Monday, June 6, 2011

Smooth out those transmission vibrations

The yacht Valhalla  has this installation of an anti vibration device. The picture say's it all.
aquadrive™  Installation  

Through the help of a friend I obtained an aquadrive that was in the estate of a yacht owner who died before the installation was done.  Follow the link for a complete description of this system but basically it is a double CV (universal) joint unit located between the engine transmission and a thrust bulkhead further connected to the propeller shaft.  The thrust bulkhead takes the force of the propeller instead of this force being transmitted to the engine mounts.
This is the completed installation:

Motor mounts: Soft motor mounts from Aquadrive provide freedom for the engine to vibrate without transmitting the vibration (and noise) to the vessel. The ones provided by Drivelines NW are exactly one-half the height of the Yanmar mounts for my 3GM30F engine. I had 'risers' fabricated locally to fill the space, which also allowed me to use the bolt hole spacings for the Yanmar mounts which are slightly longer than the Aquadrive mounts.

Adapter Plate: The one provided with the system I obtained was for another engine. I had an adapter place fabricated locally.

Thrust Bulkhead: This was the most critical piece of engineering and installation. The bulkhead must be installed a critical distance  behind the adapter plate, the rubber bushings between the aquadrive unit and the bulkhead must be at 15 mm under compression, and the thrust bearing (after end of the unit) must be in perfect alignment with the shaft going through the water (cutlass) bearing. The scarred area on the hull under the shaft is where a temporary bulkhead was installed to hold the shaft in alignment while the thrust bulkhead was fabricated and installed. The thrust bulkhead was fabricated from 1/2" King Starboard with 8 layers of fiberglass on each side for a total thickness of 3/4 ". As an aside, I had the help of a 5 foot tall Filipino fiberglass technician for this installation ... I COULD NOT have done it myself in the small space under the cockpit.

Shaft: My old shaft was pitted and in poor condition but I was lucky to obtain a used one from a friend who had upgraded from a 1 1/4" shaft to a 2" shaft. Although it was 35 years old it was in excellent condition and long enough to permit machining the ends to fit the coupling and the Autostream feathering propeller.

Permanent Shaft Seal (PSS): I opted to install a new PSS which is normally for a high speed vessel since it has a feed for water to be injected, in my case from the salt water drain of the heat exchanger. This ensures lubrication of the water bearing.

Sea trials have not been conducted other than moving from a nearby boatyard to our berth at the Subic Bay Yacht Club.  When interior varnishing is completed we will then have a chance to check out the expected improvements.

1 comment:

  1. You are fortunate indeed, to "fall into" so many good deals! Can I follow around in your wake?

    s/v Eolian


Note: Only a member of this blog may post a comment.