Valve Gear Varieties

With Trofimov (choose your spelling) valves (rather than valve gear), the valve heads are free to float on the valve spindle, so when steam is shut off, the valve heads tend to move inwards, enabling a bypass effect. As soon as steam is applied (inside admission), the valve heads are forced outwards into their usual position.

 

S160 No.6046 has Trofimoff valves. Embarrassingly, I can't remember whether S160 No.2253 also has them but I don't think it does. I'm not aware of the need to wind up to mid gear and open the regulator to re-set the valve heads.

 

Might be wise to do so, Steve, as with the shorter valve travel in mid-gear it will lessen the impact of the valve heads re-seating when the regulator is opened.

 

Possibly. That instruction was not given by the owners rep on 6046. The only advice given was to leave the cut off where it was when coasting. Thinking about it, though. If you wind it up to mid gear and re-set the valve heads, unless you leave the regulator open, one of the heads will stay where it is when you put it into full gear and how far it then has to travel will depend on where in the stroke it is. There's a need to sit down with a pen and paper and work it out, but not this morning.

 

Thanks everyone for the help. Time for some further reading. Thanks!

 

Just realised that I've an instruction plate covering this issue ex a DB Class 50 2-10-0. It states:-

Achtung! Druckausgleich-Kolbenschieber. Vor der Dampfgeben ist bei in Fahrt befindlicher Lok die Steuerung auf 0% einzuziehen u. der Regler zo öffnen.

Which I translate as saying that when under way and before giving steam, pull the valve gear up to 0% (mid-gear) and then open the regulator.

I've had a go at scanning this plate to put it on here, but (using a MacBookPro) I'm unable to drag it from Photos to Documents for some reason.

 

Sounds a reasonable translation to me.

 

To go back to the original question, in practice with slide or piston valves there are fewer varieties of valve gear than might be thought. There are three basic families of gear which will do the job -

Link motions - Stephenson/Gooch/Allan,

Radial gears -Joy/Heywood/Greenly, Hackworth, and another different Marshall,

Walschearts/Baker which is considered to be a radial gear, but is arguably a separate type.

All others are related to these, e.g. Bulleid's gears on the Pacifics, Leader, and turf burner, were all forms of Walschearts.

Unless someone on here knows different......

 

I can go along with that method of working. Taking that logic further, though, I would have thought that the instructions would also say that you should coast in mid gear. That also has the advantage of reducing wear, especially die block wear.
All interesting stuff! And is it Trofimoff or Trofinoff?

 

Surely if you try and coast in mid gear, the valve heads will be covering the ports and even allowing for the bypass effect, there will be compression in the cylinders which will stop it coasting properly?

 

Walschaerts and its derivatives are not radial gears as the valve motion is not primarily derived from an elliptical path, the axis of which is tilted to alter direction and cut-off, which is a fundamental of any radial gear.
There are plenty of other valve gears that don't fall into the link, radial or Walschaerts families. Cam operated poppet valves are just one.
Most variations in early valve gear design was to overcome patent issues. A paper published by the ILE gave details of various expansion links patented for use with link valve gears up to 1870.

 

You wouldn't wind it up to mid gear before shutting the regulator but even if you did, there is still movement of the valve due to the combination lever, which provides the lead. The Trofinoff valve heads would go to this position, which is open to admission, and remain there.

 

So the ports would be partially open.

 

I stated in my post that I was considering piston and slide valves.

 

You did. My apologies.

 

To be boring, it depends on how Трофимова has been transliterated from the Cyrillic into the Latin script. (And depending on whether you think he was either a Bulgarian engineer or a Moscow station clerk)

Where it gets complicated is that there is no standard way of transliterating between languages - hence the German transliteration will be different to a British transliteration. And even within a language transliteration will vary for example I was taught to transliterate Бори́с Е́льцин not as the standard Boris Yeltsin but as El'tsin, while in German he is Jeltzin.

I caveat this by saying that I am not a Russian speaker so I am happy to be corrected on these points.

A story which is perhaps of interest only to me, but which shows knowledge transfer. I was reading a Romanian interwar writer (in Romanian) looking for references to a Russian writer. I looked for the Russian writer under the Romanian transliteration of his name - couldn't find him. Eventually, he turned up - not with the Romanian transliteration but with the German transliteration. The Romanian had read the Russian in German.

So to go back to this point - if you read a German to English document it will probably have the German transliteration of Трофимова, if you read someone who has transliterated direct from Russian to English, you will have a different transliteration. (Or from Russian to French to English etc etc etc) because you don't tend to translate transliterated words. (Although I do know someone who translated a Dutch novel into English using the Hungarian translation).

 

It's all double Dutch to me but I get the gist of it. All the books I have refer to Trofinoff but things on the Internet seem to refer to Trofimoff. I think I'll stick with the former as I'm getting too long in the tooth to change.

 

Herewith a diagram of the valve heads in both states (from a Chinese work) which may help explain. Presumably instructions to apply steam in mid gear and increase the cut-off from there are to avoid full pressure suddenly being applied to the valve heads throwing them against the stops. All the Chinese locos fitted with Trofimov valves had power reverse, which makes life easier, but I don't know what instructions were given to drivers.

 

I wonder how many marmosets were craunched?

Tom

 

Would Trofimovs have survived a Tornado?