Discussion in 'Steam Traction' started by Eightpot, Oct 4, 2011.
Come see it on the GWSR end of May then.
That has been on my agenda for a long time. I’ll be there .
Personally speaking, I have always had a penchant for express blue paired with teak LNER coaches.
Get outta here!
Coat on and running for door...
If it's GWR stock please make sure you twist the lock in the upright position before slamming the door... As ever the Great Western is slightly different.
Fixed for factual integrity.
Maybe already repaired, but confirmation that the tube replacement is taking place at Bridgnorth.
Next FB picture showed blowing off 14 hrs ago!
The Facebook page for 6023 seems to be saying that the boiler work is complete and that it will move to GWSR Today or Tomorrow. (this info was actually posted 2 days ago where it said Wednesday / Thursday)
Bearing in mind that mainline running looks like an ever retreating target, and that the truncated safety valve cover looks frankly appalling, I wonder if she should be returned to standard height (possible exception with the cab in order to make it easier to get in and out of DRC. In that case would Mr Koopmans like to comment on the likely effects of the multiple jet blastpipe coupled with a full length chimney?
I agree it looks odd, should be fatter. Sure that Mr K would confirm that all other things being equal making the chimney taller would make it even more effective ... (perhaps too effective and you would have to open the nozzles up a bit) but you would have to maintain the same internal angle of taper... not a problem with GWR chimneys as they flare externally as well...
The small restoration crew has already said that that are too busy and would not replace the chimney. Given the extra length it would work a little better.
I have a question about the draughting. It's one I've had for quite a while, but reading the latest GWS Echo has reminded me. I realise that you may have had to simplify things for the article, so I may be writing in ignorance.
On 6023, by reducing the height of the chimney by 4", the length/diameter ratio was altered from 1.82 to 1.55, and this was deemed as insufficient. However, a quick look at the drawings provided shows that the Kings as built had a length/diameter ratio of 1.48, which remained unaltered for 25 years, until the sleeves were fitted in the early 50's. The other dimensions seem to still comply with Ell's thinking.
So the question is, why was the original arrangement satisfactory, but 6023's apparently not?
The most original chimney had a 1:7 taper and a L/D ratio as you say of 1.48 or thereabouts. If you care to look at the graph of the pressure coefficient Cp please
note that the 1:7 chimney has about the same Cp value at L/D of 1.5 as the 1:14 chimney at about 3. We only know that nowadays.
The single orifice was lowered compared to the original giving a x/d ratio of 7.1 which caused a jet being too wide for the chimney throat. So the 1:14 chimney
and the other ratios did not really improve. Only after the double chimney was mounted the ratios appeared to be improved, L/D = 2.587, D/d = 2.875, x/d = 6.5.
Most optimal for now would have been the original 1:7 chimney lowered by the 4 inches with the 4 orifices slightly more inclined, but hindsight after the casting of
the present chimney.
Aha, that would make sense. I hadn't noticed that there was such a big difference in taper, although it's quite obvious when you look at it.
In the 1930's Swindon also messed about with the draughting in the Castles. It does make you wonder what it actually achieved.
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