April 1935 Short Wave Craft
Wax nostalgic about and learn from the history of early electronics. See articles
from Short Wave Craft,
published 1930 - 1936. All copyrights hereby acknowledged.
Despite all the prefabricated, relatively inexpensive products available
these days, there are still many people who like to build their
own projects. Whether electrical or mechanical - or both - some
is usually involved. Often, you can cannibalize an existing, retired
project to use its chassis or find a product at Walmart or a home
improvement store that does not cost too much that you can buy just
to get its enclosure. Buying a pre-formed chassis for your project
can get expensive, so there are times when the best option is to
obtain a piece of sheet metal (which can also
be expensive) and bend it yourself. If you have never attempted
such an endeavor, believe me it can be pretty challenging, especially
with heavier gauge metal. It is usually best to lay out and drill
/ cut / punch / file as many holes as possible prior to doing any
bending. This chassis bending article presents a good method for
forming your sheet metal, but does omit recommending making holes
prior to bending - maybe hole cutting was in the next month's edition.
If you need a custom box but do not feel confident making it yourself,
try taking your plans to a heating and air conditioning shop that
does its own ductwork fabrication in-house. Those guys are really
good at this stuff, and you will probably get a better price than
going to a machine shop.
See all articles from
How to Bend Your Own Chassis
Fig. 1 - Simplest wooden chassis.
Fig. 3 - Simple design of metal chassis, built up from
flat pieces, without any bending. Angle aluminum or brass,
tapped for 6 or 8-32 machine screws, serve to hold the sections
Fig. 5 - The metal, aluminum or steel, is bent by hammering
back and forth along the side to be folded. Don't try to
bend it all at once, but a little at a time along the entire
Fig. 2 - More open type of wooden chassis.
Fig. 4 - Shows how typical metal chassis is laid out
before bending, which takes place along the dotted lines.
Flaps are cut out with snips before bending.
Fig. 6 - Handy way of mounting chassis so it can be rotated
while wiring. Screws permit clamping in any position.
To earn the coveted title of Advanced Constructor, you certainly
must do something about set-chassis making. It all depends on how
you go about the work. You can with advantage start off with a really
simple wooden chassis, gaining confidence for more ambitious metal
affairs as you construct various shapes and sizes.
Shall we take a look at Fig. 1, for a start? Here is the most
straightforward complete chassis we can imagine. It is made up entirely
of wood - preferably treated wood of the metallized variety. This
is available in England, but not here, to our knowledge. Metal foil
or screening could be put over the wood. Tin, zinc or brass could
be used in an emergency.
So that the design in Fig. 1, built up of metallized wood, or
metal-covered wood, is a really sound chassis. Its size depends,
of course, on your own needs. The governing considerations will
be the depth - determined by your deepest sub-chassis mounted component.
You can use 3/8 in. wood for this Fig. 1 chassis, tacking together
the top, sides and ends with 1 inch panel pins (brads). Be generous
with these pins, and then you will have a stout chassis that will
stand any amount of knocking about.
If you know that the sub-chassis wiring is going to be rather
complicated, or if there are going to be a lot of components - some
being therefore inaccessible - you might try the Fig. 2 chassis,
which is a more skeletonized version.
Tack the top portion to two ends, strengthening up the structure
with four triangular pieces of wood. Use the same wood as before,
and the same pins. With a shallow chassis this method is very satisfactory.
So much for simple wood chassis, which are becoming more popular
as amateurs realize the easy way they can be made up - and as it
dawns on amateurs that a good metallized or metal covered, as explained,
wood chassis can do all that a more ornate all metal job can do.
There are times, though, when a really nice metal chassis is
wanted - and then, assuming you are inexperienced - the Fig. 3 construction
is admirable. All you need are three perfectly flat pieces of No.
16 gauge aluminum, one for the top and two for the ends. These are
then held together by angle brackets, which you can readily buy
quite cheaply - especially in brass. But they are also available
in aluminum if you look long enough.
Now we come to the more complicated sort of chassis - a real
all-metal affair. You can see how it is dimensioned from Fig. 4.
About the bending. This is really quite an art - but an easily
acquired one if you go the right way about it. The first need is
a hardwood block to work upon. It should have true corners - to
make sharp bends in the metal when it is hit.
Hit with a wooden or rawhide mallet, too. If an ordinary hammer
is used it will badly mark the metal. You can see how this job is
done from Fig. 5.
At Fig. 6 is just a little idea for chassis experiments. Make
up a stand, with two slots in the ends, so that the chassis can
be swiveled around - then you can examine components and get at
tricky bits of wiring. -Courtesy English "Amateur Wireless."
Posted January 14, 2015