Dempster Worm Gear
Pump Jack Installation  

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Dempster’s model BB33 Pump Jack is a worm gear pump jack that can pump down to 205’ with a
1-7/8” open top working barrel cylinder pump, using a 1/2 hp electric motor.

The Dempster Pump Jack is designed to operate a hand pump or windmill pump, with an electric motor, gasoline engine or other power source. The kits described adapt the basic gearcase for the first two drives. In addition, it can be powered by any other source which is adaptable to provide up to the maximum of 40 strokes per minute ( 640 RPM shaft speed ).

The basic pump body for which this jack is designed, has a 3-1/2” outside diameter barrel and a 7/16” x 1” flatbar, to which the crosshead is attached. The gearcase can be attached to slightly larger or slightly smaller barrels by carefully shimming and positioning.

The pump jack may be used as a backup to a windmill to provide water on calm days, or if the windmill is out of service. However, since the relative strokes will not coincide, only one pinned connection must be used at a time. Ie: you can not run a windmill and pump jack at the same time. For instance, the mill wood pole must be removed from the flatbar when the pump jack is to operate. The hand pump handle must be disconnected when the jack is to be operated, just as the handle must be unpinned or the jack must be removed when the mill is operated. The handle must only be attached when pumping by hand (jack may stay in place on hand pump with the flatbar pin removed).

For this reason, carefully study the operating methods to be used to determine the appropriate positioning of the gearcase and the set of pitman holes to be used to attach the crosshead.

Pump jack load limits for the BB33 pump jack are as follows. The BB33 Dempster should not be used with a greater than 1/2 hp electric motor, or a 1-1/2 hp gasoline engine. The speed must not exceed 40 strokes per minute (640 RPM shaft speed) under any circumstances. Warranty is void if the load limits or the recommended capacities are exceeded.
GEARCASE TO PUMP BODY The length of the pump jack stroke is 6" and will generally not be the same as the windmill or hand pump stroke. For this reason, each power source must be attached separately. 
--Operate the pump jack, and locate the center of the stroke, and hold the pump rod in this position. The center of the flatbar pin hole at this distance above the fulcrum top, is the primary reference point used to determine positioning of the gear case.
--Mark the hand pump body 41-1/4" or 44-1/4" below this reference point, as appropriate to attach the pitmans for clearance of cranks, and the pump handle, ect.
--Secure the gear case to the hand pump body opposite the spout on the hand pump, using the U-bolt at this point. Tighten the nuts securely, but be careful not to crack the hand pump or the gear case bodies by over-tightening.
--Always pin the hand pump handle to the flatbar to hold or position the pump rod when changing connections. In some case, when disconnected, the free rod may drop far enough that the hole will not be accessible to attach the handle.
--Slide the cross head over the flatbar, however do not pin now.
--Attach single hole end of the wood pitmans to the crank arms, securing them with flat 1" washers and 3/16" x 1-1/2" cotter pins.
--Assemble cross bars to the cross head, and install bars in appropriate holes in pitman arms. Secure the assembly with a 3/8" x 1-1/2" bolt and hardware on each end.
--Position flatbar in cross head and install pump pin. Secure with 1/8" x 1" cotter pin. Remove the hand pump handle.
--FILL EACH SIDE of the main frame crank case, through the top plug to the Oil Level plug with 80-90 winter weight gear oil, which takes approximately 1/3 pint each end.
--Be sure to replace the plugs after filling with gear oil.
--Turn pump jack through several revolutions by rotating the drive pulley counter-clockwise, by hand, to be sure there is no interference mechanically or at either end of the stroke. Double check crank rotation as noted by arrow on the gear case.


1/3 H.P. 1/2 H.P.

Performance based on pump jack operating @ maximum speed of 40 strokes per minute ( 640 RPM shaft speed ) @ a 6" stroke, using a single action cylinder.

Electric Motor Drive is to be 1750 RPM with a 5/8" shaft 1/2 HP maximum.
-Attach the motor bracket to the cover plate with 3 3/8" x 3/4" cap screws included in the cover bosses. The motor bracket should be installed flat side up.
-Attach the motor rails, with the flat side down and the ears for the bolts facing toward the gear case.
Use 2 bolts 5/16" x 1-1/4" cap screws and nuts each. The three components are slotted to adapt to the motor and for motor adjustment purposes.
-Install the motor on the motor bracket on the motor rails loosely, opposite the flat sides. IE on top. Insert 5/16" x 1-1/4" cap screws from below, head must fit into slots.
-Attach the 8" V-pulley to the pump jack shaft with 1/4" square x 2-1/4" key and tighten set screws in the pulley hub securely.
-Attach the smaller 2-1/2" V-pulley to the motor shaft with 1/4" key and set screws.
-Install V-belt. Slide motor on rails to align pulleys and then slide the rails on the motor bracket to adjust belt tension. Proper tension is 1/2" to 3/4" detention midway between the pulleys. Tighten all rail and motor mounting hardware.
-Motor shaft MUST rotate counter-clockwise as viewed from end of shaft. IE: facing the motor end looking at the pulley and then the motor.
-Be sure the crank case is lubricated before operating the pump jack.

Electric Motor Package Components

Gas Engine Package Components.


Package Components by item number.

Part Number





Cross Bar 
(2) 900-00023  3/8" NC x 2-1/2" Hex Head Bolt
(2) 900-05011  3/8" NC Hex Nut
2 380-3-6002 1 Cross Head
3 380-3-0071 1 Pump Pin
(1) 900-22008  1/8" x 1" Cotter Pin
4 900-24010 1 Key  1/4" x 1/4" x 2-1/4"
6 380-0-00?? 1 V-Pulley - Single Groove 8" V-Pulley with 7/8" Bore 
7 903-08005 1 V-Pulley - Single Groove 8" Diameter x 7/8" Bore
8 903-00000 1 V-Belt - 34" long
9 380-3-6017 2 Motor Rails
(8) 900-00009  5/16" NC x 1-1/4" Hex Head Bolt
(8) 900-05008  5/16" NC Hex Nut
10 380-3-6012 1 Motor Bracket
(3) 900-00016  3/8" NC x 3/4" Hex Head Bolt
11 903-08006 1 V-Pulley - Single Groove - 2-1/2" Diameter x 5/8" Bore
GASOLINE ENGINE 1-1/2 hp MAXIMUM or Electric Motor 1/2 HP Maximum.
The Electric Drive Components Package #380-1-6005 comes with an 8" V-pulley for the pump jack shaft, in addition to the cross bar items. The #380-1-6006 Gas Engine Drive Components Package comes with a 8" single groove V-pulley for the pump jack shaft, along with the cross bar items.

-Attach the gear case and the pitman arms to cross bar assembly as described for the electric motor.
-Attach the pulley to the pump jack shaft with a 1/4" square x 2-1/4" key and tighten set screws in the pulley hub.
-A separate mounting must be provided for other than 1/3 HP and 1/2 HP electric motors. It is not recommended to mount any gasoline engine to the mounting bracket for an electric motor.
-Install the proper size pulley on the power unit shaft to drive these pulleys at a MAXIMUM of 640 RPM which is 40 strokes per minute.

Dempster pump jack operation.
- Be sure gear cases are lubricated before operating.
- Be sure cranks and pitman are clear of possible obstructions.
- Double check crank rotation on initial startup.
- Drain the first fill of oil after 8 hours of running, to flush any foreign matter or condensed water.
- Change oil in the crank cases annually to remove any accumulation of moisture or foreign particles.
- Periodically oil the crankpin / pitman / cross bar connections during use periods.

When using a windmill and pump jack combination, ALWAYS completely detach the windmill wood pole or the pump jack cross head, before attaching the other operating source. The operating strokes will very rarely coincide enough to allow you to operate with both drive sources, without possible interference between them.


Dempster Pump Jacks