The Chain Pumps.
As usual, TFFM gives a good explanation.
A down (Back) tube, inboard,with intake at base.
An up (Discharge) tube .
These are topped with an assembly including a wheel and roller. Surrounding these is a cistern.
The tubes are pencil-shaped,98mm long, 5.3mm wide at top and tapering to 4.0mm at bottom.
There is a consistent bore of 2.65mm, therefore the wall thickness thins significantly.
There is also a pair of Brake pumps, similar in external size but with a narrowing bore (to 2.4mm) which is essential for its mode of function.
I used 5.3x5.3 blanks, 100mmlong. Holes drilling in initial few cms. With a drill press-enure bit is centralised
Already had the jig as suggested, but my skill with a plane is lacking.
Still able to use the “7-10-7” rule as suggested, but used a mill instead.
Dusting of my Pythagorus, (? remember the song” the square of the hypotenuse….”), the depth of cut can be easily calculated.=1.1mm
The corners are milled off and we have 8 sides.
The tapering achieved by raising the lower end with a 0.65 slip of wood,remilling against the gradient with a slightly shallower cut.
The top 6mm of all are rounded (like a pencil) to a diameter of 4mm.Where this starts,a collar of 2mm black paper to mimic an iron band.
The Brake pumps have a modified band which can be fitted later.
These also have a modified lower end- inboard is shaped like a fountain pen nib.
Finally, a hole to allow a 1.6 bore pipe (a short discharge tube), to protrude aft/outwads at 45deg.- I set this after checking the upper deck level.
( I have purchased a set of Photo-etched details from a fellow Swan builder)
I tried to build the Pump Intake Chamber-too fiddly and no patience)
*****This means that the Tubes will sit lower and this should be allowed for*****
(After the complexities of the Bitts, this was FUN and I
forgot to take pictures)