Servo Arm, 51 mm

Mfn. No: PDRS008

Availability: In Stock. Ships within 24 hours.


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Spanning 51mm, or a bit more than 2", this ultra heavy duty double-sided servo arm is made of a fiber-filled engineering polymer. It's tough, like what's used in Glock handguns, while being strong enough not to deflect under flight loads. However, it can still break off during a crash, thereby helping save the servo.


Dimensions: 25-spline (Futaba-compatible)

  • 1st hole: 5/8" (16mm)
  • 2nd hole: 3/4" (19mm)
  • 3rd hole: 7/8" (22mm)
  • 4th hole: 1" (25.4mm)


An advantage of the double sided arm (versus PDRS007, the single-side servo arm) comes from being able to flip it over to the other side. As a result, often there's a more advantageous mechanical fit on the output shaft spline, e.g. requiring less sub-trim to position it for neutral. Basically, anything, which reduces the amount of sub-trim required for centering is good.


In the picture sequence (below), first is a single-side arm installed on the servo. Note how it's off to one side +12. In the next image, moving it one spline results in it being off by about -8 to the other side (from neutral). Next, a two-sided servo arm is installed. While it's off -20 in one direction, just by flipping it to the other side, presto, the difference requires just -3 of sub-trim to make it perfectly neutral, which isn't much at all. Advantage double side servo arm when building a precision model when you're wanting to minimize the sub-trim required.

The servo arm molds are made with intentional spline-position variablity for a chance at finding a zero sub-trim fit

- The servo arm molds are made with intentional spline-position variablity for a chance at finding a zero sub-trim fit



Pro Tip: These servo arms aren't injected one at a time but in a larger mold, which lets us inject several at a time for a reduced injection cycle. To make it easier to find an arm, which requires zero sub-trim, we created slight variability in how the splines are position in each. This means if one servo arm doesn't come close enough to suit you, just try another because this usually results in your finding one, which comes a little closer to perfection, e.g. zero sub-trim required.