Linear 25, 1/4-20 Thread, Std CR Servo

thingiverse

Here's another redneck linear with even more power behind it. It utilizes standard continuous rotation servos, one-fourth-twenty all thread, and boasts bearings on the spool, giving it a lot of potential applications in robotics and home automation. This linear features a one-to-one gear ratio, providing a travel of .050 inches per servo rotation. That equates to a speed of approximately 2.7 inches per minute with the Pololu 1248 continuous rotation servo or SpringRC SM-S4303R and Jameco 2128201 servos, both available for under $13.95. For those without this particular servo on hand, rest assured that Parallax's high-speed CR servo makes this linear move at an impressive pace (180 RPM), allowing it to travel approximately nine inches per minute (Parallax 900-00008). The design employs standard one-fourth-twenty nuts within the spool to facilitate the movement of the all-thread rod. To achieve smooth operation, two eighteen by twelve by four millimeter RC car/truck bearings are placed on the spool. The yoke secures the rod with a one-fourth-twenty nut while keeping the gear and motor in motion. A #4 sheet metal screw is used for fasteners, while #6 machine screws are employed for yoke pins to provide extra security. Given that continuous rotation servos rely on speed and time, long-distance linear movements would require micro switch cutoffs to land precisely at a designated spot. This linear accommodates standard twenty-five-tooth Futaba spline servo gears, but please let me know if you need other spline sizes. One note of caution: still working through threading issues; the drill size is 0 point two hundred inches and tap with one-fourth-twenty threads into the yoke.