Twiflex GMR-SH User manual

170 Mounting Hole CRS
To Edge of Disc
87 17
Disc Centre Line
ø 610 Min. Disc Diameter
110
ø 193
44
150
300
19345
Brake Disc
25.4 (GMR)
38/40 (GMR40)
212 (GMR)
223 (GMR40)
170 Mounting Hole CRS
275 New Pads
305 Fully Worn Pads
3 Holes ø 17
for M16 Mounting Bolts
40
24 (GMR)
GMR-SH & GMR40-SH Disc Brake Caliper - Spring Applied, Hydraulically Released
DB4605
The ratings shown on the above graph are based on fully bedded and conditioned brake pads. For bedding in
and conditioning procedures see Publication M1060.
Braking Force is defined as the Tangential Force acting on the brake disc at the Effective Disc Radius.
Braking Torque (Nm) = Braking Force (N) x Effective Disc Radius (m)
where Effective Disc Radius = Actual Disc Radius- 0.06
Note:
The caliper may be assembled as
drawn (right hand assembly) or with
arms and thruster oppositely handed.
Nominal dimensions given.
For specific dimensions please
contact Twiflex.
For GMR Mk 2 caliper details see DB 3604
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
32
Braking Torque kNm
Oil Pressure - bar
110
100
0
50
60
70
80
90
40
30
20
10
Minimum Pressure for Full Retraction 120 bar
Maximum Pressure 150 bar

GMR-SH & GMR40-SH Disc Brake Caliper - Spring Applied, Hydraulically Released
Thruster Type-SH
Maximum Displacement Volume 56 ml
Parts List
76 Fully Retracted
151 Fully Extended
213
1 223 28 30 10 11 12 13
9
22
25
27
8765 20
19181531
2914 21
17
16
3
4
24
Not Shown
Item Component Part No. Qty.
1 Front Cap 1
2 Rear Cap 1
3 Push rod 1
4 Barrel 1
5 Piston 1
6 Spring Plate 1
7 Spring carrier 1
8 Sleeve 1
9 Thrust Collar 1
10 Main Spring 1
11 Centre Spring 1
12 Inner Spring 1
13 Label 1
14 Stud 1
15 G 1/4 Plug 1
16 Wiper Seal 6000242 1
Item Component Part No. Qty.
17 Bush 1800372 1
18 Rod Slip Seal 6000491 1
19 Piston Slip Seal 6000492 1
20 Bush 1800374 1
21 ‘0’-Ring 6000207
22 Red Cap 1
23 G 1/4 Redcap 1
24 G 1/4 Bonded Seal 1
25 Helicoil lnsert 1
26
27 Retraction Screw 1
28 M8 x 30 Skt. Hd. Screw 8
29 M16 Nut 2
30 M8 Spring Washer 8
31 M16 Spring Washer 2

GMR-SH & GMR40-SH Disc Brake Caliper - Spring Applied, Hydraulically Released
Installation, Operation and Maintenance
1. Installation
1.1 The caliper must be mounted on a suitably rigid support, upon which braking forces of up to 35kN will be imposed.
1.2 The caliper should be positioned symmetrically with respect to the disc, as shown on the drawing.
1.3 Three fixing bolts are required, M16 grade 8.8. The bolts should be tightened to a torque of 150Nm.
1.4 If the caliper is to be mounted on an inclined surface, the caliper should be fitted with adjustable stop screw
and bias springs, included in the inclined mounting kit (Part number 6700554, drawing numbers A11074, A21183).
1.5 Calipers are normally supplied assembled ‘right-handed’, as shown on the drawing, unless otherwise specified.
1.6 The thruster is normally supplied separately from the caliper, and with the retraction screw fitted to hold it
in the ‘off’ position (see section 2.2) until it has been fitted on the caliper arm. Nuts and washers for this
purpose are supplied and should be tightened to 45Nm torque.
1.7 The two ports on the thruster are tapped G 1/4 (1/4” BSP). Either port may be used for the hydraulic supply or
blanking plug (15). However the blanking plug should be at the highest possible position to facilitate bleeding.
A flexible high pressure (150 bar) hose should be used to connect the thruster to the hydraulic supply to
accomodate movement during operation. Only use mineral based hydraulic fluids, (e.g. Shell Tellus 37, or
Castro! Hyspin AWS 32). The volume displacement of hydraulic fluid required for 20mm stroke is 32ml.
Vegetable based fluids MUST NOT BE USED.
2. Operation
2.1 The brake is applied by the thruster springs and released hyraulically. The required supply pressure varies
with the caliper rating and is given on the performance charts. Variable braking torque can be achieved by
regulating the oil pressure as shown on the charts.
2.2 Thrusters are supplied with the retraction screw (M16 x 130 part number 5350249) fitted; this is used as a
safety screw during assembly and maintenance and as a means of brake release in the event of hydraulic
supply failure. The screw is fitted through the thrust collar (9) in the centre of the rear cap and screws into
the push rod; adequate access to the back of the thruster is required.
2.3 THE RETRACTION SCREW SHOULD BE REMOVED COMPLETELY WHEN THE BRAKE IS IN SERVICE, and the
red plastic cap (22) supplied fitted in the hole. (The brake should be off i.e. pressurised, when removing the
retraction screw).
2.4 THE THRUSTER STROKE SHOULD BE MAINTAINED AT ABOUT 20mm BY UNSCREWING THE PUSHROD.
To adjust, the brake must be off (i.e. hydraulic pressure on). Pull the caliper arm away from the pushrod and
turn the rod as required; one turn gives 2mm adjustment. Release the caliper arm, ensuring that the flats on
The GMR-SH and GMR40-SH calipers are available in various ratings, as shown on the performance charts.
Part numbers are given below. These are typical performance figures for bedded and conditioned brake pads
having a friction coefficient of 0.4.
When used with standard Twiflex discs an appropriate ‘service factor’ should be applied when designing the
braking system and in the case of brakes used for holding duties or in wet conditions this should be not less
than 2.0.
Marinised versions are available to special order.
A monitoring unit is also available (Part No. 7700212) which is fitted to the back of the thruster. The unit
incorporates two microswitches, of which one indicates full retraction of the pushrod (i.e. brake off) and the
other indicates the need for adjustment due to pad wear.
Thruster Thruster Thruster Max. Braking Retraction Oil Caliper Part No.
Type Part No. Weight Kg Force kN Pressure Bar GMR GMR 40
SH 2.5 7500112 13·9 6 21 6780971 6781006
SH 4·5 7500111 14·7 10·5 38 6780971 6781006
SH 7 7500110 15·7 16·5 59 6780971 6781006
SH 8·4 7500105 16·2 19·5 65 6780971 6781006
SH 11 7500108 17·2 25 92 6780971 6781006
SH 12·9 7500104 18·0 30 100 6780971 6781006
SH 15 7500106 19·0 35 120 6780971 6781006

GMR-SH & GMR40-SH Disc Brake Caliper - Spring Applied, Hydraulically Released
the pushrod are engaged in the slot in the caliper arm. (A 17mm A/F spanner will fit the flats on the
push rod).
N.B. Keep fingers clear of the space between push rod and caliper arm at all times.
If an inclined mounting kit is fitted, the stop screw should be re-adjusted to maintain equal pad clearance
on either side of the disc.
2.5 Pad wear can be monitored by observing the gap between the lugs on the pads pressure plates and the
machined surfaces on the caliper frame, when the brake is applied. Pads must be replaced (see 3.2)
before the gap is reduced to zero. (The maximum allowable wear on a pad is 10mm).
3. Maintenance
CALIPER
3.1 Ensure that the brake pad and disc remain free from oil and grease. Clean the disc as required. If the
pads become contaminated they should be replaced. Carry out any periodic statutory testing that is
required, or otherwise check for satisfactory performance.
3.2 Pad replacement is carried out from the rear of the caliper; DO NOT release the spring clips which attach
the pressure plates to the caliper arms. With the brake off (retraction screw may be fitted as a safety
screw) remove the caliper return springs and the keep plates. If an inclined mounting kit is fitted, remove
this also. Withdraw the pads to the rear and lift out. (The hole in the end of the pad retaining plates is
provided to assist in withdrawing the pad). Fit the new pads, ensuring that the slotted retaining plate is
located around the keep disc on the pressure plate; the pads should slide freely into position. Replace
remaining parts. Re-adjust the pushrod, as in (2.4), and the stop screw if fitted.
3.3 The surface of the caliper arm on which the thruster pushrod bears should be kept well greased. The
knuckle joints between the caliper arms and the pressure plates should be cleaned occasionally, and a
small amount of grease applied; the joints may be levered apart slightly against the pressure of the spring clip.
Occasionally, or if caliper is not operating freely, inject a small amount of grease via grease nipples to
lubricate the pivot pins, then rotate pins to distribute the grease. Any grease exuding past the ‘0’-rings
should be wiped off. The pins may be turned by gripping the knurled end at the top of the caliper.
After extended (one million operations or three years) use, the pivot pins should be withdrawn, cleaned,
replaced and regreased, or replaced if badly worn.
In order not to damage the 0-ring seals on the pins, use the following procedure. Remove the top circlip,
push pin down until the lower circlip and ‘0’-ring can be removed, then withdraw the pin upwards. To
refit, reverse this procedure.
THRUSTER
3.4 Clean the pushrod as required, and inspect hydraulic connections and hoses.
3.5 In the event of leakage or malfunction of the thruster, the following parts can be inspected and replaced if
necessary, using the procedures described below, without decompressing the spring pack:-
Piston Seal (19)
Rod Seal (18)
Bush (17)
Wiper Seal (16)
Pushrod (3)
Replacement of any other components, such as rear bush (20) and springs, requires the spring pack to
be decompressed. This is not covered in these instructions, and should only be carried out by Twiflex or
their Agents. If the push rod is damaged, replace it first, as in 3.11. Otherwise proceed as below.
WARNING:- DO NOT ATTEMPT TO DECOMPRESS THE SPRINGS BY UNSCREWING THE RETRACTION SCREW.
Thruster Servicing
3.6 With the brake off, remove red cap (22), insert retraction screw and screw it fully in; finger tight is
sufficient. (If the thruster will not retract, the brake should be released using the retraction screw, which
should be well lubricated). Disconnect the hydraulic supply and remove thruster from caliper.
The surface of the pushrod should be smooth and free from serious scoring or bruising which could
damage the bush. Note that the pushrod cannot be removed while the thruster is dismantled.
For removal and replacement of the push rod see 3.11.
Withdraw the screws (28), and remove the front cap (1), and piston (5).
3.7 Leakage of hyraulic fluid may be caused by damage to the piston seals or to the housing. The piston may

GMR-SH & GMR40-SH Disc Brake Caliper - Spring Applied, Hydraulically Released
be extracted from the front cap by application of low fluid pressure to the inlet port. The piston and rod
seals each have two parts, (a P.T.F.E. sealing ring and an 0-ring) which may be extracted using a small
screwdriver or similar tool, taking care not to damage the grooves. Once removed the seal should not be
re-used.
When fitting a new rod seal (after fitting the 0-ring) the P.T.F.E. ring must be carefully collapsed into a
kidney shape (avoid sharp bends), inserted into the internal groove and then expanded into a circle
again. Note that the stepped side of the ring is the pressure side (as shown on the drawing). The piston
seal must be stretched into position by sliding it up the long taper on the piston. This requires some
force; take care not to damage the surfaces of the P.T.F.E. ring.
3.8 The wiper seal (16) serves both to retain grease and to exclude dirt. The section of the pushrod which
moves through the wiper seal should be cleaned with a very slight lubricant film.
The wiper seal is of all rubber construction and is easily replaced without tools.
3.9 The bush (17), which is pressed into the front cap, has a number of shallow circular indentations in its
surface, which retain grease. The limit of acceptable wear on the bush is 0.2mm, approximately half the
depth of the indentations in a new bearing.
A worn bush can be withdrawn (after removal of the wiper seal which may be re-used unless damaged)
using a suitable extractor. The new bush, should be pressed in until flush with the base of the wiper seal
recess.
3.10 Re-assembly of the thruster is the reverse of dismantling. Seals should be lightly oiled with mineral
based fluids to ease assembly and the indentations in the front cap bush should be filled with grease.
Tighten the cap screw to 15Nm torque.
After re-assembly, pressurise the thruster and check for leaks. Using the retraction screw to maintain
full retraction, refit the thruster to the caliper. Apply hydraulic pressure and remove the retraction screw
and replace place plastic cap in its place. Adjust thruster stroke to 20mm as described in 2.4 above.
Push rod removal/replacement Re-Lubrication of Thruster
3.11 With the thruster removed from the caliper (as in 3.6), remove the retraction screw, so that the thruster
operates through its full stroke, and the spring load is supported on the front cap. Remove the thrust
collar (9) from the rear cap (2). This is a light press fit.
Unscrew the pushrod until it can be withdrawn through the rear of the thruster. Clean and examine the
push rod, replace if damaged. Clean other parts.
Re-lubricate the front cap bearing, the internal thread of the sleeve (8), the rear cap bore adjacent to the
end of the sleeve, and the threads (internal and external) of the push rod, with grease.
Re-fit the pushrod into the thruster and replace the thrust collar (9) (if it is loose, use a low-strength
grade of ‘Loctite’ to retain it).
Pressurise the thruster, check for leaks and fit the retraction screw. Re-fit the thruster to the caliper.
(After removing the retraction screw, replace the red plastic cap into the hole).
4. Recommended Lubricants
4.1 Caliper: Medium grease containing Molybdenum disulphide.
e.g. Castrol LMM
Shell Alvania 2 + MOS2
4.2 Thruster: Medium lithium based grease with rust inhibitors
e.g. Duckham’s Keenomax L2
Castrol AP 2
Shell Alvania R2
5. Spares
5.1 A spare set of brake pads, and a set of seals, should be kept in a cool, dry, dark place where there is no
chance of contamination.
5.2 For caliper spares see Data Sheet DB 3604.
6. Service
Address all enquiries regarding this equipment to your Twiflex agent or direct to Twiflex.
Agent

GMR-SH & GMR40-SH Disc Brake Caliper - Spring Applied, Hydraulically Released
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Braking Torque kNm
Oil Pressure - bar
100
90
0
50
60
70
80
40
30
20
10
Minimum Pressure for Full Retraction 100 bar
Maximum Pressure 130 bar
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
0 2 4 6 8 10 12 14 16 18 20 22
Braking Torque kNm
Oil Pressure - bar
90
80
0
50
60
70
40
30
20
10
Minimum Pressure for Full Retraction 85 bar
Maximum Pressure 130 bar
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
Oil Pressure - bar
80
70
0
50
60
40
30
20
10
0 2 4 6 8 10 12 14 16 18
Braking Torque kNm
1 kNm = 736·6 lbf-ft 1 bar = 14·5 psi
Minimum Pressure for Full Retraction 65 bar
Maximum Pressure 130 bar
Brake performance at 30 kN braking force
Brake performance at 25 kN braking force
Brake performance at 19.5 kN braking force
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Braking Torque kNm
Oil Pressure - bar
100
90
0
50
60
70
80
40
30
20
10
Minimum Pressure for Full Retraction 100 bar
Maximum Pressure 130 bar
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
0 2 4 6 8 10 12 14 16 18 20 22
Braking Torque kNm
Oil Pressure - bar
90
80
0
50
60
70
40
30
20
10
Minimum Pressure for Full Retraction 85 bar
Maximum Pressure 130 bar
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
Oil Pressure - bar
80
70
0
50
60
40
30
20
10
0 2 4 6 8 10 12 14 16 18
Braking Torque kNm
1 kNm = 736·6 lbf-ft 1 bar = 14·5 psi
Minimum Pressure for Full Retraction 65 bar
Maximum Pressure 130 bar
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Braking Torque kNm
Oil Pressure - bar
100
90
0
50
60
70
80
40
30
20
10
Minimum Pressure for Full Retraction 100 bar
Maximum Pressure 130 bar
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
0 2 4 6 8 10 12 14 16 18 20 22
Braking Torque kNm
Oil Pressure - bar
90
80
0
50
60
70
40
30
20
10
Minimum Pressure for Full Retraction 85 bar
Maximum Pressure 130 bar
Disc Diameter mm 610 760 915 1065 1220 1370 1525 1830
Oil Pressure - bar
80
70
0
50
60
40
30
20
10
0 2 4 6 8 10 12 14 16 18
Braking Torque kNm
1 kNm = 736·6 lbf-ft 1 bar = 14·5 psi
Minimum Pressure for Full Retraction 65 bar
Maximum Pressure 130 bar
DB4605 5/19
www.twiflex.com
9 Briar Road, Twickenham
Middlesex TW2 6RB - England
[phone] Issue 06