I'm looking for what might best be described as a hybrid servo
horn/clevis. What I need is basically a one-armed servo horn, but with
a 2nd, parallel arm, spaced at about 3/32" from the first. This would
form what amounts to a clevis that attaches to a hobby servo's output
gear. It needs to be pretty strong, & I've considered making my own
out of a pair of existing horns, but I'm not sure that'll be strong
I figured that's what you're trying to do. I don't recall seeing one
ready-made (doesn't mean they don't exist), but I don't see why it
couldn't be made. To test my theory I tried one with standard nylon
horns, and did it in a couple of minutes.
On one arm I enlarged the screw hole to the same size as the spline
shaft. I just routed it out with a drill and used a rate-tail file for
touch up. That horn goes onto the servo upside-down.
I then filed off the servo shaft socket on the other to almost flush
with the face of the horn. That sandwiches over the bottom horn. I was
able to use the regular servo horn screw but depending on the horns you
use, and the length of the supplied screw, you might need a slightly
You *might* need a small shim -- a #2 or #3 washter or something --
placed over the servo shaft, as a spacer. Otherwise, the arm may sit too
low and rub against the servo since there is no longer the usual
clearance that a regular servo horn provides.
This double-horn seemed as strong, or stronger, than what someone would
make, unless it's custom-machined out of aluminum.
I reread my message and all of its typos, and just wanted to add one
thing: I tried adding a series of #3 flat washers into the bottom
(drilled-out) horn, and that did indeed prevent the bottom horn from
scraping against the body of the servo. A stack of three of them added
just enough thickness to keep the horns a fraction of a millimeter away.
You might find you need something similar.
Typos & all, I got the idea. I may or may not need the extra spacing.
Simple & head-slappingly obvious, once it's pointed out, like many
great ideas! I may do my own slightly differently, shortening the hubs
on a pair of horns to get the spacing I need.
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.