Framo Morat MINI linear actuators from R. A. Rodriguez use powerful coaxial motors to enable the required stroke force to be achieved using a minimum amount of space. Given this is the main characteristic of the overall range, the MINI 0 in this series is particularly attractive where space is tight. A further benefit of the MINI is that it is available with a wide range of options enabling it to be individually adapted for almost any application.
These credentials made the MINI 0 suitable for a hovercraft steering system designed by systems engineers, Carisbrooke Engineering (IW) Limited on the Isle of Wight. It was selected as the most suitable alternative to a Swiss made actuator that was no longer available. But as the system’s designer Mike Edwards explains: “The MINI 0 has proved to be a better product, more substantial and robust. It’s a good price too.”
Each craft system comprises two MINI 0 actuators that are fitted to the two off, 3m diameter aircraft type propellers of the hovercraft. For this application 24V DC versions were specified. As standard they are manufactured in stainless steel and IP65 rated. Complete with potentiometers, this combination allows the position of the actuators to be precisely controlled by integration with a servo amplifier, allowing full proportional control of the props in forward and reverse pitch. The servo is connected to the hydraulic “beta” valve of the airscrew in the centre of the prop hub and is working in temperatures from -30degC to +35degC.
Thermostatically controlled heating has been added to augment the -20degC manufacturers’ stated minimum operating temperature. A stroke of +/- 30mm about the centre of ram gives full movement of the beta valve with plenty of power available to cope with the low temperatures encountered. Before the prototype was fitted to the first installation it was proven on a test rig on a continuous, 6s lock to lock cycle for 2h with a load of >100lbs, with no failures.
A number of features ensure the MINI’s reliable operation in harsh conditions. These include a thermally protected motor, life-time lubrication and integral safety switches. And this reliability is complemented by economical operation, low maintenance and a long service life. The actuator can be specified with a choice of mounting and connecting arrangements and is easily interfaced to a controller.
Mike Edwards continues: “The system is looking fine and the first pair of actuators is fitted on the hovercraft that is now operating in South America. I am now working on a second system that incorporates the MINI 0 for a Canadian coastguard craft. I am really delighted with the performance of this product, and the fact that it is built in stainless steel makes it all the more suitable for use in harsh sea conditions.”
For further details about MINI linear actuators from R. A. Rodriguez, please visit www.rarodriguez.co.uk.