Sunday, July 20, 2014

Engine Beds - Part II

Notwithstanding all of the hullabaloo surrounding the prop, it was time to get the engine beds in permanently and the position of the engine defined, since so many other things - piping, for one - depend on the fixed centrality of the engine.  So out came the shaft hubs, recently machined, and the engine lift again, and all was swung inboard to begin the alignment process.

This photo was taken when things were about dialed in, however it shows the many considerations in play:  The engine is in its position fore and aft.  Though the floors are fairly true to the gunwales, I nonetheless strung a straight edge* across to make sure that the engine would be perfectly perpendicular to the plane of the waterline.  I would see where the engine was sitting with respect to the shaft hub, lift up the engine a piece, knock the beds out and plane them to where I thought they should be, re-install them, measure and fuss, lift the engine a bit, knock out the beds, etc.  *(Purists will worry about my use of a treated piece of junk pine for a straight edge, but I couldn't find my prized Doug fir batten ... One grabs what one can in situations like this.)

Finally, I had things to around 0.005" on the tips of plastic epoxy spatulas, confident that permanent shimming could be accomplished from there.  Here's a close up of the hubs all but dialed in - bright engine hub forward and gray shaft hub aft -  with the spatulas serving a nobler task than normal.  The hubs by the way, are off the shelf, Buck-Algonquin ductile iron, cast within a couple miles of our house.  The shaft hub remains stock while the engine hub has been extensive modified to clear eccentrics, retaining nuts, etc.

To the port of the engine, forward of the aft floor behind the low pressure column is where the crosshead-driven pumps will sit on their bronze bedplate.  This bedplate has to be let into the beds its thickness.  So, the lift whisked the engine back to the bench, out came the beds for the last time and out came the chisels.  With the beds then finish dressed, I epoxied them into place.  The beds themselves were left unfinished except where the bonds on the tenons and and floor shelves were made.  Later, I'll treat them with raw linseed oil and turpentine - love that old boat smell!

Here is a shot with the engine back on the bench and its hub coming off.

The hubs, bearing caps (here, in red) and other items will go out to the powder-coating shop for their final finish.  One can see the pump links, and other items, namely the exposed low-pressure valve seat on the yet unfinished engine.

Tuesday, July 8, 2014

A Steam Propeller

Some time ago, I picked up this Michigan 22 x 27 right-hand propeller for Iona.  The cost was cheaper than the scrap value and I had done enough reading on props to know that the prop had an rpm-limiting disk area, among other issues ...

Iona didn't mind, I wasn't afraid of modifications and there were enough other things to do so the prop collected dust.

Fast-forward to now - the propeller shaft is in - so it was time to re-visit the propeller.  Back to the bookmarks in the propeller tomes.  I decided on a surface area, plotted where I would modify (increase) the pitch and made a template.

Out came the center punch; a cut-off wheel was mounted on the small grinder - It was "bad haircut time."

Here's the prop with a "bad haircut."  I know about these things.  Summer of '70, the neighbor boys and I purchased black powder from the feed store.  You could do that kind of thing in those days.  We perfected our copper tubing skills by manufacturing bombs of various caliber and force.  Turns out we were challenged by that age-old problem of proper fusing.  (If we had only had the Internet!)  One of our devices experienced a premature - to us - detonation.  Half my summer-blond hair was frizzed.  Not to mention the powder grains embedded in temples, cheeks and shins.  [We are far afield from steam propellers ...]  It was the kind of thing the parents would certainly notice.  What to do?  Haircuts!  Of course, no one would notice!  So we similarly afflicted youth set about shearing each other - what could go wrong?  Followed by thorough scrubbing of the powder burns; there, we looked like we were ready for church ...

The photo doesn't do it quite justice: the chord is as thick as my little finger.  The next step was to grind a rolling foil from root to tip in a way that created lift or thrust on the back of the blade.  By dressing the foil in the way I imagined, it would increase the pitch slightly.  Oh, and I chopped the tips to fit the aperture.  Here's the first blade, with foil dressed.  (The tips will wait for balancing.)

The prop is sitting front side, up.  The major metal removal occurred on the back side in order to preserve the chord profile.

This photo uses different lighting and displays more of the overall profile.  I might keep the squarish tips, after a fashion.  They might add to "the look" whatever my profiling skills lack.  By the way, tools used were 4.5" grinder with razor cut-off wheel; 4.5" grinder with standard 0.250" wheel for roughing in; 7" slow-speed grinder with foam pad and 80 grit stick-on pads for fairing.

Balancing  and final tip dress will take place on a motorcycle wheel balancing stand.