Open Source Motion Simulation

The OpenSimCraft community is focused on open source hardware and software that is designed around the SimCraft motion simulation methodology. The SimCraft methodology claims to mirror how Earth physics works, using up to six degrees of motion freedom, in order to provide a more natural simulation experience.

Hardware vs Software

The SimCraft motion simulation methodoloy is not proprietary technology, however the SimCraft company’s software/firmware and actuator hardware implementation is.

The OpenSimCraft community is currently focused on open-sourcing existing simulator “cockpit” designs (sim rigs) that will work with motion kits from SimCraft. These motion kits include both hardware, firmware and PC software used in conjunction with a piece of simulation software running on a computer (for example, a racing simulator PC software). The OpenSimCraft community is free to develop its own open source motion kits as well.

License

OpenSimCraft hardware designs are licensed under the CERN Open Hardware License (OHL), specifically CERN-OHL-S (strongly reciprocal). CERN-OHL-S was chosen because of its strong reciprocity requirement. The OpenSimCraft community encourages innovation and encourages individuals to experiment. The OpenSimCraft community and the CERN-OHL-S license do not prohibit commercial entities from selling or supporting sim rigs / cockpits that utilize the community’s designs. However, any changes or alterations to the designs must be made publicly available per the CERN-OHL-S terms and conditions.

Repositories

Each repository in the OpenSimCraft organization should contain either all of the source for a complete sim rig, or should only contain source for a set of components that add another degree of motion freedom to an existing design.

Examples:

• 8020-1dof is a repository that contains an entire cockpit design made of 80/20 extruded t-slot aluminum that can implement 1 degree of motion freedom
• 8020-2dof is the same, but is a complete design implementing 2 degrees of motion freedom
• 8020-3rd-dof is a repository that describes how construct the necessary components to add or modify 8020-2dof to add a third degree of motion freedom

TODO: define a repository naming standard

Part Naming / Numbers / SKUs

In general, a distinct part, whether it is something ordered directly from a manufacturer, machined from scratch, or something in between, needs a distinct part number within the community. By having a unique registry of parts, the OpenSimCraft community will be able to re-use things across many differet projects.

TODO: define a part numbering scheme TODO: figure out a part registry

Required Contents

Each repository must have:

• FreeCAD is the CAD tool that the community is using, along with the Assembly4 add-on. See the CAD section for additional details on requirements.

• A bill of materials (BOM) in a LibreOffice Calc spreadsheet describing the list of components required

  TODO: define a standard which includes the 80/20 manufacturer codes

• A README.md file that describes the design and whether or not it is a complete cockpit or an additional component/system for an existing cockpit

  TODO: define a standard README layout for design repositories

FreeCAD Requirements

All designs should be created with FreeCAD. Since designs should be made up of unique parts, FreeCAD files should either contain a single part, or only a logical assembly of several individual parts. Ultimately, a cockpit design may be an assembly of assemblies, with their constituent parts.

For example, if you have four 80/20 T-slot extrusions that make a square assembly, each individual extrusion should be a part, and the square assembly should only contain linked parts for each of the extrusions. There should not be additional sketches, bodies, or other non-linked-parts in the assembly. If you needed a fastener, or an additional extrusion, or any other random widget, you would want a separate file that contains that part, and link it in the parent assembly.

The Assembly4 add-on is used to help manage part linking and part relationships. While it is not an official add-on, files will open and can be modified even without it.

FreeCAD and Assembly4 require unique names for linked parts in an assembly. When adding multiple instances of the same part to an assembly, use a hyphen followed by an English letter suffix, starting with -A, and increment for each instance of the part. If you have more than 26 instances of the same part, you would circle to the top of the alphabet and continue with two letters. So, you would have -Y, -Z, and then -AA followed by -AB, and so on and so forth.