Hewlett-Packard O-10/APA-6X oscillator
During the darkest days of 1942, USAAF countermeasures personnel had to rely on commercial equipment to do their job of detection and surveillance. This required them to fabricate special aircraft shock mounts that would fit the commercial stuff, which had varied aspect ratios different from those specified in the standard ARINC mounts used for military equipment. I needed to make the mount below to fit a military nomenclatured Hewlett-Packard audio oscillator (O-10/APA-6X) that was a development of the orignal 200A that H-P began manufacturing in a rented garage in 1939.
Here's a photo of the specific piece of equipment that needed a mount. As you can see it is wide, and not very deep from front to back. The front panel is 15" wide x 6 1/2" tall:
So...the blurry B&W WWII photos I have of such mounts showed them using the ARINC design but clearly with different dimensions. You can see one of the commercial light gray HP oscillators to the lower right side of the photo. The mount under it is probably a shop made expedient to get the capability quickly into combat.
I had an original MT-171/U using ARINC standards that was used for a great percentage of the military ECM gear, and just copied the basic components in appropriate dimensions to make it fit the oscillator. Not hard to do, but the one element that I couldn't do with a simple shear and press brake was making the clearance dimples for the rubber shock unit screws. Here is a photo of a piloted die set that I had to make for the screw clearance dimples, also showing some test samples. The little squares of plastic are from a roll of urethane die film, which prevents stretch marks during the forming process. The OD of the dies is 1.750".
Below is the completed replica mount for the Hewlett-Packard O-10 oscillator. The one I'm planning for the larger Hallicrafters S-27 and SX-28 ham radio receivers require six rubber mount units rather than four - two more in the middle of the necessary long horizontal spans. At 75lbs, those receivers are heavy, man... I'm going to rivet a .063" stainless steel shim between the end brackets to help distribute the weight evenly across the spans. This small HP oscillator didn't need that kind of support.
