Talk:Stephenson valve gear

message: The animated gif is broken.  Instead of the crankshaft rotating around the its center, and the eccentrics doing their thing, the crankshaft is rotating around the crankpin.  That results in the drawing losing all meaning.  I'd try to fix it, but I don't have the tools to that were used to create the original image.
: I left a note on the creator's talk page. He promised to fix it, but he's a busy chap...  Old Moonraker 11:58, 18 September 2006 (UTC)
thread_title: Animation

message: Hope these are alright. I have been wondering if there should not be a new article on gab motion; the trouble is that references are rather hard to come by. There were lots of operating systems, often combined with expansion valves worked by fiendishly complicated mechanisms, not really worth the study as they were a blind alley.--John of Paris 12:42, 12 June 2007 (UTC)
thread_title: New edits

message: This article covers Gooch and Allan valve gears, as well as Stephenson, so I am thinking of moving it to Link valve gears.  Please discuss.  Biscuittin 21:47, 25 September 2007 (UTC)
replies: text: Sounds like a sensible idea. I've been worried about that too.--John of Paris 15:39, 26 September 2007 (UTC)
replies: text: I think Stephenson gear notable enough to deserve its own article. Other link gears might be grouped together in another. Bill F (talk) 23:01, 30 July 2008 (UTC)
thread_title:  Title 

message: I have removed this:
"the launch link was longer than the traditional ‘’locomotive link’’, the latter being used where space was at a premium especially in the small clearance space underneath early low-pitched boilers in Britain."
and part of this:
" ... but in Europe, although occurring as early as 1846, they did not become widespread until around 1900 as boiler centre lines became pitched higher giving greater clearances underneath."
from the 'Applications' section because it makes no sense to me. If someone could explain convincingly why a locomotive link should require less space than a launch link, I would be obliged. What was the source? Bill F (talk) 23:01, 30 July 2008 (UTC)
replies: text: Has this got mixed up through succesive editions? I can imagine that internal valvegear would be contraindicated by the low C of G boilers in Britain until the advent of locos like the Jenny Lind proved low C of G not as important as people thought. Chevin (talk) 06:54, 31 July 2008 (UTC)
thread_title:  Confusion 

message: Stephenson valve gear is also widely used in non-locomotive applications, such as marine and stationary.  I suggest that :Category:Locomotive valve gear be re-named :Category:Steam engine valve gear. Biscuittin (talk) 11:10, 30 December 2011 (UTC)
replies: text: Having just purchased a book on marine engineering, in which the sole example given of valve gear is Joy's, I agree with the suggestion. Ning-ning (talk) 17:11, 1 January 2012 (UTC)
thread_title:  Categories 

message: The static drawing of the gear in this article shows the gear in neutral (mid-gear).  The crank is back dead center (fully left).  The expansion link is vertical.  If the expansion link were dropped to employ the top eccentric rod exclusively, the valve stem would move very slightly to the right, adding to the lead (not retarding).    
This is due to the fact that the top eccentric rod big end pivot point is closer, in elevation, to the crank center horizontal plane, than its small end pivot point elevation on the expansion link (14 pixels to the crank plane and 18 pixels to the expansion link pivot horizontal plane).  This would be very slightly more lead steam in full gear, than in neutral gear, with the eccentric rods not crossed.
The drawing in this article shows no reduction of lead, with the gear in the full-gear position and the rods uncrossed. This would mean that only one of the two piston strokes in the cycle would benefit from less lead in full gear!.
Why not add a statement that only half the stroke cycle in the Stephenson gear benefits from retarded lead in full gear?  Too complicated?
Douglas Nelson Turner (talk) 01:42, 12 September 2014 (UTC)
thread_title:  Variable lead , an intrinsic advantage '''(only when the crank pin shown is rotated to the right of top)'''

message: Redrose64 is re-adding large unsourced sections and filing edit-warring templates on those who remove them.  Does WP:RS not apply to railfan articles? 82.132.234.87 (talk) 15:25, 12 September 2014 (UTC)
replies: text: Your edit summaries simply said "unsourced". That is not sufficient grounds for removal, because none of them were WP:BLP violations. What are your specific problems with this article? --Redrose64 (talk) 15:30, 12 September 2014 (UTC)
thread_title:  [[WP:BURDEN]] 

message: This locomotive does have Stephenson valve gear - it was the only one of its class so fitted, see Black 5#Ivatt engines and experimental modifications.
There are two eccentrics driving two eccentric rods, attached one each end of the expansion link; this is suspended from the weighshaft and so lifts to vary cutoff; the expansion link is curved with the inside of the curve to the rear.
In the Walschaerts gear, there is one eccentric and so a single eccentric rod attached to the top of the expansion link. The expansion link is mounted on a fixed pivot, and is curved with the inside of the curve to the front, and cutoff is varied by raising or lowering the radius rod; the radius rod is not attached directly to the valve spindle but to the combination lever, a feature lacking from the loco in the photo. --Redrose64 (talk) 19:09, 2 October 2016 (UTC)
thread_title:  Black 5 no. 4767 

message: I'm not an expert in steam engines, but I understood one of the crucial parts of the Stephenson gear to be the sliding link between the two eccentric rods, which moves up or down, therefore altering the valve stroke. However, all of the images in this article (perhaps excepting the photograph on the top, which is just confusing) appear to show a solid bar of metal with pivots on either end connected to a variety of links and pivots. Where is the slot that allows it to slide up and down? To a person who doesn't know anything at all about valve gear, I cant imagine these pictures being anything besides completely confusing. Okay, they let one see how a Stephenson gear actuates a valve, but as soon as we get into talk about variable cutoffs, it becomes meaningless; the crucial piece isn't fully drawn). Or perhaps I'm totally wrong, and there is no slot, and I'm thinking of other valve gears? But no, I remember seeing what I was told was Stephenson valve gear under  steam locomotives, and there was always a slightly curved link with a slot that was the centerpiece. If I am right, the average person is not going to come away from here understanding how this device actually works, unless they are very good at visualizing vague explanations (if I am wrong, it certainly hasn't helped me to see how it actually does work, for sure!).
While I'm at it, all this talk of 'lead' and 'compression' would be bad enough if any of it was actually explained in the article about Cutoff (steam engine), and I would merely complain that (as usual) a person has to click on another article just to understand what is written in this one. however, they aren't explained in either article, and so are basically meaningless to anyone except someone who is already well-versed in steam engine jargon and operation. Seems sadly typical of Wikipedia articles; people are more worried about showing off their technical knowledge than in explaining it in a way that would be useful to someone who is new to the subject.  
  
64.223.165.28 (talk) 01:55, 31 March 2018 (UTC)
replies: text: If you enlarge , the slot is clearly visible. This loco was highly unusual in that the Stephenson link motion was mounted outside both frames and wheels - normally the Stephenson gear was inside, very difficult to examine without the loco being stripped down. --Redrose64 🌹 (talk) 19:39, 31 March 2018 (UTC)
thread_title:  Sliding link