Another build thread? Yep, my track-style T

[J. Robinson]

Although I have been busy with other things, I have managed to spend a little time in between on the roadster. It has taken me a week to do about 3 hours worth of work and I haven't had enough time in front of the computer to put together the story...

Anyway, I left my last installment at the point where I had formed the long tubes for the radius rods. The next step was notching the ends of the tubes and cutting the short little pieces that will become the rubber-bushed eyelets. These short pieces are made of the same tubing as the long tubes; 3/4" inside diameter tubing. I cut them carefully and then grind them, if necessary, to make them as close to the same exact length as possible (in this case 1 3/4").

When the little pieces were ready I welded them to the notched ends of the long tubes being careful to get them centered and perpendicular. One last step before final assembly - I cut straps from 1/8" x 3/4" flat stock, bent them into a "U" shape and welded them around the eyelets on the top tubes. Under hard acceleration, the welds on the bottom tubes are in compression (the rotational force of the rear end is pushing on them), but the welds on the top tubes are in tension (the rotational force of the rear end is trying to pull them apart). The straps ensure that everything stays together.

I said earlier that I would explain the "why" of rubber mounting, so here goes... The front axle is a forged I-beam which is pretty dense, springy material. You can use an I-beam axle with hairpin style radius rods and when the car leans over in a corner, the axle twists slightly. It acts like a sway bar and rebounds to normal when the car straightens up. A tube axle or a rear end housing (which is a big tube) has almost no torsional flexibility. If you use hairpin style radius rods on a tube axle or a rear end, you create a binding problem whenever the car leans in a corner. Something somewhere has to flex. More often than not, it is either the radius rods themselves or the metal of the tube axle or rear end housing immediately adjacent to the radius rod bracket. Eventually, the metal will fatigue and break. There are a couple of solutions to this problem: (1) use a four-bar system or a "wishbone" arrangement which does not bind or (2) use flexible bushings that allow limited movment of the components without damage. Since I wanted traditional looking rear radius rods on this car, I chose to do the latter. I have used this same method I am showing here on various cars for years and it works very nicely.