The Unofficial Mamod and Other Steam Forum

[STEAMPROPULSION]

Thank you Bugsy, but I am like Saint Thomas.
When Basil Harley will show me the ball and socket joint I will believe in it.
This engine is a metropolitan legend.
Lots of heads, lots of guesses. No sectional drawings. And nobody dares to take apart this engine down to its most minute parts.
And because of this, the number of theories grows.
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GIOVANNI
SKIPE name: ark.gsorrentino

[Bugsy]

Have a look at the third photo from the bottom on Mooseman's site, Giovanni.
It shows the internals of the engine.
I'm convinced!

Phil

[Roly Williams]

Now I'm totally confused!!! Am I right or is Basil Harley right?
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Regards
Roly Williams

"Opportunity is missed by most people, mainly because it is dressed in overalls and looks like work" (Thomas Alva Edison)

[STEAMPROPULSION]

Bugsy.
I misunderstood something: Basil Harley speaks about the ball and socket joint as an alternative design (in this engine) of the gudgeon pin (in the piston) .
Ok, I thought he was referring to the big end of the piston rod.
He (B.H.) further explains that pistons and the piston rods rotate because the gudgeon pin is tilted 45°.

Movement of a few degrees each way as the pistons rise and fall is imparted by pins set in the balls at about 45 degrees engaging in slots in the pistons. On the down stroke the piston is brought into coincidence with the steam inlet by this movement and on the up stroke the exhaust port is uncovered.

Sorry, but with all my good will, I can't imagine a piston gudgeon pin set at 45° unless I see it.


There is another explanation, completely different from that of Basil Harley.
Please look at this:
http://www.btinternet.com/~sylvestris/steam/BM.html

Here you see the engine in is most naked form.

Look at the last picture and you will notice that the right crank-pin in slightly tilted from the crankshaft center line: this is what the author calls "skewed crank-pin".
Thus by twisting the pistons as they rise and fall the steam space in each cylinder is alternately connected to the inlet and exhaust.   This twisting is done by skewed crank-pins and the connecting rods are articulated to cope with the angular movement. Pins and shafts appear to be a press fit and the drilling and assenbling must have taken some rather ingenious jig design to keep the two ends of the shaft in alignment.
What is not explained here is the type of connection there is at the big end with the skewed crank-pin.
As I said I do not own a portable x-ray equipment, but I imagine that the big end should be of a fork type enabling to transform the oscillations of the skewed crank-pin into a rotation of the piston rod.
I am in favour of this interpretation rather tan that of Basil Harley.
Which is what probably Roly has thought.
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GIOVANNI
SKIPE name: ark.gsorrentino

[Roly Williams]

That explanation agrees with my understanding. It seems strange that Basil Harley should come up with such a detailed description if he was guessing. I wonder if there was a change of design at some point???
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Regards
Roly Williams

"Opportunity is missed by most people, mainly because it is dressed in overalls and looks like work" (Thomas Alva Edison)

[Bugsy]

It would be interesting to hear from Odilon.
I'm sure he has worked it out.
It certainly is a mystery.

Phil

[hellequin]

Well I thought I knew now Im just totaly confused its an engine I want to build I can figure out how to do either exhaust or inlet but not both.Is the small end a ball joint and what are the pins or blanks on the cylinder frame.I had thought of cutting a helix on the pistons with guide pins to rotate the piston between the inlet/exhaust ports but still have to cut any metal to prove the idea.
best wishes

[kno3]

[Roly Williams]

[hellequin]

OK, iv read the the articals but how does the piston twist as it moves up and down . Must be very simple but i just cannot see how a twisted crank gives a rotary motion to the pistons.The big end bearing is that a pin sticking out?
My head hurts

[Cowboy]

[xlchainsaw]

strip one down and have a look instead of guessing.i find that a rotating piston... moving in guides a mechanical nightmare and an area of wear that would quickly render the engine useless. i guess thats why not many engines are around today. i do however find the principal interesting.
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mistakes are only made by those who try!

[scorpion2nz]

does the piston rod turn or just the piston
I would favor  just the piston turning and the conrod not
I would also think the conrod connected to the piston via a pin that fits into slots inside the piston skirt that are straight (not curved) and also on an angle  .
you will ask how to get the slots inside the piston skirt ??
easy  they will be cut into pipe that is then slid inside the piston skirt and soldered into place .
but what would I know as I am only a Kiwi  who has not seen one
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Cheers
Dennis

[Roly Williams]

[hellequin]

Thanks Cowboy the penny has dropped
best wishes