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Tapered frame rails


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I've been working on a frame for chuckt's rebuild. In the pdf on building a frame, I covered tapering the front of the frame rails. I thought this would be a good time to show how I do this with pictures.

This frame is made from 2"X3", 3/16" wall tubing at Chucks request. I prefer to use 1-1/2"X 3" tubing, but the proceedure would be the same.

The first picture is the layout of the taper. The front cross member is a piece of 2"X 5/32" wall dom tube. There will be a wrap of 1/8" material around the crossmember at the ends of the side rails. Starting with a 3" tube, subtracting 2-1/4", will leave us with a 3/4" to 0" pie slice 25" down the tube. This is set at 1" from the end of the tube or half the dia. of the front crossmember.

What typically happens when you make a cut like this is the tube will have a curve to it when you're done cutting it. This is due to the stress in the metal from the tube forming process. Any heat build up will release this stress causing the warpage. When you layout the tapers, leave a couple of spaces in the cuts. This will help keep the warpage to a minimum. This is shown as the area between the 2 red marks on the wedge. I cut both sides of the tube, leaving these cuts last. You will still see some warpage, but it will be less.

The secnd picture shows the cut finished. It takes a little time, but the results make it worth while.

In the third picture, I clamp the ends together and then true up the cuts by using a 1/16" cutoff wheel. This will also set up a 1/16" gap for welding.
After grinding a bevel on the edges of the seam, lay the 2 rails back to back and clamp them together. This should eliminate any distortion caused by the cuts.

Tack the seam every 6". Keep these tacks light so as not to close up the gap. A piece of your welding wire in the gap will help hold it. Tack both sides. Now you're ready to start welding. Lay out marks every 1-1/2" along the seam and number them 1, 2, 3, and 4, on both sides. Weld the #1's first skipping from one side to the other.When you're done with the #1's, wait 'til you can hold the tube with your bare hand before going on to the #2's, then the #3's and finially the #4's. At this point, your tubes should look like the second picture.

Welding tip: When welding a seam like this, end the second weld on the start of the first weld. this will give you the best penetration.
Very nice work. I prefer using 1 1/2" x 3" x 3/16" tubing also. It gives a much more proportional look to the build and is plenty strong for what it is being used. But as they say, "the customer is always right."
I'm going to extend this thread a bit and cover the assembly of the frame.

Here is the front spring perch. The plate, retainer and gussets are 1/4" stock and the boxing is 1/8". I like to build these off the cross member on the table. It's just easier to detail them that way. The gussets are full circle so I'm not worried about welding them on the outside only.
I can understan why people use 3/16" wall tubing. If they are bolting crossmembers and brackets to the rails, it dose give you more thread contact. I'm a welder by trade. If I can weld something and make it turn out, then that's the way I tend to go. Other that a couple of ordered frames, I like 10g wall. IMO, people tend to over build frames and in some casses that's OK. I beleive a well designed frame merits the thinner wall tubing. JMO

very nice work....clean and simple
Wow very nice perch.Where were you when i was building?:)
The first picture is the layout for the front cross member. For a 2" measure back 1" from the end of the tube and 1-1/8" down and center punch there. Use a 2" hole saw to open the tube up for the crossmember. Trim down the top and bottom sides at the 1" line and grind a radius on the outside to cap the crossmember tube. Important: you are making 1 right and 1 left. You are going to hate yourself if you make 2 of 1 side.

Second picture is what it should look like at this point. Tack your time fitting the front crossmember tube here. The better the fit up, the easier it'll be to assemble all the pieces.

Grinding tip: Use disc' to grind this seam down. Keep the disc as flat as prevent gouging into the base metal. Grind in a sweeping motion

Next picture is the sides going together. The extra tube on the top of the rear rail is to check if it is parallel to the front rail. Just measure in 2 spots and it will tell you how good your cuts are. Once you have the first rail positioned, clamp it down and weld the 3" sides. Let it cool to the touch, then turn it over. I use 1/4" spacers to raise it above the table, 2 on each section, and clamp it down. Use a straight edge to be sure all 3 pieces are on the same plane. When you are satisfied, place tacks on the 2" side and weld the 3" sides.

Now for the second side. Again, using 1/4" spacers between the tubes, set the pieces for the other side on top of the first side. Take care to see that second side is directly lined up with the first one. Using a tri-square as shown in the picture makes this easy to do. Clamp the pieces down and double check to see everything is located right. Satisfied? Tack the 2" side and weld the 3" side. After it cools, clamp the second side down with the spacers and weld it too.

Before you weld the 2" side, grind the tacks out on the tops of the rails. Then turn the rails over and grind the tacks off on the bottom and weld. Grinding these weld is up to you. Only grind them if you feel the welds are sound.
Opps, I hit submit instead of preveiw. Here's the pictures.
Thanks Rick. I'm a firm believer that you can not spend too much time detailing the front end of your car. Think of it this way. There are 5 or 6 T's parked side by side. What is the first thing a person sees when they walk up? The front of the car. Be carefull here though. Little details up there will have them searching for more on other parts of your ride.

One thing I didn't take a picture of was the rear crossmember. The frame is 26" wide. I cut a piece of 2"X3" tube 25-5/8" long. I then cut 1-13/16" back from each end. When the tube is positioned on the back of the side rails, it leaves you with a corner to corner joint. This will give you the same penetration as grinding a bevel on a butt joint.

As I've said before, I like to have as much as possible in front of me when I start a build. That means sub assemblies. Here's all the parts for Chucks frame. Now the easy part...puttin' it all together.

Next is the frame pieced together and clamped into place. Now I get to boast a little bit. On the inital set up, this baby was plumb level but 1/32" out of square. I can fix that though.

That's it for now. I've been welding it today and writting this during the cooling times. I'll post the rest tonight.

To be continued;

Nice Ron :cool: I'll have to refrence this for my next build. :)
The first picture is of the temporary cross member I tacked to the frame before finish welding it. This really helps stablize the frame. It measured the same after welding as it did before. Even so you want to skip around when finish welding.

The next picture is the front cross member. The next is the kick and rear cross member.

And the last is the frame waiting for Chuck to come and get it.
I'd like to see the pics but they aren't showing for me for some stupid reason.

Anyone else?

Sorry about that. I must have screwed up some where. Lets try it again. And heeerrrreeee they are;
Youngster said:
Sorry about that. I must have screwed up some where. Lets try it again. And heeerrrreeee they are;

Dang those rails are awsome NOBODY grinds the welds smooth like that.You da man.
I guess that's one advantage to using 3/16" wall tubing. You can really burn the welds in and still have all the strength you need after grinding them down.


P.S.-I still like 1-1/2"x 3", 10g. better.

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