21mm in OD, the round servo-horn is often referred to as a wheel-arm. Injection molded in rugged nylon 6.6, which is a type of heavy duty plastic (fiber-filler engineering polymer), this is the same stuff used in 9mm handgun frames because it's so tough. Simple in appearance but complex in execution (what makes making these actually rather pricey), the molding for this arm has a total of 13 bores (that's what we call them, but everybody else calls them holes). Of course, there's one on center for the M3 bolt to secure it to the 25T spline output shaft. The remaining 12 are dispersed 6-each on the two axis arranged 90° to each other (+15mm and -15mm off center). The 3-holes on each of four sides are spaced 5mm apart with the two complementary bores rotated 30°off axis. This means the variations in which the bores can be arranged are thus, nearly infinite!
Funny thing about this specialized horn is it's the one everybody just throws away when we include it for free (everybody being defined
as modelers). Thus, in recognition it's wasteful to make everybody pay for something very few make actual use of, we decided to offer them as an accessory for those who really need them. So who does? Principally the folks involved in the field of robotics. How? In practice, these are typically used as an intermediary mount, e.g. an adapter to a specialized fitting. The reason probably has to do with this being considerably less costly than broaching their fitting to 25T. Anyway, as an indication of how very useful these things actually are, while we offer them in quantity 1, 5, and 25 we often ship them by the hundreds to consumers.
Dimensions: OD=21mm, spline is ø6mm, 25T-spline (Futaba-compatible)
- 1st bore: 15mm
- 2nd and 3rd bore: 15mm x 30°axial shift (+/-)