'The Bath and Bristol Christmas Markets'. Thurs. 28 Nov

Just found this on YouTube, a fantastic vid of the events as they unfolded on Parkstone.

 

Ah I can now see the confusion James/Tom . I was meaning normally rostered (ie = 7) and therefore a regularly worked day in day out proven loading for the class type over a route with inclines to show a comparator that works not the theoretical maximum. With a support coach in the loading on a main line run therefore that equates to 6 for punters without a banking diesel or double headed class 5s. Even if you go to 7+1 for the 8 as you've mentioned in comparison to the NYMR's set max then the train in question on Thursday appears to have been optimistically planned at best as it exceeded both the regular 7 and the NYMRs calculation as 8 for the maximum.

 

Good find video. Memory is that the flange oiler is just south of the station (i.e. before she finally lost the adhesion battle) and I think is visible in the film. Does a steam engine risk blowing loose oil up onto the rails & wheel tyres if the steam sanders are on when it passes an oiler?

 

From IR himself over on TW "Circumstances permitting, all of the December work for our locos based at Southall will now be both black fives."

 

Er, the technical bit is fairly routine.
It's the £££££££s that are not so routine!

 

I think you are taking my initial suggestion of an M7 rather more seriously than I originally intended!

Tom

 

It's a sad time when you have to get cotton wool out to prove the condition of the rail.
But if the need was felt this should be done and was to blame, wouldn't the prudent thing to have done been to try to mitigate that risk before departure ?

I'm not going to say this train was overweight, after seeing 45305 do the first WCME with a similar load in a blizzard over Shap with a pendo close behind, following a week of "will there be a diesel on the back" on here, I was in the "should we really be leaving Carlilse" camp at the time... It did it, nicely, so I am a believer in the power (but not speed) of a 5 's capability to do this job.
Maybe a 5MT should really be 5P7F

 

With all due respect Shap southbound is quite different to Parkstone.

 

Sorry, but you are letting an enthusiasts passion override the laws of physics.

Shap is mostly 1:125, with a very short section of 1:106. (Profile here: http://spellerweb.net/rhindex/UKRH/LNWR/ShapGradientProfile.jpg). Yes, it is a long climb, but that is a test of steaming, and the fireman's ability to maintain a good head of steam.

Parkstone is more than twice as steep (mostly 1 in 60 with a short bit at 1 in 50). OK, it may not be as long, but steam, or rather lack of it, was not a problem on this trip (as the fact that the loco was feathering at the safety valve even as it came to a halt). The problem is simply one of gravity - with that load, on that gradient, the simple gravitational pull back down the hill (before any other resistive forces are taken into consideration) is very close to the maximum force that the loco can exert even in ideal conditions. That's simply not a question on Shap with a similar load.

Tom

 

I think everyone has forgotten this..



riley 5, less load, similar gradient, similar outcome… but one definitely does not look and sound like the other.
The crucial difference being 44871 was speeding merrily, and suddenly started dancing like a car on ice (or Tangmere on Martin Mill, depending on your pov)..
where as 45407 was truly defeated by gravity without a slip and half the load, similar weather.

I still maintain Railhead was the factor here, not load, I've seen 44871/932/5305/407 act like an 8f when needed, true they have limits and science can calculate it..

 

Not quite true, it was slippy upon starting out from Poole and carried on being so towards to Parkstone and as a result never got up to a comfortable speed to tackle the worst part of the bank after the station. It's all about momentum, take Beasdale on the Jacobite for example. With a 5 the drivers will always hit the bottom at a good speed as an insurance for a slip or two, you might lose 5-10mph but you'll make it past the reverse curves near the top. Stop on Beasdale and you won't restart with a Black 'un.

In hindsight the diesel should have stayed on, or both fives go down, or of had 45407 instead but it's a bit late for all of that now. Hopefully lessons will have been learnt and it won't happen again!

 

sorry to labour the point.. but if what you are saying is correct, then 44871 wouldn't do it even on a sunny day with the wind behind it ??.. your saying not now not ever ?
this was a guaranteed fail right from the decision to use it ?

Ive ridden behind trips on the mainline which have come to a stand, invariably its not been down to load, but factors which prevented it handling the load.

 

That wasn't the point I was making at all. I'm sure on another day with the same length train and a good railhead condition 44871 would have made it, likewise with a shorter train in bad rail conditions. Combine that length of train with the bad rail conditions experienced then it becomes tricky.

 

Can't fault the driver and the fireman gave him the steam. They did their jobs as required.

 

I'd have thought pretty marginal. The gravitational pull alone uses about 80% of the force available if the loco is developing its maximum TE; the curvature will add to that through rolling resistance. If you had a graph showing how the TE falls as a function of speed, you could fairly easily calculate the speed at which the various resistance forces (gravity and rolling resistance) just balance the maximum force the loco can exert: at that point, the speed will be constant, i.e. the loco can't go any faster, no matter how fast the fireman shovels in coal. I'd suspect that for that combination of loco and load, that speed is probably not more than about 10mph. In other words, without a slip, the loco could plod up the grade at 10mph, but one or two slips and you are down to a standstill.

Again, I'd urge you to calculate the gravitational pull resisting progress of, say, a Black 5 and 11 coaches on a 1:60 gradient; and the same on a 1:125 gradient. The difference is a huge proportion of the available force. Do the same analysis of fall of TE with speed and find where it balances the gravitational and other resistance, and you'll find the equilibrium point is at a much higher speed. Which gives far more of a safety margin in case of a slip.

I'm sure you would have had lots of fun arguing with St Thomas Aquinas about Angels on pinheads!

Tom