Report To The Cabal: A 1/48 SEAWOLF Pump-Jet, Part-8

Well, the master work is finally done! From here it's tool making, then production of the parts, send them to the client, and I'm done with this 1/48 SEAWOLF pump-jet project ... then on to other paying customers.

In the middle of this project two important leads developed: information that the rotor contained six blades and that the rotor tips connect to a ring, the ring setting within an annular groove within the shroud. That information coming in just in time for me to make the incorporation without any back-stepping.

Just as soon as I get off the keyboard here, it's back to the shop where I'll cut up
some sewer-pipe (to form tool rubber containment), mount the masters in clay
and hopefully, before bedtime, I'll pour the first of the rubber needed to make the
production tools of the five-part PJ.

Looking into the intake of the PJ - the last thing seen if you fall over the side while underway on the surface - pay attention, it all happens very quickly: First, you're swept up into the intake, formed by the shroud leading edge and pre-swirl stator blades, your neatly cut halves are then greeted by the quickly spinning rotor where you are further diced, accelerated both axially and radially, then served up to the post-swirl stators which do their job of sending your many, finally ground bits out in a nice linear flow astern, with nary a helical twist to 'em.

Nasty!

Another look at the intake end of the PJ. Note that the majority of the hull section (to which are affixed the pre-swirl stator blades) is hollow - I did this to minimize the amount of resin used to cast the eventual part. Excessive cross section to polyurethane resin parts produces too much exothermic heat, which contributes to excessive shrinking of the eventual plastic part. Also note the X-Acto knife and handle in foreground to give you some sense of scale.

Looking into the discharge end of the PJ. The post-swirl stator is shown off to good effect here. At this point the shroud halves, and where they mount to the tips of the stators, are only friction fits -- a lot of careful work went into achieving that little feat ... Damn, I'm good!

If you look very carefully you can just make out the radial seam that denotes where the forward and after portions of the shroud masters separate.

After I turned the rotor ring from a Renshape 40 blank on the wood lathe, I mounted it to the tips of the rotor with CA adhesive. Fillets were built up from Evercoat Glazing Putty filler (a two-part polyester filled paste), using a dapping tool to insure a constant diameter fillet. Final fillet work was done with modified rattail files and sanding sticks. The final filing and sanding operations done wet. This exposed some of the metal at the tips of the blades, so everything had to be pickled, rinsed, dried and primed. Final spot putty work was done with the air-dry lacquer based, Nitro-Stan, putty which was worked with rolled up pieces of #600 sandpaper used wet. A final priming completed the rotor master.

Test fitting the rotor into the just enlarged groove of the shroud -- checking for clearance.

I made a special compression type holding fixture, mounted to the faceplate of the wood lathe head-stock. This was used to permit me to cut out the inside groove into the after section of shroud, to fit the rotor ring. Here I'm using that holding fixture to secure the primed shroud halves prior to final sanding. The white disc is a jam fit within the after shroud half. The disc is pulled toward the head-stock when a nut is driven down on the central threaded stud -- all this to pull the work tight against the head-stock mounted holding fixture.

It works.

I found that the friction fit between the two shroud halves was enough to hold the forward half in place during spinning -- as long as I kept the rpm's down and did not place too much transverse load on the forward section as I sanded it.

The two halves of the shroud connect through a 'Z' shaped flange-to-flange fit. Note the compression disc securing the after half of the shroud to the head-stock of the lathe through the holding fixture. A nice tight friction fit between forward and after half of the shroud master permits me to work them while spinning.

The completed PJ masters. Everything (other than the rotor-ring unions) are friction fits.

Only the ringed rotor ... ah ... er ... 'rotates'. The five masters of the 1/48 SEAWOLF pump-jet.