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PTO Shaft Friction Torque Limiter – FFST Series (Splined Shaft Welded Assembly)
The PTO Shaft Friction Torque Limiter – FFST Series (Splined Shaft Welded Assembly) is a premium-quality friction torque limiter specifically engineered for PTO (Power Take-Off) drive shaft systems used across agricultural, industrial, and forestry machinery. Also known as a PTO slip clutch, PTO safety clutch, or tractor PTO overload protector, this device safeguards your expensive equipment from damage caused by sudden torque overloads, obstructions, and operational jamming.
Available Models: FFST1, FFST1D, FFST2, FFST2D, FFST2C, FFST2E, FFST3, FFST4, FFST4D, FFST4C, FFST4E
Torque Range: Torque: 900–1200 Nm
Spline Options: 1 3/8″ Z6, 1 3/8″ Z21, 1 3/4″ Z6, 1 3/4″ Z20
Key Components: Belleville spring, Pressure plate, Friction discs (Qty.=2), Hub, Taper pin sets (with nuts), Bushing, Splined shaft welded assembly, Complete bolt (Qty.=8)
Technical Specifications & Dimensions
| Series | Max Torque (Nm) | Friction Disc | Spline | A (mm) | B (mm) | C (mm) | ||
|---|---|---|---|---|---|---|---|---|
| FFST1 | 900 | Φ140 | 1 3/8″Z6 | 1 3/8″Z6 | 161.5 | 30.5 | 38 | Φ180 |
| FFST2 | 1200 | Φ160 | 1 3/8″Z6 | 1 3/8″Z6 | 161.5 | 30.5 | 38 | Φ200 |
| FFST3 | 900 | Φ140 | 1 3/8″Z6 | — | — | — | — | Φ180 |
| FFST4 | 1200 | Φ160 | 1 3/8″Z6 | 1 3/8″Z6 | 177 | 29 | 38 | Φ200 |
* All dimensions in millimeters. Torque values in Newton-meters (Nm). Spline specifications follow ISO/ASAE standards. Contact us for custom configurations.
Key Features & Advantages
⛳
Sealed & Protected Design
Grease-lubricated internals with dust seals protect against contamination in harsh agricultural environments.
📈
Wide Torque Selection Range
Available in multiple torque ratings (900–1200 Nm) to match virtually any PTO-driven implement requirement.
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Safety Certified
Manufactured under ISO 9001:2015 quality management with CE marking for European and international compliance.
📦
Compact & Lightweight
Engineered for minimal additional length and weight on the PTO shaft, preserving driveline balance and clearance.
🔁
Multiple Output Configurations
Available in yoke, splined shaft, and flanged output variants to suit any installation requirement.
🔒
Precision Overload Protection
Calibrated to disconnect at exact torque thresholds, preventing costly damage to gearboxes, bearings, and implement mechanisms.
How It Works — Operating Principle
This friction torque limiter uses Belleville disc springs (conical washer springs) instead of conventional coil springs to clamp friction discs against the hub. Belleville springs provide several critical advantages: they maintain consistent clamping force across a wide temperature range, they have a compact axial profile, and they can be stacked in series or parallel to achieve precise spring rate and preload characteristics. When the torque exceeds the friction capacity set by the Belleville spring preload, the discs begin to slip progressively, absorbing excess energy without abrupt disconnection. The torque setting is adjusted by changing bolt tension on the spring pack. This design delivers tighter torque tolerance and more repeatable performance than coil-spring friction limiters.
Reset Method: Automatic — continuous slip and re-engagement
Best Suited For: Precision applications requiring tight torque tolerance, temperature stability, and compact installation length
Typical Agricultural Application Scenarios
Rotary Tillers & Cultivators
Guards the tiller gearbox and tractor PTO when tines encounter buried rocks, roots, or compacted soil layers that can generate extreme torque spikes.
Manure Spreaders
Protects the beater mechanism and gearbox from overload when encountering frozen clumps, foreign objects, or uneven material distribution in the hopper.
Feed Mixers & TMR Wagons
Safeguards the mixer auger drive from damage caused by twine wrap, frozen feed blocks, or excessive loading that generates torque beyond design limits.
Grain Augers & Conveyors
Prevents auger tube distortion and gearbox failure when grain bridges, moisture-swollen grain, or foreign objects create sudden resistance in the conveying path.
Post Hole Diggers
Absorbs extreme torque shock when the auger bit strikes rock, buried concrete, or dense root masses, protecting both the auger drive and tractor PTO.
Torque Limiter Type Comparison
| Feature | Ball Detent | Friction Disc | Shear Pin/Bolt | Ratchet (Pawl) | Automatic (Cam) |
|---|---|---|---|---|---|
| Torque Range | Low–Medium | Medium–High | Low–Very High | Low–High | Medium–High |
| Speed Range | 540–1000 RPM | 540–1000 RPM | 540–1000 RPM | 540–1000 RPM | 540–1000 RPM |
| Reset Method | Automatic | Automatic (slip) | Manual (replace bolt) | Automatic (ratchet) | Automatic (cam) |
| Best Application | Light implements | Frequent moderate overloads | Infrequent severe overloads | Frequent transient overloads | High-utilization, no consumables |
| Consumable Parts | None | Friction linings (long life) | Shear bolts | None | None |
| Torque Precision | Moderate | Good (adjustable) | Excellent (bolt-grade calibrated) | Good | Very Good (adjustable) |
Installation & Usage Guide
Installation Steps
Step 1: Verify that the PTO shaft spline size matches the torque limiter spline specification (1 3/8″ Z6, 1 3/8″ Z21, 1 3/4″ Z6, 1 3/4″ Z20). Clean all spline surfaces thoroughly.
Step 2: Slide the torque limiter onto the PTO shaft spline, ensuring full engagement. Secure with the provided push pin kit or retaining hardware.
Step 3: Connect the output side (yoke or splined shaft) to the implement input shaft or gearbox. Ensure proper alignment and secure all fasteners to the recommended torque.
Step 4: Apply grease through the grease nipple to lubricate the spline interface and internal components. Use lithium-based EP grease (NLGI #2).
Step 5: Perform a low-speed test run to verify correct engagement and smooth operation before full-power operation.
Safety & Maintenance Tips
⚠ Always disengage the tractor PTO before inspecting or servicing the torque limiter.
⚠ Use only genuine replacement parts specified for your series to maintain the correct torque rating.
⚠ Re-grease spline connections every 8 operating hours or as specified in your equipment manual.
⚠ Inspect for wear, cracks, or damage before each season. Replace worn components immediately.
⚠ Never operate with damaged or missing PTO shaft safety shields.
Selection Guide — Choosing the Right Model
Selecting the correct torque limiter requires confirming the following parameters:
✓ Required Torque Rating (Nm): Match the implement’s maximum operating torque plus a 20–30% safety margin.
✓ PTO Shaft Spline Size: Commonly 1 3/8″ Z6 (6-spline) or 1 3/4″ Z6/Z20. Verify both input and output spline requirements.
✓ PTO Speed: Standard 540 RPM or economy 1000 RPM — confirm your implement’s requirement.
✓ Connection Type: Yoke output for standard shaft tubes, splined shaft for inline assemblies, or flanged output for direct gearbox mounting.
✓ Overload Frequency: Frequent overloads favor auto-reset types (ratchet, friction, automatic). Infrequent but severe overloads suit shear bolt types.
✓ Environmental Conditions: Consider dust, moisture, temperature extremes. Sealed automatic and friction types offer superior protection in harsh environments.
Need help choosing? Contact our engineering team for personalized selection assistance.
Quality Certification & Service Commitment
✅
ISO 9001:2015
Certified quality management system ensuring consistent product excellence
✅
CE Marked
Compliant with European safety, health, and environmental protection standards
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12-Month Warranty
Full warranty against manufacturing defects under normal operating conditions
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Global Shipping
Fast worldwide delivery with professional export packaging and documentation
Frequently Asked Questions (FAQ)
What Our Customers Say
🇦🇺 James M. — Grain farmer, NSW, Australia
“We fitted these torque limiters on all our header drives after losing a gearbox last harvest. They’ve triggered twice on hidden rocks and saved us thousands in repairs each time. Absolutely essential equipment for Australian broadacre farming.”
★★★★★
🇩🇪 Hans K. — Agricultural contractor, Bavaria, Germany
“Excellent build quality — typical of what we expect for professional machinery. The torque ratings are accurate and the fit on our Walterscheid PTO shafts is perfect. We’ve standardized on these across our fleet.”
★★★★★
🇧🇷 Carlos S. — Sugarcane equipment dealer, São Paulo, Brazil
“Reliable performance in extremely tough conditions. Brazilian sugarcane operations are brutal on drivelines, and these limiters consistently protect our customers’ equipment. Great value for the price.”
★★★★★
🇨🇦 Robert T. — Hay producer, Alberta, Canada
“Running on our round balers through three seasons now without a single issue. The auto-reset feature is a huge advantage during busy harvest — no stopping to replace shear bolts when you hit a gopher mound.”
★★★★★
🇮🇳 Vikram P. — Farm equipment distributor, Punjab, India
“Excellent product for the Indian market. Compatible with all major tractor brands including Mahindra, TAFE, and Sonalika. Our customers appreciate the reliability and competitive pricing.”
★★★★★
Related PTO Shaft Products & Accessories
PTO Shaft Components
Complete range of PTO shaft yokes, cross bearings, tubes, shields, and adapters for all standard sizes.
Agricultural Gearboxes
Matched gearboxes designed to work seamlessly with our PTO shafts and torque limiters.
Available PTO Accessories:
• PTO shaft yokes (plain bore, splined, quick-release)
• Safety shields and guard tubes (EN 12965 compliant)
• Spline adapters (1 3/8″ to 1 3/4″ conversion)
• Cross bearing kits and U-joint repair kits
• Telescoping PTO shaft tubes (triangular and lemon profile)
• Push pin kits and retaining hardware
Ready to Protect Your Equipment?
Whether you need a single replacement unit or bulk OEM supply, our team is ready to help you select the perfect torque limiter for your application. We offer competitive B2B pricing, technical consultation, and fast global delivery.
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