SJM-P Type Double Flexible Diaphragm Coupling with Brake Disc
The SJM-P Type Double Flexible Diaphragm Coupling with Brake Disc integrates a caliper disc brake rotor directly into the SJM double-diaphragm coupling hub, combining zero-lubrication flexible power transmission with compact disc braking in a single assembly. Available in 10 sizes from 420 N·m to 25,410 N·m at up to 13,000 rpm, with brake disc diameters from 315 mm to 1,000 mm — the precision braking solution for servo hoists, stage machinery, and drives where separate brake wheel mounting space is unavailable.
What Is an SJM-P Double Diaphragm Coupling with Brake Disc?
The SJM-P double flexible diaphragm coupling with brake disc solves a common design challenge in braked drive systems: how to integrate a precision flexible coupling and a disc brake into the tightest possible axial envelope without compromising the performance of either. Traditional approaches mount a separate brake disc on the shaft adjacent to the coupling — consuming additional axial space, requiring a second shaft keyway, and introducing concentricity errors between the disc and the shaft centreline. The SJM-P eliminates all three problems by casting the brake disc flange directly into one coupling hub.
The SJM double-pack diaphragm architecture ensures all the advantages of a metal diaphragm coupling are preserved: zero lubrication, torsional rigidity, misalignment compensation, high-speed capability, and a temperature range (-40°C to +280°C) far exceeding any elastomeric alternative. The disc brake adds precise, controllable braking torque proportional to caliper clamping force — ideal for servo-controlled or VFD-braked drives where stopping position accuracy is a specification requirement.
Four Design Advantages of the Integrated Approach
Brake disc and coupling share the same hub casting. Axial length equals one coupling hub plus the disc width B — significantly shorter than a coupling plus a separate disc carrier on the same shaft.
Disc flange and bore are machined from the same casting in a single setup. Runout between disc face and shaft centreline is defined at the machining stage — no bolted disc-to-hub interface to introduce eccentricity.
One hub replaces two separate components (coupling hub + brake disc hub). Only one keyway needed on the drive shaft; no risk of key-shear under braking torque transmitted through a separate disc mounting.
Both drive and driven shaft bore lengths can be specified to customer requirement, accommodating non-standard shaft protrusions from motor, gearbox, or ball-screw assemblies.
SJM-P vs LMZ Drum Brake Coupling
| Feature | SJM-P (Disc Brake) | LMZ-I / LMZ-II (Drum Brake) |
|---|---|---|
| Coupling element | Stainless steel diaphragm | Polyurethane spider |
| Lubrication | None | None |
| Torsional stiffness | Very high | Low–medium |
| Max operating temp | +280°C | +80°C (spider) |
| Brake type | Caliper disc (proportional) | Shoe drum |
| Braking torque control | Proportional to caliper force | On/off |
| Lining inspection | Visual — no disassembly | Drum cover removal |
SJM-P Coupling Specifications and Dimensions
Materials
Diaphragm packs: stainless steel sheet. Hubs and brake disc flange: alloy steel. Brake disc friction surface: hardened alloy steel. Bolts: high-tensile grade 12.9. Shaft bore and length customisable to order.
Ordering Mark Example
→ SJM-P type, size 09P | Disc: D0=500 mm, T=30 mm, X=165 mm
→ Drive: Y-bore A-keyway d=80 mm L=170 mm | Driven: Y-bore A-keyway d=60 mm L=77 mm
Complete Parameter Table — SJM-P Sizes 05P to 14P
D0 = brake disc outer diameter (mm). T = disc thickness = 30 mm (standard). X = disc centre distance from coupling face. Shaft bore lengths L1 and L2 to customer specification. Misalignment compensation same as SJM double-pack standard.
| Size | Nom. Torque N·m | Max Speed rpm | d1 max mm | d2 max mm | D1 mm | D mm | D0 (disc OD) mm | L1 mm | B mm | C mm | X mm | L mm |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 05P | 420 | 13,000 | 60 | 50 | 135 | 126 | 315 / 355 | 85 | 42 | 127 | 80 | 290 |
| 06P | 772 | 12,000 | 70 | 60 | 150 | 143 | 315 / 355 / 400 | 110 | 48 | 127 | 105 | 333 |
| 07P | 1,270 | 10,000 | 80 | 75 | 180 | 168 | 400 / 450 / 500 | 110 | 58 | 127 | 105 | 343 |
| 08P | 2,080 | 10,000 | 90 | 82 | 210 | 194 | 500 / 560 / 630 | 140 | 64 | 140 | 135 | 392 |
| 09P | 3,328 | 9,000 | 110 | 95 | 230 | 214 | 500 / 560 / 630 | 170 | 77 | 152 | 165 | 447 |
| 10P | 4,900 | 8,000 | 120 | 108 | 260 | 250 | 630 / 710 | 170 | 89 | 178 | 165 | 487 |
| 11P | 6,368 | 6,300 | 135 | 118 | 290 | 290 | 630 / 710 / 800 | 210 | 102 | 178 | 205 | 540 |
| 12P | 8,900 | 6,300 | 135 | 110 | 290 | 290 | 630 / 710 / 800 | 210 | 128 | 153 | 205 | 541 |
| 13P | 15,280 | 5,000 | 160 | 135 | 320 | 320 | 710 / 800 / 1000 | 250 | 160 | 172 | 245 | 637 |
| 14P | 25,410 | 4,700 | 180 | 155 | 360 | 360 | 710 / 800 / 1000 | 250 | 182 | 190 | 245 | 682 |
Note: Multiple D0 options available per size — select the disc OD matching your caliper geometry. Disc thickness T = 30 mm standard. X = disc centre distance. L = total coupling length. Bore lengths L1 and L2 to customer specification.
How to Select an SJM-P Coupling
Design Torque Calculation
K = service factor | P = motor rated power (kW) | N = operating speed (rpm)
Brake Disc Selection Steps
- Calculate required braking torque: Confirm the caliper's maximum clamping force × effective disc radius exceeds the required stopping torque. Ensure this does not exceed the coupling's nominal torque Tn.
- Select disc diameter D0: Choose from the available options for the selected coupling size. Larger D0 reduces the clamping force required from the caliper for a given braking torque.
- Confirm X dimension: The disc centre distance X determines caliper mounting position. Match X to your caliper bracket geometry — custom X values available.
- Verify radial clearance: Disc OD protrudes beyond coupling OD. Confirm clearance to surrounding structure and caliper body.
Related Diaphragm Coupling Types
9.8–8,100,000 N·m · No brake · General industrial drives
Zero backlash hub connections — CNC, servo, heavy industrial
420–25,410 N·m · Integrated disc brake · Servo and VFD braked drives
40–180,000 N·m · Rod-type · Long shaft spans · No brake
63–180,000 N·m · Rod-type · Maximum misalignment · No brake
For drum-brake integrated couplings, see the LMZ-I and LMZ-II jaw coupling types in the GBC range.
Applications
Counterweight fly-tower and motorised scenic drives demand simultaneous flexible coupling and precise braking — the SJM-P's disc caliper enables proportional braking compatible with servo position control. The diaphragm's torsional stiffness prevents compliance-induced position drift when the brake is applied mid-stroke.
Variable-frequency hoist drives require a coupling that can coexist with fast-acting regenerative braking. The SJM-P disc brake integrates with the VFD's brake chopper circuit; the diaphragm pack absorbs the dynamic torque transients during deceleration without transmitting them as impulse loads to the gearbox.
Rotary indexing tables, transfer machine drives, and servo-controlled assembly equipment require precise stopping position combined with torsionally stiff power transmission. The SJM-P provides both within the tightest axial envelope available in the brake-coupling category.
Register-critical web offset printing and precision slitting/rewinding drives use SJM-P for its zero-lubrication diaphragm pack (no contamination risk) and the ability to brake to a defined rotational position in mid-revolution using a servo-controlled caliper.
Precision transport drives and electrode winding machines require braking that is both contamination-free and positionally accurate. The SJM-P's all-metal construction is clean-room compatible; disc brake residual particles are orders of magnitude lower than those from elastomeric couplings with drum brakes.
Mooring winch and dynamic positioning thruster drives exposed to marine environments benefit from the SJM-P's all-stainless diaphragm pack and the visual lining inspection advantage of disc brakes — critical where confined access makes drum cover removal a safety hazard.
Installation and Maintenance
- Hub fitting: Press or heat-fit hubs onto both shafts (induction heater ≤120°C). Torque setscrews to specification.
- Alignment: Align shafts with laser equipment to within SJM angular (2°) and radial compensation limits. Correct alignment extends diaphragm service life and reduces disc runout.
- Diaphragm packs: Fit both packs; torque mounting bolts in three cross-pattern passes per specification.
- Disc runout check: Measure disc face runout with a dial gauge (≤0.1 mm TIR recommended). Runout above this value will cause brake pulsation under partial engagement.
- Caliper mounting: Position caliper to the specified X dimension; set pad-to-disc clearance per caliper manufacturer's requirement (typically 0.2–0.5 mm per side).
| Symptom | Likely Cause | Action |
|---|---|---|
| Brake pulsation / judder | Disc runout; glazed pads | Check runout ≤0.1 mm; bed-in new pads |
| Drive vibration during running | Shaft misalignment; diaphragm fatigue | Re-align; inspect both diaphragm packs |
| Position error after braking | Brake drag (pads not releasing fully) | Check caliper release; inspect pad retraction springs |
| Disc overheating | Excessive duty cycle; insufficient cooling | Review thermal budget; increase disc D0 |
Customer Case Studies
Australia — Performing Arts Centre
SJM-P 09P with D0=630 mm on four motorised flying rig winches in a major concert hall. The servo caliper disc brake provides the proportional braking control our automation system requires for silent, smooth deceleration. Diaphragm coupling torsional stiffness eliminates the position compliance we experienced with jaw couplings. Zero maintenance interventions in 22 months of continuous production use.
Stage Automation Engineer, Sydney NSW AU
★★★★★
Germany — Printing Machinery OEM
SJM-P 07P on the impression cylinder drive of a high-speed UV offset press. We needed a coupling that could brake to precise angular positions for plate change cycles at 15,000 impressions/hr. The SJM-P's diaphragm stiffness eliminated register drift under braking; the disc's visual inspection capability simplifies our CE-required monthly lining checks.
Mechanical Engineering Lead, Stuttgart DE
★★★★★
South Korea — Semiconductor Fab
SJM-P 06P on electrode winding drives in a lithium battery cell production line. Clean-room Class 10 environment — any particle generation from the coupling is a yield risk. The all-metal SJM-P passes our particle count validation; the disc brake's caliper wear is verifiable without disassembly. No coupling-related yield events in 18 months.
Process Reliability Engineer, Gyeonggi KR
★★★★☆
Norway — Offshore Winch OEM
SJM-P 11P and 12P on mooring winch drives. Stainless steel diaphragm pack handles the salt-spray environment. Disc brake lining inspection during offshore maintenance windows takes under 5 minutes — critical when weather windows are short. Rated for -30°C winter operating temperature without any performance degradation.
Mechanical Design Engineer, Stavanger NO
★★★★★
Frequently Asked Questions
▶ How does the SJM-P differ from LMZ-type brake couplings?
The SJM-P uses a stainless steel diaphragm pack for torque transmission — torsionally stiff, lubrication-free, rated to +280°C, with zero elastomeric element to age or harden. LMZ types use a polyurethane jaw-coupling spider (rated to +80°C, degrades over time) with a drum brake. SJM-P disc brake provides proportional braking force under caliper control, suitable for servo and VFD position-controlled stopping. LMZ drum brakes are on/off. Choose SJM-P for precision positioning and high-speed; LMZ for heavy hoist and crane duty where drum braking is specified by regulations.
▶ What brake disc diameters are available?
Available D0 ranges from 315 mm (size 05P) to 1,000 mm (sizes 13P and 14P). Each size offers multiple D0 options — for example size 08P offers 500, 560, or 630 mm. Select the disc diameter that matches the required braking torque and the caliper's rated clamping geometry. Larger D0 reduces the required caliper clamping force for the same braking torque.
▶ Can the SJM-P be used with a servo-controlled electro-hydraulic caliper?
Yes. The disc brake interface is caliper-type agnostic — the coupling presents a standard flat disc rotor of the specified D0. Any compatible hydraulic, pneumatic, electro-hydraulic, or electro-mechanical caliper can be mounted at the X dimension. For servo position control applications, a proportional hydraulic or servo-electric caliper provides the modulated braking force profile the SJM-P's torsional rigidity is designed to exploit.
▶ What disc runout tolerance should I target after installation?
Target ≤0.1 mm TIR (total indicated runout) measured at the disc friction face. Runout above this value causes periodic variation in caliper-disc clearance during rotation, resulting in brake pulsation under partial engagement and inconsistent stopping position. Because the disc flange is machined concentric with the bore in one setup, inherent runout is low — most variation in installed runout comes from shaft runout and bearing clearance rather than the coupling itself.
▶ Is the SJM-P available with a locking disc (Z7B) hub connection instead of keyway?
Yes. The SJM-P hub can be specified with a Z7B locking disc connection (YP variant) for zero backlash and keyway-free shaft mounting. This is recommended for servo position control applications where keyway clearance would introduce rotational play that defeats the purpose of the precision disc brake. Specify YP bore form when ordering. Contact GBC engineering with shaft diameter and torque data to confirm the correct locking disc size.
Source SJM-P Brake Disc Couplings for Your Drive System
GBC supplies all 10 SJM-P sizes with full dimensional documentation, customisable disc diameter and X dimension, keyway or locking disc hub configurations, and material certificates. Send your motor power, speed, shaft diameters, and caliper specification and our engineering team will confirm the correct size and disc configuration within 24 hours.
The SJM-P Type Double Flexible Diaphragm Coupling with Brake Disc integrates a caliper disc brake rotor directly into the SJM double-diaphragm coupling hub, combining zero-lubrication flexible power transmission with compact disc braking in a single assembly. Available in 10 sizes from 420 N·m to 25,410 N·m at up to 13,000 rpm, with brake disc diameters from 315 mm to 1,000 mm — the precision braking solution for servo hoists, stage machinery, and drives where separate brake wheel mounting space is unavailable.
