Soft Serve: Replacing Air Pump Gearbox

SS: Replacing Air Pump Gearbox

How-To Guide :: Soft Serve :: Replacing Air Pump Gearbox

Spaceman soft serve machines use a belt-drive system where a motor is connected via a belt and pulleys to a gearbox that turns the auger in the freezing cylinder to agitate the product.  Occasionally, these gearboxes need to be replaced.  This article will go over the steps on properly replacing your gear box.  This article refers to air pump gearboxes for models with a belt-driven air pump.  For instructions on replacing standard gearboxes on models without an air pump, please see the SS: Replacing Standard Gearbox article.

Part Ordering:  Replacement gearboxes can be purchased at PartsTown.  Please see the Spaceman Gearbox article for more information on selecting the correct gearbox for your machine.
Note:  Spaceman has updated gearboxes in newer models with larger mounting brackets and more robust mounting points on the gearbox.  New gearboxes can be installed on older models; however, a new bracket and coupling may be required.  Please see the Spaceman Gearbox article for more information.


Required Tools
  1. Flathead screwdriver
  2. Philips head screwdriver
  3. Metric Hex driver or Allen key set
  4. Metric or adjustable wrench set
  5. Metric Socket set
  6. Needle Nose Pliers

How to Replace Gearbox

  1. Turn off and unplug the machine.  
  2. Follow the instructions in the Operator Manual to properly drain, disassemble, and clean the machine.  This process cannot be performed when the machine is assembled.

Warning: The machine must be unplugged as power may be available to certain components even with the machine power switch in the off position.

  1. Using a flathead screwdriver move quarter-turn panel locks to unlocked position and remove side panels and rear panel as able.
  2. Using needle nose pliers to pinch the tensioning post, and an adjustable wrench or socket, loosen the tension on both motor mount springs to loosen the main belt tension.
  3. Remove the Air Pump clutch
  1. Remove the toothed belt between the air pump pulley and the gearbox clutch
  2. Locate air pump clutch and cut zip-ties off the metal clutch mounting bracket.  If the machine has two flavors, this must be repeated for both sides, even if not replacing both gearboxes.
  3. Using Philips head screwdriver and 8mm wrench, remove Philips screws and nuts holding air pump clutch assemblies to the clutch mounting bracket.
  4. Using Philips head screwdriver, remove mounting screws from both sides of the clutch mounting bracket.  Remove the clutch mounting bracket from the machine.
  5. Use a 10mm wrench to remove the center bolt from the air pump clutch attached to the gearbox being replaced.
  6. Pull the front cover off the clutch.
  7. Using pliers, carefully remove the key from inside clutch. 
  8. Slide the rest of the clutch assembly off the gearbox shaft.  Take extra care not to lose any Shims (0-3) or spacers (2).  Notate placement of shims and spacers.
  1. Remove the belt(s) between the motor and gearbox.
  2. Locate the two set-screws on the large top pulley attached to the gearbox.  Use an appropriate allen wrench to remove the two set-screws (3mm or 5mm depending on model).  
  3. Install one of the set screws you just removed into the center set-screw hole on the pulley bushing.  Tighten until the pulley and bushing separate.
  1. Tightening down this set screw can sometimes seem difficult.  Apply additional pressure until you feel set screw loosen the pulley assembly come free of gear box.  
  1. Remove the pulley and bushing from the gearbox, and set the set screws aside.
  2. Use a large socket or adjustable wrench to remove the four bolts from the gearbox mount.  Take care while loosening the last bolt as the Gearbox will fall off without support.  
  1. Machines utilize a 12mm, 13mm, or 14mm bolt-head depending on model. 
  1. Separate and remove the gearbox and gearbox mounting bracket.  Notate orientation of gearbox and mounting bracket.

Note: Spaceman has updated gear boxes and mounting bracket sizes on newer models.   Newer gear boxes may require replacing the mounting bracket with a larger mounting bracket.  For more information, see the Identifying Correct Gear Box article.

  1. Clean the gearbox mounting bracket and inspect for cracks or damage that would require replacement.
  2. Install new gearbox to the mounting bracket and place assembly into the machine, holding in place by lightly attaching all four mounting bolts.
  3. Using the appropriate socket or adjustable wrench, tighten the four mounting bolts in a cross pattern.  While tightening, ensure gear box remains centered to mounting bracket, and mounting bracket stays centered to rear of cylinder.  Bolts should be torqued sufficiently, however, take care not to over-tighten.
  4. Reinstall the gearbox pulley, and place bushing inside center of pulley and align.  The gear box pulley should be directly in-line with motor pulley below.  
  5. Install set screws into the two side holes on the bushing, attaching the pulley to the bushing.  Prior to tightening, check again to ensure gearbox pulley is in line with the motor pulley below and adjust, as necessary.

Warning:  Ensure Pulley and Bushing are fully installed on Gear Box shaft.  The shaft should slightly protrude through the rear of the bushing.

  1. Inspect the belt for excess wear or damage and reinstall the belt on the pulleys.  
  2. Check belt tension.  There should be approximately +/- 0.5 inches of play in the belt.  
  3. Using needle nose pliers to hold the motor tensioning shaft and an appropriate wrench or socket, tighten the motor mounting springs until the belt tension is set correctly. 

Warning:  Do NOT over-tighten belts.  This may cause overheating and damage to the motor or gearbox.

  1. Lubricate and install drive shaft and drive shaft gasket into cylinder.  This will ensure the gearbox is aligned correctly to the freezing cylinder.  You should be able to turn the belts by hand and not feel or hear any binding, grinding, or other noises.
  2. Plug in and power on the machine.  press the RESET button and then WASH button.  

Warning:  Do NOT place hands or tools inside machine or freezing cylinder while machine is in operation, serious injury or damage may occur.

  1. Inspect the belt and pulleys to ensure the belts are not binding, running vertically, and the pulleys are not wobbling.
  2. Using a clamp-style amp-meter, check the amperage on one leg of the motor power.  Amperage will differ depending on the motor, but should generally be around 1.0 Amps.
  3. Press RESET to stop the machine operation.
  4. Re-install the air pump clutch(es)
  1. Slide the smaller spacer onto the gearbox drive shaft.
  2. Slide the back of clutch onto the gearbox drive shaft.
  3. Slide the larger spacer and shims onto the gearbox drive shaft.
  4. Reinstall the clutch key onto the gearbox drive shaft; pinch firmly into place.
  5. Line the front of clutch up with the key and slide onto the gearbox drive shaft.
  6. Place the washer on the front of the clutch, making sure that the rough side is facing the clutch face.  
  7. Use a 10mm wrench to install the clutch screw to the drive shaft.
  8. Re-install the toothed air pump belt between the air pump pulley and clutch.  This belt should remain tensioned from before.
  9. Re-install the clutch mounting bracket to machine frame.  Ensure that the bracket lines up with the mounting holes on the front of the clutch.  Only tighten screws loosely.
  10. Secure the clutches to the mounting bracket using an 8mm socket wrench.  The clutch locating tab (screw hole) needs to be on the backside of the mounting bracket.  If installed incorrectly, the clutch will not work
  11. Tightly secure the clutch mounting bracket to the frame, and reinstall any zip-ties to secure wires in place.
  12. Repeat steps 21-24 to test the belt tension and verify functionality.  
  1. Re-install and secure outer panels.  

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