Leaving Antigua, W. I.

Thursday, January 13, 2011

To Help Pass the Time...

Top down view of engine template.  Red box is at front end.  Feet are optional.
 Side view, showing 7 degree angle of simulated transmission output flange.
 Seen from the front end.
Seen from the back end.  Simulated flange is square, with horizontal and vertical centerlines.

To help pass the time and sharpen our perceptions of spatial relationships, we built a three-dimensional template of the new engine today.  This was a 4-hour project, but it'll save a lot of time and energy later, as it is featherweight and embodies all of the critical dimensions of the new engine.  It is much easier to move around than a 400 pound diesel.  2x2 inch by 1/8 inch aluminum angle worked well for this, and when the job is done, it will be dismantled.  The short pieces of angle come in handy for all sorts of on-board projects.  We've normally kept a bit of it aboard anyway, and now we have plenty to make mounting brackets for all the odds and ends that will no doubt appear in connection with the new engine. 

There are four 1/2 inch holes where the engine mounts will go.  Rather than use the actual mounts, we'll use 1/2 inch threaded rod to simulate the mounts, because it will allow a much greater range of adjustment than the actual mounts will allow.  This is important at this stage, because we can set the template in place on the old beds and adjust the threaded rod to align the simulated coupling flange to the flange on the propeller shaft.  By subtracting the length of the threaded rod from the nominal height of the Yanmar engine mounts (100 mm), we can calculate how much of the existing bed we will cut off in order to put the engine in the proper vertical position.  Note that the corner of the longitudinal angle lies in the vertical plane of the centerline of the engine.  The simulated transmission output flange is set at a 7 degree angle to the axis of the engine, and it is the proper distance below the transverse angles which represent the engine mount brackets (111.5 mm, in the case of the 3JH5E with KM35A down angle transmission.)  All measurements are taken from Yanmar's engineering  drawings, which are readily available.

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