We’re continuing on from Part 1 of Bob Hamilton’s street rod chassis build for his 1927 Model T roadster project. In these first two parts we’re covering the build of a tapered street rod chassis from just in front of the firewall back to the rear crossmember. In Part 3 we’ll cover construction of the frame front and explain why it’s being built in two sections. Remember, all of this detail and a ton more is included in Bob’s StreetRod 101 Hot Rod Frame and Chassis Construction DVD.
Bob continues to describe building this street rod chassis in his own words.
The rails are set up aligned on the table and squared using the ¼ – 20 studs or pins and use a tape measure that has an end with a ¼ inch hole in the end, commonly known as a carpenters tape. Do not use a tape that just has a 90 degree hook on the end. The measurement can and will be off. Measure corner to corner diagonally and adjust by moving one rail forward or backward. Make sure that the width of the rails is what you want also. When set, take a couple of 3/8ths pieces of flat bar and tack the rails and then double check before moving on.
This is just another view showing the frame tacked i place with flat bar and the two bends in the rail. This frame is pretty simple. I am not trying to follow the contour of the body real close. Years ago, I built a Model A roadster and it took 29 cuts and bends on each rail to make the frame exactly fit the body the way I wanted. How close of a fit you want the frame is your decision. Most highboys I build will have from 4 to 9 cuts per side depending on the body manufacturer. This car is a highboy but it is also set over the frame about 3/4th of an inch and also is going to be built old school and won’t be as critical or showy as most of the cars I build. This car will look good, run good, and just be fun to play with.
With the side rails squared and in position, I build the rear kick. I am using 1 ½ in x 3 x .188 wall tubing for the rear kick, instead of the 1 ½ x 4 x .188 for the main rails. The small 1 inch gap you’ll see above will be filled and then finished. I built the rear kick to be a 45 degree angle. This means that each cut is 22 ½ degrees. This is the same for the upper angle winding up with a 45 degree cut on the rear part of the crossmember to give me a 90 degree rear frame member. The two pieces that make up the rear frame were done on the bench and finish welded and then clamped to the side rails with flat bar and everything leveled. The rear cross member is then figured and cut. I do it this way because for some unknown reason, if the rear crossmember is precut – it’s either too long or too short. Too long is OK, but too short is not good!
The rear cross member is squared and held in place using C-clamps and flat bar. Use the tape and measure crosswise from the reference pins and adjust the cross member until they are as close to square (equal measurements) as possible and then tack in place.
Another shot showing the alignment set up.
Now that the center and rear section of the frame are in place, it is time to set the body on and double check the fit and see if there needs to be any modifications. Now is the time to make changes, not after all the brackets are in place.
We’ll continue Bob’s street rod chassis build how-to in tomorrow’s Part 3 installment. But by now you’ll probably want to go ahead and order Bob’s incredible how-to DVD on street rod frame and chassis building so you’ll have ALL the information you’ll ever need on how it’s done.
You can just sit back and follow along as you learn from Bob’s years of hot rod building experience. Here are some of the things you’ll learn about hot rod chassis building in this 4 1/2 hour video:
- Building a transmission cross member that also strengthens the frame
- Where to get your “almost free” transmission for mock-up
- Learn how to construct a modified K-member
- How to build a fixture to set frame height and level to ensure proper rear end installation
- How to properly set your pinion angle
- How to center your rear end
- Using frame reference pins to square the rear axle
- Installing rear coil-overs at the proper angle, allowing for overall weight and frame drop
- Getting proper clearance for coils from rear axle
- How to make your own shock absorber brackets
- The magic of using reciprocal angles to set rear coil-over position
- How to protect chrome and aluminum when welding
- How to gusset brackets for added stability
- Avoid worry about shear forces on coil-over bolts by “encapsulating” your brackets
- How to avoid rear coil-over shock binding
- The theory of building a chassis with as many adjustments as possible
Click here to order your own copy today!