascinating.
whatever get the desired results. by pie cutting to create the Z the frame will be shorter equal to the sum of the two sections measured at the flange. the angle cut and lapped Z can leave the frame length unaltered but you are limited to the depth of the frame for the step depth using an added section for the angled portion can can give a deeper step and still leave the frame the same length on my current ride I chose to pie cut a relatively shallow step resulting in moving the rear cross member forward four inches, I also used a spring behind setup to move the axle centerline even further forward. here's a link to it: http://www.jalopyjournal.com/forum/showthread.php?t=14629&highlight=pinch+step
I liked the step up a Hamb'er did a tech on by adding an "S" to the frame. He flame/plasma cut "S" shaped piecs, it looked clean and almost stock.
I did the add in method... I chose this method because I figured I could weld all the way arround it. Also it did not change my wheel base. This is the Front "Z" by the way Here's a few pics...
The deal with overlapping the 2 peices of framerail by double the depth of the frame is basically the "effective weld area". The greater the overlap, the more length of weld area there will be. The reason this type of joint is not as strong as the full Z is that you are only getting weld onto one face of each section of frame. With a full Z you are applying weld around the total perimeter of both frame sections. I am going to attempt to insert 2 images here. The blue frame is a deeply z'd frame I built for a 27 roadster I built about 10 years ago. The black frame is that of my current ride, a 31 roadster pickup with the rear of the frame only z'd the depth of the frame.---As I said in the earlier post, either method is acceptable.
The Jalopy Journal
