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Cut PVC pipes
For cutting a thick PVC pipe, you require some concentration and idea. If you cut halfheartedly, a gap between the start and the end of cutting may be brought about, as shown in fig. A.
For clear cutting, wind a paper with a straight edge around the pipe, fix it with a gummed tape, draw a line with a magic marker along the edge of the paper, as shown in fig. B.
Then take away the paper and begin to cut the pipe carefully along the line with a pipe-saw, simultaneously rotate the pipe slowly, form a shallow groove first, then gradually deepen it. After several rotation, cut off a piece of the pipe, plane the end of it with a flat file.
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Purchase cabtire cables
Cabtire cables are used for an electric wiring and may be available at a DIY shop.
Single (solid) copper wire is desirable because its stiffness may prevent unwanted vibration and may be favorable for sound quality.
Generally speaking, you should get two or three kinds of cabtires with different diameters, and measure the gap between inner and outer tubes. Then select cabtires as following equation.
(gap) + (0.5 to 1.0 ) = (sum of diameters of selected cabtires) = (width of partition plate)
Partition plate completed may be wider than the gap with addition of glue layer. This is important for getting strong adhesion between the plate and the outer tube.
I used to go to nearby home center or DIY shop and buy two kinds of cables. One is gray and flat type with 6.3 mm thickness, and another is the same type with 5.9 mm thickness for 30 mm gap.
(6.3 x 3 turns) + (5.9 x 2 turns) = gap 30 + 0.7
Thinner cable should be used for the first and second turns.
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Prepare for inner tubes (or inner rods)
(1) Draw two lines along the axis of inner tube. The two lines, front and back lines, must deviate exactly 180° degree each other.
The left picture indicates a method to draw the lines.
Using something like a carpenter's square, scratch the surface of the two inner tubes simultaneously and draw lines with bruise. After that, draw lines with a magic marker over the bruised lines.
Repeat this process by turning the two inner tubes upside down.
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(2) Mark with a magic marker on the two lines to indicate locations of the upper surface of the partition plate.
The locations on the two lines, front and back, are as left for Helix150.
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Wind the first turn of cabtire
Wind a cabtire cable on the inner tube along the marks as smooth as possible, and fix both ends with duct tapes or cramps as a left picture.
Cut the cabtire at the points of sticking out about 2 inch from the both ends of the inner tube.
Apply low viscosity cyanoacrylate adhesive (for instance ARON ALPHA® 201 or Loctite 4206) from both sides to join the inner tube with the cabtire.
The vapors of cyanoacrylates are mildly irritating in very dry atmospheres (below 50% Relative Humidity). Use it in a well-ventilated room or in the outdoors.
Wear protective glasses.
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Wind 2nd to final turns of cabtire
Wind the next turn of cabtire on the outside the previous turn. Fix it with duct tape. Cut at the points of sticking out about 2 inch.
Confirm if all turns of cabtires stand horizontally using a right-angled jig as indicated in the left picture.
Mr. Hayashi proposed the nail method for confirming the cabtires configuration, which is showed in the left pictures.
But it is almost impossible to place the cabtire neatly side by side, and imperfectness is tolerable.
Apply cyanoacrylate adhesive from both sides to join next turn with previous turn cabtire.
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Cut the extra ends of cables
Cut the extra ends of cables with a pair of sharp scissors or with metal-saw.
Now the spiral body has been completed.
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