Peteric '76 Alloy Head Bearing System

History

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 the Outer Race of the bearing.

One of the Kenny Units had a modification before filming that added weight relief holes to the Outer Race. Because of this modification there were two slightly different versions of the Alloy Head Bearing used in the first film. A version with weight relief holes for the Kenny Units 1, 2, and 4. A version without the weight relief holes for version 4, 5, 6, and 7.

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.

Current documentation indicates that a few of the outer races with dome pins still exist in the hands of a private collector but that none of the inner race assemblies have survived intact.

Replica

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 engineering 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 but these were changed to locating pins on all of the units before filming began. The locator pins were reverse engineered using production photos.

Parts List

  • (1) Bearing Outer Race
  • (3) Locator Pins
  • (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

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.

Prior to filming weight relief holes were added to the Outer Races on the Kenny models. Three sets of 22 5/8" holes were drilled or milled into the Races, This significantly reduced the weight the parts from 66.2oz to 58.4oz.

Threaded Studs/Locator Pins

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.

 

Prior to filming the threaded studs, washers, and nut was replace with a locator pin. Its not really clear how the crew would have access to tighten or loosen the nuts. The nuts were likely impractical and thus eliminated.

 

Outer Race Subassembly

 

 

Inner Race Subassembly

Physical Parts

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

 

The 1976 RC version of the Aluminum RC Head Races have arrived. This is the version of the head race that is used on the remote control units that do  not have weight relief holes drilled. The cost of each race came to about $300.00 USD.

The 18.25" x 1" 1976 Aluminum RC Head Races are machined out of a single piece of 6066 plate. The races have an internal key slot for the nylon wedge bearing, three tapped holes on the upper face for the pins for the head, and an inner clearance notch on the bottom face.

 

(note: retake at 4K)

The holes are tapped 1/2" - 20 TPI.

(note: retake at 4K)

The key slot is machined with sharp crisp corners.

(note: retake at 4K)

This validation of the of the geometry of the 1976 head race was 100% successful.

Motor Drive Gear Insert

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