Tests on Lempor Fitted S160 No 5820

On Saturday 4/2/17, Jamie Keyte, Mike Horne and John Hind went to the Keighley and Worth Valley Railway to log the smokebox vacuum on S160 5820, a 2-8-0 built by Lima in 1945 for the United States Army Transportation Corps.  A Lempor exhaust for 5820 was designed by the Advanced Steam Traction Trust and fitted in 2013.

The day was not specifically organised for our benefit.  The KWVR, were running their normal public service with the Taff Valley tank No85 and were running 5820 on a test train to prove operational procedures for the visit of Flying Scotsman in April 2017.

Under normal circumstances steam banked passenger services are not permitted. Flying Scotsman is a thoroughbred and the lifting of a heavy train on the steep curve out of Keighley and up Keighley Bank is not what the A3 Pacific was built for. Banking assistance is required to ensure that the services operate without hitches and delays, should the Pacific need assistance out of Keighley.

The train was 5820 leading, 7 coaches and WD 90733 banking.  The train was not open to the public and 3 runs were made during the afternoon.

The preparation work that Mike Horne had done at the Kirklees Light Railway on commissioning our data logger paid off and it worked flawlessly, so we were able to log vacuum readings at 1000 samples per second.  From Run 3 alone, we obtained 800,513 sets of data, which we are now starting to analyse.

In addition to smokebox vacuum, we have the ability to record steam pipe and blast pipe pressures and temperatures, cylinder pressures and crosshead position, giving us the ability to generate super-accurate indicator diagrams.  The test runs on 5820, were arranged at short notice, so we only had time to set up for measuring the smokebox vacuum.

The trains ran non-stop from Keighley to Haworth, with a slack before Damens and slowing at Damens Signalbox to pick up the token. After re-starting at Haworth the trains continued to Oxenhope before returning downhill to Keighley.  On Runs 1 and 3, 90733’s driver, was briefed to bank out of Keighley and take its own weight for the remainder of the run.  On run 2, 90733 assisted throughout the run.

What was apparent during the day was that 5820 had uneven exhaust beats which have developed over time since the locomotive was returned to traffic in 2013.

The uneven beat shows up on the data.  We had not expected that smokebox vacuum would show up problems with valves or cylinders to the extent that it can show a problem on one beat.  This was an unexpected bonus. If we had been able to fit crosshead position sensors we could have said which valve head has the problem – as it is, we know that a valve head on one side has a problem.

The data logger stores the data, which can be watched in real time on a laptop PC and downloaded for later analysis.  The data clearly shows the pulsing of the exhaust (the chuff) and the logging speed means that every chuff can be seen.  We can calculate train speed by measuring the time between pulses.

We had wanted to measure smokebox vacuum for some time. The view is that the engine is performing better with new exhaust, and ‘to measure is to know’.

It is too early to draw full conclusions, but some key data – on the climb out of Keighley on a 1 in 57 gradient at 14 mph an average vacuum of 8.16 inches of water with a peak of 16.6 inches was measured.  Further on at Ingrow, when the engine had been notched up and at a speed of 24 mph, an average vacuum of 7.48 inches of water was measured with a peak of 12.23 inches.

The only performance data for S160’s that we have seen, is that measured by the French Railways and published in Chapelon’s classic book ‘La Locomotive a Vapeur’. This gives an average vacuum of 8 inches of vacuum after a modification to reduce the blast cap area to 99 cm2the key difference is that 5820 is operating with a blast nozzle choke area equivalent to 140cm2 – 41% larger. So 5820 is working at a lower backpressure therefore more economically and producing less CO2 emissions.

More details will be published, once there has been a fuller analysis of the data.

Pictures taken on the day can be found here – https://youtu.be/rVzQu16R3bw

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