An aluminum block was attached to the plate at the front with two screws from the bottom and
fitted with two small pins and a tapped hole. The 3/8" square steel arm for locating
the guide tongue is placed against these pins and held in place with a clamp.
The clamp can be loosened and the arm can slide lengthwise, using the pins to guide it.
When the desired guide lead dimension is reached, the clamp is tightened and the arm
is firmly set. This same design will be used on my new jig to locate the front axle,
using two additional arms (see diagram below).
The pin held in the arm is 3/16" diameter, to fit modern guide tongues. I will probably
make the guide arm for the new jig double-ended, with a 3/16" pin at one end and
a 1/8" pin at the other to build for vintage guides. The guide pin is held in
the arm with a setscrew in the end (not visible). This allows the chassis to be freed
from the jig during construction without losing the setting of the arm. The new jig
will look a lot like this one, except there will be 3 arms instead of just one. The
two outer arms for the front axle will have 1/8" pins at the ends.
The jig axle shown is 1/8" diameter stainless steel rod, and the jig wheels are aluminum,
fitted with setscrews. I made several pairs of these in different sizes to build chassis for
various tire diameters. The jig axle is clamped to the rear pins with two Parma alligator clips.
The two small pins seen ahead of the jig wheels were installed when I built the
Gulf Porsche 917 for the 2002 Marconi race. At the time, it seemed I needed them,
but the new jig will not have any extra pins - I find it just ain't necessary!
Although this jig was built with machine shop equipment,
the ideas could probably be used on a homemade jig with a
little adaptation, so I hope you found some inspiration to give it a try.
Larry Geddes March 29, 2003