Of all of life’s little mysteries, a hot rod frame ranks up there as the highest. You’ve got one crowd that swears S10 frames are the cure all, opposed by the crowd that hunts and scratches for an old worn and rusted out 1920’s or 1930’s frame of some type. I think that the reason most builders shy away from constructing a new frame from scratch is fear of the unknown.
The Reasoning Behind A Do-It-Yourself Frame
By now you’re pretty mad if you’re into S10 frames, but hear me out. At today’s prices, you can buy enough steel to build your own frame for $60 to $80. This is for 2x3x1/8-inch wall tubing. This will be more than strong enough, and it’s lightweight – which is a major bonus. The frame will be tied together so that it won’t twist unless you are mounting a top fuel dragster engine. Lucky for us, we are not talking about top fuel dragsters. We’re talking about inexpensive hot rods on a budget.
If you were to hunt down an old frame, you would still have to box and reinforce it in a million different ways. It will cost a small fortune and you will still have to tweak it to fit your particular hot rod. So, we’ve removed one of those unknowns, the cost. Now we need to remove the next fear: How to do-it-yourself.
Lucky for us, we are not talking about top fuel dragsters. We’re talking about inexpensive hot rods on a budget! – Tommy Ring
We’ll be building the frame for our 1948 Ford that we’re featuring in this series, and you’ll see how easy it is to build your own frame. The pattern for car and truck frames varies only slightly. The same is true for T- buckets or whatever concoction you are into.
The 2x3x1/8-inch tubing will probably come in 24-foot lengths, which means you will need another 8-foot stick. We’re going to provide the layout for the 1948 truck rod that we are building, but will also give you the details for a coupe, sedan, or T-bucket frame as well. We started by measuring from the back of the cab to the front of the firewall. This measurement will be for the body rails.
But, we need to add 9 inches to that measurement to get a total body rail length. That is because 3-inches of that is extra length behind the back of the cab for the “L” kick-up to sit on. The other 6 inches will be in front of the firewall for the engine rails to sit on. The front will be cut at a 45-degree angle. Once the engine rails are attached, it will give you 3-inches more height and the appearance of a Z’d frame. You could also cut a 45-degree angle on the rear of the body rails, but there is no reason to. You will still have your kick-up and this way will be stronger.
The reason we do an “L” on a truck and not a “Z” kick up is because of wasted space. That space leaves an ugly spot that you just don’t need. Another reason is so the cab will sit right against the “L” for more support. If we were building a coupe or sedan, we would use a “Z” kick up, and allow 2 extra inches for the 45-degree cut. More on the body rails and an explanation on how this all ties together in a minute, First, we need to cut our engine rails.
So far we’ve got the basic idea for the two body rails. Next we need to cut two engine rails and work our way back. Obviously, different engine combinations will require different engine rail sizes. The most common engine used in rat rods is the popular and inexpensive small-block Chevy (SBC). The SBC engine requires a base 36-inch engine rail to span the engine from distributor to fan. If you plan on running a radiator on the inside of the frame, you will want to add 3 inches to that measurement. Assuming you are running this combination, you will cut two pieces of tubing 39 inches in length.
The cross piece at the very front of your frame will vary according to your firewall and cowl width. If we were building a T-bucket, or a Model A, the front of the frame would be 26 inches measured outside-to-outside of the tubing. The rear of the frame should measure around 36 inches outside-to-outside of the tubing. This measurement gives the frame roughly a five degree flair from front to rear.
In the case of our 1948 Ford, the firewall is a bit wider, so we started with a 30-inch measurement from outside-to-outside for the front. This put us at 32 inches at the firewall, and 40 inches at the extreme rear. To get the 30-inch measurement at the front, we cut a cross piece of 26 inches. This piece welded between the tubing that is 2 inches wide on each side, and together, adds up to 30 inches. With one front cross piece cut at 26 inches, and two engine rail pieces cut at 39 inches, we can now move on to the body rail cuts.
Body Rails And Bed Rails
Most truck cabs from the 1940’s and 1950’s will measure between 55 to 59 inches from the front of firewall to the back of cab. In our case, the cab measured 55 inches. After we added the 3 inches in back for our “L” kick up, and the 6-inches in front for our “Z” look, we wound up with 64 total inches for our body rails.
The “L” or “Z” kick up will measure out according to your desired ride height. The taller the kick up, the lower the car will sit. At Ring Rods, we like riding about 6 inches off the ground, so we use 16 inches from the bottom of the frame to the extreme top of the bed rail. Remember to account for the 3-inch thickness of both the body rail and bed rail. This means our kick up tubing will be cut at 10-inches to give us the total of 16 inches we need.
A short bed, like one on a T-bucket, looks ugly on a bigger body. A long bed tends to look too long and drug out, so we settled for a happy medium. For this reason, we chose 40 inches as our bed rail length. Our rear cross piece was cut at 36 inches to give us a total of 40 inches of frame width when welded to the bed rail tubing. This means we have a 10-inch flair from the front cross piece to the rear cross piece.
Laying It All Out
Now that we have two 39-inch engine rails, a front cross member of 26 inches, two 64-inch body rails, two 40-inch bed rails, a rear crossmember of 36 inches, and two 10-inch kick ups, we need to it all ready for welding. We used a 24-inch framing square, a measuring tape, and a piece of chalk to lay out the work properly. We will discuss the differences between coupes and sedans and how they differ as we layout our frame.
When doing this at home, pick a spot on your garage floor where you have 10- to 12-feet of clear area to work in. Mark a front line with chalk and determine the width of our frame. In our case that is 30 inches in the front. Next, use the framing square to get two 24-inch lines going toward the back. These lines will keep you honest and provide a reference so that you can check yourself as you go. But, we will actually be flaring off these lines by 5 degrees.
Next, add up the lengths of the bed rail, body rail, and engine rail pieces for the total length of your frame. Measure from the front line and make a chalk line on the floor for the rear measurement. You can use a chalk line to mark a line from your front mark to your rear mark, which will leave you with a rectangular box outline on the ground. Because the plans call for a wider rear, you’ll need to measure 5-inches outboard on both sides of the rear mark, then re-chalk your lines front to back. This will give you the 5 degrees or 10 inches for flair from the front to back. Place the steel tubing to the inboard side of each line and begin tack welding the pieces together.
Welding It Up
Once the steel tubing is lined up on the chalk lines, you can begin tack-welding the joints together using very light tack welds so you can adjust as you progress. Solid welds will only be required once your frame is squared and perfect. You can go to Ring Rods Hot Rod Shop on the net, and click on products to order my 3-1/2 hour DVD that will cover this process in greater detail.
The best way to accomplish the welding is to start by tacking the “L” kick up pieces onto the back of the body rails. Then, tack your two engine rails onto the front of the body rails allowing 6-inches of overlap. The front cross member is next, followed by the two bed rails with rear cross member tacked in. If you are a one man show, you can set the rear cross member and bed rails on a bucket to hold it up while you tack this section.
I will step out on a limb and make you a promise. This sixty to eighty dollar frame will be the best money you’ve ever spent. – Tommy Ring
I will step out on a limb and make you a promise. This sixty to eighty dollar frame will be the best money you’ve ever spent. It will fit your hot rod like a glove, be light weight, and look great.
Finally, we need to discuss how frames differ for coupes and sedans. The T-bucket will be the same pattern we talked anbout, except for having shorter bed rails. For coupes and sedans, the body rails are determined by a measurement pulled from the front of the firewall to the center of where your rear axle will be located. Coupes and sedans do not have beds, therefore, the bed rail measurement becomes a tail section measurement, which is measured from the back of the coupe or sedan to the center of the rear axle as well. You’ll add 8 inches to that measurement for coil springs or coilovers to mount. It is best to cut a 45-degree angle on both ends of the “Z” kick up and tack it to the tail section. Wherever the “Z” kick up lands on the body rails will determine the length needed for the body rails.
The length of the “Z” kick up, just as on the truck “L” kick up, will be determined by the ride height you want. Once again, 16-inches total distance from the extreme bottom to top of the rear tail section will make your rod run about 6 inches off of the ground if you are using standard coilovers. If using coil springs, it will vary by the length of the coil. If you need to drop it some, you can cut one and a half rounds off the coil and not change the ride too drasticly – any more than that and it will ride like a log wagon. One last tip is there will be a piece of the frame material that will run from side to side right where the kick ups are. This ties the frame together in the middle, and serves as a mounting bar for your panhard bars or four-link system, depending on your choice of rearend locating methods.
Stay tuned for the next episode of the El Cheapo rat rod build when we set up the rearend and all of its components.