Ball Lock Clutch Maintenance (twin disk)

DAVID BRADLEY Ball Lock Clutch Maintenance Twin Disk

These instructions pertain to the twin disk style ball lock clutch as found on most pre-1955 DB tractors with 1/2" V-belts. This clutch featured two asbestos facings which floated between the outer pressure plates. The outer pressure plate is threaded onto an adjustment sleeve in the hub. These instructions have been paraphrased from an actual David Bradley owner's manual.

CLUTCH ADJUSTMENT

This clutch is a ball lock clutch, and it is necessary to push the handle forward until the clutch snaps into the engaged position. Although this clutch is very durable, adjustment may be necessary at some point. This is accomplished by removing the Allen set screw from the outer clutch, and turning the clutch plate clockwise exactly 30 degrees. Replace the Allen set screw in the second threaded (formerly empty) hole in the outer clutch plate. Only one set screw is used, leaving one open hole in the sheave. The set screw must line up with a flat on the threaded hub to avoid damaging threads. The two hole arrangement allows adjustment in smaller increments. Do not put set screws in both holes! To do so would cause thread damage due to one or the other not lining up with a flat on the hub.

If the clutch sheave is difficult to turn on the adjusting sleeve, you will need to find a way to hold the threaded hub while you turn the outer clutch plate. This may require some imagination. Most of the threaded hubs have two holes into which two nails (pins, bolts, etc.) may be inserted to hold steady with a screwdriver (prybar, etc.). Many collectors make up a tool for the hub with pins or bolts in the end of a piece of flat steel bar, spaced to match the holes in the hub. There really are no good tools for the early clutch plates. Sometimes a long bolt threaded into one of the set screw holes (not all the way down to the hub) is enough to get a little leverage. A pipe wrench also works, but it is frowned upon because it will leave jaw marks on the part. In tough cases, use lots of penetrating oil and lots of patience. Once the clutch is apart, take the opportunity to clean up the threads and add a bit of lubrication.

If the facing becomes glazed or covered with grease or oil, it may need to be cleaned. Wash the facing with gasoline or kerosene and wipe dry. Brake cleaner is a more modern alternative which also works well. Just be careful of the paint. A glazed surface can be broken up with a wire brush.

REPLACEMENT AND REPAIR
Ball Lock Clutch (twin disk)

FACING

1) Disengage clutch

2) Loosen Allen set screw (16) in clutch plate (6) and unscrew clutch plate from adjusting sleeve.

3) Remove groove pin (4) and adjusting sleeve (5).

4) Remove all burrs from groove pin and shaft.

5) Remove pulley (13) and facings (19) from the shaft. Leave inner clutch plate in place. Watch for falling balls! There are 10 (sometimes 11) steel balls inside the collar on the opposite side of the clutch pulley, behind the pressure washer (11). If you are careful (and lucky) the pressure washer (11) might keep them in place around the shaft when the pulley is removed. However, it is possible that vibration or other factors might cause the washer to slip a bit and the balls may spill on the floor. If that happens, be sure to catch them.

6) Thoroughly clean all parts of grease and oil.

7) Reverse above procedure to reassemble, being sure that all balls are in their proper position. See below for more instructions on installing the balls.

8) If other parts are replaced besides the clutch facing, be sure that each part slips freely over the input shaft of the transmission. These parts must slide freely.

PULLEY BEARING

In the event the bronze bearing (2) in the clutch pulley (13) should need to be replaced, the manual instructs as follows:
Align new bearing against the old one. Drive out old bearing using a soft wood block.
However, if you have access to, or can make a bearing driver, use the driver in conjunction with an arbor press (if available) or use a hammer with caution.

THRUST COLLAR

1) Remove pulley and facings as outlined above.

2) Slip inner clutch plate from shaft (see note above about balls).

3) Remove Cotter from control rod and handle, and remove rod from clutch yoke lever (14).

4) Remove cotter (18) and rivet (1) from clutch yoke (14) and transmission.

5) Slip clutch yoke lever (14) and pressure ring (10) from input shaft, being careful to catch all (10 or 11) of the balls from the pressure ring (10).

6) Remove clutch pressure washer (11).

7) Pry Thrust collar (9) from input shaft. Use equal pressure from both sides if possible.

8) Replace (new) thrust collar (9) by sliding over input shaft and tapping carefully, using a piece of pipe or tube for a driver.

9) Reverse above procedure to reassemble. The steel balls (8) may be inserted after the pressure ring, clutchpressure washer and hypro key have been slipped into place. Tilt tractor backward until back end of handles are touching the floor, and turn the pressure ring so that the hole in the pressure ring in in the uppermost position, and drop the balls in through this hole. This operation is a bit tricky, and many collectors resort to simply turning the transmission on its side so the balls don't spill on the floor. Complete reassembly can now be made, reversing above procedures.

This style of ball lock clutch was used on the following models: 57560, 57561, 57571, and 57584.

Since 1/2/4