The tractor units are frames that hold two 4-inch rollers with Kaydon bearings, which are coupled directly to AC servo motors through flanges shrink fitted onto the rollers. These units have to be assembled carefully to give the right fits; they are designed with very few adjustments, although the flanges must be shimmed properly to align the motors with the drive cylinders to prevent binding.

1. Press rollers into place in the drive-tractor bodies. This is a multi-step process. First, press a bearing onto one end of a roller with the special tool 10-100 (see drawing AST-10-P20). Set up the deep tool 10-101 on the press, place the tractor upside down on top of this tool, and orient the roller with the bearing on it in the bore of the tractor, using the alignment jig (10-102), then press the bearing into the bottom of the frame until the tool bottoms out. Turn the frame over and support it and the end of the roller on tool 10-100. NOW, REMOVE THE ALIGNMENT JIG! Next, press the second bearing onto the projecting end of the roller, then into the bore, using tool 10-101 and pressing it to its end of travel. Repeat for the second roller. The tractor is now ready to receive its flanges for mounting the motors.
2. Set up heater (hot plate and oil bath) for heating the flanges. You will need the hot plate, a sause pan with cover, wire to suspend the part above bottom of pan, wood splints to hold the part, insulated gloves, and a thermometer that goes up to at least 300 F.
3. Shrink fit the flanges onto the rollers and check runout (especially after first one). Use utility-knife blades as shims to orient the collars; design clearance is 0.042 inches between bottom of collar and top of frame. Heat to at least 200F to give >= 0.017 inch clearance. Interference is 0.0010 to 0.0018 inches, corresponding to a temperature difference of up to 65F.
4. Put locking compound on screws to attach the motors and cover plates.
5. Set up an accurate dial indicator to measure the axial runout of the flanges and mark deviations around the edge of the flange.
6. Attach motors to flanges with M6x20 socket-head cap screws and measure runout of of the top mounting surface of the motor as you rotate the roller. This runout should be no more than about 0.0004 inches. Shim the motors, if necessary, and remeasure the runout.
7. Attach flexure holders around motors with 1/4-20x1/2 socket-head cap screws.
8. Measure relative positions of motor bases and top of flexue holders and decide if shims are required for the bases. In practice, these tractors do not seem to need such shims.
9. Attach flexures to motors with M6X15 hexagonal-head cap screws and to the flexure holders with 1/4-20x3/8 socket-head cap screws.
10. Attach cover plates to bottoms of tractors with 1/4-20x3/8 socket-head cap screws.
11. Add the guide rollers to the ends of the tractor.

1. Support the tractor on the special cart and screw the flexure into the hole provided.
2. Attach lifting hardware to top of tractor. This involves adding two 1x3x1/8-inch steel clips to holes in the top and bottom plates with 1/4-20 screws, then attaching the special sling made of wire rope between them. Next, hook the crane to the sling and tie a safety rope around the tractor and through the hook of the crane.
3. Raise the tractor off the cart, being careful to keep the flexure from banging into the floor.
4. Raise the tractor until it is even with the middle of the drive sector. Push it up against the sector, and hold it in place with the two special roller attachments with screws into the sets of holes between the drive motors.
5. Lower the tractor along the drive sector, guiding the threaded end through the hole in the attachment block. You may have to remove the cross piece in the bumper stand to do this.
6. With the two guide rollers still in place, add the tensioning springs to the tensioning frames for tilt. Snug up the springs, and remove the guide rollers. Add the washer and nut to the end of the flexure (rod) and tighten the nut with a special socket from the tool chest.
7. Finsh tensioning the springs and test the drive with the hand controller.

1. Support the tractor on the special cart and add the special sling between the two lifting eyes in the top edge of the cans over the motors.
2. Tie the rope from the winch on the lifting frame to the sling, and lift the tractor off the cart.
3. Add the flexure (attachment rod) to the end of the tractor, if you haven't done so already, position the tractor with the lifting frame, and press the tractor up against the drive wheel. Use the winch on the lifting frame to orient it properly.
4. Slide the tractor into place past the left side of the tensioning frame, guiding the threaded end of the flexure through the hole in the attachment piece. Put the washer and nut on the flexure loosely. You may have to loosen the flexure in the tractor to get these parts to go together; tighten it once the flexure is through the attachment hole.
5. Assemble the hanger to support most of the weight of the tractor, and adjust the level to place the two top guide rollers on the top of the drive wheel.
6. Assembe the tensioning frame around the tractor, add the spring tensioning devices, and tension the springs to keep the rollers from slipping.
7. As for the tilt tractor, test the drive with the hand controller.