Duchess of Delthak Controls

While re-reading the Safehold series for the umpteenth time I started to wonder about control systems in a non-electric world, particularly those for the Duchess of Delthak. I have no issue with imagining some system of wires and gears to manage the control surfaces of the airship. But how do they start and stop the Praigyr steam engines?

My impression is that the engines are mounted on some sort of outboard pylons directly connected to the propellors, i.e. "the pair of podded engine nacelles thrusting out on either side of the thirty-foot-long control cabin." So how do you cut the engines? I guess closing the kerosene valve would do that. But how do you start the engines up again. Does someone climb out on the pylon with a match? Alternatively, a wire-controlled steel striker that makes sparks seems really unreliable.

This issue doesn't arise with steam-powered warships, cars, tractors, trains since you can easily imagine someone striking a match to light the engine. But on a dirigible several thousand feet up in the air?

If the engines are inboard and power is transferred to the propellors by some arrangements of belts and pulleys, that too seems very complicated.

Anyhow, comments are welcome.

A bit of reading on Wikipedia provides an answer. Apparently there are pneumatic starters where compressed air is used to spin a turbine and initiate the engine cycle. Once running, the engine power can be used to re-charge the compressed air tank.

There also are hydraulic as well as spring starter systems. Lot's of choices none of which involve electricity (or lighting a match).

Most likely simple; by the mechanics in the nacelles.

Mark Time wrote:A bit of reading on Wikipedia provides an answer. Apparently there are pneumatic starters where compressed air is used to spin a turbine and initiate the engine cycle. Once running, the engine power can be used to re-charge the compressed air tank.

There also are hydraulic as well as spring starter systems. Lot's of choices none of which involve electricity (or lighting a match).

US nuke subs carry a spare diesel engine for emergencies. On top of it is mounted an air cylinder and an attached pneumatic torque wrench to start the diesel in case of emergencies. The thought is if you're starting the diesel, nothing else is probably working right so you better have a powerless starting solution at hand.

Another starting solution is some piston planes had essentially oversized shotgun shells as a emergency starter - the exploding powder in the shells would turn the crank, starting the engine. Some Engines had 6-12 starter shells available.
https://en.wikipedia.org/wiki/Coffman_engine_starter

SNIP

Theemile wrote:Another starting solution is some piston planes had essentially oversized shotgun shells as a emergency starter - the exploding powder in the shells would turn the crank, starting the engine. Some Engines had 6-12 starter shells available.

Not just older piston-driven aircraft, but also more modern aircraft with turbojet engines. See the two following YouTube videos:
Video 1 https://www.youtube.com/watch?v=9JC8DlnJSVU in an inset (bottom-right) shows the installation of the gas generator into the engine.
Video 2 https://www.youtube.com/watch?v=tXE4igocAbg shows a B-52 scramble launch from (I believe) Barksdale AFB in Shreveport, LA (the "Cajun Air Force").

The gas generators are (as you allude) similar to oversized shotgun shells but are actually fast-burning high-volume gas generators that burn long enough and generate enough gas volume at high enough pressure to overcome the inertia of the engines. They work in this application because you're starting a turboJET, not a turboFAN engine. The fan section of a turbofan is much larger in diameter and thus has much higher inertia to overcome when starting. Typically, in a scramble scenario, the crew would start two of the eight engines that way, then start the other six engines "normally" while taxiing to the runway.

WeberFan wrote:SNIP

Theemile wrote:Another starting solution is some piston planes had essentially oversized shotgun shells as a emergency starter - the exploding powder in the shells would turn the crank, starting the engine. Some Engines had 6-12 starter shells available.

Not just older piston-driven aircraft, but also more modern aircraft with turbojet engines. See the two following YouTube videos:
Video 1 https://www.youtube.com/watch?v=9JC8DlnJSVU in an inset (bottom-right) shows the installation of the gas generator into the engine.
Video 2 https://www.youtube.com/watch?v=tXE4igocAbg shows a B-52 scramble launch from (I believe) Barksdale AFB in Shreveport, LA (the "Cajun Air Force").

The gas generators are (as you allude) similar to oversized shotgun shells but are actually fast-burning high-volume gas generators that burn long enough and generate enough gas volume at high enough pressure to overcome the inertia of the engines. They work in this application because you're starting a turboJET, not a turboFAN engine. The fan section of a turbofan is much larger in diameter and thus has much higher inertia to overcome when starting. Typically, in a scramble scenario, the crew would start two of the eight engines that way, then start the other six engines "normally" while taxiing to the runway.

Some of the earlier aircraft, ww2 and before had a spring loading system. Wind up the spring with a crank, pull out the crank and pull a lever to release the spring and spin the engine to start. Come to think of it, I've seen lawn mowers with this system. Never owned one though...

Don

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