Hagglunds’ Compact range of motors is smaller and lighter, while providing more torque and power than those of competitors. For marine applications it is important to maintain product reliability even during brief periods of extreme operating conditions, such as high or low ambient temperature, water, impurities in the hydraulic fluid, and severe operating cycles. All of this has indirect influence on the components of the hydraulic transmission, which must be designed with greater durability.

Hagglunds develops its products using a well defined process and a strong theoretical model, backed by laboratory tests and field trials. Improvements over the years are often the result of many small modifications. Thirty years ago Hagglunds motors were five times heavier in order to give the same power and service as today. Trends towards smaller size, greater power and longer life put high demands on the strength of the individual motor components.

In the latest development of the Compact motor series, the focus has been on areas such as lubrication, viscosity, surface structure, coatings and seals. Contact between roller and cam ring is one area where considerable resources have been engaged in development and where big improvements have been achieved.

Since the introduction of the Compact motor, the piston assemblies have also been subjected to substantial improvement. Improved shape and surface finish have given better hydro-mechanical efficiency, better resistance to seizing and less wear. Improved tolerances have resulted in better volumetric efficiency.

Developments in recent years towards higher power in hydraulic motors have resulted in the radial seals which keep hydraulic fluid inside the motor housing being subject to greater demands than ever before. The growing awareness of environmental concerns also lowers the limit for when a seal is considered to leak.

The seal previously used by Hagglunds was fitted with a polyurethane foam dust shield, which had a fairly high contact pressure and caused considerable heating of the wear ring. Small particles could be dislodged and enter the sealing area. Together with a supplier, Hagglunds designed a new seal with a smaller contact width and an integrated dust lip. This development has allowed maximum speed to be increased from 280rpm to 400rpm with reduced leakage and a longer life.