[17]). Replace parts as necessary with
complete assemblies.
E. Solenoid lever and pinion assembly
replacement
If pinion (32) teeth are worn, replace entire
assembly (8). Consult appropriate parts list for
kit number. Check sector gear of lever arm (17)
for wear.
If sector gear teeth of lever arm (17) are worn,
replace entire lever arm assembly available as
a kit from appropriate repair parts list. Also
check pinion (32) teeth for wear. See Item 8.
F
. Pressure spring stud and nut
replacement
On older designs of these brakes, item (152)
was a threaded shoulder stud nut (19), item
(152P) was a solid pin. These items have been
replaced by a spring tube, cap screw and
spring pin. Replacement of any individual
component requires replacement of all three
older style components. Consult appropriate
repair parts list for complete retrofit kit.
IV. Troubleshooting
A. If brake does not stop properly or
overheats, check the following:
1. Is manual release engaged, and is motor
energized?
2. Friction discs may be excessively worn,
charred or broken.
3. Hub may have become loose and shifted
on shaft.
4. Is hub clean and do friction discs slide
freely?
5. Are controls which govern start of brake
cycles operating properly?
6. Are limit switches, electric eyes, etc.
functioning properly?
7. On vertically mounted brakes, are
springs in place in disc pack? See P/N
8-078-937-05 (Sheet 301.3).
8. Have mounting faces loosened?
9. Pressure spring may be improperly
assembled or broken.
10. Is solenoid air gap adjusted correctly? (See
Self-Adjust Maintenance
, Section III,
Item D.)
11. Check linkage for binding. The approximate
pressure applied to the top of the solenoid
link to move plunger is:
If excessive force is required, determine
cause of binding and correct. Do not
overlook bent, worn or broken plunger
guides as a possible cause for binding.
12. Solenoid lever stop (22) must be in place
on support plate.
13. Solenoid may not be energizing and
release the brake. Check voltage at the coil
and compare to the coil and/or nameplate
voltage rating.
14. Whether brake is AC or DC a voltage drop
may be occurring. If excessive drop in
voltage is noted, check wire size of power
source. Correct as needed.
Note: A method to check voltage at coil is
to insert a block of wood of the
approximate thickness of the solenoid air
gap between the solenoid frame and
plunger. (The block will prevent brake from
releasing when coil is energized.) Connect
voltmeter leads at the coil terminals or lead
wires. Energize coil. Voltmeter needle will
not fluctuate and reading can be taken.
Reading should be taken immediately and
the coil de-energized to prevent
overheating of the coil. Compare voltage
reading with coil rating.
15. If brake is DC solenoid style, check switch
actuation and condition of coil. The switch
should open with the following approximate
air gap. (This is plunger travel remaining
before plunger seats to frame.) Solenoid
size is used for reference.
If actuating arm is bent, replace plunger.
Check switch contacts. If pitted, replace
switch.
16. Check slots of endplate for wear at the
areas where stationary discs are in contact.
Grooves in the slots can cause hang-up or
even breakage of ears of stationary discs.
If grooving is noted, replace endplate.
17. Check that heads of mounting bolts do not
extend above wear surface of endplate.
18. On vertical above brakes, check the
vertical mounting pins to be sure shoulder
of pin is flush with wear surface of
endplate. Be sure pins are straight and the
pressure plate and stationary disc(s) are
free to slide on the pins. Be sure springs
and spacers are installed in proper order.
See P/N 8-078-937-05 (Sheet 301.3)
19. Check pressure spring length to insure
correct compressed height. Approximate
original spring lengths are given in the
following table so that correct setting may
be verified and corrected if necessary. With
worn friction discs, add amount of wear to
the approximate spring length shown in
table.
20. If a heater is supplied and excess rusting
has occurred in brake, check power source
to heater to be sure it is operating and that
heater is not burned out.
21. If stopping time is more than two seconds
(rule of thumb) and/or the application is
more than five stops per minute, check
thermal requirements of load versus
thermal rating of brake.
22. Use Loctite
®
242 to secure link screw nut
(13N) to link screw (13C) if vibration
causes nut to loosen.
B. If brake hums, solenoid pulls in
slowly, or coil burns out, check the
following:
1. Voltage supply at coil versus coil rating.
2. Is solenoid air gap excessive? (See
Self-
Adjust Maintenance
.)
3. Shading coils may be broken.
4. Plunger guides may be excessively worn.
Does solenoid plunger rub on solenoid
frame laminations? If so, replace plunger
guides.
5. Solenoid frame and plunger may be
excessively worn.
6. Is solenoid dirty?
7. Solenoid mounting screws may have
become loose, causing frame to shift and
plunger to seat improperly.
8. Sector gear and pinion teeth may be
jamming due to excessive tooth wear.
9. Excessive voltage drop when motor starts.
Check size of lead wires for motor starting
current and solenoid inrush current. See
Section IV-A, Item 11, 12, 14 and 15.
C. If brake is noisy during stopping:
1. Check mounting face run out, mounting
rabbet eccentricity and shaft run out. See
Installation Procedure
, Section I, Note 1.
Correct as required.
2. Check for signs of the outside diameter of
the friction disc(s) rubbing on the inside
diameter of the endplate. This would indicate
brake is eccentric with respect to the motor
shaft and/or the shaft is deflecting during a
stop. Check alignment and shaft diameter.
Also check for worn motor bearings. If
realignment does not correct the problem, a
larger diameter shaft may be required. Shaft
deflection may also be caused by excessive
overhang of brake from motor bearing.
Additional shaft support may be required.
3. In cases where motor shaft extends through
a fan casing or guard, the clearance hole
may not be adequate. Rubbing of the shaft
may occur causing a noise during a stop. If
required, enlarge clearance hole.
4. Check for bad motor bearings. Replace if
necessary. Check for excessive shaft
endfloat. Correct as required.
Copyright© 1997 by Rexnord Industries, Inc.
www.rexnord.com
Rexnord Industries, Inc., Stearns Division, 5150 S. International Dr., Cudahy, Wisconsin 53110, (414) 272-1100 Fax: (414) 277-4364
16 lbs
#8 coil
9 lbs
#6 coil (25 lb-ft)
5-1/2 lbs
#6 coil (15 lb-ft)
3 lbs
#5 coil
#5 or 8 solenoid
3/16” to 7/32”
#6 solenoid
7/32” to 1/4”
Color
Torque (lb-ft)
Compressed
Spring Length
Blue or Black
6
3-1/2”
Blue
10
3-5/16”
Yellow
15
3-9/16”
Red
25 & 50
3-3/8”
Green
35, 75 & 105
3-3/8”
Black
10
3-1/4”
White
15
3-1/4”
Orange
25 & 50
3-1/4”
Purple
35, 75 & 105
3-1/4”
