Chassis / Frame Design for the 1928 to 31 Model “A” Ford Street Rod – Part 6

Chassis / Frame Design for the 1928 to 31 Model “A” Ford Street Rod – Part 6 

One of my main goals in the design for the 1928 to 31 Model A Ford Street Rod chassis / frame was to incorporate as many of the 1986 C4 Corvette suspension components as possible.  Initially, I even wanted to use the front mono composite spring from the Corvette.  This spring is huge and at the time did not seem like a practical idea.  Having acquired a variety of automotive parts over a short period of time, I had sitting in the shop, 4 Jaguar coil over shocks.  The distance between the mounting holes was prefect for my application.  These shocks came from the rear end of a mid 1980’s full size Jaguar Sovereign 4 door car.  The Jaguar Sovereign is a heavy car, and my 1929 Ford Roadster hot rod would be much lighter.  I thought there might be a possibility to use the coil over shocks on my hot rod.  Temporary mounting brackets were made for the shocks.  The motor and transmission were temporarily mounted into the hot rod chassis / frame.  I even added several bags of sand for added weight.  The shocks were mounted to the front of the new 1928 to 31 Model A Ford Street Rod chassis / frame.  I measured the ground clearance for a reference point then stood on the chassis and started bouncing my 6’-4”, 250 pound body up and down on the chassis as hard as I could.  Very little movement was observed.  It was then I realized that I could save a bit of money for the time being and use the Jaguar coil over shocks in the front of my 1929 Ford Roadster.  Later on, once the car is on the road, I do intend to replace these shocks with nice and shiny chrome coil over shocks.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - the upper control arm mount is tack welded in place and the lower right angle cross memeber gussets have be installed.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - the upper control arm mount is tack welded in place and the lower right angle cross member gussets have be installed.

Everything is starting to come together nicely with the front 1986 C4 Corvette suspension for the 1928 to 31 Model A Ford Street Rod chassis / frame.  The front suspension mock up produced favourable results with the desired ride height.  Not only that, all of suspension components taken from the1986 C4 Corvette look great on the new hot rod frame.  Now it came time to create a proper chassis cross member, and the required mounting brackets for the front suspension.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - outside view - these brackets are welded to the outer edge of the chassis rails. The chassis rails have a slight taper to them.  The chassis rail width is narrower in the front than in the rear.  I mounted both upper control arm brackets parallel to each other.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view - the shocks are mounted and tested to determine if the spring rate is adequate.

For the cross member I used  2” x 4” x 0.1” rectangular tubing, heavy wall 1.25” round tubing for the lower control arm mounts, and 0.25” plate steel for the upper control arm mounts.  Inside the 1.25” heavy wall round tubing, bronze bushings were pressed into each end providing an inner diameter of 0.5” for the lower control arm mounts.    Originally the lower control arms were fastened to the 1986 C4 Corvette cross member with metric bolts about 3” long for each pivot point on the lower control arms.  I did notice a minor amount of wear on the original C4 Corvette cross member mount holes for the lower control arms.  The design for my hot rod will allow for sealed lubrication in the lower control arm cross member round tubes eliminating wear problems.  The only thing left to do, is enlarge the inside bushing diameter of the C4 Corvette lower control arms.  This was accomplished very carefully, using a 0.5” cobalt drill bit.  High speed drill bits will not work for this task.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the gussets for the upper control arm brackets.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the gussets for the upper control arm brackets.

Wanting a strong chassis / frame, one that will not flex when picked up by one corner of the chassis, I welded in right angle gussets from the lower front cross member to the inside of the frame rails.  Scraps of 2” x 4” rectangular tubing was used for this job.  Now this created a minor problem for the stock 1986 C4 Corvette steering rack.  The steering rack and the intermediate steering shaft needed a bit of clearance space notched out of the right angle gussets I just welded into the cross member / chassis.  To solve the problem, a very small section of round exhaust tubing was moulded into the gusset.  This took a few hours to do and make it look nice.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the gussets for the upper control arm brackets. Now a bit of grinding is in order to make everything smooth.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the gussets for the upper control arm brackets. Now a bit of grinding is in order to make everything smooth.

Work on the upper control arm brackets started.  Using the plasma cutter, and a wooden template, I cut out 2 identical brackets.  The plasma cutter produces a very clean cut, so it didn’t take too long finishing the edges of these brackets.  The highest part of these brackets would stand a little more than 4” from the top of the frame rail.  Again, wanting everything very strong, I fabricated gussets to strengthen the upper control arm brackets to the frame / chassis.   

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the exhaust tubing massaged into the cross member.  This is required to have the proper clearance for the 1986 C4 steering rack and intermediate shaft.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the exhaust tubing massaged into the cross member. This is required to have the proper clearance for the 1986 C4 steering rack and intermediate shaft.

Now it was time to weld everything in place.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - outside view showing my first version of the upper mount for the coil over shock.  I didn't like the way this looked and ended up removing it.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - outside view showing my first version of the upper mount for the coil over shock. I didn't like the way this looked and ended up removing it.

Come back next week to see how this progresses more towards the final product and finished state.  Of course you can have an advanced look at the completed hot rod frame / chassis for my 1929 Ford Roadster.  Just go the “PAGES” section new the top right of the screen and click on “Preview of the 1929 Ford Chassis with C4 Corvette suspension. 

This frame / chassis will work for any Model A Ford from 1928 to 1931.

I am currently working on CAD drawings for this entire chassis complete with template drawings for all brackets.  This will be available soon on this WEB site.

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2 Responses to “Chassis / Frame Design for the 1928 to 31 Model “A” Ford Street Rod – Part 6”

  1. Rick Escobedo says:

    I just recently purchased a 1930 Fordor and my intentions were to put a Corvette C4 suspension system. I only have the body, fenders, running board with no frame an I would surely purchase your detailed plans on building a frame such as yours. I only hope the plans would also work on my model A.

    Thanks and keep up the great work.

  2. hot rod says:

    Hello Rick: My chassis should work on any 1929 to 31 Model A Ford. My current project is a high boy roadster (no fenders). The front upper control arms from the C4 Corvetter are a bit bigger then after market control arms and just might be a bit of a problem for fender clearance were the controls arms bolt to the frame. I am not 100% sure about this. As always with this craft, problems can be over come with a bit of thought. I will have the plans available sometime in June or July. Just keep watching the web site, I will have announcement once they are ready. Thanks for your interest in 1929fordhotrod.com . Very best regards and good luck with your project, John

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