Robo-CD Changer DIY Notes.

The mechanical portion of the Robo CD changer is made of 4 main parts:

The Base. Holds the rails that the Gantry slides on.
The Gantry. Slides back and forth on the rails, holds the Tower.
The Tower. Goes up and down. Holds the Jaws.
The Jaws pickup a single CD from a stack and release the CD into the Reader.

The motors and gearboxes I used are from Tamiya:

The Base is made of a set of legs, held apart by a Back Panel, and supports 2 rails.

Leg A was a scrap piece of Poplar 1x3 13" long.
Leg B is Baltic Birch 1/2" plywood 3-1/4" x 16"
The Back Panel is a piece of 3/16" ply 32" wide by 8" tall.

Dimensions are not critical.

Leg B has a cut-out for the lower rail:

The cutout is 8-1/4" from the bottom of the leg.
The cutout is 7/8" deep by 7/8" wide.

The two rails are 1/8" thick aluminum L-channel from the hardware store.

The top rail is 1-1/4" x 1-1/4"
The bottom rail is 3/4" x 3/4"
Both are 32" long.

Both have cut-outs about an inch wide on each end so the rails mount easily on the legs.

The Gantry is a square piece of 1/2" Baltic Birch Plywood 7-1/2" on a side.

The Gantry hangs from, and rolls across the narrow edge of the top track using two screen door rollers:

I changed the hardware to use lock nuts, bolts for solid axle shafts, and used extra nuts and washers to adjust the spacing of things.

The Gantry is stabilized and kept from swinging backwards into the base by the bottom screen door roller rolling across the flat part of the lower rail:

The center of gravity is being held in front of the top suspension rails. Gravity wants to swing the gantry and tower back into the base.The wheel rolling against the lower track gives a rock solid linear reference for the gantry. (it travels in a very straight, and repeatable motion) The 3 point suspension gives a very stable, smooth, low friction ride for the gantry.

The Tower is a piece of 1/8" basswood from the hobby store 16" x 2" - anything flat, stiff and thin will do.

The tower is suspended by the string that pulls it up and down, and kept in place by 4 modified screen door rollers:

Here's the back of the tower, showing the pulley the suspension string goes around, the black strip for the top of travel sensor, the micro switch for detecting if a CD has been picked up, and the block of wood the jaw solenoid is attached to.

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