After replacing the steering actuator a couple of days ago Simon conducted some Internet research and discovered that not only was it possible to open up the broken unit but some spare parts are also available. Given that the unit is 15 years old that is surprising but good news. Far better to repair than replace, especially if the price of a complete new part is in the thousands.
The actuators job is simple, all it has to do is hold still, push or pull on the rudder quadrant when told to do by the steering controller. It is made up of an electric motor, a magnetic clutch and small planetary gearbox. Spin the motor one way it pulls, the other way it pushes, disengaged the magnetic clutch it holds.
So the stage was set for the postmortem, an old oily cloth laid out in the cockpit and a collection of the best surgical tools available.
In fact, much to our surprise, the actuator came apart easily, no broken bolts, no sized screws and no blood. Almost as if it had been designed to be maintained. Once inside the cause of failure was obvious, the magnetic clutch was just warn out and the more it wore the harder it had to work until it could take no more. The poor thing had overheated and burned out. Dust from the clutch plate was everywhere but no other signs of damage.
Without the clutch the motor could try to push and pull on the rudder but the unit couldn't hold it still on course which was what was happening on the night it failed.
The good news is that a replacement clutch is available at a tenth of the price of a new unit. We put the unit back together to await the delivery of spare parts, they will probably be brought out from the UK next season. It will live again, hopefully never needed, but available from its home under the fore cabin birth.
Tim