On Fri, 21 May 2010 16:46:31 -0500, cavelamb
wrote:

Joseph Gwinn wrote:
In article ,
Richard Smith wrote:

Hi DoN and

DoN - that's right - of the nautical type. There is a capstan lathe
which I guess is named because the massive rotating tool-holder is
rather capstan-like - seen a derelict World-War-2 one in a thoroughly
modern (!) Fab. shop I worked in (a new Rumanian guy was speechless
with shock as he sat at his first tea-break - he'd never seen anything
like this place in Western Europe or even in Rumania).

Glenn - speed - yes - assume electric motor was 1500RPM (50Hz power
here) - so running gearbox at up to double that. Problem? Don't
know. Reduction ratio is already low enough at 50:1

I've thought of a design where the tube which becomes the capstan
barrel is welded to a disk of slightly larger dia. than the tube /
barrel, then the periphery of the disk protruding beyond the tube
becomes the rotating part of a big all-around sliding bearing. The
load is transfered to a steel plate "deck" under which the gearbox is
mounted - tried to sketch in ASCII text


|| ||
\\ //
\\ //
\\ //
// \\
// \\
// \\
|| ||
__ || X || __
| ===========X========== |
--------------------- X ----------------------
X

Then the drive shaft from the gearbox only has to keyway to the disk
(it serves that purpose as well - picking up the drive)


Another question for everyone...

Previous calculations I sketched out suggest a capstan barrel diameter
at the waist of 150mm (6"). The whole design is intended to be
matched to 12mm (1/2") rope [3-strand layed polypropylene - which
should have breaking strength of 2.2Tonnes-force].
So is 150mm (6") the right capstan waist size for 12mm (1/2") rope?

Rich Smith

I would make sure that the capstan will not spin free and drop the load should
the capstan drive system break under load. Even if the load is of no
importance, whoever was pulling on the rope when the capstan failed could be
pulled into the capstan and mangled.

There must be many patents on better designs for marine capstans. Some research
may be helpful.

Joe Gwinn


On the other hand, there are times when that "drop" capability
had to be designed in.

Lowering an anchor at capstan speeds could take half the day.

When you are located where you want to be, you want that anchor
to hit bottom as soon as possible.


Yes, usually there is a clutch built into the hub, but more and more
the high end anchor winches are power up - power down and if there is
a clutch it is seldom used.

Of course that usually applies only to the "gypsy" side. the capstan
side is usually keyed to the shaft. If a horizontal winch :-)
John B. Slocomb
(johnbslocombatgmaildotcom)