AstroDroid '76 (Peteric) Head Bearing System - Rev A


The rotation of the head on the original units produced by Peteric Engineering in 1976 was designed in conjunction with the center foot leg drop system. The 1" aluminum ring  that is part of the props exterior is actually a functional part of a working bearing system. This ring rotates with the head and is functionally the outer race of the bearing.

The rotation of the heads in the original movie was done manually by hand. There were no motorized articulation. This rotation system was replaced in later movies with various different setups including a fully motorized remote control version.

The initial version designed on the blueprints appears to have be modified with an upgrade from the threaded studs to machinist locating pins prior to delivery.


From the Peteric blueprints for the leg drop system, we have the exact dimensions of the aluminum outer race. This has been confirmed both photographically and through measurements of the original props.

From the Peteric blueprints for the leg system, we have a cross section of the inner race assembly. The blueprints does not have any information about the width of the Mounting Bracket or the width of the Nylon Insert. This information was reverse engineered to the best accuracy possible using production photos and measurements of what remains on the original prop.

The blueprints specify the locating mounts for the head as threaded studs.

Parts List

  • (1) Bearing Outer Race
  • (3) Bearing Outer 1/4" - 20 UNC Studs
  • (3) Bearing Outer 1/4" - 20 UNC Nuts
  • (6) Bearing Outer 1/4" - 20 Washers
  • (3) Bearing Inner Race Mounting Bracket
  • (3) Bearing Inner Race 1/4" Stud
  • (3) Bearing Inner Race 1/4" Nut 
  • (3) Bearing Inner Race Nylon Wedge

Head Bearing - Outer Race Subassembly

The outer race is defined on the leg drop blueprint.

The outer race is milled from a single piece of solid aluminum. The bearing is 18.25" in diameter, 1" in height, and 1-1/4" thick. There is a slot cut into the interior which creates the bearing surface. There is a clearance notch cut into the bottom that may have been need for clearance of rivets that attach the leg drop frame to the uppermost body frame flange.

The Head Assembly sits on top of the Outer Race over three threaded studs. The threaded studs locate and position the Head. The washers offset the Head from the Outer Race by 1/8". The nut locks the Head down.

The Bearing - Outer Race Subassembly is comprise of (3) 1/4" - 20 UNC threaded studs, (3) 1/4" UNC nuts, (6) 1/4" UNC washers, and (1) outer race.


Head Bearing - Inner Race Subassembly

The inner race assembly is defined on the leg drop blueprint.

The inner races brackets are made from 1/8" stamped 5052 aluminum brackets.

The inner bearing is made from nylon.

The nylon bearing is attached to the bracket with a 1/4" - 20 UNC stud and two 1/4" UNC nuts.

The inner bearing assembly is comprised of (2) 1/4" UNC nuts, (1) 1/4" - 20 UNC stud, (1) nylon bearing, and (1) bracket.

Head Bearing - Complete Assembly

The complete assembly is assembled from (1) Inner Race Subassembly and (1) Outer Race Subassembly.


Physical Parts

The head bearing blanks are waterjet cut from an 18.500" OD by 15.750" ID aluminum 6061-T6.

The outer races are CNC machined down to 18.25" x 1",  are drilled and tapped for three 1/4" - 20 UNC holes on the upper face for the locating the head, and have an inner clearance notch on the bottom face. 

The races have an internal key slot for the nylon wedge bearing,  The key slot is machined with sharp crisp corners.

The inner races are made from 1/8" stamped 5052 aluminum brackets assembled to a nylon bearing via a 1/4' - 20 UNC stud.

For the first time since 1976, the original R2-D2 head bearing system is available. 

Motor Drive Gear Insert

An optional nylon gear insert is available to fit into the underside clearance groove in order to articulate head rotation. The insert requires no modification of the original geometry.


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