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Welcome to the community build guide for the Open Source Sex Machine (OSSM). In this section, you’ll learn the major components and the build sequence you’ll follow to assemble a fully working OSSM from a DIY kit.

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OSSM overview

The OSSM has two main groups: the actuator and the mount.

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Actuator

The actuator is the functional core of the OSSM. It contains:
  • Mount interface (PitClamp or Pivot)
  • Motor and pulley
  • Linear rail and carriage
  • Belt and rear/front tensioners
  • End effector (toy mounting hardware)
Most of your build time will be spent assembling the actuator and setting belt tension.

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Frame

The frame is the structural stand that holds and positions the actuator. You can build on the basic mount or an extrusion stand depending on your setup. See OSSM: Basic Mount V2 for mounting options.
There are pinch points around the rail and carriage. Keep hands, cables, and anything sensitive away from the moving rail during assembly and testing. The OSSM can generate significant force—always be able to stop or move away quickly.

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Build sequence at a glance

You’ll assemble the actuator first, then install electronics, wire everything, and run an initial test.
1

Install the rear tensioner

Mount the rear tensioner and thread the belt through the rear path.
The rear tensioner sits square to the rail and the belt moves freely with light finger tension.
2

Attach the end effector

Install the threaded end piece or preferred toy mount onto the last three.
The end effector fasteners are snug and the mount aligns with the rail centerline.
3

Fit the front tensioner (loosely)

Install the front tensioner but leave it slightly loose. You’ll set the final stroke limit and belt tension later.
The carriage can travel the full intended range without binding.
4

Bearings + Motorhead bottom

Assemble bearings and the OSSM motorhead bottom, then secure to the linear rail.
With gentle hand pressure, the carriage glides smoothly end to end.
5

Install the pulley on the motor

Place the pulley onto the motor shaft and secure it per the hardware kit.
Confirm pulley alignment with the belt path. Misalignment increases wear and can cause belt walk.
The pulley set screw(s) are tight and the pulley does not rock on the shaft.
6

Attach the motorhead middle

Fit and secure the middle section of the motorhead.
No cables are pinched; the belt tracks cleanly through the assembly.
7

Add the motorhead cover

Install the final cover for the motorhead assembly.
All fasteners are snug; no rubbing or scraping noises when you move the carriage by hand.
8

Set belt tension

Use the tension bolt to set final belt tension. The belt should be taut without causing bearing grind.
A good starting point is firm finger deflection of ~2–3 mm at mid‑span. Adjust during testing if you hear belt chatter or see missed steps.
Manual carriage motion feels smooth and returns to the same positions consistently.
9

Mount the electronics

Install the OSSM control board in its enclosure and mount it to your frame.
The board is secure, connectors face a convenient direction, and ventilation isn’t obstructed.
10

Wire power and data

Connect the motor power and PH04 data cables to the board. Follow the wiring order in Wiring Your Gold Motor.
Red/black power leads are in +/– terminals; PH04 is fully seated; no stray wire strands are exposed.
11

Initial firmware + motion test

Power the OSSM, allow it to home, then run a short test at low speed. If needed, update firmware using Flashing your OSSM.
Homing completes without grinding or stalls, and motion is smooth at low speeds.

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Threadlocker and fastener retention

Use a medium‑strength threadlocker (e.g., blue) on metal‑to‑metal fasteners to keep them from loosening under vibration—especially bearing nuts, pulley set screws, and frame hardware. Avoid getting threadlocker on plastic parts or inside bearings.
No threadlocker on hand? A tiny dab of plain white PVA glue on the thread tips can add light resistance in a pinch. Let it dry before use.
Applying threadlocker to the motor shaft/pulley can help prevent slip, but it makes removal difficult. Confirm pulley position and belt alignment first, apply sparingly, and allow full cure time before testing.

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Where to go next

For stability during testing and play, use a weighted base or the included sandbag with your stand. A heavier base reduces vibration, keeps belt tension consistent, and improves motion quality.