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Antique Steam Engine from Doorknob

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roy entwistle22/05/2019 09:15:52
1046 forum posts

If it's brass, and it looks like it, do NOT use WD40, WD40 is not a penetrating oil. Use something like Plus Gas


SillyOldDuffer22/05/2019 09:16:55
4774 forum posts
1011 photos
Posted by Hopper on 22/05/2019 08:22:46:
Posted by SillyOldDuffer on 20/05/2019 11:54:39:

Now there's no evidence of a coaxial crank I've gone off the idea in favour of this suggestion:


I'm not convinced on this exact set-up, but rather something similar but different, for several reasons. One being that the stroke of the cross-head is significantly longer than allowed by the small crank in red. In fact it would be the same dimension as the main crank, which obviously would clang into the main crankshaft. The other being that there is no facility for the "needle" to pivot at the top, as would be required in a crank and rod type situation. The notch in the brass flange where the needle would run tends also to indicate it does not move from side to side.

I'm thinking there must have been something that allowed the "needle" to move straight up and down. So something more like a pushrod pushing a lever, in effect a rocker arm, without the two being firmly joined. Or perhaps a short crank arm as shown in red but the pushrod passing though a loose hole in the end of it, with two collars on the pushrod that allow it to move the crank arm a short distance at the end of each stroke, but slide through without moving the crank until the other end of the stroke. You thus have a lost-motion linkage in effect. So it provides a sort of "switching" motion at TDC and BDC rather than a continous cranking motion. This would be consistent with switching the valves from open to closed and vice versa at the end of each stroke, as required for a single-acting cylinder.

Just a thought.

I like it!

It's true the crank suggestion isn't convincing. A reason I suggested ornamental was because I can't imagine how a crank would communicate sensibly with whatever valve is inside. (Might be because I don't know enough about valve gear and there is a simple solution!) And ornamental doesn't fit well with the maker going to the trouble of drilling that large hole - surely it has purpose.

Hopper's suggestion of a mostly up down movement using collars to flip the valve is much better than any of my over-complicated musings. Something like the valve trip arrangement on James Watt's early engines perhaps. I'd love to know what's inside!


Michael Gilligan22/05/2019 09:35:33
14121 forum posts
614 photos
Posted by roy entwistle on 22/05/2019 09:15:52:

... Use something like Plus Gas


+1 for that

Plus Gas Formula A, in a good old-fashioned can, is effective and economical.


Hopper22/05/2019 11:18:07
3735 forum posts
76 photos

Posted by SillyOldDuffer on 22/05/2019 09:16:55:...

...Something like the valve trip arrangement on James Watt's early engines perhaps. I'd love to know what's inside!


I'm thinking some kind of simple (yet cunning) rotary valve. Something like a piece of round bar inside a hole drilled in a solid block. The block has two small ports drilled right through it, each port connects to the cylinder above. Below, one port to the steam inlet pipe, the other to the exhaust. Two small holes drilled crossways through the round bar, at 90 degrees to each other, would allow through-flow through one port at a time. The round bar is rotated through 90 degrees by the "needle" and crank arm at the end of each stroke.

Or offset the ports slightly and file flats on the round bar to give finely tuneable valve timing and perhaps less than 90 degrees of rotation needed to make it work. My mental CAD abilities end about there. I need the back of a fag packet and a burnt match to take the concept any further.

Hopper22/05/2019 12:08:10
3735 forum posts
76 photos

Rotary valve shown here could be something like what's inside there *LINK*

Michael Hudson 622/05/2019 13:08:03
22 forum posts

A small update from me - have ordered some plus gas, have kept away from the wd40.. Very intrigued regarding the possible valve arrangement. I think I will try and talk to our vet and see if they will oblige with an X-Ray or two

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