Steam Actuated Inlet Valves?

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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Lopez Mike
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Re: Steam Actuated Inlet Valves?

Post by Lopez Mike » Thu Apr 12, 2018 3:56 pm

Here in the states we subjected our British motorcycle systems to as good deal of good natured (usually) opprobrium. "Lucas, home before dark", and the like. There was some option that Lucas might have been the manufacturer of refrigerators thus the consumption of warm beer in the isles. Batteries placed high in the frame so that gravity could help the electrons along. Just as stone weird were the Spanish and Italian ignition systems wherein the ignition system had a ground return through the stop light. Bulb failure meant a engine stoppage when you applied the rear brake.

My 1956 B.S.A. Gold Star Clubman had a light bulb in the headlight. In an evil moment I replaced the whole assembly with a sealed beam until. The Magdyno charging device could not keep ahead of the sealed beam's draw.

To be quite fair, we knew that there was no extra capital floating around in G.B. for any new developments thus we were dealing with prewar designs. The stuff on Harleys was every bit as primitive. My first Japanese bike in the sixties was startling to ride at night.

I am guilty of thread hijacking in the first degree. Enough!

Bart is mud wrestling with a new job or he would be chiming in here about his new uniflow engine. Cam driven poppet valves on the intake and cylinder ports for the exhaust I believe.
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Re: Steam Actuated Inlet Valves?

Post by DetroiTug » Thu Apr 12, 2018 4:36 pm

My older brother bought a brand new 1968 BSA 650 Lightning. It was burgundy and I thought it was the most beautiful thing I had ever seen, he paid $1100 for it, and remember thinking it's going to take him forever to get that paid off :lol: He kept it about three years and it ran beautifully and he never had a minutes trouble with it. He married a girl that didn't like motorcycles and that took care of that.

Mike, one of my steam buddies is your age and is an old Trials rider, he still rides an old Bultaco even now, You and him would have lots to talk about I'll bet.

Fred, Another steam buddy of mine was one of the principle engineers on the SES Dodge Monaco steam conversion project that you mentioned for General Motors and DOE.

Yes, sorry for the thread Hijack, back to steam operated valves.

-Ron
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Re: Steam Actuated Inlet Valves?

Post by fredrosse » Thu Apr 12, 2018 7:39 pm

Ron gets the first prize for the proper name as I have known it for many decades:

George Lucas, The Prince of Darkness.

"Lucas was the successor of Powell & Hanmer of Birmingham England, they made the Kerosene and carbide lamps that are on my Locomobile, over a hundred years old still working..."

Do any of us have an ELECTRIC lamb that is 100 years old and still working?

Enough Humor, back to the serious business of Steam!
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Re: Steam Actuated Inlet Valves?

Post by DetroiTug » Tue Apr 24, 2018 5:31 pm

Fred,

On Saturday at the North American Model Engineering show, someone coincidentally brought up Mr Lucas and remarked he was called "The prince of darkness" and followed up with Lucas light switches had three positions "Dim, flicker and off". And the reason some Britons liked warm beer is because they owned a Lucas refrigerator.. No offense to anyone of course.

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Re: Steam Actuated Inlet Valves?

Post by PeteThePen1 » Wed May 30, 2018 9:17 pm

Sorry, this is off topic too, but thanks for the photos of the new hull Mike. From this side of the pond I think it looks lovely and something of which to be proud. How you get such an amazing sheen on a first coat of varnish is probably a closely guarded secret handed down from your Granny! Apologies to everybody, I have been getting a bit behind with the various threads.

Regards

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Re: Steam Actuated Inlet Valves?

Post by Lopez Mike » Wed May 30, 2018 10:05 pm

The shop cat peed on it at least once. Seems to keep the other cats away.
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Re: Steam Actuated Inlet Valves?

Post by barts » Fri Jul 13, 2018 4:40 pm

Catching up on an older thread... As Lopez Mike mentioned, I've been heads down w/ a new job this year. However, I'm on Lopez for a month, working half time (4 day weekends are great!), so I'm catching up, doing some badly needed replumbing on our new to us steamboat (Rainbow) and will be talking w/ the architect/builder of our house here.

Anyway, back to the what this post is all about - getting intake valve motion the way you want it on an engine w/ separate valves. There's not much point in trying to design short cut-off gears for slide or piston valves; the heat leakage is too large, and the only way towards a more efficient design is to add more cylinders.

Traditional valve gears use simple harmonic motion (eccentric) and tune the valve events by positioning the ports such that steam is admitted for the desired interval. Getting short cut-offs with this sort of motion is very difficult, and requires long travel, high eccentric loads in the case of slide valves.

Poppet valves driven by cams are of course suited for short cut-offs, but short duration cam timings present their own difficulties. One method often used in Europe was the Lentz valve gear - a rocking cam actuating a poppet valve, with the cam driven from an eccentric. In order to get shorter cut-offs, rather than use a single eccentric to drive the cam the motion of two eccentrics was combined - one running at two or three times engine speed, the other running at engine speed. This meant that the only one of the movements of the high speed eccentric per engine revolution had any effect on the valve, and allowed nice smooth harmonic motion (albeit the sum of two different speeds) to approximate the desired 'jerky' motion of the cam. Adjusting throw and phase angle on one of the eccentrics adjusted the engine timing. These engines were typically stationary, and ran at constant speed driving generators, pumps, etc. Fuel prices were apparently much higher in Europe than in the US during the age of steam, and this led to many of the innovations to improve engine economy taking place there. The author of the Audel's Guides on steam engines often bemoaned the inefficient practices commonplace in the US....

Skinner of course used two cams running running at the same speed, and adjusted the phase angle between the cams to achieve a wide range of cut-offs, from 5 or 10% to over 50% - necessary since those engines were often used in direct reversing marine service, and reliable reversing is essential. This of course meant three (or more) cylinders as well. These engines were large and ran at relatively slow speeds since they directly drove props; that plus roller tappets and robust construction kept the rather brutal cam profiles from causing mechanical issues in the valve gear.

As I've described elsewhere, I'm building a single cylinder poppet valve marine uniflow for Sea Lion (37'); I'm hoping to avoid reversing and maneuvering issues w/ a Kitchen rudder. I'm still uncertain as to the valve gear details, but since the engine is intended to run continuously in the same direction until we're anchored/moored, several options are possible. Lentz-style rocking cams would definitely look neat :); it would also be possible to avoid right angle gear drives with such a set-up.

Solenoid driven valves are of course possible; a quick test could be done using a inexpensive car woofer voice coil assembly. With a single beat (automotive style) poppet valve using a light spring, the voice coil could drive the valve open and closed. Personally, I don't need electronics for the engine, but it's fun to consider on the test bench.

Back to work replumbing Rainbow's safety, whistle, etc.

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Re: Steam Actuated Inlet Valves?

Post by TriangleTom » Sat Jul 14, 2018 4:26 pm

barts wrote:Skinner of course used two cams running running at the same speed, and adjusted the phase angle between the cams to achieve a wide range of cut-offs, from 5 or 10% to over 50% - necessary since those engines were often used in direct reversing marine service, and reliable reversing is essential. This of course meant three (or more) cylinders as well. These engines were large and ran at relatively slow speeds since they directly drove props; that plus roller tappets and robust construction kept the rather brutal cam profiles from causing mechanical issues in the valve gear.

-= Bart
I'll be the first to admit I'm pretty ignorant when it comes to the Skinner's valve gear, but that sounds very similar to a Caprotti valve gear, which uses two cams to actuate a poppet valve and controls the timing by phasing the relative angle between the two cams. Apparently in locomotive service it could deliver cutoffs from 3% to over 90%, and could control the timing of exhaust valve events as well.
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Re: Steam Actuated Inlet Valves?

Post by barts » Sun Jul 15, 2018 1:10 am

skinner.png
skinner.png (10.66 KiB) Viewed 243 times
Caprotti valve gear is more complex. Skinner valve gear is pretty simple to understand the two cams in the center have their motion effectively averaged by the followers, so one cam controls admission and the other cut-off. The max cut-off possible is when both cams are aligned.

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