R/C'ing the Trumpeter 1/144 SEAWOLF (SSN21) Submarine, Part-8

A report to the Cabal:

Almost two weeks of solid work on this project and yesterday I can honestly say I finally have it done to a point were it's about ready for some in-water tests. Just have to outfit the WTC with r/c and other gear, install the initial amounts of lead weight and foam, pull pack the tarp on the kiddi-pool and toss her in.

All the preliminary work: careful layout and manufacture of the masters, the constant test fitting of stabilizers and yoke masters on and within the hull, and the work involved in translating those masters into usable model parts, it's all worked out to my great satisfaction. The last few days have been the pay off; the opportunity to finally stick the parts onto the kit hull. And it hit me: the only thing original to the Trumpeter 1/144 SEAWOLF kit is the hull and the sail -- everything else in this r/c version of the kit is indigenous to me, D&E Miniatures. That stuffing realization sunk in, I did the math: was $35 spent on the kit worth the eventual use of only the hull and sail parts? And the answer was quick and sure: Damn right it is!

This will be it for the Cabal Reports for a couple of weeks: I've got a lot of backordered WTC's, SKIPJACK hulls, and other products to get out of here; turnkey jobs, old and new to finish, test, and get off to they're new homes.

And Wonderfest is coming up next May, a science fiction convention known for its high quality model contest and vendors area -- that's an event I want to make this year. I plan to bring one or two models to enter, and time is getting short. So, you'll be seeing some SF model building projects continued here. I want to jump back on that Flash Gordon ship Steve Hickman designed embodying a very strong Mac Raboy influence. Those masters are well underway and have to be fleshed out.

And there is the Jack Coggins classic space station which I've documented with the kind assistance of a surviving relative of his -- you children of the 50's will recognize and love that thing once it begins to take form in my capable hands.

And then there's the Charles Forbin figure I've been working on, and ...

Oh ... and I'm supposed to start up with Rick Teskey to get his eighteen-inch wide Flying-Submarine model up to speed so he can start kiting those things in mass. He's doing the hull proper and I'll be adapting it to receive super detailed fittings and practical propulsors and WTC.

And Adam Carlson is coming over this Christmas holiday and we'll finish his big Type-A midget submarine masters ...

I've got the model structurally done and have outfitted it with all the linkage and drive train needed to animate this thing. I've still to outfit the WTC-2.5/SEAWOLF with r/c gear, servos, APC-4, fail-safe, a high capacity 7 Volt Lithium-Polymer battery, switch harness, voltage regulator and a speed controller (one that works, Damit!). Once the WTC is ready I'll take this thing to the kiddy pool and trim it out. Then, on to the big Dive pool at the Lynnhaven Dive Center where I'll see just how sloppy a turning radius this thing really has. Reports from others who have r/c'ed this kit indicate that this thing turns (particularly on the surface) poorly.

In the inverted upper hull you can make out the 1/16" aluminum bow plane pushrod (aluminum to keep the topside weight down) and the four doughnut shaped bearings, all sized to fit within the concave depression formed in the hull by the topside flushing tube fairing that runs nearly the entire length of the SEAWOLF deck. At the extreme after end of the bow plane pushrod you can see the white plastic pusher plate. Another pusher plate, connected to the after end of the WTC pushrod engages the bow plane pusher plate -- and that's how I interlock the WTC and bow plane elements of the bow plane linkage during hull assembly. Skip Asay, the Godfather of American r/ c submarining, gets the credit for this neat device.

The WTC has been removed in this shot so you can make out better the two stern control surface pushrods, rotor drive shaft, and the yokes that work around that shaft. The pushrods make up to the bell-cranks of the yokes with simple 'Z' bends at their ends. The forward end of these control surface pushrods make up to the WTC pushrods through mechanical connection blocks, described in more detail farther along in this installment.

To interconnect the bow planes -- who's linkage is predominantly in the upper hull, well removed from the WTC which is mounted in the lower hull -- I used two pusher-plates, one slaved to servo travel, the other spring loaded to always maintain contact with the other pusher plate. The bow plane pusher plate is spring loaded to travel aft. The WTC pusher plate, when the two hull halves are joined, bears against the compressed linkage of the bow plane and drives it, as commanded from the transmitter, to any position between full rise and full dive, depending on the Driver's wants.

It just occurred to me: There's room to install an extended WTC in this hull. I could make a 'special' WTC with a dry space forward to house one of the SubTech ADC-1 depth controllers. It would be nothing to put that in the loop of the bow plane and have the model seek and maintain 'periscope depth' autonomously. Hmmm, food for thought ... Maybe I'll fix something up in time for next years Carmel SubRegatta.

Note that I worked out the geometry of the two pusher plates on a piece of .040" polystyrene sheet with pen compass and ruler before hacking them out on the bandsaw. The top edge of each pusher-plate bears against the inside diameter of the hull, keeping the pusher plates from twisting as they travel axially as a consequence of servo motion.

The 'spring' in this case is a rubber-band at the forward end of the bow plan pushrod

Serendipity every now and again smiles. Such is the case with the Trumpeter SEAWOLF injection formed hull and the concave depression formed by the topside flushing tube fairing -- it was a natural place to run the bow plane pushrod, even though there is ample annular space between the WTC and the hull to run the pushrod lower in the hull. The lightweight aluminum tube pushrod runs through little lathe turned doughnut bearings cut from polyurethane waste sprue material. The removable bell-crank is one of the cast metal parts produced in the centrifugal disc tool. The bell-crank secures to the transverse operating shaft with a 4-40 set-screw.

The bow planes rotate within the fairings that are glued to the hull. The bow planes are tight friction fits to the operating shaft, this feature permits me to remove all parts for replacement, repair, or adjustment. I build as much 'accessibility' into an r/c models subassemblies as possible.

The bow plane and WTC pusher plates seen to good advantage here. The radial pencil lines I marked within the upper hull indicate the full-rise and full-dive positions of the pushrod. Similar lines within the lower hull told me were to position the face of the WTC pusher plate (you Orion fans hot yet?) pushrod. Final adjustments of bow plane 'center' is done by sliding the WTC pusher plate along its pushrod, a set-screw fixes the pusher plate to the pushrod.

A close look at the mechanical interface points for the control surface linkage of the model and those of the WTC. Also a good presentation of how the Dumas universal coupler makes up the motor output from the WTC to the rotor drive shaft. The setscrew set within the body of the WTC pusher plate is evident here.

Square sectioned mechanical connection blocks were machined on the mill from brass round stock, drilled, tapped, each equipped with two 4-40 set screws, and used to secure the control surface pushrods to the WTC pushrods. Though not as convenient as the Du-Bro snap-connectors I favor these connection block type mechanical connector is economical of space which is at a premium aboard 1/144 scale model submarine subjects.

Note that the ahead and astern shaft loads are absorbed, not by the after bearing, but the Oilite bearing glued atop the lower hull semicircular bulkhead. A wheel-collar astern and ahead of the bearing, pressing against a stainless steel thrust washer, transfers the shaft thrust loads to the bearing with minimal friction losses.

I used identical 3/16" o.d., 1/8" bore non-flanged Oilite bearings at the pump-jet end and at the extreme forward point of the rotor drive shaft. Just to show you some other type Oilite bearings, here is an array of 1/4" bore and 3/16" bored flanged bearings of different lengths. You can buy solid sintered, oil impregnated Oilite stock and turn it on your lathe for specialized applications.

The upper items in the photo illustrate how I press fit an un-flanged Oilite bearing within a bearing mount -- that mount a piece of lathe turned and bored polyurethane resin sprue remnant. Note that I leave a bit of Oilite bearing projecting from each end of the mount to provide an unobstructed seating surface for the thrust washers. As it turns out the bore of the mount is about .185" and the diameter of the bearing is .187" which makes for a good tight interference fit between the two -- an important consideration as it's impossible to glue Oilite's directly to anything (unless you first vacuum out the majority of the impregnating oil, then heat the bearing to carbonize out the remaining oil, glue the Oilite bearing to whatever, then pressure jam the oil back in ... but all that nonsense would be stupid, wouldn't it!?!). No. You press-fit the Oilite into a foundation and glue, bolt, weld, or press-fit that foundation to the structure.

I'm forever talking about 'Oilite bearings'. Time to give you a bit of background about these low friction items:

Oilite is a trade-style. The proper description of these things is: sintered bronze (open cell), oil impregnated bearing. Oilite bearings are very low maintenance, low friction bushings that are most suitable for our r/c model submarines -- vehicles that spend most of their time in air, but get the occasional dunking. All the maintenance that is required of these corrosion resistant bearings is the occasional drop of oil. Don't give yourself the headache of maintaining roller or needle bearings aboard your r/c sub ... not worth the maintenance time and sweat.

A good source of these bearings and also a good text that better describes the construction and use of these bearings can be found at, http://www.smallparts.com/ products/descriptions/tbb-sbb-fbb.cfm?Source=GG&cpgn=Sintered%20Bronze% 20Bearings&grp=Sintered%20Bronze%20Bearings&strg=Oilite% 20Bearings&gclid=CMX_3PD41YgCFSLrPgodVw6tlA

Here's a close-up of the press-fit un-flanged Oilite bearing within its polyurethane bearing mount. Note the glob of catalyzed CA adhesive that bonds the foundation to the lower hulls after semicircular bulkhead. The wheel-collars at each end of the bearing transmit the rotor shaft ahead/astern loads, through stainless steel thrust washers, to the submarine structure -- this unloads both the WTC and the pump-jet housing from axial loads.

As tiny as the WTC-2.5 is I still managed to work in five penetration points at the end of the motor bulkhead to accept either 1/16" water tight seals (encapsulated quad-seals within solid resin bodies) and/or specialized fittings, such as the threaded equalization valve you see on the starboard side of the unit. The fourth pushrod seal is there to permit me to turn the onboard battery on and off without need of accessing the interior of the WTC.

At the extreme bottom of the motor bulkhead are alternate power lugs that are capped with 6-32 thumbnuts, used if I chose to deliver power to the WTC from a battery mounted in the wet section of the hull. However, this version of the WTC-2.5, the WTC-2.5/SEAWOLF is intended to make use of an internal control/propulsion battery. Though I have yet to identify a specific unit, I plan on using a small, high capacity 7 Volt Lithium Polymer battery within the WTC.

Here you see how a saddle cradles and holds the WTC in place with a rubber band. Also note, within the clear Lexan cylinder, a short brass pin projecting from the center of this forward saddle. The pin mates with a hole in the cylinder (this is in the ballast tank section of the WTC, so the hole is not a big issue). The pin insures exacting registration of the WTC within the hull.

The two cast resin WTC foundation saddles were roughed up with #100 sandpaper on their outer faces as were the areas within the lower hull that would received them. I drilled out 1/16" holes in the saddles to receive brass wire 'hooks' used to make up to the securing rubber bands -- this work done before installing and gluing the saddles within the hull. Bonding was achieved with thin formula CA after positioning each saddle in place.

You're looking at the inverted WTC in foreground. The big hole in the clear Lexan is the flood/drain opening of the WTC's gas-type ballast tank. The small registration hole that accepts the saddle pin is just forward of the big flood/drain hole.