Traction Motors - Lucas Windsheild Wiper Motor 17W


The motors used to drive the orignal 1976 remote control R2 units are Lucas Windshield Wiper Motors Model 17W. The Model 17W was made in both a single speed configuration and a dual speed configuration. The gearbox incorporates an automatic limit-switch which switches the motor off and provides an electical circuit which cause regnerative braking of the armature to ensure consistent parking of the wiper blades. The Lucas 17W motor was most frequently found on the Austin Morris J250 mini truck in Engalnd in the 1970s.

Tracking down the orginal motors was a decade long effort that started with discussions from r2 enthusists like Oliver Steeples sharing the idea that the original motors may have been windsheild wipers possibly a wiper model made by Lucas. In 2020 I was able to acquire an orignal prodcution hand drawin line drawing orginal sourced directly from John Stears. The line drawing showed a unique asysmtrical bolt pattern that turn out to be the key to finally identifying the orginal motors.

A 3 month long effort of searching the internet daily for an hour or two each finally turned up a Lucas wiper motor with what looked like the correct bolt pattern. I purchased 6 of the motors from eBay in the UK and had them shipped to the US. The motors matched the drawing perfectly. With the physical motors in hand, we were able to match a number of physical features of the motors back to production photographs.

Traction Motors - Introduction
This is a photo of an orginal Lucas 17W wiper motor. The motor consists of an armature housing and a cast gearbox. The single spead variant has two wires going from the gearbox to the two amature brushes. The dual speed variant has three wires going from the gearbox to three armature brushes.

Traction Motors - Speeds
R2-D2 has three forward speeds, but no reverse. In order to achieve forward motion, the two rear legs have individual traction motors which drive twin inline wheels. The traction motors operate at 36V for full speed, and 12V or 24V for reduced speed. This production photo shows one of the motor covers removed exposing a Lucas 17W motor.

Traction Motors - Orientation
The Lucas 17W has an asysmtrical mouting pattern. This in not an issue on vehicles as a single Lucas 17W motor drives both windsheild wipers. This does present a slight design challenge in that R2-D2 requeires 2 motors on smytrically opposite feet. The practical solution was to mount one of the motors forward of the the center line of the traction foot and mount one of the motor aft of the center line of the other traction foot. This prodction photo shows right motor mounted aft while the left motore is mount forward.

Traction Motors - Production Drawing
A unique hand drawn production used outline of the various mechanics and build up of R2-D2's foot. The large sheet features original hand drawn pencil line drawings comprising of a cross section of the side of the foot, a front view, wheel detail, several small sketches and a few numbers written in hand. Dating from the very early stages of production on Star Wars A New Hope, circa 1975/76. This piece was originally sourced directly from John Stears, special production mechanical effects supervisor on production, just prior to his immigration to the USA in the early 1990's. This is the drawing that held the key to identifying the original motors, the asymetric motor mount bolt pattern.

Traction Motors - Feature Match
Laying the Lucas 17W motor over the orginal production line drawing shows the gear casting mounting bosse geometry and autopark geometry both match the drawing.

Traction Motors - Feature Match
Creating mounting plates on the mill to orginal production line drawings shows that the mounting pattern on the plates is a 1:1 match. Its a perfect fit to the Lucas 17W.

Traction Motors - Feature Match
The shape of the armature bearing seat, the grommet. the power wires to the armature brushes, the aramture magnet rivet, and the slotted screwss that mount the armature cover are all visual matches to the Lucas 17W wiper motor.

Traction Motors - Open Source 3D Model
The NOS (New Old Stock) traction motors have been sourced on eBay, dissassembled, laser scaned, and in the process of being modeled.