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RG74DXH Operator · Service · Maintenance Manual
Operation
Electric Brake System
This machine requires periodical adjustments to the electric
brakes on all wheels.
Brake Operation:
1. When electrical current is supplied to the system
controller, it flows through the electromagnets in the
brakes.
2. The electromagnets are energized and are attracted to the
rotating armature surface of the drums which moves the
actuating levers in the direction that the drums are turning.
3. This resulting force causes the actuating cam block at the
shoe end of the lever to push the primary shoe out against
the inside surface of the drum. The force generated by
the primary shoe acting against the adjuster moves the
secondary shoe out into contact with the brake drum.
4. Increasing the current flow to the electromagnet causes
the magnet to grip the armature surface of the brake
drum more firmly. This results in increasing the pressure
against the shoes and brake drums until the desired
stop is accomplished.
Use of Electric Braking System:
1. The brakes are designed to work in synchronization with
your tow vehicle brakes.
NEVER Use your tow vehicle alone to stop the combined load!
2. Your brake controller must be set according to the
manufacturer's recommendations to ensure proper
synchronization between the tow vehicle and the trailer.
Additionally, you may have to make small adjustments
occassionally to accommodate changing loads and
driving conditions.
3. Proper synchronization of tow vehicle to trailer braking
can only be accomplished by road testing. Brake lockup,
grabbiness, or harshness is quite often due to the lack
of synchronization, too high of threshold voltage (over
2v), or under adjusted brakes.
4. Before any synchronization adjustments are made, the new
brakes should be burnished-in by applying the brakes
20-30 times with approximately a 20 mph decrease in
speed (e.g. 40mph down to 20mph). This allows the
brake shoes and components to wear-in.
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5. To insure safe brake performance and synchronization,
read the brake controller manufacturer's instructions
completely before attempting any synchronization
procedure.
BEFORE ROAD TESTING, MAKE SURE THE AREA
IS CLEAR OF VEHICULAR AND PEDESTRIAN
TRAFFIC. FAILURE TO BRAKE SAFELY COULD
RESULT IN ACCIDENT AND PERSONAL INJURY, OR
INJURY CAUSED TO OTHERS.
6. Make several hard stops from 20mph on a dry paved
road free of sand and gravel. If the trailer brakes lock
and/or slide, decrease the gain setting on the controller.
If they do not lock and/or slide, then slighty increase
the gain setting. Adjust the controller just to the point
of impeding brake lockup and wheel skid.
7. If the controller is applying the trailer brakes before the tow
vehicle brakes, then the controller adjustments should be
made so the trailer brakes come on in synchronization with
the tow vehicle brakes.For proper braking performance,
it is recommended that the controller be adjusted to
allow the trailer brakes to come on slightly ahead of
the tow vehicle brakes. When proper synchronization
is achieved there will be no sensation of trailer "jerking"
or "pushing" the tow vehicle during braking.
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