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Building a Retro Pro Car

Part 2

by Philippe de Lespinay as appeared in Slotblog (2012)
 

 

BUILDING THE NEW KILLER MACHINE

The Goal: 60 grams with no loss of strength or handling qualities. SIXTY GRAMS!!!

The Design Stage

First, I am no computer genius and do not know how to use a CAD program, I am old fashioned and simply draw what I need. The old car had its rails soldered on the sides of the brass-plate front end, but they parted company twice before I tied them to the plate, meaning, added weight. This itme, the main rails would be keyed into the plate, and so would the inner U-shape rail. The one-piece outer rail should be strong enough simply soldered against the tow main rails.

Second, I decided to remove every little amount of un-necessary weight. The body-mount torsion bars would now be made of .032" wire, U shaped to retain shorter, lighter sections of square tubing. Tiny aluminum tubing sections would act as spacers, raising the mounts high to save the body from splitting in crashes.

Third, as much as possible would be shaved from the rear-axle brass tubing. A gram is a gram!

Fourth, the guide tongue treated-steel reinforcement piece and assembly would go through a diet. Lots of un-neededweight there.
So this is what I came up with:

Construction

Using this pattern as a guide, I shaped the four rail pieces and adjusted them carefully so that none would be in tension:

Careful fitment is critical and I took my time to adjust the pieces so that they became friendly with each other, with no stress anywhere:

 

The rear-axle tube receives a notch for the left-side front rail, and any un-necessary weight is cut off in two stages to allow a nice radius in the cut section, that will render it stronger than a plain square cut:

Once more, everything is being checked before any solder is splashed over it...

Time for the Dreaded Acid!

Next, I used my R-Geo building jig to make sure that the thing would be properly assembled and unlike the one I previously built not go down the straights like a crab!

Here we go, the thing is now on Rick Bennardo's great building fixture:

Once everything is aligned, a couple of clamps keep all bits in place. By now, I have recut some old Champion jig wheels to a .710" diameter minus a couple thousands just to make sure I pass tech! Ok, a few points of solder here and there, to tie the parts and make sure that everything lines up properly. The solder I use is very strong but does not make pretty joints, I will have to fix that later!


 

Quick checking over the drawing:

Quickie cleanup to detect any bad join. I fitted a jig motor with the correct gearing just to make sure that nothing clashes. Barney The P is going to be so happy to find out that I no longer need to butcher his motors for clearance, as this chassis took in consideration the mistakes made in the first example!