Talk:Whitbread Engine

Power disputed

The article summarises the engine's specifications as 25-inch piston, 6 foot swing, 20 rpm, mean effective pressure of almost 5kg to the square inch, 35 hp (70 hp after conversion to double-acting). The reference is Boulton & Watt Rotative Steam Engine (1785) asme.org.

The article notes that Powerhouse Museum documents dispute the power. From the reference "Statement of significance" P1306 photograph of drawing:

Unfortunately, the caption below the photograph ['Erected for Messrs Whitbread & Co, 1785, as of thirty-five horse power. Altered in 1795 and increased in power. Removed 1887.'] perpetuates the myth that the engine's output was originally 35 horsepower and that this was doubled to 70 horsepower in 1795. These figures were included in a plaque that was once attached to the engine but which probably never left England. ... From other evidence, both documentary and based on the bore and stroke of the engine, the engine's original output was closer to 10 horsepower and its final output was 15 or 16 horsepower.

The article does not mention that there is a more thorough denial of the power achieved. From "History notes" 18432 Boulton and Watt steam engine:

The engine was originally rated at 10 horsepower. When it was made double-acting in 1795, the owners were offered the choice of having it produce 15 or 20 hp. They chose 15 hp as this meant they paid a lower annual premium to Boulton and Watt. During the term of Watt's patent, the firm charged engine owners an annual premium; this kept the up-front cost of their engines low and eventually made both Boulton and Watt wealthy. The premium was based, in the case of a pumping engine, on the saving in fuel compared to a Newcomen engine doing the same job. For rotative engines, the premium was based on power.

I think the asme.org summary has less plausibility than the object 18432 reference above, but there is no need to rush, so I haven't "corrected" the article. I might get a chance to find some other sources, and will report back. In the absence of new information, I would be inclined to quote the PHM figures, and note the 35/70 hp claim as an interesting historical quirk (i.e. reverse the current article which quotes 35/70 hp, and notes the PHM quirk).

The PHM documents agree with the 25-inch piston, 6 foot swing summary. However, I haven't seen any support for the assertions of 20 rpm or mean effective pressure of 5kg/square inch (a strance mixture of units). Also, it's not clear what rotates at 20 rpm. Any thoughts? Johnuniq (talk) 09:43, 17 March 2009 (UTC)

I'd agree with that. PHM, being in possession of the engine, is probably more reliable here. The support for 20rpm and 5kg/inch² are from asme. But the metric and imperial in 5kg/inch² needs to be separated. —Anonymous Dissident^Talk 05:13, 19 March 2009 (UTC)

Pictures and Media

Some suggestions for pictures and media of the engine, that the Powerhouse Museum might be able to provide. John Dalton (talk) 11:49, 19 March 2009 (UTC)

• The separate condenser
• The parallel motion (or video of it in motion)
• The sun and planet gear (or video of it in motion)
• The centrifugal governor (or video of it in motion, during a speed change)
• The cylinder, showing the valve gear used to achieve double action. John Dalton (talk) 22:37, 19 March 2009 (UTC)
• An overall picture (and video)
• The engine in its engine house at the old museum site John Dalton (talk) 13:14, 19 March 2009 (UTC)
• The engine temporarily installed at Castle Hill
• The engine installed at Whitbread's???????

I just emailed PHM to see what extra info might be available (after checking with Witty Lama that he didn't know of anyone else who had done that). I think image 01 would be good as the lead image, and it might be used to give more detail about engine operation. You are welcome to email me if you want to track the response. Johnuniq (talk) 21:18, 19 March 2009 (UTC)

I would prefer an overall photo as the lead photo. The PHM engine is one of the few in the world installed in such a way that the whole engine is visible at once. Let's use that feature/advantage! A photo is also more engaging than a drawing. I see a place for image 01 in the technical section, which I plan to (one day) expand dramatically based on the sources added below (if no one beats me to it). Thanks for emailing. John Dalton (talk) 22:35, 19 March 2009 (UTC)

Sources

• A useful document to work into the article. John Dalton (talk) 15:01, 19 March 2009 (UTC)
• More useful info from the book "A History of Beer and Brewing" by Ian Spencer Hornsey. John Dalton (talk) 15:38, 19 March 2009 (UTC)

Engraving of the engine house in 1792 ??

The door to the engine house is just above the horse's saddle?

Amazingly, the Garrard engraving would seem to show the engine house seven years after the steam engine was installed. The City of London has put together a conservation document for the Chiswell St. Brewery [1]. Page 7 bottom right contains a site plan, drawn in 1788, three years after the engine was installed and 4 years before the engraving. Comparing the 1788 plan with the later plans on pages 8 and 9, looking at the administrative boundary shown on the plans, and using the knowledge that the engraving is a view from the east of the yard [2] (looking west), and keeping in mind that the 1788 plan is "upside down", with north downwards, it seems that the 1788 plan covers the western half of Whitbread's south yard, precisely the area depicted in the 1792 engraving. The artist was positioned just off to the left of the plan, roughly at the centre point, looking towards the right (west). The corner of the gateway at the bottom left of the plan is just out of view on the right hand edge of the engraving. The bevelled corner of the building midway up the left hand edge of the plan is the bevelled corner of the building right in the middle of the engraving. As additional corroboration, the same artist did an engraving of what appears to the eastern half on the yard in the same year [3]. What looks like the bevelled corner is just visible on the right of the second engraving.

Back to the 1788 plan on page 7. What looks like a horse wheel, with berths for six horses, is visible in the upper left of the plan (the big circle). The circles in the room to the right of the horse wheel could be the four malt grinders (half the room is missing from the plan as it is cut by the administrative boundary). One of the article sources places the steam engine across a corridor from the horse wheel. That would make the engine house the rooms to the left of the horse wheel. The narrow enclosure immediately across from the horse wheel, in line with its centre, could well be the location of the Boulton Watt engine. The round thing nearby is the boiler. It would be fascinating to compare the 1788 plan with whatever plans the Powerhouse has, especially if we can get a decent copy of the 1788 plan.

Put it all together and the conclusion is that the 1792 Garrard engraving looks directly onto the engine house containing the Boulton Watt engine. The engine is probably immediately through the door which is partially obscured by the horse's saddle. The leftmost chimney is that of the boiler supplying the steam engine. John Dalton (talk) 04:23, 20 March 2009 (UTC)