Test build of Virtual 2315 Cartridge Facility enclosure and mini disk drive

ENCLOSURE TO MOUNT VIRTUAL 2315 CARTRIDGE FACILITY IN IBM 1130

The Virtual 2315 Cartridge Facility (V2315CF) is installed inside an IBM 1130 computer with the main enclosure, constructed of acrylic, bolted to the top of the internal 2310 disk drive of the computing system. Cables from that enclosure connect to other elements of the V2315CF, as well as to the 2310 disk drive and the 1130 system itself. The 2310 disk drive accepts 2315 disk cartridges, which enclose a 14" disk platter that holds 512K 16-bit words of 1130 data. 

The enclosure front plate houses the main electronics of the V2315CF on the left and a miniature version of the front of the 2310 disk drive on the right. Mini 2315 cartridges are inserted into the mini disk drive, in the same way the real 2315 is inserted into the 2310 drive from the front of the IBM 1130. A switch on the miniature disk drive is an analog of the motor on/off switch of the real 2310. 

The mini 2315 cartridges hold a microSD card inside them that stores the 512K words of data that would reside on a real 2315. When the mini cartridge is inserted into the mini drive of the V2315CF, the motor switch on the mini drive turned on and the switch on the main electronics panel is flipped to Load, the contents of the mini cartridge are read and copied into RAM inside the main electronics. The File Ready lamp on the IBM 1130 console turns on when the V2315CF is ready to let software read, write and seek between cylinders of the virtual disk drive. 

The V2315CF supports two modes - real and virtual. In real mode, the physical 2310 drive in the IBM 1130 is switched on with a dummy 2315 inserted. It spins and the disk arm moves around as commanded by software in the 1130, while the V2315CF transfers data from the mini cartridge instead of the disk heads of the real 2310. In virtual mode, the physical 2310 drive is not turned on, but the V2315CF instead simulates its behavior so that the 1130 software can access the mini cartridge. 

When the motor is turned off and the main electronics switch flipped to Unload, the contents of RAM, which may have been updated as the 1130 software wrote new data to sectors of the 2315, will be transferred back to the microSD card inside the mini cartridge. Thus, the data is permanently saved on the mini 2315 just as it would be on a physical 2315 cartridge used with an unaltered 1130 and its 2310 disk drive. 

PROTOTYPE ENCLOSURE LASER CUT AND GLUED TOGETHER

My friend Barry Ward cut the design on some smoked black colored acrylic and glued it together. I added the support brackets and tested the mounting of all the components. Here I am looking to discover all the interference issues or other changes that will make the production version easier to build and service. 

TESTING PROTOTYPE OF MINI DISK DRIVE DESIGNED BY BARRY WARD

Barry Ward measured the front entrance of the 2310 disk drive from the IBM 1130 system at my workshop, along with a 2315 disk cartridge, and modeled miniature versions that will be used with the V2315CF. 

The mini 2315 cartridge is 3 3/4" in diameter and proportional to an IBM built 2315 cartridge. It mounts a PCB underneath with a microSD socket, a few components and a male 2x4 header that is in the rear. That header plugs into a female socket inside the disk drive when the mini cartridge is slid into the mini drive.

The front of the disk drive in the IBM 1130 is accessed by swinging the right front door open on the 1130 system, where you see the opening of the disk drive, with a blue handle used to open and close the drive, plus a motor switch. 

The drive handle is opened in the real 2310 drive, allowing a 2315 disk cartridge to be slid into the drive or pulled out. When the handle is returned to the vertical position, the cartridge is ready to be used. 

Prototype without motor switch mounted

The motor switch can be recreated with a very small toggle switch that is only a bit out of proportion (bigger than the real drive scaled down). Barry and I did some careful modeling in CAD and he is test fitting the modified front bezel right now. 

What a real 1130 internal drive front looks like

Barry has laser cutters and 3D printers in his home (and heavier duty machinery in his workshop). He is making the next revision of the prototype while I finish the work on the enclosure and other parts of the V2315CF.