BR Standard class 6 No. 72010 'Hengist' and Clan Discussion Thread

Having read the above link, I feel obliged to comment. In it reference is made to the paper "The exhaust of locomotives " by Professor A.J. Porta and C.S. Talidriz. The authors were Ing. Livio Dante Porta and Ing. Claudio S. Taladriz, so certainly not a "Professor A.J." As for the theory in that paper, I reject outright the inclusion of the momentum of the combustion products into the equations. The consequence of the inclusion is a travel into a mathematical jungle to justify the outcome vs the actual results.
For those with interest in this matter, a partial justification of the Lempor concept can be found in the recent (2018) paper by Benham et al. "Optimal control of diffuser shapes for non-uniform flow". Thanks to Creative Commons it is available to us all!
Kind regards
Jos

 

Hmmm. Dont you just love it when intuitive practice and in depth scientific analysis (Almost) converge

 

Jos. Thanks for that. I used extracts from the ASTT report which must be incorrect. I've corrected the web page. I can't comment on your rejection as I am nowhere near qualified to do so! We are trying to arrange a meeting with ASTT so I will bring up your comments then

Ian

 

I saw the correction, it is also Ing. Dante Livio Porta. As far as I am concerned, it is Trevithick who first noted the effect of an upright blast, his letter about it is quoted in the books about his life.
Apart from that the Lempor enthousiasts claim a number of advantages, these are opinions and not proven facts, as a consequence of the process I went through at Sheffield University I am now allergic to that.
As for a flat velocity profile, both mixing chamber and diffuser are simply too short for that. Regarding the Laval nozzles and their supersonic behaviour, the Lempor is now available since 1982 and measurements that transsonic velocities occur have not been made available. The angle of inclination of the orifices is also a point a discussion. There is no systematic test in which these angles were varied and as Wardale shows in his book that a 12 degree angle is better than an 18 degree angle, I am wondering whether that effect would not continue towards smaller angles.
Sorry for riding my wooden horse again!
Kind regards
Jos

 

Not a problem. We're at a very early design stage with the blastpipe type and pleased to hear all views. If you are near Sheffield sometime, call in and have a talk to us. We will be having an open day in April.

 

As far as I am aware, the team are very happy with them. We have two other P tanks, one of which definitely needs new cylinders and no doubt the other will in due course, and the intention I believe is to go down the same route for those as well, particularly now we have the drawing in suitable format. the second (and third...) set should be much easier to produce as the drawing and expertise now exist. Other groups have also done similar for cylinder castings I believe.

With that in mind, I was interested in your earlier comment:

As I said, long term we will need three pairs of cylinders for the P tanks, but have still preferred to go the CAD / poly pattern route. In your situation if you make a wooden pattern for the Clan cylinders, you will make two from the same pattern, but then with any luck you probably won't need any more for perhaps 50 - 100 years depending on usage. For any physical pattern to still be useful at that point, you have got to commit to storing it securely until it is needed again, which is conceivably easier with an electronic file than a large chunk of wood. Where individual railways have been fortunate enough to come into possession of original BR era wooden patterns, continuing to use them makes sense. However, if you are having to start from scratch, particularly for low volume items, then having the burden of storing a large number of wooden patterns for perhaps decades in secure, dry conditions is quite a big commitment, relative to having all the intellectual property stored electronically from which patterns can be made on demand.

Tom

 

Tom

Thanks for the insight. I was watching Youtube videos last night showing the process being used for cylinder heads and engine blocks so it must be cost effective where you have to remake the pattern. Fully agree about patterns - we've learnt the hard way that if you don't store your patterns in ideal conditions, then the patterns aren't much good. For interest, which company are you using for the cylinders?

 

Premier Patterns. I believe they also made the cyclinders for the Patriot project, which are obviously rather more comparable in size to what you would need.

Tom

 

Whether its an ethos thing or a gentlemans agreement thing with the BR slog but if a reuseable pattern might be used by other BR Standards then its considered worthwhile producing one, this one would be good for the Brits, and with a little modification 9F's also...

Whatever Lempor enthusiasts claim, there can be little doubt that experience with the things shows that they work well enough and so the calculations/ proportions are reasonably near.
The question is that with Lempor, Kyllchap etc - how much of the paraphernalia actually offers a return compared to simpler well proportioned multijet blastpipe and chimney arrangement.... ?

 

Without looking it up, but if I recall correctly, Peter Townsend wrote that with the fitting of the double Kylchap to the A4s, the coal saving paid for the conversion in three weeks.

 

But the same applies to an electronic file from which a poly pattern can be produced on demand. Moreover, an electronic file can be modified for the 9Fs while still preserving the original for the Clan / Britannia... If you are basing an argument on using wooden patterns for reuse at some uncertain point in the future by other loco owners, you still have to answer who picks up the overhead of possibly decades of secure, dry, physical storage. That's a task not to be under-estimated: no point digging a pattern you haven't checked on out of store after twenty years only to find one corner has rotted away completely and the woodworm are having party at the other end!

Tom

 

and your point is.. ?

 

I am not so sure about the experience, Australian R711 and UP's Challenger had their Lempors removed. If anything the Challenger should have shown a proper relation between performance and
the calculation. As for the Kylchaps, Lemaitres, Giesls and Lempors, they all work on the same principle of using the chimney as a combination of model chimneys which increases their relative length and
allows proper transfer of exhaust steam momentum. So the front end with most orifices wins! Double chimney with 8 orifices would be best, but a 4 or 5 orifice blastcap with an existing chimney would win costwise!
Kind regards
Jos

 

Good idea, but I am afraid not, sir. Britannias and Clans have different smokebox diameters.

 

That fitting a double Kychap to the LNER Pacifics not only saved coal, but also produced a more free-running and better steaming locomotive as compared with the single blast pipe arrangements that they had until then.

 

And also imposed stresses that the frames had never been designed to accept, which led to many withdrawals with cracked frames, as the NRM found out the hard way.

 

?? If a group of locomotives, build between 1922 and 1935, is fitted with a Kylchap in 1957-1958 and start developing cracks is the cause of the cracks the Kylchap or the misuse/overloading of the locomotives which the Kylchap allowed.
Old age may have its influence, but cause and effect should be clearly defined!
Kind regards
Jos

 

I thought it was obvious. He was answering your question "The question is that with Lempor, Kyllchap etc - how much of the paraphernalia actually offers a return compared to simpler well proportioned multijet blastpipe and chimney arrangement.... ?"

 

From Peter Townends book "Top Shed" when Kylchap exhaust systems were fitted to the A3 and A4s in the 1950s

"The results were now conclusive and showed a saving of about 7lb of coal per mile in favour of the Kylchap A4"

"The savings in coal came out a little less with an A3 compared with an A4 of about 6lb/mile"

"The ‘A3s’ particularly were given a new lease of life. Whereas it had been the practice to keep these locomotives off the most arduous turns to Newcastle whenever possible in preference to the more powerful ‘Als’ and ‘A4s’, the ‘A3s’ once again handled any of the main line expresses from Kings Cross to Newcastle and Leeds, and were frequently used on the tightly-timed ‘Talisman’ and ‘Tees-Tyne Pullman’ trains "

 

Very true, but there were many differences in the frames of the A1s/A3s and A4s, the latter being beefed up to cope with the increased power.

In designing a locomotive, weight is critical, but adds strength - at least if added in the right places. So you don't over-engineer; you design your frames to deal with the forces they're going to absorb. The A1s went through several phases each boosting power output: short to long valve travel; 180 p.s.i. to 220 p.s.i.; then the draughting modifications and, in 4472's case, a further pressure increase to 250 p.s.i. Know the limits of what you have.