FR & WHR & WHHR News

Just watched "Moving Pictures No.31" .... most enjoyable, but a (possibly daft) question .....

Looking at the L&B powered half of 'The Snowdonian", the exhaust on 'Lyn' is virtually invisible, when compared with 'Lyd'. Is this a result of a higher exhaust temperature, or merely a result of improved use of steam ('Lyn's' economic use of water has been commented upon, during it's Snowdonian sojourn)?

 

Is Lyn superheated?

 

Yep ..... isn't Lyd?

 

I believe the FR engines are generally fitted with quite a low degree of superheat. I've just checked, and there are 2 flues per barrel for a double Fairlie (except DLG, which I think has more), while Lyd has 8 flues in its single barrel. If you're retrofitting superheat to slide-valved engines, low degree superheat is generally considered sensible, although I suspect in later LNER years quite high-superheat boilers ended up on Ivatt Atlantics which had not received piston valve conversions.

Lyn, on the other hand, is a piston valve engine and was designed as such from the outset. She has eleven flues, so to a first order approximation will have a considerably higher degree of superheat. This carries through to exhaust temperature. Notched up, this might not make so much difference, but working hard at medium cut-offs and large regulator openings, the exhaust will be a lot less visible. I remember seeing videos of SAR 25NCs working hard in the cold Karoo. The exhaust would be invisible, until it suddenly appeared in a giant plume a few feet above the chimney.

*Edited to reflect actually taking the time to check my numbers.

 

Many thanks for a comprehensive explanation .... I did originally say it was possibly a daft question!

Thinking back, I do seem to recall a shot of Lyd's front tube plate during construction and recognise your description from that. A quick shuftie at Lyn's construction pages confirmed the degree of superheat applied.

From various sources concerning it's visit to the FR/WHR t'would appear Lyn's performance has impressed folk all round. It certainly looked the part in all the clips and stills I've seen .... especially (IMHO) as it wasn't spewing the filth beloved of too many photographic types!

 

Likewise the Brighton Atlantics (H1 - originally saturated and slide valve and H2 - originally superheated and piston valve) which by the end of their lives were all fitted with superheated boilers, with 32 flue tubes (4 rows * 8 flues). I suspect lubricant technology developed considerably between, say, 1910 and 1950; no doubt the two wars and the need for high performance aero engines acted as a spur to innovation in lubricant technology.

Tom

 

Looking at recent photos and videos of 'Lyn', the loading gauge seems very close to that of the FR . Would 'Lyn' actually be capable of traversing the whole FR, or would Garnedd Tunnel be the pinch point?

Frank N.

 

Lyd doesn't have much superheat really. They aren't the same design as the other FR locos with an out and back loop on each element. They consist of a tube within another tube. So there is less surface area per element. They were also shortened over the winter because of cracking.

Tim

 

T'will be interesting to see how knowledge gained during the two (rather spledid) L&B recreations will translate into the design stage for the planned next pair.of MWs.

(Part of me is still half wondering whether future L&B requirements might tempt 'em to build 'County Gate's' 009 2-6-6-2t Mallets for real .... note running number!

Image from www.009.cd2.com and well worth a butcher's!)

 

Quite an entertaining model but I have a nagging doubt that that boiler wouldn’t keep pace with all those the cylinders! (And where is the ashpan supposed to sit? )

Tom

 

Gas fired compound perhaps?

 

Oh, that is interesting, so coaxial superheaters like you find in some models (except those tend to be in stainless and extend into the firebox)? The other downside of those is no matter which way you arrange it, you end up having the hot return flow losing heat to the cool incoming steam. So Lyn is likely to have a really quite significant advantage in steam temperature, which probably explains the notably good water consumption previously commented on.

 

Tom,
Firstly, you're no fun any more...
Secondly, presumably these guys have ash pans? https://upload.wikimedia.org/wikipe...emin_de_fer_du_Vivarais_à_Tournon_en_1978.jpg
Thirdly, you don't need to worry about ash it you follow the prototype and simply fit a really big can motors where the boiler should be ...

 

If it's working a heavy train on a decent run yes. I expect on 1 mile of L&B the loco will be quite wet because the superheaters don't have time to start working. You could have an endless debate on if the extra cost of superheating is really worth it on railways where you stop every 2 miles.

Tim

 

WHR event booking form and timetable teasers: https://www.festrail.co.uk/content/uploads/1/WHR-PPF_Booking_Form_v2_1.pdf

Details and how to book for the solo Russell trips to Beddgelert: https://www.facebook.com/WHHRly/posts/2718600661515762 Relevant info in quote below for those who don't do FB

 

I'm getting Error 404 on this.
Ray.

 

Try https://www.festrail.co.uk/content/uploads/1/WHR-PPF_Booking_Form_v2.pdf
£50 for a day rover - surely a record for a NG event! By way of reference a quick check and Hunslet 125 was £30. No doubt a significant draw to see Russell (note the plan appears to be to offer a Park and Ride to ease traffic etc) but wonder what the feedback etc will be.

 

Wow!! It doesn’t cover the whole WHR either - from the website:
“Can be used during all three days for travel on all RhE • WHR trains between Porthmadog and Beddgelert, on event trains between Porthmadog and Boston Lodge and on all WHHR public trains.”

 

I think with superheat, if you want it to work on short runs, there's no point just tickling it. You need a lot to get the benefits quickly, since the superheater is going to get up to operating temperature in much the same time no matter how many flues worth you have, whereas the hotter the steam the faster the cylinders (which are the real thermal lag in the system) warm up. Lighter cylinders help here, I wouldn't be surprised if the Lyn's fabricated cylinders are also an advantage. Sentinels are obviously quite an extreme manifestation of this approach.

The Ffestiniog, with its long steady uphill from one end of the line to the other, is probably one of the few preserved lines where low superheat still pays off, and the smaller your engine the faster it all comes up to temperature; a 2 foot gauge engine is a very different proposition to a standard gauge engine in this respect.

 

Sorry about that. It seems they updated the pdf and the link I posted became broken as a result. The post has been updated with the current link.