A1SLT additional tour added this Thursday

[Mercator II]

Below has been cut & pasted direct from the A1SLT own web pages and makes very interesting reading. I for one am very excited with the speed in which this the next project is progressing, along with the bond early repayment happening at the end of this year, how long I wonder before we are looking at fund raising for the build...

2013 - The model is further refined

The results of the study were submitted to the Trust by Owen Evans of DeltaRail in report ES-2013-003 at the end of February 2013. The following is a summary of the report and its findings. The new models of No. 2001 (‘as built’ P2) and No. 2007 (‘improved P2’ with V2-style pony truck) include some graphical information to allow much better plots to be produced than for the Tornado model. Here is the complete ‘as built’ model, showing the suspension arrangement:

P2 chassis

This is the detailed view of the pony truck:

P2 pony truck

The first simulations carried out with these models was to run them round an ‘assault course’ of smooth, sharply curved sections of track. This begins with a straight, then increasing curvature to a 6 chains radius curve, followed by a further increase to 4.5 chains (with a mirror arrangement back to straight). The models were run round this track at 5 mph, and results were produced for the forces between the wheels and rails, both laterally and vertically.

This simulation enables the study of the ‘track shifting’ forces; that is the total force from each wheelset that is trying to ‘straighten out’ the track. Because the coupled wheelsets are constrained to be parallel to each, they are not all aligned with the curve and have what is known as an ‘angle of attack’. In this case, not only do the wheelsets try to shift the track, they also try to spread the gauge, i.e. to force the rails apart. On gentle main line curves with good quality rail fastenings this is not too much of a problem, but in depots and sidings where curves can be much sharper there is a limit beyond which there is a real risk of derailment. There is also a link to the vertical loads on each wheel. If the lateral load (the track shifting force) builds up too much, the effect will be to push the wheel clean off the rail (ie reducing the vertical load to zero) – not a desirable result! Having explained all this, we can look at the results as Tornado, No. 2001 and No. 2007 were run round these curves.

Here is the comparison of Tornado and No. 2001 on the 6 chain curve:

Tornado 6 chain
2001 6 chain

Careful study will show the greater build-up of opposing lateral (green) forces for No. 2001 and that the red (vertical) arrows on No. 2001 are quite uneven from side to side – this is most noticeable on the front pony truck. Moving on to the 4.5 chain curve, here is No. 2001:

2001 4p5 chain

This is quite scary - the outer wheel of the third coupled wheelset has actually lifted off the rail, and you can see that the engine is doing its very best to straighten out the curve. No. 2007 actually fared little better. The work included a certain amount of adjustment of hornguide clearances to achieve the best performance for No. 2007. The conclusion was that Tornado can just manage a 4.5 chain curve whereas the minimum radius that could be achieved for No. 2007 with reasonable increases in the lateral hornguide clearances will be about 5.7 chains. It was established (from the original drawings) that No. 2001 already had thin flanges on the intermediate driving wheelsets and this feature will be retained with No. 2007. Given that such sharp curves only appear in yards and sidings, this was deemed not to be a ‘show-stopper’, so the simulations moved on to more general behaviour out on the main line. These were based around the high speed test run with Tornado between York and Newcastle on the evening of 18th November 2008. Much useful data was gathered during that test, mainly in the form of accelerations on Tornado and her tender, as well as a full speed profile for the southbound run. Courtesy of Network Rail, the measured track geometry data for the Up Fast line between Newcastle and York (as recorded by the New Measurement Train about two weeks after the test) was recovered and fed into VAMPIRE, and the Tornado model adjusted to improve its accuracy. All three models (Tornado, No. 2001 & No. 2007) could now be put through their paces over the same track data to provide a true comparison study.

A lot of information was generated, relating to ride quality, track forces and derailment risk. In some cases the P2s were better than Tornado, for example much of the ride (especially for No. 2007) and some of the track forces (remember this route is pretty straight). In some cases No. 2001 was better than No. 2007 and in others the opposite was true. Overall No. 2007 looked better than No. 2001, but would still benefit from further refinement.

One final check was ‘peak counting’. This is a somewhat complex calculation (done automatically by VAMPIRE). It looks at the lateral and vertical accelerations on the body of a rail vehicle and uses them to assess whether the vehicle is dynamically unstable. If you have ever pushed a supermarket trolley too quickly and seen the caster wheels start to vibrate rapidly from side to side, or seen a caravan snaking down the motorway, you will have witnessed dynamic instability. You can imagine that a railway vehicle behaving in this way would be quite frightening. Additionally, lack of vertical damping means that a vehicle can build up an increasing ‘bounce’ in response to features in the track to the point where it can momentarily jump clear of the rails!
Looking at our engines, the vertical behaviour is fine for all of them, even when the section between 75 and 80 mph is analysed. This is an excellent result, borne out by the actual test results from Tornado. Looking at the lateral results, some adverse behaviour is predicted, but some of this is caused by the piston thrusts causing the engine to ‘waggle’, and this is not the same thing as dynamic instability. Even so, only the fronts of the engines exceed the limits to any significant degree, and the P2s are generally better than Tornado (happily, this is an aspect where the longer rigid wheelbase is almost certainly an advantage!). Given that Tornado is now accepted as a mainline loco then this is an area where the comparison argument will be a likely way forward in terms of acceptance

Overall therefore, the verdict is that the P2 project should proceed on to the design development phase (involving more detailed dynamic analysis). Looking back, this has been quite ground-breaking work, as it is almost certainly the first time that VAMPIRE has been used in this way for steam locomotives. Delta Rail have completed an impressive report and we look forward to working with them further on the project.

For the full History of the project, please see the Trusts web
http://www.a1steam.com/index.php?option ... Itemid=247

oOo

Brian

[Atlantic 3279]

Very interesting Brian. Ta for drawing attention to this.

[LNER Fan 60008]

Quite the studies they've done for the new P2 - thanks for posting. Will be fun to see how it all progresses over time.

[Blink Bonny]

Ay up!

Looking forward to this....

[Mercator II]

Have just been advised that the Trust has been asked to cover the Cathedrals Express tour from London to Lincoln this coming Thursday 5th September due un-avalability of Bittern

I am hopefully going to be at Lincoln to help out on the service/lay over

As soon as times are avalible I will let you know, timings should be up soon also on uksteam.info

oOo

Brian