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Mine Exploration Forum

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Author Power of Beam Engines
mappakernwick

Joined: 22/10/2007
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Power of Beam Engines
Posted: 16/02/2009 00:14:29
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Anyone know how powerfull in Horse power single acting Cornish engines were. In particular 80" late 19 cent early 20th Cent?

I have lots of detail on duty but not power.
IP: 81.135.113.109
Morlock

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Power of Beam Engines
Posted: 16/02/2009 00:45:41
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mappakernwick wrote:

Anyone know how powerfull in Horse power single acting Cornish engines were. In particular 80" late 19 cent early 20th Cent?

I have lots of detail on duty but not power.


If you know the lift in feet and gallons min/hour you can work out the lift horse power bit, 1 HP+ 33,000 ft/lbs per minute.
Not sure what the friction losses would be for the engine.

Have a read of this.
http://www.kerrier.gov.uk/media/docs/l/9/CORNISH_BEAM_ENGINE_Feasibility_Study.doc
IP: 82.3.234.52 Edited: 16/02/2009 00:57:40 by Morlock
royfellows

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Location: Great Wyrley near Walsall

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Power of Beam Engines
Posted: 16/02/2009 14:48:50
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Without referencing any written work I would tend to suggest that actual horsepower is an arbitrary value.
Generally, an engine that was being overworked would only manage a decreasing number of strokes per minute as the mine gradually deepened, hence the gallons of water lifted per minute would be a decreasing amount. Therefore, to keep the mine in fork would require a larger engine, as we would call today, an "upgrade".
I have copies of “Taylor on Pumping”, “Mitchell and Letcher and of course, everyone’s standard reference, “Bradford Barton”. Without looking, I am on my way out right now; there will be tables that relate engines to requirement. However, remember that the beam engine went through different stages of development from the early atmospheric engines to the later 40 psi sophisticated designs of the 19th century.


--

'There's a lot of activity for a disused mine!' - Bond in 'A view to a kill'
IP: 78.150.35.187 Edited: 16/02/2009 14:49:37 by royfellows
spitfire

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Power of Beam Engines
Posted: 16/02/2009 17:33:53
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The power of a watt engine may be determined as:
P x L x A x N divided by 33,000 .
P= pressure L= length of stroke A= area of piston N= number of strokes.
For a Cornish engine it is a little different as expansion has to be taken into account and is as follows :
MEP x L x A x N divided by 33,000
MEP= Mean expansive pressure

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Morlock

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Power of Beam Engines
Posted: 16/02/2009 17:59:55
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spitfire wrote:

The power of a watt engine may be determined as:
P x L x A x N divided by 33,000 .
P= pressure L= length of stroke A= area of piston N= number of strokes.
For a Cornish engine it is a little different as expansion has to be taken into account and is as follows :
MEP x L x A x N divided by 33,000
MEP= Mean expansive pressure


I'm sure the condenser vacuum should be added to "P". Big Grin
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Peter Burgess

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Location: Merstham. Or is it Godstone ...... ?

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Power of Beam Engines
Posted: 16/02/2009 18:28:15
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Doesn't that depend on whether P is absolute or gauge pressure?

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Hey, who turned out the lights!
IP: 92.2.125.24
spitfire

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Power of Beam Engines
Posted: 16/02/2009 19:00:11
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The vacuum can be discounted as when the equilibrium valve opens this cushions the stroke with steam

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Morlock

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Power of Beam Engines
Posted: 16/02/2009 19:40:02
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Peter Burgess wrote:

Doesn't that depend on whether P is absolute or gauge pressure?


Yes, as long as absolute units are applied across the piston during the power stroke.
The vacuum would still need to be considered as it is never absolute, 26 inches HG being about average (I think).
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Morlock

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Power of Beam Engines
Posted: 16/02/2009 19:46:40
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spitfire wrote:

The vacuum can be discounted as when the equilibrium valve opens this cushions the stroke with steam


I believe that if you discount the vacuum there will be a 20-30% loss of power?
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spitfire

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Power of Beam Engines
Posted: 16/02/2009 20:25:48
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The steam on an engine in good condition is cut off at one fifth stroke allowing expansion to do the rest of the work. When the steam valve closes the equilibrium valve opens and dumps the steam beneath the piston, this will not result in a loss of power certainly nothing as drastic as 30%.
There will be a slight loss of power compared to the Watt engine but this is more than compensated for in economy of working

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royfellows

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Power of Beam Engines
Posted: 16/02/2009 21:22:49
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After "the dumping of the steam below the piston" the exhaust valve would open which connected the space below the piston to the condensor. The steam below the piston would therfore condense forming a vacuum below the piston. Apart from initialising the power stroke, this would add to the power of the engine not detract. Once a vacuum was obtained below the piston, the engine would go 'solid' and become self acting.

--

'There's a lot of activity for a disused mine!' - Bond in 'A view to a kill'
IP: 78.150.35.187 Edited: 16/02/2009 21:26:58 by royfellows
Morlock

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Power of Beam Engines
Posted: 16/02/2009 21:24:52
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Are we talking about the same type of engine, i.e. the type where the vacuum is an integral component of the power stroke?
http://i158.photobucket.com/albums/t101/Mondeo2006/Odds/ValveEvents1.jpg

Edit: royfellows, my thoughts exactly
IP: 82.3.70.109 Edited: 16/02/2009 21:45:22 by Morlock
royfellows

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Power of Beam Engines
Posted: 16/02/2009 21:28:46
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Sorry Mr Morlock, cannot view your image.

EDIT
I see your edit, do I take it that we are in agreement?

--

'There's a lot of activity for a disused mine!' - Bond in 'A view to a kill'
IP: 78.150.35.187 Edited: 16/02/2009 21:30:16 by royfellows
Morlock

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Power of Beam Engines
Posted: 16/02/2009 21:32:42
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royfellows wrote:

Sorry Mr Morlock, cannot view your image.

EDIT
I see your edit, do I take it that we are in agreement?


We are. Thumbs Up

How do I get the image to work?
IP: 81.105.51.219 Edited: 16/02/2009 21:33:24 by Morlock
royfellows

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Power of Beam Engines
Posted: 16/02/2009 21:37:16
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Morlock wrote:



How do I get the image to work?


I have pasted your URL into the address bar of my browser and got a photobucket error message

"Image moved or deleted"

Is your URL correct?


--

'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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Power of Beam Engines
Posted: 16/02/2009 21:47:48
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royfellows wrote:

Morlock wrote:



How do I get the image to work?


I have pasted your URL into the address bar of my browser and got a photobucket error message

"Image moved or deleted"

Is your URL correct?


It's the right link, it works now I've removed the image tags, just paste the link.
IP: 82.3.70.109
royfellows

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Posted: 16/02/2009 21:55:33
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Just tried it, still NG
OK why not upload the image to aditnow?

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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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Power of Beam Engines
Posted: 16/02/2009 22:06:26
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Ah, joy. Much larger in the album. Smile

IP: 82.20.17.163 Edited: 16/02/2009 22:08:11 by Morlock
royfellows

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Power of Beam Engines
Posted: 16/02/2009 22:20:15
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This looks really good.
In effect, Boulton and Watt manages to produce an engine where the 'spent' steam was put to very good use, both automating the sequence of events relative to the operation of the engine, and also, to a degree utilising some of the power of the earlier atmospheric engines.
Actually, as I have written in my yet to be published book!

What I did not know about was the "hardwood friction slides" that were provided to fine tune the operation of the valves.
This raises questions about the reputation of some engines as "bad engines" whereby they would require about 20 minutes or more of manual operation before they would go 'solid' and continue to operate automatically. Some engines gained this reputation when new, others due to natural wear and tear.

So was it lack of operator knowledge after all?

Finally, Mr Morlock, can you please give the details of the publication from which you kindly display the image?

--

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

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Power of Beam Engines
Posted: 16/02/2009 22:37:24
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Several times have I watched with fascination the starting of the engines at Kew Bridge. It doesn't normally take very long before they can be left alone to run very nicely.


--

Hey, who turned out the lights!
IP: 92.2.125.24
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