Hot Rods ?on Stretching A Frame

want to stretch my A frame as I have purchased 2 repop roadster doors and 6" extended quarters (brookville) for my RPU. pics & info will explain what i plan to do. looking for a second (third, fourth) set of eyes to double check me, or tell me another route before i cut my good frame.

plan is to cut the good frame as shown on the junker in grey paint, extend by adding the 6" piece taken from junker frame, welding them in in a straight line to the original. this will add more taper at the front, but I am installing a WelderSeries flat crossmember anyway.
all input is appreciated. thanks, mike

 

I say go for it, I like your offset and that should add some strength while making it harder to Crack along the Weld.

Only thing I would add is a small diamond plate over the Weld added to the inside of the rail. This would add plenty of strength and should be stronger than the rest of the frame. Even if your going to box the frame I'd still add the "fish" plate to the inside Weld.

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I've done a couple, but I prefer the offset to be on the sides of the frame rails, not top and bottom. I see no way the top/bottom offset adds to the strength once it's welded back together. But a side offset would be stronger than a straight cut down the sides. I start with a straight cut through the whole frame, and then remove part of the frame on the top, and from the bottom on the other side. It's easier, and quicker than trying to make the offset cuts, and you're going to be splicing it anyway, so making life simpler only cost a few more inches of donor material to the filler.
Once I've done the offset on the sides, and pieced in my donor material, I plate the inside with a plate that covers the joints, and I plug weld and perimeter weld the plates to add strength.

 

Looks too late now, but if you have 2 frames, I would have looked at using the front of one spliced to the rear of the other, in order to only have one joint.

 

Yeah, two splices instead of four!

 

If it is a roadster pu, why stretch the frame…just mount the body back from the stock location.

 

I don't think he is looking for engine room, I think he is trying to accommodate the 6" stretch in the body. Another option is to mount body in the normal spot on a stock length frame, and take 6" out of the box.

 

Scotty is correct
using two frames: the A frames are tapered, they will not match up if you cut one 6" longer
Mounting the body in the stock location: with 6" extended quarters that leaves the stock box and stock rear fender mount centerline 6" beyond the rear axle centerline.
i have thought of doing this, see sketch

 

A Model A frame has a double-taper.

When I have been called on to stretch them, I do it in the rear taper, right at the transition between the two tapers. So cut off the rear tapered section, and add on to the ends.

In order to make things work, make slices in the rail just ahead of the brace by the rear crossmember. One saw blade width, followed by another 1-inch away, as needed, to move (bend) the frame rail back to to meet the front half.

Fish-plate the inside, box it, weld it all up.



This way the the front half of the frame remains exactly the same.

 

so, you are saying to cut the frame in two at the point the rear taper starts, add my 6" extension to the front half, slice thru the upper & lower part (top & bottom of the "C") at rear crossmember, pull the wider rails together near the center and weld. that seems easy enough. thank you.

 

Mount cab normal stretch quarters 6”, then shorten front of box 6”!

 

Are you using fenders? Using a stock bed? Stock length hood? If you want all your stretch in the body area only., I think you should do the frame stretch behind the center crossmember. Might be a good opportunity to do a small 2" Z at the same time. Cut the extra frame the length of your stretch, plus two inches, about 6 inches in front of the rear crossmember. Lay the new rear section on top of the old section with that two inch overlap (plus the lengthening). Box the inside.

You will need to fudge the new rear kick a little to make it level because the bottom of the frame is tapered, but that is small potatoes.

I don't think the outward taper will be much different at all. Maybe a quarter inch at the mounting point, and you can probably make those match up with some straight taupe and clamps. File the rearmost body mount hole to match.

All this 2" Z section will protrude up in the mounting area of the bed. Nobody will be the wiser from the outside. Will need to trim the bed cross subrails a little, but it's no hill for a climber.

 

i like Gimpys plan, gonna keep the bed original size, or make one a little longer

 

I'd add the extensions to the back half. The relief cuts by the rear crossmember will facilitate pulling the newly extended rear rails into place. And yes, just cut the short-legs of the c-channel, leaving the long side intact. Doing a few relief cuts allows the bend to be distributed over a gentle curve, and will be hard to notice, once sanded smooth.

If you attach them to the front rails, at, or behind the where the two tapers meet, you will likely end up with three tapers. You want just two, like the factory did, just with a slightly different taper in the rear.

 

You'd be better off using an "AA" frame as it is easier to shorten than lengthen.

 

Here is a 28-29 roadster pu with the body moved back to make room for the engine.
You could lengthen your quarters and shorten the front of the box, to make room for the longer quarters…without having to lengthen your frame

 

@A ***** snuck in while I was typing. But;
I'm with stock wheel base, shorten the box crowd. Look back at the '60s mags, more than few '29 roadster PU's with the body moved back for Caddy & Olds mills. Hemi's too.
Full fender Model A's look kinda goofy with an extended wheelbase.
Best one I saw had the stretch split between the doors and quarters, to me the longer Brookville quarters don't seem to match well with stock length doors.

 

Do you have a ***le that matches that rusty frame ? If not start with new metal. I'm sure one of the frame builders that build model A frames will build you frame rails the way you want

 

the rusty frame is my extension donor. i have a nice frame to use on the build. i don't want to shorten the box, in fact i have some bed sides made for another project that i will probably use to make a longer bed. i am using what i already have and will lay out the plan on paper as Gimpy explained before doing any cutting. if anyone has pics of what they did please post. and thanks to all who responded so far.

 

Here's a hint: center punch your frame at a convenient distance (usually 1") on either side of your cut lines. When you are lining up your splices, use the center punch marks to keep it even side to side (desired stretch + 2") .

I used to stretch/shorten a lot of big trucks and always used this way to keep everything right.

 

If I'm understanding this correctly, it would seem that no matter how you cut the two frames there will be some mismatch when you rejoin them. I would simply make the cut like you planned.......maybe a little longer than what you show in your picture. Then when you cut it, don't cut them exactly the same. Leave one of them with a little additional metal on it. Put the first cut off/stepped frame rail in place and then heat the second one so you can adjust it to fit the top or bottom edge. Might even have to make a small slice horizontally in the frame to allow the movement for alignment. Once you have it tacked, scribe a line on the excess/overlap and use a thin cut-off wheel to remove the excess. Then remove the tack welds and it should be a smooth transition when you slip it together and weld it all up. A flat plate on the inside of the frame to back up the splice with some rosette welds, and then box the whole frame.
If I didn't explain well, the basic idea is to make a longer cut, and heat the frame so you can pry it till the edge aligns where you plan to weld it. By leaving a little excess metal on one rail, you can trim it to an exact fit with gap to fill.

 

Add extended quarters…move stock box back to fit…move rear fenders forward on box to mount to splash aprons and running boards.

 

Cutting the donor frame to accommodate for the mismatch is not a tough task either. Simply cut the good frame and use the donor to back half the front half. The use a pie cut on the side to gradually taper the frame down to fit the same. Once it's fitted and welded you can weld up the pie cut on the rear half and plate/box it all.

 

I don't like the type of cut you plan to use. IMO those corners where I've added the arrows will leave leave stress points that will be prone to cracking. I'd just make an angled cut such as the blue line to eliminate those stress points. Add fish plate and box and you'd be good to go.

 

What you will end up with is a welded connection. Maybe start there. Over welding is as bad as under welding but...todays weld metal far exceeds the material strength of that old frame so frankly, I'm not that concerned if it at least welded half *** properly.
More weld length equates to greater heat input. That leads to a greater risk of warpage and distortion. Measure the inches in how you decide to mark and cut the frame. Me, I'd cut 90 degrees. Not because it's easier but because it's smarter, less to screw up.
For starters it's going to be a **** joint. But will that be a single V groove prep or will it be a double V? What sequence for welding will be followed?
As for fish plating, boxing or crossmembering the location...I say this. Most car frames don't break beause they flex, twist and rarely are over loaded. Truck frames however are something different. Looking at your pictures of the frame, you stiffin to much and the flex is lost, transfering stress to a new focal point.


It's traditional. This book was copyright 1931.






Maybe just step back and think about it? Where you're doing the splicing, what's close by for crossmembers, loading that may be applied, and with the kiss principle, best of luck.

 

blues4u, i think you're correct and i will use the angled cut as you have shown. i havn't sat at the drafting table yet to lay out Gimpys plan but will post the pics when i do.
noelc, i have seen the plating technique before as shown in the very first drawing in your welding book, and i will NOT weld the plate solid around the ends

 

Mr.Chevrolet, I don't see where it shows to weld the ends? All images say, do not weld there?

 

thats right, you DO NOT weld the ends. lots of guys do. i first saw this here on the HAMB when someone had pics of a very old book on welding. they stressed weld the length, but not the ends

 

Z cuts are very strong, because they give more length to the weld, plus multiple angles. I've welded front axles together after narrowing using Z cuts, and they've held just fine. The longer the offset on a Z cut weld, the more surface and strength it has. The corners aren't a issue unless your welds didn't penetrate, and you didn't plate over the backside.

 

Kudos to 1971BB427 as he said in post 23 what I was trying to say in post 21......only he did it better.

Mr. Chevrolet
There are lots of ways to do this, and while angling the cuts provides more welding area, it also makes it much more difficult to get your length and fit between the parts correct. Much easier to end up with gaps. As far as not welding the ends/corners, of backing plates, how can you not weld them? They will be a collection point for moisture and rust......especially if you box the other side of the rail. If you box the rail its going to be a lot stronger than it ever was before. Again, its difficult to make angular cuts and have everything line up perfectly in a joint...and get frame length correct ........on two different frame rails with an angular cut. If you are worried that the corner where the cuts meet may be a stress point, then drill a small hole at that juncture before you make the cuts. Then it gets welded solid when you weld the cuts. Also remember that you can run a weld bead on both sides of the frame rail along the cuts as the inner one will be hidden by the boxing anyway...... or a small flat plate on the inside. Lots of ways to make it strong.