![background image](http://html.mh-extra.com/html/otis/s-71/s-71_technical-information_1658597004.webp)
4
Page
OTIS S-71 GENERAL INFORMATION
INTRODUCTION
The Otis S-71 Golf Cart has a fiberglass body on a tubular steel frame, and uses six 6-volt
batteries to power a GE 36- volt series (the field and armature are connected in series) DC
motor. Speed is controlled by adding or removing resistance in series with the motor
voltage. The S-71 provides four speeds forward and reverse. Reverse is accomplished by
reversing connections to the motor armature. The S-71 weighs 740 pounds without
batteries [1] and about 1100 pounds with batteries. Top speed is 12 miles per hour [1].
SERIAL NUMBER
If the S-71 was ever given a serial number I have found no mention of it, or where it
might have been placed.
OTIS S-71 ELECTRICAL
MOTOR
The motor is a General Electric DC Motor, Model 5BC48JB517B rated on the nameplate
for 55-amperes at 36-volts DC. The nominal shaft horsepower rating is 2.0. The motor
terminals are not labeled- I have arbitrarily labeled them 1 through 4 for correspondence
with the diagrams on the following pages. Terminals 1 and 2 go to the field winding.
Terminals 3 and 4 go through brushes to the armature. Brushes are accessible by
removing the rubber plugs next to the terminals.
Most electric motors have the field and armature connected in parallel. When motors are
used for propulsion the field and armature are usually connected in series as this provides
maximum torque at low speed. However a series-connected motor MUST always have a
load on it or its speed may rise to an unsafe value [2]. This will not be a problem here
unless the motor is removed from the S-71 for bench testing.
DIRECTION CONTROL AND INTERLOCK
The Forward / Reverse lever directly operates the high-current DC polarity reversing
switch. To prevent arcing, a microswitch is activated when the lever is in the full
“Forward” or “Reverse” position. These “normally-open” switches close ro allow the
solenoids to operate ONLY when the lever is in the full “Forward” or “Reverse” position.
Brake
Assembly
Shaft to
Differential
DC MOTOR
(Top View)
1
2
3
4