Reversability of a single

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Anne from Little Britan
Anne from Little Britan
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Reversability of a single

Post by csonics » Wed Nov 18, 2009 6:02 pm

Posted on behalf of Froya66:

Froya66
Just Starting Out


Joined: 12 Oct 2008
Posts: 9
Location: Esbjerg, Denmark
Posted: Fri Sep 25, 2009 11:43 am Post subject: Reversability of a single
Dear fellow steamboaters.

My single cylinder engine has a bore of 45 mm and a stroke of 64 mm. In and outlet ports are large 5 mm x 35 mm resulting in a rather large slide valve measuring 45 mm x 40 mm.

At max gear the filling is about 70 %. When puffing, the live steam pressure is between 7 and 9 bar and the speed is 250 – 270 rpm.

At max filling the engine runs very well with little or no cylinder lubrication, but if I cut off earlier it runs clearly with increased friction, and lubrication does not help.

I am practically unable to reverse with open regulator due to friction. Not surprisingly everything point at a bad combination of a large valve and a high pressure, and I intent to install a piston valve instead.

I only wander why the engine seems to run so well with the late cut off.

My own idea is that the valve is loaded with the high differential pressure only for a short time period per revolution, which allows an adequate lubrication film. When the cut off is made earlier this period is enlarged, and the lubrication film brakes down before the valve is partly unloaded and can build up a new film.

Any comments to my description?

To maximise the reversibility of a single, I imagine that a late pre opening (if any at all) and a large flywheel is essential.

Any comments or advises on this?

Best regards
Jørgen Hansen
FRØYA
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87gn@tahoe
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Joined: 23 Feb 2009
Posts: 148
Location: South Lake Tahoe, CA
Posted: Fri Sep 25, 2009 10:53 pm Post subject:
I would think that a balanced slide valve would be much easier to retrofit your engine with(as opposed to a piston valve), and would solve your binding problems just as a piston valve would.
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Wesley Harcourt
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mcandrew1894
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Joined: 11 Oct 2007
Posts: 149

Posted: Sat Sep 26, 2009 8:57 pm Post subject:
Additionally, I would check your timing , specifically your angle of advance, as it sounds off.....I think advanced too far.


Can you give some details of the valve lap, lead and stroke?...
Is the lap and lead equal?


Dave
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Froya66
Just Starting Out


Joined: 12 Oct 2008
Posts: 9
Location: Esbjerg, Denmark
Posted: Sun Sep 27, 2009 10:50 am Post subject:
Hi Wesley

The valve box is sandwiched together with the cylinder which makes it possible to change to a piston valve design without grate trouble (besides the trouble with the construction itself)

Of course you are right, a balanced slide valve is easier to adopt, so I will go for that as the first step.

Best regards
Jørgen Hansen
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Froya66
Just Starting Out


Joined: 12 Oct 2008
Posts: 9
Location: Esbjerg, Denmark
Posted: Sun Sep 27, 2009 11:01 am Post subject:
Hi Dave

Sounds interesting!

As soon as I get the engine taken out of the boat and get the valve dismantled, I shall revert with some info.

The design was made partly in the lathe, so I do not have drawings of all details.

Best regards
Jørgen Hansen
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