is the text of a tech session presented by Paul Horton
at the 2002 Syracuse Nationals
Street Rod Chassis
A discussion about street rod chassis building (1948
and older vehicles).
My name is Paul Horton. I've been able to turn our
hobby into a business by designing and building street
rod frames and chassis parts and by selling parts
made by other street rod companies. In 1978 my wife,
Dorothy, and I were the whole staff. The company grew
to a staff of 12. We still manufactured our product
line and also repaired street rods and we custom-built
the beginning of the year 2000, the company made a
successful transition out of the custom work and repair
business back to manufacturing a standard line of
frames for Model "A" to 34 Fords and parts
for a broader range of street rods, as well as continuing
to serve as a dealer for major American manufacturers.
I say a successful transition because some of our
old staff carried on in the custom work field with
their own businesses and we now count them among our
customers. We designed and built the basic frame for
last year's Syracuse Nats give-away '32 Ford coupe,
built by Tucci Engineering and we have built the basic
frame for next year's '32 roadster give-away. Dave
Tucci (Tucci Engineering) is in charge of the overall
Keep It Simple & Safe
During this session I'll outline my ideas on simple
street rod chassis design. Our company has used the
acronym "KISS" in our catalogue and promotional
material. KISS has various meanings in different contexts.
We used "Keep It Simple and Safe". This
has always been my philosophy, although there have
been times when I fell off the wagon. There are lots
of workable ways to build your street rod. Probably
most of you are here because of the creativity that
street rodding encourages and accepts. I hope this
session feeds your imagination.
Frame cross sections
frames are 1 of several cross sections (with variations):
Channel: e.g. Ford "T" thru' 1940.
"Top hat": e.g. Chev 1937-48.
Box section: e.g. Ford 1942-1948.
Ford frames (up to 1932) were channels with straight
crossmembers. (The '32 had a "K" that made
it slightly stronger.) They had little torsional strength.
(The whole frame could twist.)
was known that a tube had more torsional strength
than a channel, so builders began boxing early Ford
frames. There are several ways to box a frame...
3 ways to box + "Step Boxing"
are advantages to corner-to-corner and step boxing.
Corner-to-corner weld penetrates 100%. Cosmetic grinding
does not have to remove much weld. I feel it is easier
to clean a corner-to-corner boxed frame than a step
boxed frame.Step boxed frames offer a protected area
for hoses and wires.
/ outside / corner-to-corner / step box
hat" Cross Section
Chev "Top hat" frames are already a box section.
We find that they are susceptable to rusting along the
bottom of the rail. Our front end kits, and those of
some other companies, include plates to weld to the
frame to spread the stress load over a larger area.
Ford cross section
The suspension needs a firm foundation to work properly.
The strength and rigidity of the frame has a great impact
on the ride "feel" of the car.
1933, Ford strengthened their frames by adding a second
channel inside the main rail, and by incorporating
an "X" center section. After
1940, Ford reversed the inside channel, effectively
boxing their frames.
- 40 / 41 - 48
strengthens the side rails, but the center section provides
torsional strength or resistance to twisting. The frame
is the foundation for the vehicle. If the frame twists,
the body has to absorb and resist the movement. This
can result in cracked body panels or doors that pop
open. A pure "X" is the strongest center section,
because the twisting force has to bend both lengths
of the "X". Street rod chassis builders use
channel sections or round or rectangular tubing to fabricate
their center sections. The main point is to transfer
the stress through the center section and use the opposite
frame rail and the center section to resist the twist.
We use a triangulated tower design in our '32-34 Ford
frames. This is not as strong as a pure "X",
but is plenty strong enough for 400 HP. It provides
space for exhaust above the lower tube. This section
is easy to install at home. It is in the Syracuse Nationals
frame from last year and next year's car, too.
"A" Fords have fairly short and narrow rails.
We have not found the twisting to be as much a problem
when the rails are made using 2x4x1/8 wall HSS (Hollow
Structural Section) tubing with the transmission crossmember
welded in place.
a street rod requires a mix of 5 things: time, talent,
facilities, sources, and money. This is an entry sentence
to whether original rails or repro rails are "better".
I feel a quality street rod can be built using either.
Repro rails will save time. We find this is necessary
in building frames to sell.
don't think there is a significant difference between
stamped or welded rails. The stamped rails give a
more original radius at the corners. The welded rails
are available boxed, saving time.
nuts, riv-nuts, weld nuts, plates
Body, fender and running board mounts can be put in
the frame in several ways: Nuts welded inside the box
section, riv-nuts, weld nuts, or plates.
/ riv-nut / weld nut / 3/8" plate
can be welded inside the frame. This has been done
for decades. Usually they must be tapped because the
welding distorts them.
are like pop rivets with an internal thread. They
are an easy way to get a quality threaded fastener
into a tube section. We have found that bolts can
freeze in a riv-nut, causing the riv-nut to spin.
This can be very frustrating. One way to clear the
bolt is to drill a hole in the head the same size
as the bolt or larger.
nuts are small plates with a threaded hole. They get
welded on the inside of the frame. Their advantage
is that they don't distort the thread.
way to mount the body or other parts is by welding
a small 3/8" thick steel plate inside the frame.
After the body, fenders, or running boards have been
positioned, drill a hole where you need it and tap
the required hole.