Servo mount for 2" horizontal blinds

thingiverse

Remix of Payloader's servo mount, customized to fit 2" Better Homes and Gardens horizontal blinds currently sold at Walmart. I have the CORDLESS version which is where my measurements came from, I'm honestly not sure if it will fit the corded version because I don't have any to measure. (For some odd reason the site keeps insisting on putting the gears as the remix source. The mount source from Payloader is https://www.thingiverse.com/thing:1573867) I found Payloader's original design trying to find a way to mount servos in my new blinds for automation. Unfortunately it seems that the tilt mechanism in these blinds is different from any of the other examples that people have posted over the years. The rod is low and centered, which means direct coupling to the servo shaft is impossible at any orientation which fits entirely inside the header (even if the mounting tabs on one end of the servo are cut off as one maker did), so an offset gear drive is required. It was exactly what I was looking for, so I printed it out. Unfortunately I made the mistake of not checking the measurements first. It is the proper width, but way too tall, and the rod hole sits too high. I have reduced the overall height so it snaps tightly into the header channel (friction fit, no screws or adhesive required), and placed the rod hole correctly. Because of the height of the tilt mechanism, the servo sits higher than the the rod centerline, so basically it has to be installed into the header "backwards" of Payloader's original design - with the servo body pointing AWAY from the tilt mechanism, and the rod will not go all the way through, it ends inside the gearbox. I have also remixed his 1:1 gearset to work in this mount. (available here: https://www.thingiverse.com/thing:5431806) The lower rod hole means the gears need to be smaller. In addition the rod in these blinds is only 4mm (the original gear has a 6mm square hole). The original gear measurements just happen to be such that scaling the print down to 67% makes everything roughly the correct size, so that's what I did for my first attempt. However, they become pretty thin as well, and when mounted they didn't mesh very tightly and had a tendency to shift around and jump teeth or jam. So I redesigned the gears to be the correct diameter, but also increased the height to 7mm. I also added a collar to the rod gear to maintain the correct spacing from the servo body. A loose spacer is also included for the other side of the gear, if you need it (the tightly meshed herringbone teeth makes lateral slop unlikely though). It has a tiny lip at one end to make it a tight friction fit, optionally you may drill a hole through the side for a setscrew. The original servo gear was meant to be glued to a round servo horn, then the entire assembly screwed onto the servo with the horn screw (the screw head recessed into the servo gear). I chose a different method, although the remix is still 100% compatible with the original mounting (by flipping both gears - with the spacer collar on the rod gear facing the tilt mechanism, and you can cut the loose spacer in half to use if needed). The size of the hole in the servo gear has been reduced, and it can be pressed (hard) directly onto the splines - the nylon or brass shaft is harder than PLA and the splines will "bite" into the hole - with the center screw securing it. The shaft hole is 2.9mm deep, and the shaft will bottom out before it can cause binding so drive it all the way on.