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Author Power of Beam Engines
spitfire

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Power of Beam Engines
Posted: 19/02/2009 22:44:51
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Are we now agreed that the HP can be worked out without involving the condenser?

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spitfire
IP: 81.141.104.176
Morlock

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Power of Beam Engines
Posted: 19/02/2009 23:56:19
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spitfire wrote:

Are we now agreed that the HP can be worked out without involving the condenser?


Certainly not, in the case of the Crofton engine the 6 PSI MEP provides less power than the vacuum.
Work it out, the steam povides a 6 PSI push on the piston.
The vacuum provides another 12 PSI pressure difference accross the piston.
As explained earlier the vacuum can never be greater than -14.7 PSI, this means the power contribution decreases as a % of total power as the steam pressure increases.

Think of a modern steam turbine at say 1500 PSI, any amount of the atmospheric back pressure that can be removed at the outlet in effect increases the pressure drop across the turbine, this is what determines the turbine or engine power.
A vacuum at the outlet will be the same as increasing the steam pressure to 1514.7 PSI.

Edit: I think we can agree that a condenser is an effeciency device as it improves the fuel economy on all engines, problem is it supplies a major porton of the power on older engines. Smile



IP: 86.10.19.236 Edited: 20/02/2009 00:44:58 by Morlock
royfellows

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Location: Great Wyrley near Walsall

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Power of Beam Engines
Posted: 20/02/2009 11:34:19
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Gentlemen, as this discussion appears to be turning back towards the purpose of the condenser etc, I hope that you will both forgive me for this posting. The reason for this is that I feel that in my previous postings I failed to make clear my perception of this.

As Mr Spitfire stated in a previous posting, “the steam has to be shut of at some point”, this is of course obvious.
In the event that this was delayed to the point where the piston was almost at the end of the power stroke, then there would logically be a residual pressure above the piston, and there is no way that the engine could go solid, that is become self acting. Shutting off the steam too early would waste a proportion of the stroke of the engine, by this I mean that there would be a proportion of the stroke that was not producing any power. That is assuming that the piston did actually reach the bottom of its stroke, I rather think not.

By shutting off the steam early, and allowing the space below the piston to fill with the ‘dead’ steam, the air is displaced. Then opening this space to the condenser causes the steam to condense creating a vacuum below the piston. So in effect, at this point the engine becomes ‘atmospheric’.
When the piston finally reached the bottom of the stroke, all things will equal zero.
There is no remaining space below the piston, therefore there is no vacuum.
There is no pressure remaining above the piston.
My understanding of the starting of an engine is that the engine does not go solid until a good vacuum is obtained below the piston.

Also, there is the matter of the weight of pump rods, you gentlemen will be aware of this; it is for benefit of others.
The excess weight of the pump rods is counterbalanced by the balance bobs, usually one at surface and others at regular intervals for the depth of the shaft. We all know that apart from the single bucket lift, the ‘puppy’ pumping from the shaft sump, all other pumping was done by plunger pumps whereby the pumping was done by the weight of the pump rods.
The weight of each balance would be finely governed so that the weight of that section of pump rod would only just exceed that of the water being displaced by the pole pump. Otherwise the engine would be doing unnecessary work and wasting coal, and of course there is the matter of the shock on the engine and other shaft fittings.

My point here is that the whole system is very finely balanced and finely tuned. The guys who built these things knew what they were doing. The first beam engine, albeit an atmospheric one, was installed in 1712 at one of the Earl of Dudley’s coal mines, a few miles from where I live. There is a working replica of it in the Black Country Museum. From the early atmospheric engines with boilers that leaked like sieves, up through the high pressure steam engines of the late 19th century, these things were produced for nearly 200 years. Enough time to get the job right.

I have read and reread this posting before uploading it, and feel that I cannot say any more, this may be a relief to you!
Thank you both for your tolerance.


--

'There's a lot of activity for a disused mine!' - Bond in 'A view to a kill'
IP: 78.150.35.187 Edited: 20/02/2009 11:36:22 by royfellows
Morlock

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Posted: 20/02/2009 14:59:48
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Thanks Roy.
As you may gather I have a firm belief that the vacuum provides a considerable portion of the power in low pressure engines (40 PSI and lower).
This belief is based on the simple calculation of pressures and area's.
Anyway the bottom line is that a lot of these engines cannot perform a full indoor stoke on steam alone, normally, the first stroke or two will be short strokes to manually transfer steam below the piston. I confirmed this today with the engineer at Crofton Pumping Station.
You may be interested in the start up procedure in the link.

http://www.croftonbeamengines.org/hwhowtworks.html
IP: 86.0.105.7 Edited: 20/02/2009 15:01:08 by Morlock
royfellows

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Power of Beam Engines
Posted: 20/02/2009 15:03:48
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Morlock wrote:

Thanks Roy.
As you may gather I have a firm belief that the vacuum provides a considerable portion of the power in low pressure engines (40 PSI and lower).
This belief is based on the simple calculation of pressures and area's.
Anyway the bottom line is that a lot of these engines cannot perform a full indoor stoke on steam alone, normally, the first stroke or two will be short strokes to manually transfer steam below the piston. I confirmed this today with the engineer at Crofton Pumping Station.
You may be interested in the start up procedure in the link.

http://www.croftonbeamengines.org/hwhowtworks.html


Complete agreement.
Sooner a vacuum is obtained below the the piston, sooner the engine go 'solid'.

--

'There's a lot of activity for a disused mine!' - Bond in 'A view to a kill'
IP: 78.150.35.187 Edited: 20/02/2009 15:05:32 by royfellows
spitfire

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Posted: 20/02/2009 15:08:03
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When I first replied to this thread I came up with two equations that could be worked out while eating the cornflakes.
One for a Watt engine the other for an engine working on the Cornish cycle. both of you have disputed this from the outset which is your perfect right to do so; I have no problem with that. What you have both failed to do is to come up with an alternative.
The Robinson engine has a well documented and recorded HP of 335 which I arrived at with an error of less than 21/2%
The gauntlet is down
Come up with an equation that arrives at that figure; use what method you like but it must be based on the Robinson engine as that has a known HP. let's see if you can get it as close as I did without filling up a A4 sheet. Best of luck

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spitfire
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Peter Burgess

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Power of Beam Engines
Posted: 20/02/2009 15:16:54
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If mining engineers of the 20th century ended up disputing simple mechanical principles like you lot, it's no wonder they all went over to electric pumps. Laugh Wink

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Hey, who turned out the lights!
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Morlock

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Power of Beam Engines
Posted: 20/02/2009 15:26:25
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Peter Burgess wrote:

If mining engineers of the 20th century ended up disputing simple mechanical principles like you lot, it's no wonder they all went over to electric pumps. Laugh Wink


Elektrickery, now there's a subject. Big Grin
IP: 86.26.98.29
Morlock

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Power of Beam Engines
Posted: 20/02/2009 15:36:38
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Spitfire, I never disputed your formula, I merely stated that the vacuum played a part in the power output dependant on the ratio of inlet pressure to final condenser pressure.

If you re-calculate and increase the steam pressure by the amount of vacuum available will you find the extra 2-1/2%?
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stuey

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Power of Beam Engines
Posted: 20/02/2009 15:36:47
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Interesting point there, Roy.

I'm sure somewhere I read about shutting the steam off early causing bigger loadings of the pitwork and breakages. If I recall rightly, there was an expensive moment at United Mines (Gwennap) where they broke something really expensive and it became a policy to run it for a minimum duration.

I'm not aware of the finer points of operation, but I gather it was possible to increase efficiency with the negative being harsh loadings.

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spitfire

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Posted: 20/02/2009 17:20:07
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I did post an apology, for one brief moment I thought you were right. I have re-calculated and that takes the figures way over the top. Try it yourself.

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spitfire
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Morlock

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Posted: 20/02/2009 17:38:38
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spitfire wrote:

I did post an apology, for one brief moment I thought you were right. I have re-calculated and that takes the figures way over the top. Try it yourself.


Yes, takes it up 8%+ @ 26 inches HG.

The problem is that these engines are rated as pre-war cars were, i.e. on a system other than measured output power (BHP), as a result the figure is the power of the engines steam consumption. If this is the system in use I have no problem but I would expect a variation either side of that calculated figure. That make sense?

Edit: To save confusion I would expect a variation between calculated and actual HP.

IP: 82.13.35.90 Edited: 20/02/2009 18:03:15 by Morlock
royfellows

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Posted: 20/02/2009 17:58:44
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In my first post:
"Without referencing any written work I would tend to suggest that actual horsepower is an arbitrary value."

Further
I don’t think anyone owes anyone an apology, we have all been scrupulously polite with each other, and the whole object is to take our mutual knowledge forward. I for one admit readily to learning something from these discussions.

As far as any attempt to calculate actual horsepower, I will politely bow out now.


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'There's a lot of activity for a disused mine!' - Bond in 'A view to a kill'
IP: 78.150.35.187
Morlock

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Posted: 20/02/2009 18:10:13
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An in depth discussion between gentlemen, facts and figures produced by all sides, magic. Smile IP: 82.13.35.90
Tezarchaeon

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Power of Beam Engines
Posted: 20/02/2009 18:31:23
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Talking of beam engines... Is it true that the last drivers of Taylors engine at EP etched their names into the glass in one window? IP: 90.240.11.214
spitfire

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Power of Beam Engines
Posted: 20/02/2009 18:41:46
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Regarding Taylors engine ,yes I believe that to be right. I have the privilege of being old enough to be taken into the engine house with my uncle and father when the engine was working and the same applies to Robinsons

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spitfire
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carnkie

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Power of Beam Engines
Posted: 20/02/2009 18:56:27
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Tezarchaeon wrote:

Talking of beam engines... Is it true that the last drivers of Taylors engine at EP etched their names into the glass in one window?


As Spitfire said this is indeed true. I tried to photograph it but it's bit tricky. Even a professional who happened to be there had little success.

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The past is a foreign country: they do things differently there.
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Tezarchaeon

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Posted: 20/02/2009 23:57:48
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My Grandmother's Aunt used to own the Railway Inn in Pool and my Grandmother recalls being able to hear a consistant pump sound from down underground when her head was on the pillow at night. The miners would always be comming into the pub after shifts and she was always telling me about hearing the Italian workers singing as they made their way down to the mine for the night shifts.

One former East Pool miner, Bobby, can be seen in Chasewater cleaning the streets quite regularly, used to coach me when I was on the football team in School.
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spitfire

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Posted: 21/02/2009 12:31:17
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That was very interesting about your grandmothers memory regarding the pumps at East Pool. This sounds a bit of a tall one but it's perfectly true, those clacks could be heard at night as far away as Redruth and that has to be two miles even as the crow flies

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spitfire
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Tezarchaeon

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Posted: 21/02/2009 19:37:47
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I suppose that back then there was less noise from cars around so it would seem possible that you could hear an engine so large as Taylor's at work.

Just imagine what it was like when Dolocath, Carn Brea, Basset, Crofty and East Pool/Agar where all at work! Stamps, pumps, hammering, blasting... would have been amazing to see/hear/smell the place at the time of it's peak.
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