Mounting a Traditional Transverse Rear Leaf Spring
My traditionally built Model A roadster is set up and built the way it would have been in 1955. It is a ’29 Roadster on Deuce rails and for the rear cross member, I welded in a trimmed-up stock model A which allows the use of a high arch spring. My spring was junkyard fresh, but I disassembled, cleaned, and tuned it up before bolting it back together. The rear end is located with split ’36 Ford bones giving me all of the ingredients my Grandfather might have used back in the day for a hot rod chassis.
The first order of business for mounting the rear in the car was to locate the wishbone mounts. I had two c-brackets cut, and I welded them onto the housing being careful to locate the shackle holes 42-inches apart. I found this measurement by talking to other hot rodders using a similar setup. I used a bar bolted to each wishbone to keep the 42-inch measurement accurate while welding the mounts on.
Once my brackets were welded on the housing and the bones were bolted up, the only thing left to do was to mount the spring. It would surely be easy I thought to myself. People have been doing it for years so how hard could it be? After a cursory search on the web, I read about people using and sometimes building their own spring spreader tools. It made sense to me, so I went right to work building a tool that would spread the spring wide enough that the shackles would slip right in.
I pulled together some heavy-duty all thread, some thrust bearings, nuts, and an old wishbone. With a little cutting and welding, I quickly came up with a tool that seemed like a no brainer, easy to use a piece of equipment for spreading my spring.
I cut the ends of the old bones to fit snugly under the eyes of the leaf spring. Once I had it in place, I started cranking on the adjuster nut which increased the width of the spring spreading it out smoothly at first. As I turned the nut, I could see the spring spread out. I turned and turned and turned, but as I continued, a voice in the back of my mind started speaking to me. Feeling the pressure of the spring press against the spreader as the nut became harder to turn, I could sense the immense amount of potential energy waiting to come unglued, and I was nowhere near close enough to even imagine slipping in the shackles.
I had a long way to go and could see my spreader tool beginning to bend like a hunters bow. I realized I was being really ignorant and at any moment, something could slip and the tool was capable of going through the wall of my garage, if not taking my head off in the process.
I decided the spreader tool was not going to work.
I went back to the drawing board and asked an old hot rod buddy. My friend Dennis knew just what to do. He explained I should not start with a complete spring assembly but instead spread the main leaf out on its own. After doing this, I should add the remaining springs onto the stack and run a long piece of all-thread through the hole. I liked the sound of this.
I took the spring back apart, which is also a job that must be done with care as the single bolt is under pressure even without being mounted in a car. Once I had the main leaf all alone, I installed the shackle on the passenger side of the rear end. After having done this, I could push the spring down by hand to connect it to the other side. As I was told by my friend, I used all the threads to line up the remaining spring stack. I cranked it down to begin drawing the springs together.
It didn’t take long for me to notice the nut was becoming difficult to turn as it compacted the spring. Be aware that if the all-thread would break, it too could become a bullet whizzing through the air trying to kill you. I decided once I had the spring-loaded slightly with the all-thread, I would tuck it into the cross member of the frame. By doing this, I provided myself some protection in the event of a break. Once the spring was compressed enough to slip the u-bolts on, they become the ultimate method for drawing the spring together.
Getting closer to done, I used a combination of the U-bolts and all thread to bring to spring to its final compressed tension. At this point, some people simply cut the extra length of all-thread off and leave it. You can also remove all the thread and replace it with a grade 5, or stock replacement bolt. I decided to order a new bolt with the proper square head. It was a snap, knocking it out with a punch and replacing it.
With regard to the task of mounting the spring, I certainly took more time figuring it out than most, but I learned a lot along the way. The most important thing that was reinforced for me in this exercise was to be safe above everything else and trust your intuition. If something seems dangerous, it probably is, and it is better to stop and rethink things!
Now that I have the rear-mounted in the car, I am one step closer to rolling down the road and am glad to have it crossed off the list!