Resources/Information for Crank Lubrication?

A special section just for steam engines and boilers, as without these you may as well fit a sail.
Lionel Connell
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Re: Resources/Information for Crank Lubrication?

Post by Lionel Connell » Mon Mar 26, 2018 7:33 am

... They were happy to overcome it by other methods; it can also be achieved by machining the piston with more surface area on the bottom to match the small amount of area taken up by the piston rod (in cross section), though I've not come across many asymmetrical pistons on locos or traction engines.
I am sorry but that while changing the profile of the piston faces can add surface area to them, it does not change the force that is applied to the piston in line with the piston rod and bore as the added surface area is not perpendicular to the bore. Piston valves were sometimes made with the rod end head and bore larger in dia. to achieve this effect though.

Cheers

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Re: Resources/Information for Crank Lubrication?

Post by Lionel Connell » Mon Mar 26, 2018 8:35 am

As for Mr Connell, most engineers would tell him that vast amounts of steam entering a cylinder is "lost" to work by being condensed into water, the reasons are many.
How is the steam being "lost" to "work" by being condensed into water?

:Lionel
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Re: Resources/Information for Crank Lubrication?

Post by Lopez Mike » Mon Mar 26, 2018 11:09 am

Here, here.
Galileo - Great mind.
Newton - Genius mind.
Einstein - Extraordinary mind
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Re: Resources/Information for Crank Lubrication?

Post by DetroiTug » Mon Mar 26, 2018 1:23 pm

Quote: "How is the steam being "lost" to "work" by being condensed into water?"

Thermal loss. And it's an area of major concern.

All of this wrangling over valve events will soon fade into obscurity when you start running your steamplant.

Remember this as it is very important and it is the key to efficient plant operation:

Temperature and pressure go hand in hand. Think of temperature and pressure as two meshed gears with equal teeth, if the RPM of one is known, the RPM of the other is known. If temperature is being lost, pressure is being lost and vice versa.

Ideally there would be no pressure lost all the way to the exhaust event, but it's the real world and unless one employs some sort of cylinder heating nothing close to that is going to happen. Unfortunately, most of our engines use the same passage for steam admission as they do exhaust, The passages are continually being heated and cooled and somewhere in between is a mean temperature resulting in a Mean Effective Pressure or MEP. As the steam expands in the cylinder the pressure drops, as does the temperature. This is why the Unalfow and L-head poppet valve designs are more efficient designs, steam admission is through one port and exhaust is through another, this helps maintain a higher MEP equaling more work for the same amount of steam consumed and maintained.

It all starts at the fire. and ends at the engine exhaust stroke. Running a small plant is all about generating an ample amount of steam and minimizing the loss all the way to the exhaust stroke.

On our little steam carriages we have a leather apron or curtain that hangs down in front of the engine and boiler. Driving down the street, if the apron is pulled up, the car slows down a bit, drop the apron and it speeds back up ;)

-Ron

P.S. Why did the Navy say one thing in their manual, and wind up with engines that contradicted it? Who knows, probably a case of purchaser and manufacturer unaware of what was in the manual. What they wrote in their manual made perfect sense.
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Re: Resources/Information for Crank Lubrication?

Post by Oilking » Mon Mar 26, 2018 5:51 pm

Please forgive the multiple attachments, but I had to do multiple scans to keep the files small enough to post. The following post will contain the diagram referenced.
FYI: this comes from is Part IV of a 1946 Pub that was primarily intended for instruction at the Naval Academy it is not a manual as such and contains a range of what was considered common practices of the day and may not just Navy.

Dave
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Re: Resources/Information for Crank Lubrication?

Post by Oilking » Mon Mar 26, 2018 5:52 pm

Diagram.
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Re: Resources/Information for Crank Lubrication?

Post by gondolier88 » Mon Mar 26, 2018 7:16 pm

steamboatjack wrote:Mr gondoliers comments about the use of tail rods, to use the correct term, is strange. These items were/are fitted to guide the piston or guide rod rather than equalise the net force on the piston etc. There are many reasons why the up and down forces on the piston can never be totally even, many due to the angularity of the various rods...
Jack,

I was suggesting that 'tail rods' would be a simple way to make the surface area the same, not that manufacturers had used them to this end, this is why I called them piston rod guides and not pressure equalising guides, but it's nice to learn the term 'tail rods', thanks!
Oilking wrote:Diagram.
This is another reason to look into the use of radial valve gear- in particular Marshall- the travel of the valve is also unequal, but in a manner that compensates for crank error.

Greg
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Re: Resources/Information for Crank Lubrication?

Post by Lionel Connell » Tue Mar 27, 2018 1:55 am

Ron,

Yes, I miss took Jacks meaning when he said " Lost to Work" after driving home I realized that my use of that term is 180deg from what Jack meant. In Australia if we say for example that a man is lost to drink or lost to love we mean that he has been consumed by that thing. So when Jack wrote that the steam is lost to work it didn't make sense to me. The energy is lost to condensation and not available for work was his meaning, yes I understand that or I would built a twin :D .
P.S. Why did the Navy say one thing in their manual, and wind up with engines that contradicted it? Who knows, probably a case of purchaser and manufacturer unaware of what was in the manual. What they wrote in their manual made perfect sense.
The article being quoted as pointed out later by Greg is a training publication written 130 years after the event so I actually think that the Navy developed the engines to the point of using Stephenson's link in the way that it was designed to be used, as Naval engineers would have understood the concept, and then perhaps the later a training manual was assembled from a scattering of data some of which was already outdated.

A straight link can be used if only full forward and full reverse are to be used, and where the power output and efficiency in reverse is not a consideration, no doubt at all.

As you have stated there are many losses which cannot be addressed to much improvement, some that can be addressed to some extent, and none that can be eliminated. The valve events are one area where there is a considerable difference between a good setup and a bad setup. It is obvious that you have no desire to take my word for it, but there is plenty out there for interested people to read on the subject. On the Web at least, there is a lot more information by way of engineering analysis and live testing available for railway engines than marine engines. For railway engines there is significant data showing the improvements that were made, as well as why and how those improvements were implemented. From and engineering perspective railway had the advantage that weather conditions played less havoc with analysis and also that many more engines of the same design were built, meaning that some could be altered in search of improvement with direct comparison of engines with various modifications pulling the same load over the same line being available.

In taking with Jack's good wisdom I have said enough on the subject and need to concentrate more on my workshop, I have new 9 axis CNC machining center that I am still getting my head around.
cheers
Lionel,
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Re: Resources/Information for Crank Lubrication?

Post by steamboatjack » Tue Mar 27, 2018 6:15 am

The vast majority of marine steam engines (all sizes) were built with Stephenson gear, I believe this was because it was well known to the designers of the time and well understood by operators and was easy to produce. the various radial type gears were largely the product of locomotive design which of course have different needs. Of all these I think Joy gear would best suit our purposes at least for outside admission valves.
Some people complain of noisy links etc. This is due to poor maintenance not poor design!
Jack
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Re: Resources/Information for Crank Lubrication?

Post by RGSP » Tue Mar 27, 2018 9:21 am

steamboatjack wrote: I would suggest that people get off their computers and into the workshop!
Regards
Jack
Ah yes, that's why I'm reading these postings today rather than yesterday. You CAN turn quite large lumps of steel using a medium-size-and-weight lathe, but it's undoubtedly a slow job and needs patience. Or even Patience, if she's willing to stand and watch a lathe running slowly and with a fine automatic feed while it chews across several inches.
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