Wednesday, July 5, 2017

A New Line of Transceivers ~ DifX

Homebrewing a Chassis, Cases and Enclosures

Make your Rig Look as good as it Sounds!

There is just something about a rig that has that finished look when it has a painted case. Yes, it is something that came out of your garage or workshop but there is no reason why it can't look "finished". Long ago I adopted "Juliano Blue" and perhaps there was an unconscious bent to that decision based on my very early solid state experiments with the distinctively Blue CK722 transistor. Go Blue!
Of late I am not satisfied with a project unless it resides in a Blue Case --a Juliano Blue Case. So how do you get to the point of homebrewing a chassis, cases or enclosures. The first part is the right tools --no you don't need a $250 K CNC mill but for about $50 you can purchase a bench type metal break from Harbor Freight.

When I bought mine about 10 years ag they could be had for about $25. The type I have is 18 Inches long. The next thing you need is some stout metal bars in various lengths. The tool from Harbor Freight comes with an 18 inch bending bar. By using smaller bending bars in the 4, 6 and 8 inch range you now have a box break where you can easily make 6 X 8 inch chassis boxes -- thus the smaller bending bars.
For a chassis I make it in three pieces. Two pieces are "L" shaped and the final piece is the to cover. The two "L" shaped pieces are formed with ears so you can bolt/fasten to the pieces. Fastening also include "pop riveting". Two Chassis' are shown below one is a general purpose chassis and the other was one made for a transmitter power supply. Believe it or not most of the materials are galvanized metal available from Home Depot. The power supply chassis shows the "L" structure of the pieces and make for a very rigid chassis. The Sheet metal is very inexpensive and with a couple of homebrew chassis bulds you will recover the cost of the metal break.


In the photo above there is a trick to making these "L" section and it all has to do with the sequence of the bends. Excellent measuring skills are needed to pull this off and laying out the bends and cuts has to be done carefully. this is even extended to when the metal is in a flat state and that is when I actually drilled the holes. I have a stock of manila folders and so my first step is to make the part out of the manila folder stock. This in essence is a template. The first pieces bent are the top and bottom lips which are about 1/2 inch wide. At the location of the bend line I cut a 45 degree angle of material to the bend line on both the top and bottom sections. This when this is bent at a 90 degree ange the pieces meet up perfectly. Both sections are identical only in one of the pieces the end section is bent up at 90 degrees at each end. This is where the smaller bending bars come into play. Essentially an end of the bending bar is placed perpendicular to the bend line and the larger piece is bent upward. For normal operation the bending bar is "C Clamped" to the bed of the metal break and so with the smaller bars you can make boxes. the following two photos give a bit more detail of what is described here.

Now I would like to spend some time on how I build cases using angle stock readily available from Home Depot. The metal plate can be ordered from a company called "On Line Metals"

Yes this is an old project when I actually built analog VFO's as evidenced by the National Velvet Vernier. As soon as I started using the Si5351 I gave this rig away since I didn't want any evidence in my shack of an analog VFO. The aluminum angle stock makes for a very rigid structure and you can easily screw sheet metal to the sides and top.


The next critical issue is one of materials. Use what you have or think out of the box (enclosure). Sheet metal (versus aluminum) is readily available and inexpensive. Home Depot is a good source. I also have used single sided copper PC Board which often can be had a really good price. ABC Fab up in New Hampshire (eBay) sells various packages of boards. Recently I bought 18 pieces of 4X6 inch heavy duty board for about $1 a board --delivered. I also bought some 8.5 Inch by 12 inch board from the same source and two of my rigs have that for a base plate. One ham shared he found a source for large square tin cans which he cut open and flattened. Also check out computer shops as you can often find CD/DVD units which are defunct but its the case you want. Cookie tins are another great case source. So open your mind to the possibilities.
Oh --it is not a real case unless it is painted Juliano Blue!!!!!!
Pete N6QW