Many pneumatic stepper motors, rotary engines and other pneumatic devices were developed during our research. Several were published in research papers and/or 3-D model websites. This page lists nearly all of them, alongside with the most important properties and a link to the downloadable model (if available). If a motor design is not yet downloadable then you can send me a request for it.
Certain motors have extensive printing and assembly instructions and/or a video compilation. If you are interested in 3-D printing one of these motors then there should be plenty of information and designs to start with.
At the moment I subdivided the motors into five categories: linear, rotational, curved, rotary engine and dual. The motor name consists of a character (or two in case of dual-speed) plus a number and sometimes a postfix.
First character(s): T=linear, R=rotational, C=curved, D=dual, H=hollow. The following number indicates the major dimension (length or diameter) of the motor, in mm. The “B” postfix indicates a redesign of an existing model.
In theory it is possible to scale any design along (some combination of) its axes. This should work with some experimentation.
If you need help with a motor then you can post a comment on the associated Printables or Thingiverse (or MyMiniFactory) webpage, and I will look into it. You can also contact me directly at v.groenhuis@utwente.nl. If you designed something cool based on these designs then I am always happy to see it!
Designs are for non-commercial use only (i.e., research, education, hobby). Contact me for IP related questions.
Linear, rotational and curved stepper motors
More stepper motors and rotary engines
Linear stepper motors
| Picture | Name | Size (mm³) | Step | Force | Piston size (mm²) | Links | Notes |
 | T-08 | 8×8×5.5 | 0.2 mm | 2.5×2.5 | STEP+STL+Solidworks Printables MyMiniFactory YuJa (from 1:35) | Smallest linear pneumatic stepper motor. Challenging to print. | |
 | T-15 | 15×15×11 | 0.25 mm | 4×4 | STEP+STL+Solidworks YuJa (from 1:25) | ||
 | T-26 | 26×21×16 | 0.25 mm | 63 N | 10×10 | STEP+Solidworks Paper YouTube | Used in Sunram 4. Printed at Objet Eden 250 in high quality mode with FullCure 720 material. |
 | T-29 | 29×25×19 | 0.25 mm | 10×10 | STEP+STL+Solidworks | ||
 | T-32 | 32×30×16 | 0.3 mm | 12×10 | STEP+Solidworks MyMiniFactory Paper | Pistons are combination of 3D printed part with laser-cut teeth. Difficult to prototype. | |
 | T-48 | 48×44×34 | 0.67 mm | 20 N | 12×5 | Paper | Laser-cut cylinders. Three-cylinder design. M4 screws. Used in Sunram 3 as “Blue” actuator. |
 | T-48B | 48×44×34 | 0.67 mm | 50 N | 20×8 | Thingiverse MyMiniFactory | M2 screws. Three-cylinder design. Improved version of T-48, with 3-D printed cylinders. |
 | T-49 | 49×40×31 | 1.0 mm | 100 N | 14×14 | STEP+STL+Solidworks MyMiniFactory | Easy to prototype. M4 screws. Used in Sunram 3 as “T-49” actuator (but with larger housing). |
 | T-63 | 63×52×36 | 1.0 mm | 330 N | 20×20 | STEP+STL+Solidworks MyMiniFactory Paper YouTube | M4 screws. |
 | T-63B | 63×52×36 | 1.0 mm | 570 N | 24×24 | STEP+STL+Solidworks | Housing glued together. Top and bottom can be laser-cut so you can see inside. More robust pistons than in T-63. |
 | T-84 | 84×64×32 | 2.0 mm | 20×20 | Thingiverse MyMiniFactory | Easy to print and assemble. Three-cylinder design. M4 screws. |
Rotational stepper motors
| Picture | Name | Size (mm³) | Step | Torque | Piston size (mm²) | Links | Notes |
 | R-10 | 10×10×10 | 12.9° | 0.0012 Nm | 3×4 | STEP+STL+Solidworks MyMiniFactory | Smallest rotational motor. Gear can be laser-cut. ⌀1 mm shaft. |
 | R-25 | 25×25×20 | 6.9° | 0.10 Nm | 10×10 | Housing held together with small clips. Teeth are relatively thin. Superseded by R-25B. | |
| R-25B | 25×25×20 | 10° | 10×10 | STEP+STL+Solidworks MyMiniFactory | Housing glued together. More robust than R-25. | ||
 | R-40 | 40×40×16 | 1.01° | 0.47 Nm | 10×10 | STEP+STL+Solidworks MyMiniFactory | Laser-cut gear. |
 | R-44 | 44×44×31 | 10° | 0.45 Nm | 14×14 | STEP+STL+Solidworks STL | M4 screws. |
 | R-54 | 54×54×16 | 0.00101° | 0.24 Nm | 14×10 | STEP+STL+Solidworks | Completely useless except for demonstration purposes. |
 | R-64 | 64×64×32 | 15° / 7.5° | 24×24 | Thingiverse MyMiniFactory | Three-cylinder design. M2 screws. | |
 | R-80 | 80×80×37 | 10° | 3.7 Nm | 30×20 | STEP+STL+Solidworks | M4 screws. Top and bottom can be laser-cut. |
 | R-90 | 90×90×32 | 90° | 1.6 Nm | 30×20 | Thingiverse MyMiniFactory YuJa YouTube | Bourke engine design. M4 screws. |
Rotary engines (continuously-rotating motors)
| Picture | Name | Size (mm³) | Piston size (mm²) | Links | Notes |
 | R-66 | 66×66×43 | 24×14 | Thingiverse MyMiniFactory YouTube | Five-cylinder rotary engine. Cylinders can be straight or curved. |
 | R-52 | 52×52×36 | 18×18 | Thingiverse MyMiniFactory YouTube | Bourke rotary engine. Easy to construct. More robust and powerful than R-38 or R-66. Used in Pneumatic Screwdriver. |
 | R-38 | 38×38×48 | 16×12 | Thingiverse MyMiniFactory | Bourke rotary engine. Used in Pneumatic Screwdriver. |
Curved stepper motors
| Picture | Name | Size (mm³) | Step size | Radius of curvature | Piston size (mm²) | Link | Notes |
 | C-90 | 90×48×32 | 1° | 100 mm | 20×20 | Thingiverse MyMiniFactory | Similar design as T-84. Part of Pneumatic Ferris wheel. Easy to 3D print. |
 | C-30B | 30×27×14 | 0.5° | 80 mm | 10×10 | STEP+STL+Solidworks MyMiniFactory | Multi-material print. |
 | C-30 | 30×23×14 | 0.25° | 50 mm | 10×10 | STEP+Solidworks Paper YouTube | Fine pitch, difficult to fabricate. |
Dual-speed and multi-axis motors
| Picture | Name | Size (mm³) | Step sizes | Force / Torque | Piston size (mm²) | Link | Notes |
 | DR-32 | ⌀30×32 | 10°, 12.9° | 0.074 Nm | 10×10 | STEP+STL+Solidworks Paper YuJa | Combination of two motors. Accuracy 1°. |
 | DT-50 | 50×32×14 | 1.7 mm, 0.3 mm | 24 N | 10×10 | STEP+STL+Solidworks Paper YuJa | Combination of two motors. Accuracy 0.1 mm. |
 | R3-43 | ⌀43×19 | 12×10 | STEP+STL+Solidworks | Three cylinders. Four pneumatic lines. Three concentric output shafts. M2 screws. | ||
 | R6-56 | ⌀58×25 | 0.056 Nm – 0.114 Nm | 18×13 | STEP+STL+Solidworks Paper YuJa | Four cylinders. Five pneumatic tubes. Six concentric output shafts. M2 screws. |
Multipurpose stepper motors
| Picture | Name | Size (mm³) | Step sizes | Force / Torque | Piston size (mm²) | Link | Notes |
 | M-45 | 45×40×15 | Shaft: 6.9°, 5.3° Rack: 0.46 mm, 0.60 mm | Shaft: 0.5 Nm | 12×10 | STL Printables DOI | Rack is straight, or curved with customizable radius. Used in earlier versions of Sunram 7. Superseded by M-45B. |
 | M-45B | 45×40×15 | Shaft: 6.9° Rack: 0.60 mm | Shaft: 0.36 Nm | 12×10 | Significantly more robust than M-45. |