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The Type 1 chassis is the chassis design documented
in the book,
Build Your Own Sports Car for Under 250 Pounds -
and Race It
written by Ron Champion (Haynes Books)
This design is usually referred to as a
LOCOST 7
and is the general starting point for all the
other
chassis designs presented here. The image below shows the
chassis structure.
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This
chassis is constructed from round and square
rectangular tubing. The main chassis structure is
fabricated from
one inch (25 mm), 16 gauge square tube. The
transmission tunnel region is fabricated from
three-quarter inch
(19 mm) square tube. Some diagonal elements and the
rear cargo area are fabricated from 19 mm round tube.
Sheet steel of varying thicknesses is applied to
several areas.
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The image
above shows a 3D wireframe structure used to perform a simple
stress analysis for this chassis design.
The analysis involved applying a couple (two forces of equal
size but opposite direction, to create a purely torsional
load) to the front of the frame while holding the rear of the
frame fixed. The relative rotation of the front of the
chassis under this load is an indication of the torsional
stiffness of the chassis.
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The image
above shows the predicted stress levels (axial stress along
each tube) in the chassis structure
due to the
applied torsional load. The red colour indicates the most
highly stressed chassis members.
Yellow
indicates moderate stress levels while blue indicates low
stress.
This chassis was tested for theoretical torsional stiffness in
two different configurations. It was tested in the form
described in the book, with a combination of two sizes of
square tube and round tube. This gave a value
of 1219 lbs.ft/degree. The same structure was then tested
with all members using 25 mm square tube.
In
this configuration the theoretical torsional stiffness was
1219 lbs.ft / degree.
For comparison a live
test
value for a Locost 7 chassis was measured as 1187 lbs.ft / degree.
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