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The pulley transfers power from the motor to the belt, driving the linear actuator. Proper installation and alignment of the pulley on the motor shaft is critical for smooth operation and optimal belt tension.

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Required Components and Tools

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Components

ComponentCountSpecification / Notes
Motor1With a flat spot on the shaft
Pulley1To be mounted on the motor shaft
Grub Screws2Used to secure the pulley to the motor shaft
Belt1Remaining loose end from previous assembly steps

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Tools

ToolCountSpecification / Notes
2 mm Hex1Fits the grub screws (also called “Small Allen”)
The motor shaft must have a flat spot machined on it. This flat spot provides a secure surface for the grub screws to grip, preventing the pulley from slipping during operation.

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Step-by-Step Assembly

1

Mount and lightly secure the pulley

Slide the pulley onto the motor shaft. Align one of the pulley’s grub screws with the flat spot on the motor shaft.
If the pulley bore feels too tight to slide onto the motor shaft, the bore may have burrs or debris from manufacturing. Before requesting a replacement:
  1. Check the grub screws — Ensure they are fully backed out and not protruding into the bore
  2. Inspect the bore — Look for visible burrs, rough spots, or debris inside the pulley bore
  3. Remove burrs — Lightly sand the interior of the bore with fine-grit sandpaper (320 grit or higher) to remove any manufacturing burrs
  4. Clean and retry — Wipe out any debris and try sliding the pulley onto the shaft again
This usually resolves tight-fitting pulleys. If the pulley still doesn’t fit after removing burrs, contact support for a replacement.
Use the 2 mm hex tool to lightly tighten the first grub screw. The pulley should not spin freely, but it should still be able to slide slightly up and down the shaft for adjustment.
Light tightening allows you to adjust the pulley’s vertical position while maintaining enough grip to prevent rotation. This is important for achieving proper belt alignment in the next step.
The pulley should be secure enough that it doesn’t rotate, but loose enough that you can still move it vertically along the shaft with gentle pressure.
2

Align and finalize tension

Route the belt over the pulley and gently pull some tension on the belt. The tension should pull the pulley into its correct vertical alignment on the motor shaft.
Do not apply excessive tension at this stage. You’re using the belt tension primarily to align the pulley vertically, not to set the final belt tension.
The pulley should be properly aligned vertically with the belt path. The belt should sit correctly in the pulley grooves without binding or misalignment.
3

Tighten the grub screws

Fully tighten the first grub screw that you initially set. Ensure it is firmly against the flat spot on the motor shaft.Rotate the pulley to access the second grub screw. Align this second grub screw with the flat spot on the motor shaft and tighten it completely.
Both grub screws must be firmly tightened against the flat spot on the motor shaft. If either grub screw is not properly aligned with the flat spot, the pulley may slip during operation, causing damage or poor performance.
Both grub screws should be fully tightened and firmly seated against the flat spot on the motor shaft. The pulley should not be able to rotate or slide on the shaft.
4

Set initial belt tension

Tighten the belt just a little on the open side to hold the pulley’s alignment. This provides initial tension to maintain the pulley’s position.
This is an initial tension setting to maintain alignment. Final belt tensioning will occur in a later step after all components are fully assembled.
The belt should have light tension that holds the pulley in its aligned position without being overly tight.

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Next Steps

With the pulley securely mounted on the motor shaft and the belt initially tensioned, proceed to the next section to continue the motor head assembly.