[David Dunlop]

Well it took a while, but my spare parts receiver has now finally been carefully reduced to its basic chassis assembly. It has been an interesting and informative bit of work. I now have a far greater appreciation of the incredible amount of design and planning work that goes into producing a piece of equipment like this in the pre-computer era. I started out just thinking of the line workers actually assembling it, but it is so much more than that, involving a lot more people with a huge variety of other skills.

The process also gave me a much better understanding of the layout of all the components and their interactions with one another in the various circuits in the receiver. Useful things to learn in this project!

The basic foundation of this receiver chassis turns out to be just four pieces of 13-guage, steel, sheet metal.

The main piece of sheet steel runs from the ½-inch lip at the upper rear, across the top, down the back and forward across the bottom, where it then drops to form the lower front section of the chassis and ends with another ½-inch lip folded under the front lower edge. Half-inch tabs are also present on this piece, folded back along the sides where they meet up with the two side panels. These side tabs provide a means for the spot welding to take place joining the three main chassis pieces together. The overall size of this piece would be on the order of 25-1/8 inches long and 15-7/8 inches wide. Where any tabs are located at folds, they were designed that outside corners would be full open at 90 degrees and any inside folds were set up for a 45-degree mitre.

The two side panels are basic dimensional mirror images of each other, 11-1/4 inches wide and 14-7/16 inches long, with ½-inch tabs, front back and bottom only. They really differ only in the hole patterns punched in each.

When the cutting, punching and brake work was completed on these three pieces, they were inspected and a small circular CMC Inspection Stamp was punched into them, ready to move down the line. The first two photos attached highlight these features.

The fourth piece of sheet metal making up the receiver chassis is a strip approximately 1-1/8 inches wide, folded in half lengthwise down the middle forming two ½-inch tabs at 90 degrees. This piece is 13-3/4 inches long with straight cut ends, and forms the lower rear edge of the chassis. It is butt welded in place with all external seams filled and ground smooth.

The spot-welds on the tabs connecting the main and side chassis panels are approximately 1 inch apart wherever possible and ¼-inch in diameter. The second photo also shows how the lower chassis strip and the upper rear edge both have all their external seams filled and ground smooth.

Photo 3 shows the inside of the lower chassis strip with the unfinished butt welds. Note that the zinc plating covers these welds. By ensuring all these external seams are smooth, it makes sliding the receiver in and out of its relevant Carrier that much easier for the Operator.

A number of smaller sheet metal pieces are spot welded to the chassis prior to it being zinc plated, but I am not sure if these small pieces would have been added to the individual chassis panels before they were assembled into one unit, or after.

The first two are the Upper Mounting Brackets passing through slots on either upper front side. These are made of heavier, 11-guage sheet metal. They have an offset stamped into them such that when the rear portions of them are spot welded to the chassis sides, the outside faces of the front sections projecting through the slots, line up perfectly with the outside face of the chassis side panels. This ensures a good fit when the receiver chassis goes in and out of its Carrier. The last photo in this Post shows this offset on the Upper Left Side Mounting Bracket.

The fourth Photo here gives a rear view of what is going on around the Right Side Mounting Bracket. Two other 13-guage metal strips are also fitted here.

The long vertical strip is a stiffener to support the Upper Front Right Subpanel Assembly. This is the small panel that sits directly behind the removable Upper Front Panel of the receiver, which supports the BAND Switch, FREQ ADJ Switch and AERIAL Terminals visible outside the receiver, as well as the Gas Discharge Tube Clips mounted inside, behind the two Aerial Terminals.

The larger, horizontal strip of 13-guage steel mounts the AirLoc Fastener Receptacle. A blue, spring steel spring assembly is held inside this receptacle. Note that the entire thing is covered in zinc plating.

The rest of the chassis information will follow shortly.



David