6023

The other aspect of efficient draughting is the reduction of back pressure on the pistons. This leads on to a reduction of coal and water consumption. Due to limited supplies, water consumption on the main line is more important now than it was in the old days.

 

In addition a more photogenic and probably well publicized would be a run from Bristol (or beyond) to Kingswear.

 

Well that's a bit of a result - kids were asked by my better half what they wanted to do as a birthday treat for me this weekend - suggested going to watch car racing at Castle Coombe. Kids (clearly well trained/indoctrinated) turned that down in favour of "taking" me to Didcot - so I get to see 6023 in action for the first time since the launch weekend a few years back.

(Its also a result for the GWS because I stupidly forgot to renew our membership on time so won't have the new membership cards back in time to get in at members rate - although to be honest I regard the membership as a minimal means of supporting the organisation and paying for entry to events is another way of supporting things whilst I can't actively help).

Even NR are co-operating by allowing the mainline between Bath and Didcot to remain open this weekend - seems like forever since I looked at a Didcot weekend without the line being closed!

 

Birthday & on the train, so long as your kids are old enough they couldb buy you a pint of beer to help 7202 as well

 

I think I might have to raid their piggy banks and buy it myself as I'm sure you won't be serving 11 and 9 year olds! More likely my youngest will decide to get me one of your heavy freight T-shirts (if they still exist) to back up his claims I need to lose some weight!

 

Correct on serving your kids, seems you would have to buy your own, sorry. The Heavy Freight shops should be open, selling a range of t-shirts ands sweatshirts.
Enjoy your day.

 

On the subject of efficient draughting, and in the spirit of my forum name, I'm wondering how big an effect the length of a smokebox has on efficiency. I've got in mind the fact that Prince of Wales will have a longer smokebox than the original P2s due to the shorter Tornado type boiler. Will this require fundamental redesign of the draughting arrangements compared to the original locos?

 

I am afraid you have to perform your own research here. It was investigated by the Master Mechanics Association (USA)
and Goss reported about it in his book "Locomotive Sparks" which is available on the web in downloadable form.
"The smokebox could be made shorter than was the common practice in 1896".
Kind regards
Jos Koopmans

 

The length of the smoke box has a limited effect on the actual draughting. The difference would be in the gas flow resistance of the boiler and its heat transfer through the tubes defined by there length and gas flow resistance per tube. In the calculations it is the heating area of the boiler which defines the chimneys gas flow area. In principle the calculations should be re done to the old set up to check this. Additionally a greater smoke box length allows for a better flow of gasses round and through the spark arrester plates.

While I am posting I would like to point out the importance of streamlining and avoiding impingement surfaces in an exhaust system which creates back pressure and thus the inability to allow energy to be given up to the piston. The result is an increase in steam required for a given amount of work. The greater the noise, the greater evidence this is an issue.

 

Intuition tells me that a smokebox of greater volume will help smooth out the low pressure pulses due to the blast. Again intuitively, a steady draught ought to be better for the fire, rather than a series of sharp pulses.

Even if the above assumptions are true, however, it's debatable whether they would actually improve efficiency to any degree. And in any case, it's quite plausible that most gains will be achieved with quite a short smokebox, and going longer simply takes you into diminishing returns territory.

The point about the spark arrestor is a good one though, and would probably be worth exploiting if you are going to end up with a long smokebox anyway (e.g. P2).

Just a few thoughts, I have no evidence to back any of this up.

Dave

 

All I have on the matter of smokeboxes are these Swindon Engineering Society lectures:—

No. 84:– “Locomotive Smokeboxes” read by H. Arkell, Feb. 25th 1908

No. 111:— “Smoke-Box Design,” read by G. Goddard, Jan. 30th 1912

 

Interesting thanks.

Some of that suggests that my intuition may not have been too far wide of the mark. Unless thinking has changed a lot since then, which wouldn't be a massive surprise.

Dave

 

Its often revealing to see old papers like that annotated by a modern expert to understand what they knew and what they didn't at the time. I note that, without using the actual word, the second paper comments on the desirability of streamlining the exhaust passages.

 

Goddard wrote also "Smokebox construction and design" The Locomotive 1919 page 180.
Philipson quotes the American Railway Master Mechanics Association as (length) E = 0.6 D (smokebox diameter) or 0.9 D,
"but not intermediate values".
Kind regards
Jos Koopmans

 

Earlier in this thread somebody said that owners of Bulleid Pacifics should be ashamed for not adopting the draughting arrangements suggested by Meneer Koopmans. I put this to my colleagues and the reactions varied from a loud guffaw to remarks I couldn't post on here. On the NVR 34081 burns more coal lighting up and standing still that it does hauling trains. Most of her line work is done at quite low power settings as a six coach train on virtually level track at 25mph doesn't involve much hard work. Not a great scope for savings, unlike a main line loco working close to its maximum. Given the nature of her usage, we would be interested to know how much fuel would be saved by modified draughting. Also why should anyone who has saved a loco from the scrapyard, restored it to working order and overhauled it all over again, feel ashamed just because they haven't adopted an unproven modification to the front end?

 

You shouldn't be ashamed it's your loco (or your groups) and you can do what you like with it, and if anything you should be proud that you and your colleagues have got off their behinds and restored/overhauled the thing. It's just like livery froth lots of noise from those who in general do nowt! As you say with a loco trundling at very much below peak output there is unlikely to be much benefit, however hang 7 Mk 1's behind a humble 0-6-0 with a steep hill to climb then there may be a good case for such a modification.

 

Fascinating, and good to see Mr Stanier in the chair for the 1912 example.

Just out of interest are these available on-line or are they copies you have scanned yourself - I know my father would be fascinated if they were online?

 

Our thoughts exactly. I hasten to add that it wasn't Meneer Koopmans who said we should be ashamed.

 

So what modifications have you developed for the Bulleid Light Pacifics? Radically different from the original or just gentle tweaking?

 

Sorry, see my #731!
Kind regards
Jos Koopmans