Post by J. J. Lodder Post by Janet
This is the last sea-going paddle steamer
As frequently seen from my kitchen window. She doesn't emit steam.
"Waverley is powered by a three-crank diagonal triple-expansion marine
steam engine built by Rankin & Blackmore, Engineers, Eagle Foundry,
Greenock, Scotland. It is rated at 2,100 IHP and achieved a trial speed
of 18.37 knots (34.02 km/h; 21.14 mph) at 57.8 rpm. Passengers can watch
these engines from passageways on either side of the engine room
The main crank is solidly attached to both paddle wheels so they cannot
turn independently of each other. The Waverley therefore has a much
larger turning circle than modern ferries."
Your remark intrigued me,
so I wondered why they would have built Waverley that way.
In the 19th century paddlewheel tugs survived for some time
(despite losing dramatically from a propellor driven tug
in a much published ompetition)
precisely because having indepent drive made them more manouvrable.
(they could turn on their axis, which is clumsy with a propellor)
Wikip does provide an answer, but unfortunately I don't understand it.
European sidewheelers, such as the PS Waverley, connect the wheels with
solid drive shafts that limit maneuverability and give the craft a wide
turning radius. Some were built with paddle clutches that disengage one
or both paddles so they can turn independently. However, wisdom gained
from early experience with sidewheelers deemed that they be operated
with clutches out, or as solid shaft vessels. Crews noticed that as
ships approached the dock, passengers moved to the side of the ship
ready to disembark. The shift in weight, added to independent movements
of the paddles, could lead to imbalance and potential capsizing. Paddle
tugs were frequently operated with clutches in, as the lack of
passengers aboard meant that independent paddle movement could be used
safely and the added maneuverability exploited to the full.
How does having independent drive on the paddles lead to capsizing?
I would have thought that paddle wheels do not give rise
to significant vertical forces.
The padle going in lifts the side, at coming out it drags down.
Can anyone here elucidate?
my only comment is the the Waverley is an "ocean going" vessel. As such it
has to be able to cope with significant waves. That might well have been a
factor in its design.