Reciprocating engine cylinder question

Z

Zjef Van de Poel

Member
Hello,

I am modeling one of the reciprocating engines of Titanic in Autodesk Inventor, a school project for mechanics.

So far I have made the base and supporting frame, and the crankshaft.
Now I have come to the cylinders, but I'm facing a problem.
The IP and LP cylinders seem to have 2 slide valves, as you can see here: Titanic Tech Questions

How does this work? All the examples I have seen only have 1 valve per cylinder.
I suppose there is only one rod for these 2 valves?
How does that work? The drawings show them as two separate cylinders, but since there is only one way where the steam enters, I suppose they are connected somehow.

Another thing: in the schematics I have seem from other engines, the slide valves are right next to the cylinder. In the engine of Titanic however, there seems to be quite some space in between. What was there?
Take the IP cylinder in the link for example; you can see a heart shaped figure, with 3 circles. But what is in between them? Empty space, or steam?

Thanks

Zjef
 
The HP has a single piston valve as is usual.
The IP has a pair of piston valves connected to a single valve linkage and with their steam passages piped in parallel. This gives enough total valve flow area while minimizing spacing between the cylinders.
The LPs have a single slide valve but it is so wide it has two valve rods from the driving linkage.
In all 3 places a bar would bridge between the 2 valve rods with the driving rod in the middle. The center of this bar would slide in a small guide.

Broadly the valves and pistons in Bill Sauder’s drawing are coloured and what’s left represents the cylinder castings containing them and the steam passages. The steam only enters the cylinders at the very top or bottom while the valves supply the steam at roughly the 1/4 and 3/4 vertical marks (supply and exhaust get the middle and end positions) so significant longitudinal space is needed for passages to carry the steam from the valve to the ends of the cylinder.

Your good curiosity over the details is exactly what a course in mechanics should be encouraging.

Bill
 
>>You may find Titanic's Prime Mover to be of some use.<<

I found this article during my 'research', and it was very helpful indeed.

Now, I'm still struggling to picture it correctly (in particular the LPs).
Therefore I have made a very 'raw' sketch in paint how I have it my mind right now.

You said the LPs have one valve, but two rods. Do you mean two rods inside the casing and one driving rod, or two driving rods connected to only one 'Stephenson linkage bar'?
 
Michael, it was the Marconigraph link I was pointing to.
Sam you’re right, it is 2 valve plates in the one chest.
Zjef, the latter. I picture one rod up from the Stephenson link connecting to a cross bar outside of the valve casing. The cross bar connects to 2 valve rods that pass into the casing where each connects to its own valve plate in the common chest.

Bill
 
Thanks for all the help.
The model is almost finished now (I have got one and a half more week to hand it over).
Due to time limits it's not the most accurate model (I improvised a bit for some parts).

For those who are interested, I have posted 2 small videos on my site:
http://student.vub.ac.be/~zvdepoel/Inventor.html

All comments are welcome! (As long as they are not too difficult to implement
happy.gif
)

Zjef.
 

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