SpryDrive is an affordable actuator based on the quasi-direct drive (QDD) scheme. It is composed of a brushless outrunner motor, a low-cost metal gearbox, and a 3D-printed housing. Inspired by Gabrael Levine’s OpenTorque actuator, but takes up less volume. The lower cost of the smaller bearing makes up for the added cost of the steel gears.
Custom aluminum adapters are used to transfer torque between the motor and sun gear as well as the carrier and output plate. As far as custom metal parts go, these are dirt cheap. I ordered them from SendCutSend for a total of $29 with free shipping. Despite the low precision of laser cutting, concentricity tolerance isn’t an issue as the sun gears are already mounted and centered on the 3 mm motor shaft tip. They also don’t add backlash, as they’re press fitted.
So far, I have tested an output torque of 33 Nm, but theoretically the actuator should be able to go much higher (in burst).
Links
Specifications
- Output Backlash: ~0.13 degree - Gear Ratio: 7:1
- Motor: Herlea X8318S or Turnigy 9235