Tank Servo Door Opener Mechanism,

thingiverse

Here is a Door Opener I'd like to share with everyone. It works really well and should be useful for just about anything with small moving doors. This design uses a regular size MG996 180 degree servo, controlled by an Arduino board or RC transmitter-receiver. The door opens in a wide arc from minimal movement of the servo and has great leverage for the start of the lift. It pulls the door shut and holds it firmly. I've got the servo working from 13 degrees closed to 150 degrees fully open, so there's still plenty of room for bigger doors or longer arms. This is quite powerful, with a delay built into the software to make it look more realistic. The servo slams the door pretty fast without it, though. In this application, the gear case positions the arm in the middle of the servo, but it should work just as well with RC airplane-type push rods directly on the servo. My first design used linear movement at the door instead of upward motion like this. You can see it in action here: https://www.youtube.com/watch?v=vqUzjV5_Pv4 I had some interesting findings when working with the length of the servo arm. One side needed less throw than the other, and I was surprised by that discovery. The mechanism works fine, though. The doors don't close exactly the same but reach their ends simultaneously, which is kind of cool. To fine-tune the doors, I had to adjust the length of the bone arms connected to the servo arm. If you need some assorted-length Bone arms, just let me know! I've also added a PDF with pretty accurate anchor placement measurements for you. This project comes with Tank Track 2in, Tank Idler arms, pins, and other tank parts that are included in my stuff. 11/26/2014 I recently replaced the old gears with heavy-duty ones because the original gears didn't print well and couldn't hold their teeth. The new HD gears have fewer teeth but are larger and can be printed solidly. Instructions: I've added a PDF layout sheet to help you adapt this design to whatever project you're working on. Feel free to play around with it until it fits your needs. To assemble the gear case, screw it into whatever the servo is mounted on using a #4 x 3/4" screw. Make sure to drill a hole that's about .120" and use a raft for support during printing. For the gear case cover, print without a raft and use four #4 x 3/8" screws to secure it in place. To make the servo gear, you'll need to drill a little smaller than your servo shaft and attach the gears with a machine screw (3mm). It's helpful to be able to turn the gear on the servo to synchronize the timing.