Technical Support Document 012 - 7/95

CHANGING MOTOR DRIVE PINION GEAR ON SENTINEL ENLARGER MOTOR PINNED PINIONS

The Sentinel Motor drive pinion gear meshes with the rack on the front the enlarger's column. This gear is "pinned" onto the motor shaft. Since both the installation and removal of this pinion gear from the motor shaft requires special tools, it is recommended that only personnel who are qualified to do mechanical work perform this task.

The tools and parts required for pinion replacement are as follows:

REMOVAL OF PINION GEAR FROM MOTOR SHAFT

Before a new pinion is installed, the old one must first be removed. The following procedure outlines this process:

1. On the edge of the brass pinion collar, locate the roll pin end. The diagram below, left, shows a typical pinion installed:
   

2. Clamp the Pinion and Brass Collar in a vise, such that one end of the roll pin is at the top. (See above, right.) The body of the motor will hang off one side of the vise. This will allow the Roll Pin to be tapped out easily. Be sure the grip is tight, but not so tight as to overtly distort the shape of the brass collar.

3. Using the pin punch and hammer, tap the roll pin out. If this tapping causes the vise's grip on the collar to slip, tighten the vise a little.
   
4. Once the pin falls through the bottom, remove the Collar and Pinion from the vise.
   
5. Pull the Pinion and Collar from the motor shaft. Typically, some force will be required to do this. A large, flat-head screwdriver may be used to pry the Collar and Pinion from the shaft. The Collar and Pinion should come off as one piece.
   
6. This completes the removal of the old Motor Pinion.
   
   

INSTALLATION OF NEW PINION ONTO MOTOR SHAFT

The following procedure outlines how to install a new pinion onto an AF Motor for use on the Sentinel enlarger.

1. Insert the shank of the new Pinion gear into the new brass Collar, if this has not already been done. This will require some force to fully seat the Pinion into the Collar.
   

2. Place the completed Pinion and brass Collar assembly onto the motor shaft. For proper positioning, use the Pinion Positioning Tool between the base of the Collar and the body of the motor. To achieve the spacing required (1/4inch between Collar and motor body), slide the Pinion Positioning Tool around the motor shaft between the Collar and Pinion, and the motor body. See the diagram below:

3. Leaving the Positioning Tool in place, gently clamp the motor lengthwise in a vise, such that pressure is applied to the end of the motor pinion, keeping it pressed against the Positioning Tool. This will keep the pinion straight while the new hole for the pin is drilled. The Diagram below shows the motor so clamped in the vise: Warning: Tighten the vise only enough to keep the motor in place. Overtightening will destroy the motor.
   

   
   
   

   If the motor will not fit in the vise in the above orientation, some means of holding the pinion in place must be found for the next step. Placing the motor vertically on a flat hard surface, and pressing down on the pinion with a block of wood of metal will suffice. See diagram at right, above.
   

4. Using the 3/32" Drill, drill a hole completely through the brass collar and motor shaft as shown below, while the motor is still clamped in the vise (or while pressure is being placed on the end of the pinion with the wood or metal block). Be sure that the Pinion Positioning Tool is still in place.
   

5. Once the hole is drilled, clamp the pinion by its collar into the vise so that the hole is vertically aligned. This will allow the new roll pin to be tapped into the hole. Do not clamp too tightly, so as to avoid distortion of the brass collar, and do not damage the nylon pinion. Try not to move the position of the Pinion/Collar assembly on the motor shaft. Before proceeding, view down the hole to make sure that the Collar and motor shaft holes are aligned so that the pin will travel through them easily.
   
6. Carefully tap the roll pin into the hole until it is full inserted. Be extremely careful not to strike the motor body with the hammer while doing this. When finished, there should be no portion of the roll pin protruding beyond the collar surface.
   

Inspect the newly-installed pinion. It should be relatively straight on the shaft and at the proper distance from the motor body.