Archive for March 20th, 2010

The Rear Suspension for the 1929 Ford Roadster – Part 1

Saturday, March 20th, 2010

The Rear Suspension for the 1929 Ford Roadster – Part 1

One of my design goals was to use as much of the C4 Corvette suspension as possible. On the rear of my 1929 Ford Roadster hot rod, I thought that I would try using the original C4 Corvette composite mono spring. The only problem is that the 1986 Corvette is a fair bit heavier than what the 1929 Ford Roadster will be. With the spring installed on the 29 Roadster and the body on the chassis, there was not much movement in the suspension, no matter how hard I jumped up and down on the back of the roadster. Not having too much to loose, I decided to narrow the composite mono spring. A bit of masking tape was laid down along the edges of the spring. This was used to mark cutting lines on. I started cutting a ¼” to ⅜” off each side of the spring. My first cut was made on my large 20” wood band saw. Forgetting that the composition of the Corvette mono spring is very abrasive, my blade only lasted about a minute and only managed to make a very small cut in the spring. The band saw blade was ruined. Then I realized the better option for cutting the composite Corvette spring would be on my metal cutting band saw. This worked out much better. After removing the first strips off each side of the spring, I mounted it back on the car and checked the spring rate. This continued this routine for sometime. I eventually stopped when the spring was approximately the same width along the length of the spring. Still, this provided me with a very stiff spring rate that was totally unacceptable. Taking a close look at the composite spring, I decided that I could make the spring thinner in the middle section of the spring. I did this using my 6” stationary belt sander using a 24 grit sanding belt. To keep the dust down, the shop vac up connected to the belt sander. The dust from the spring is very hazardous and I did not want to breathe in the dust.

C4 Corvette composite mono spring.  Masking tape is use to scribe lines onto for easy visibility while make the cut on the bandsaw.

C4 Corvette composite mono spring. Masking tape is use to scribe lines onto for easy visibility while make the cut on the bandsaw.

C4 Corvette composite mono spring. Ready to be cut on the bandsaw.  Material must be removed by equal amounts on both sides.  This will provide the same spring rate for each rear wheel.

C4 Corvette composite mono spring. Ready to be cut on the bandsaw. Material must be removed by equal amounts on both sides. This will provide the same spring rate for each rear wheel.

Finally after a full day of this, I finally achieved the spring rate that I needed for the 1929 Ford Roadster. This should be fine and safe for the roadster. I took some of the castings that I cut off and tried to break them by bending them into extreme shapes. Not one of the pieces broke. If this does turn out to not work out once the car is on the road, I have made provisions to install coil over shocks on the back of the 29 Roadster. The true test will be when the car is on the road.

The modified C4 Corvette composite mono spring installed on the 1929 Ford Roadster.  The spring was cut so that the spring was the same width for the entire length of the spring.  I also removed a bit of material from the center section of the spring to make it a bit thinner.  This gave me the desired spring rate for my hot rod.  The edges still need to be smoothed off before this modification is considered complete.

The modified C4 Corvette composite mono spring installed on the 1929 Ford Roadster. The spring was cut so that the spring was the same width for the entire length of the spring. I also removed a bit of material from the center section of the spring to make it a bit thinner. This gave me the desired spring rate for my hot rod. The edges still need to be smoothed off before this modification is considered complete.

Next week I will start installing the C4 Corvette sway bars onto the 1929 Ford Roadster hot rod frame.

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