Hercules Steam Crane Tubal Cain

I am making the steam crane but going by the book of Tubal Cain, I am not using any castings just brass and what's about in the shed.

I cant understand the drawing in the book on the cylinder steam ports that connect to the standards.

The standards have four holes, drilled No 46 but cant understand how this fits to the cylinders,the drawings are sectioned drawn as two holes.

I'm obviously missing something here, any help please, I've made about 1/3 of it so far and hope to finish it.

Bob

Can you post a photo or scan of the page as I doubt many have the book but may be able to work out what the drawing shows

Just had a look at what it is like. The 4 holes in the standards are the usual two exhaust and two inlet holes you find on a double acting oscillating engine and there should also be a central pivot too. so the standard will look something like this

The cylinder will have a central pivot and two holes on the same diameter as the 4 in the standards and look like this

as the cylinder moves from one side to the other each end will alternately connect to inlet then exhaust. Like this

Edited By JasonB on 16/01/2020 18:34:00

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There’s a brief explanation of how this type of engine works on page 14 of my copy of Tubal Cain’s book (Building Simple Model Steam Engines, 1997 reprint)(Chapter 2, Polly steam plant, introductory paragraphs).

Edited By Maximiser on 16/01/2020 20:05:54

Thanks Jason and Bill

Its so obvious looking at the photos and the word oscillating, I had it fixed in my head that the cylinders didn't move.

Looking forward to get it sorted tomorrow.

Bob

Thanks,Maximinster.

Bob

I am making the cylinders out of brass and about to put the steam ports in, I was thinking of putting two condensation taps on the two cylinders.

I have made a boiler and have tried it out on one of my stationary engines but had more hot water coming out of the exhaust as the cylinders were cold so I gave up on that. The boiler works well with a good amount of steam which incorporates a superheater.

I will make a boiler as shown on the steam crane drawings but have others that have made the crane had the problem of wet steam, and would two taps make much difference.

Bob

As nobody else has replied I would say add the drain cocks as it is easy to do at this stage as they can only help with getting rid of any condensate in the cold cylinders when you first start the engine. Or if you don't want to spend out on a pair of cocks you could drill and tap for them and just make up a couple of plugs then see how things go, if you get a condensate problem then just swap the plugs for drains.

I would think that drain cocks would not be necessary on an oscillating engine. Surely the cylinder will lift off the standard allowing any condensate to escape? John

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I made one of these more years ago than I care to remember. I can't recall if the original boiler drawing specified it, but I piped my steam outlet down to the burner area and formed a loop of pipe to pass through the flame, gave me a bit of superheat. I also directed the exhaust into a glass screw-top jar fastened underneath the main platform,with an outlet through the screw-top - that kept most of the condensate in the jar, which i could unscrew and empty at the end of a run.

I was surprised at just how heavy a weight the crane could lift, given that the boiler red-lined at 30 psi, very impressive.

Well if a single acting with open end to the cylinder then only one would be needed but you can get single acting ones where there is a cylinder cover that acts to guide the piston rod so any steam getting past the the piston that condenses will find it hard to get out as the passage is on the other side of the piston.

Regarding lifting off the port face again depends on the engine as not all have a simple spring, you can get ones that have a pivot on the opposite side to the ports with a screw adjuster that won't allow for any lift.

Drains can also be opened and steam allowed to flow through the cylinder which will warm it which will help reduce condensate on start up.

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Thanks for the replies, as stated the cylinders do look rather small and would look out of keeping for drains but worth some holes that can be plugged .

A slow progress picture that Bill asked for.

The large gear was slightly out of centre so I had to offset the bearings by .2 mm for it not to bind with the other gear, plus not as the drawing owing to what I could find in the shed.

Bob

Regards cylinder lifting off port face, I completely agree with you Jason about some oscillators not being able to lift off but after looking at the design for this engine/crane it can lift. It uses a spring to keep cylinder on portface. Whether you wish to add drain cocks or not is down to personal choice but Tubal Cain didn't appear to think them necessary. John

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I tried that but it put the burner out

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