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David Merriman's 57" Seaview
part 4 [more] |
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Not everthing created to detail the SEAVIEW interior could be rendered as cast resin/metal parts. Two items were so complex of
shape to preclude easy tool making. So, with those items I elected to make them directly from the raw materials, and to place them into service as kit parts. The spiral stair case located at the after
starboard corner of the OC; and the circular guard rail around the FS-1 access hatch center, just behind the windows.
Soldering is not welding -- none of the base material (brass wire and brass
sheet as applied here) is caused to change state from solid to liquid. No. Soldering is not welding. Soldering employs the principle of adhesion. Welding is cohesion, the intermingling of the bass
materials across their former union points.
Solder, an adhesive, is introduced between the two items being joined. Soft or hard solders (we use mostly soft, low temperature solders, an alloy of
either Tin/Lead or Tin/Antemony) is heated to its melting temperature at which point the solder flows into the gap between the items being stuck together, forming an adhesive bond between the bass
metals. At no time in soldering does the base metal change state (melt).
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Soldering can be looked on as gluing -- that's what it is, after all. An Adhesive!
Pictured are the tools and consumable
needed to effect a strong solder bond: The solder, in this case good old 60/40 Tin/Lead; flux; and a heat source, here a thirty-Watt soldering iron.
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Flux (usually in the form of a paste), when heated during the soldering process, greatly reduces the surface tension of the
liquid solder permitting it to flow freely and to permeate the tightest gap between the metal parts being joined. The secondary job of the flux (be it a rosin or acid type) is to lift oxides off the work
(either there previous to the operation or formed as a consequence of heating a contaminated joint area), oxides that would otherwise inhibit penetration of the solder onto the surface of the parts being
bonded.
The best possible solder penetration is achieved with the aid of acid type flux. But, care has to be taken to wipe the excess flux off after the work cools. Remaining flux is removed by
dipping then scrubbing the joint while immersed in a base solution or simply scrubbing the work with an aceton/lacquer drenched piece of steel wool, my usual practice.
Never use acid type flux on
electrical connections, be the soldering performed on a printed-circuit board or wire -- residual acid (which will leach up into the wire under its insulation and between components and the board) will
oxidize the metal areas of the circuit over time and change the conductivity of the circuit or even open it all together. Only use rosin type fluxes when soldering electrical circuit connections
The key to strong solder joints is to clean the metal to a shiny finish, to quickly flux the work, and then getting on with the application of a quick heat and introduction of the solder to the joint. In
the photo you see a small brush in a dish of acid type flux. It's my practice to literally paint on the flux to the joint area to be soldered -- you can't use too much flux!
There are many ways
to apply the heat to the joint area: soldering iron, soldering gun, open torch flame, resistance soldering machine, inductive soldering machine, candle or match, dip-bath, or rubbing the parts together
real quick (sonic soldering). The stairs and guard railing units seen here were soldered up from brass sheet and wire with the aid of a simple thirty-Watt soldering iron and the ever reliable 60/40 (60%
Tin, 40% Lead) solder.
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Looking at the assembled spiral stair unit would make you wonder just how the hell such a complicated structure could be held
together effectively as all the little components were soldered together. As it turns out, if a few simple preliminary steps are taken, the spiral staircase structure can be built quickly, and with
reasonable symmetry.
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After all, the most complicated of shapes can easily be defined as a hybrid of the three basic geometric shapes that comprise
its matrix. The trick is to work out what items of the whole can be built as stand-alone elements, how to fabricate those elements, and later how to join those elements to achieve the ultimate structure.
Methodology, the fabricators ability to formulate a plan of construction/assembly/painting/weathering. Can you, or can you not devise a practical sequential order of steps to achieve a goal? Do
you posses the ability to employ a rational methodology that will achieve the goal with the minimum of complexity?
One of the demarcation lines between a common kit-assembler and Model Builder is
the ability to devise a plan and to then execute that plan with precession; methodology and technique. You either have those skills or you don't. You're not born with these skills, you learn them!
Where was I?.... Oh, yeah ... soldering up the spiral staircase structure.
Each spiral staircase consisted of four specific type pieces: the spiral brass sheet ribbon, rail, rail stanchions,
and steps.
First step was to determine the diameter, width and height (pitch) of the 'spiral' outer staircase structure, a helically wound ribbon of thin brass sheet. Initial examination of the
Barr drawings and production stills indicated that the spirals pitch (the linear, vertical distance from floor to ceiling for one 'twist' of the spiral structure) was equal to the compartment height.
Simple enough.
I turned a wooden dowel on the lathe to the diameter of the spiral. With a pen I marked off two radial lines indicating the distance from deck to overhead (pitch). Then,
experimenting with a ribbon of paper, its width equal to that of the eventual brass spiral piece, twisting it around the mandrel in a helical fashion until I found the angle that would make one complete
circuit of the mandrel within the two height points. I then traced the outline of the paper stencil onto the wooden mandrel, those lines to later guide where to lay down an annealed strip of brass sheet
as it was bent to conform to the helical (spiral) shape indicated.
An annealed brass wire 'handrail,' mounted atop the spiral ribbon, upon vertical stanchions, was also wrapped around the wooden
mandrel to capture the correct diameter and pitch -- the same helical twist as that of the brass sheet 'ribbon' piece.
(Two spiral stair units were made, though only one is needed for the model.
The extra unit presented in this series of pictures is there to better demonstrate the procedures involved in spiral staircase fabrication -- it's an extra. I'll likely use it in the Teskey SEAVIEW when
that kit finally arrives. That model will be mine, damit! Building these turnkeys for clients is killing me ... after years of making perfectly good toys for others. I want to play too! Ain't fair!).
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Each staircase step consisted of a flared strip of brass sheet soldered to a short length of brass tube, oriented perpendicular
to the plane of the step. The brass tube element of each step piece would later slide onto a central aligning brass rod preceding attachment of the stair steps to the inboard side of the brass spiral
ribbon piece.
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Examination of the assembled spiral staircase shows that each stair step is staggered a specific angular distance from the one
atop and below it. This angular distance -- a specific ratio of the vertical distance between steps -- is driven by the length of the steps perpendicular brass tube. Initial trials, varying the length of
the step tube, determined the tube length required to achieve stair step height that looked reasonable for a 1/96 model (though, between you and me, I would prefer, on the next effort, to stagger the
steps a bit less and have them piled a bit closer together -- in other words, make the step tubes a bit shorter in height).
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I then went about the task of making a marking/sizing/soldering/holding jig to mark out brass strips for cutting to the outline
of each step, hold each step securely in space, and to also secure a sized piece of brass tube for soldering to the inboard end of each stair step. This jig was nothing more than a piece of veneered
particle board with a circle marked on it representing the inside diameter of the spiral ribbon (equal to the diameter of the spiral mandrel).
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Within the center of this circle was drilled a hole to receive a pin that would hold short brass tubes as they were soldered to
their associated stair steps. Note that also marked out on the jig are radiating lines that denote the shape of the stair steps.
Each stair step was cut out with tin snips from brass strip and the
shape refined with a Moto-Tool cutoff wheel, file and sanding block.
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The trick to successful soldering of intricate structures like those that make up the spiral staircase is to 'tin' all parts at
their joint lines/edges prior to assembly. Tinning is simply pre-soldering the parts at their joint points.
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A part, say one of the stair steps, is scrubbed in lacquer thinner with a small wad of steel wool. It is then slathered with
flux and a small amount of solder flowed onto the inboard and outboard edges where the step will solder to its short length of brass tube and to the inboard wall of the spiral wound ribbon. of course
each step/tube assembly has to be held in the assembly jig to insure that the applied heat used to tin the assembly does not cause the tube to de-solder and fall out of alignment with its step.
I
found it a simple matter to completely tin the inside of the spiral ribbon, the entire spiral handrail, and each handrail stanchion in their entirety. Excess tinning solder can be wiped off with a dry
cloth while the solder is still in its molten state.
The soldering of the spiral staircase assembly was surprisingly easy: All the stair step pieces were run up over a brass rod that fit the bore
of the step tubes. Using a clothes pin, the upper stair step was held against the top inboard portion of the spiral brass ribbon piece. The same was done with the lower step piece ... and, like magic,
the center of all stair steps became instantly centered with the helically wound spiral ribbon piece!
It was then a simple matter to rotate the individual stair steps to fit against the inboard
face of the ribbon, brush on acid flux to all joint lines, and then to apply heat with the solder iron. Since everything had been pre-soldered during the tinning operation, the existing solder, which had
platted the parts, began to flow into the adjoining seams, effecting low radius, perfect solder unions.
It was then a simple matter to solder on the vertical stanchion wires against the inboard
side of the ribbon, and to then solder atop each stanchion the continuous running helical wire forming the stair handrail.
The completed spiral stair assembly was then dunked in lacquer thinner
and scrubbed with steel wool to kill and remove excess flux. A little work with file and sandpaper readied the unit for pickling.
The FS-1 access hatch guard railing was soldered and dressed in a
similar fashion.
The two soldered assemblies were then pickled in Ferric Chloride acid, rinsed in a base solution (water doped a bit with baking soda) to kill the acid. Rinsed in fresh water,
dried, and primed. Readying them for final painting.
The pickling etches in millions of microscopic pits onto the surface of the brass and solder, producing a 'mechanical tooth' that greatly
enhances the primers ability to adhere to the work (this pickling process is also a boon to you figure guy's who are tired of seeing your gorgeous paint jobs peeling and chipping off cast white metal
figures). It's not enough to dunk and scrub metal pieces in lacquer thinner to make them receptive to primer and paint.
Break out the hot acid, breath deeply, and let the games begin!
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onto part 5 |
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