Product Overview
The SCM-108W-P-SC4-C14-R1M-100 is the flagship bent-axis fixed displacement axial piston motor from the Swedish manufacturer Sunfab’s SCM Series, representing over 70 years of Sunfab’s technical expertise in mobile hydraulics. The SCM Series features a unique spherical piston design and bent-axis architecture, characterized by compact construction, very few moving parts, high starting torque, and high reliability. The series covers displacements from 25 to 108 cm³/rev, with a maximum working pressure of 400 bar (5,800 psi) and maximum speed up to 4,700 rpm, widely deployed in winch, slewing, wheel drive, and track drive applications in mobile hydraulic systems.
The specific model covered in this document — SCM-108W-P-SC4-C14-R1M-100 — is the largest displacement configuration in the SCM Series (108 cm³/rev), featuring independent rotation direction (W), high-pressure high-temperature shaft seal (P), SAE-C 4-hole mounting flange (SC4), 14-tooth spline shaft (C14), and R1M configuration code. The motor is manufactured to original Sunfab specifications with 100% drop-in interchangeability, requiring no modification to mounting interfaces, port positions, or hydraulic connections. Every unit undergoes 100% simulated operating condition testing at the factory, including rated pressure loading, volumetric efficiency verification, seal integrity assessment, and low-speed smoothness validation prior to shipment.
Sunfab was founded in 1925, produced its first axial piston pump in 1954, and has over 50 years of experience manufacturing piston pumps and motors. Headquartered in Hudiksvall, Sweden, with subsidiaries in Germany, France, USA, Italy, and Spain, Sunfab products are distributed in over 60 countries worldwide.
Technical Specifications
SCM-108W-P-SC4-C14-R1M-100:
Series / Type: Sunfab SCM Series bent-axis fixed displacement axial piston motor
Displacement: 108 cm³/rev (6.59 cu in/rev)
Design: Bent-axis, spherical piston design, fixed displacement
Rated operating pressure (continuous): 350 bar (5,075 psi / 35 MPa)
Maximum working pressure (intermittent): 400 bar (5,800 psi / 40 MPa)
Peak pressure: 480 bar (6,960 psi)
Maximum speed: 4,700 rpm
Maximum continuous power: 255 kW
Theoretical torque at 100 bar: approximately 172 Nm
Torque constant: 1.72 Nm/bar
Direction of rotation: Independent (W configuration, bidirectional adjustable)
Shaft seal type: FPM high-pressure high-temperature seal (P configuration)
Mounting flange: SAE-C 4-hole flange (SC4 configuration)
Output shaft: 14-tooth spline (C14 configuration, SAE-C size)
Bearing arrangement: Double tapered roller bearings, permitting high shaft loads
Housing material: High-strength cast iron
Minimum operating temperature: -25°C (standard; contact Sunfab for lower temperatures)
Approximate weight: 21–25 kg
SCM Series displacement range (for reference):
SCM-025: 25 cm³/rev
SCM-034: 34 cm³/rev
SCM-040: 40 cm³/rev
SCM-047: 47 cm³/rev
SCM-056: 56 cm³/rev
SCM-064: 64 cm³/rev
SCM-084: 84 cm³/rev
SCM-090: 90 cm³/rev
SCM-108: 108 cm³/rev
Note: Technical data above is sourced from Sunfab SCM 025-108 M2 official technical catalogue and authorized distributor technical data. The SCM Series covers displacements from 25 to 108 cm³/rev, with maximum working pressure of 400 bar, continuous working pressure of 350 bar, maximum speed of 4,700 rpm, and maximum continuous power of 255 kW. For precise configuration parameters of the SCM-108W-P-SC4-C14-R1M-100, always confirm against the official Sunfab technical manual or the product nameplate data.
Key Technical Advantages
1. Unique Spherical Piston Design with High Starting Torque
The SCM Series employs Sunfab’s signature spherical piston design, with piston ball ends running directly in output shaft sockets for the shortest torque transmission path and highest mechanical efficiency. Compared to conventional swashplate designs, the bent-axis architecture delivers high starting torque instantaneously upon startup without requiring oil film pressure build-up, making it ideally suited for travel drive applications involving frequent start-stop cycles and heavy-load starting. The motor maintains smooth operation across the entire speed range without stick-slip phenomena — critical for winch and slewing drive applications requiring precise speed control.
2. Patented Hardening Technology for High Reliability
Sunfab employs patented hardening technology to specially harden critical running gear components such as pistons and cylinder barrels, achieving extremely high product reliability. This technology significantly increases surface hardness of critical friction pairs while maintaining good toughness, providing excellent wear resistance and fatigue resistance under high-pressure and high-speed operating conditions. The motor’s high level of reliability is based on the choice of materials, hardening methods, surface structures, and the quality-assured manufacturing process.
3. Double Tapered Roller Bearings for High Shaft Load Capacity
The SCM Series employs double tapered roller bearings supporting the output shaft, permitting high shaft loads and leading to excellent speed characteristics. The engineering advantage of this bearing configuration lies in its ability to directly absorb radial and axial forces generated by driven components (gears, sprockets, pulleys) without requiring a separate bearing support housing — simplifying system design and reducing installation costs. Due to its high rotary stiffness, the motor is particularly suited to applications with high angular accelerations.
4. High Speed and High Efficiency
Thanks to the spherical piston design and compact rotary group, the SCM-108W tolerates speeds up to 4,700 rpm. The motor maintains high efficiency across the entire speed range, minimizing energy losses from internal leakage and friction. The compact structure achieves high power density within a limited envelope, with maximum continuous power of 255 kW — a power-to-weight ratio that leads its class among comparable 108 cm³/rev displacement motors.
5. High-Pressure High-Temperature Shaft Seal with Wide Temperature Range
This model is equipped with an FPM (fluorocarbon rubber) high-pressure high-temperature shaft seal (P configuration), capable of withstanding higher case pressures and a wider operating temperature range. For mobile hydraulic systems requiring continuous operation in high-temperature environments, this seal configuration significantly extends seal service life and reduces downtime from seal failure. Standard configuration is suitable for minimum operating temperatures of -25°C; contact Sunfab for lower temperature applications.
Application Areas
Construction equipment: Rotary drilling rigs, road rollers, loader travel drive systems
Lifting and transport machinery: Crane slewing drives, winch drives, hoists
Agricultural machinery: Combine harvesters, tractor auxiliary drives, balers
Material handling: Forklift travel drives, aerial work platforms
Mobile vehicles: Transit mixer drum drives, concrete pump truck auxiliary drives
Mining machinery: Mining drills, underground transport vehicle drives
Marine and offshore: Deck machinery, windlass drives, fishing vessel winches
Industrial hydraulic systems: High-pressure oil stations in cement plants, slag conveyors in power plants
Expert Maintenance Tips
1. Fluid Cleanliness Management Is the Primary Task
The SCM-108W operates with micron-level clearances between spherical pistons and cylinder bores and between the valve plate and cylinder barrel face. Particulate contamination in hydraulic fluid is the leading cause of piston scoring and valve plate wear. Systems must be equipped with filtration rated to ISO 4406 18/16/13 or better. In dusty construction machinery environments, consider shortening fluid change intervals to 1,000–2,000 hours or every six months.
2. Case Drain Line Configuration Requirements
Case drain from the SCM-108W motor must be routed to the reservoir through the highest drain port, with case pressure strictly controlled within specified limits. Excessive case pressure will cause shaft seal failure; insufficient pressure will reduce lubrication and heat rejection effectiveness. The case drain line must terminate below the minimum oil level in the reservoir to maintain positive return flow under all operating conditions.
3. Pre-Start Case Filling and Air Purging
Before first startup after installation or repair, the motor case must be filled with clean hydraulic fluid through the highest case port until fluid overflows. The SCM-108W bent-axis spherical piston architecture creates a complex internal case cavity geometry; starting an un-purged motor can cause dry friction damage between piston ball ends and socket bushings, leading to irreversible premature wear.
4. Output Shaft Spline and Mounting Alignment
This model uses SAE-C 4-hole flange mounting (SC4) with a 14-tooth spline output shaft (C14). During installation, verify that the output shaft spline is properly aligned with the mating component, and that spline engagement length meets design requirements. Installation misalignment will cause abnormal spline wear and bearing side loading, significantly shortening service life. Tighten mounting bolts in stages to the specified torque value and re-check torque after 500 operating hours.
5. Rotation Direction Adjustment Considerations
This model features an independent rotation direction configuration (W), with rotation direction adjustable to system requirements. The cylinder block stop shoulder design permits changing rotation direction, but before changing rotation direction, verify that system piping and valve configurations allow reverse operation to avoid system failure from incorrect operation.
6. Restart Procedure After Extended Shutdown
If the motor has been idle for more than three months, manually rotate the output shaft to confirm freedom of movement, and inspect the case oil level and shaft seal for leakage before restarting. Extended shutdown can cause oil film drainage from piston-slipper interfaces, creating a dry-start risk. Before restarting, replenish clean hydraulic fluid through the case fill port and operate at low speed and reduced load for 10–15 minutes before returning to normal duty.
