Brighton Atlantic: 32424 Beachy Head

From the video's it comes across as very loud, this is probably a stupid question, but what is the air pump actually required for as isn't she vacuum braked?

 

The loco itself is air-braked (engine and tender). In addition, the reverser is air-assisted when moving towards back gear (to assist with lifting the weight of the motion) and has an air-operated clutch to prevent racking back through the reverser. So there is quite a complex air system in place.

Tom

 

This is one of the things which fascinated me about the production of Beachy Head, the "air clutch" suggesting that this was a quite sophisticated design for its time, and indeed, our time.

 

I think you need to interpret the word "clutch" to mean "grip" (i.e. to "clutch hold of something") rather than the meaning that probably immediately comes to mind of a device that engages / disengages drive between an engine and gearbox. So in this case, there is a device that "clutches" the reversing gear weigh shaft (the transverse rod that rotates, translating the back / forth movement from the reverser mechanism to a lifting / lowering of the valve gear.

Without the clutch, the fore / aft motion of the valve rods can translate back through the die block, link and weigh shaft into a forward / back oscillation on the nut that engages on the reverser screw. That would lead to rapid wear of either the nut, or the reverser screw thread, or both. So the weigh shaft is gripped by a clutch to stop that motion. To move the reverser, the clutch is released and - if moving towards back gear - the air assistance engaged, both via a small valve in the cab. The reverser is then wound to the correct setting in the normal way and the reverser catch engaged, after which the clutch is engaged.

The other loco I can think of that has a similar clutch is the U boat 1638. Interestingly, on the GNR Society website it says, of the GNR large-boilered Atlantics: "Another point of interest is the reversing gear, which has a vacuum lock of Mr. Ivatt’s invention fitted on the middle of the reverse shaft, this holding the gear in any set position." - which sounds suspiciously similar in intention but different in mechanism. (https://www.gnrsociety.com/locomotive-class/c1/)

As for the air-assisted reverser: I believe Stroudley's larger locos had them, for example the Gladstones. So good Victorian (and Brighton!) provenance.

Tom

 

Doesn’t your S15 have a vacuum operated lock on the weigh shaft, Tom? 825 certainly does. Due to the layout of the valve gear, with a pendulum link to support the radius rod, the lock isn’t really necessary in forward gear as there is little die block slip, but put it into back gear and you can really feel it kick at the reverser, so much that I’ve known it knock it out of the catch and cause the hand wheel to spin quite severely. Schools also have a reverser lock.

 

Here's the loco on the launch train for the major project supporters and those involved in building the loco; it followed a short ceremony to hand over the loco to the railway.

Later in the day I was lucky to go on a familiarisation trip to Horsted Keynes and back - what a machine! (But also a quirky one; you aren't just going to get on it and make it perform straight away).



Tom

 

How does it compare with other loco's?

 

Especially in leaf fall season, in a cutting, up a 1 in 75 heading out from East Grinstead, when you have not the room to take a run at it.

 

After lots of testing, the passenger load limit to normal timings on our line has been set at 185 tons. To put that in context it is the same as the E4, C, Dukedog or BR Std 2MT tank. The O1 and H are 150 tons; the U and Q are 260 tons (though they’d bark a bit with that!)

To put that in context, a six coach set of Mark 1s is typically about 210 - 220 tons, depending precisely on which carriages. A five coach set would be about 175 tons. The Golden Arrow in its current configuration is I think 136.

So in effect we are calling it a class 2, which fits the tractive effort. (It’s about 20,000lbs; the C class is 19,500). BR called them a 4P, but that was with 200psi boilers, ours is set at 170psi. But unlike our other class 2s, it’s got a load more boiler power.

10 miles up and down last night with no timetable (“go when ready”) is hardly a basis to form a settled detailed opinion, so I am sure we’ll learn more in the months and years to come. But a few points from a firing point of view were notable. The first is that the grate is very shallow - the bottom of the door opening is probably only about six or eight inches above the grate. So it might have a big grate area, but there is no depth to the fire. That’s exacerbated by the brick arch, which is really low. So in practice, you have to fire very thin, but it steams really well like that. It also has a GNR-style firebox door with flap to fire through. So it steams well, but a definite technique is required, and not one immediately transferable from any other loco we have.

The other point is that the tops of the gauge frames are very high on the boiler and if you filled it right to the top, there is almost no steam space and a strong risk of picking up the water. So there is a very strong injunction not to fill the boiler above a line drawn about 2/3 of the way up, and to keep the top of the water in sight at all times with the regulator open. That’s a big change if you have grown up on SECR locos where the water disappears out of sight as soon as the regulator opens on a gradient and the normal rule of thumb is “if you can see the top of the water approaching a summit, you probably have too little to go down the other side when the regulator shuts and the engine goes nose down”. On the H2, starting with half a glass is the right level. We’ll get used to it. Fortunately the injectors are very reliable and not temperamental.

The steaming rate is sensitive to the damper.

I haven’t had to prep it yet (which I can see is likely to be another challenge - wide firebox, no drop section so everything sliced out). Equally, I can’t comment on anything to do with driving.

In summary, it’s a large class 2 with a big reserve of boiler power. So it will do the same as the E4 or C, but - subject to accurate firing - the boiler won’t have to be pushed as hard to do so.

Tom

 

Playing fat controller,how will it compare to a Schools class?

 

GWR4707 may not be aware that the LB&SCR (the 'Brighton line) was an air-braked line and that its neighbours - the LSW and the SECR - were vacuum-braked. As built the LB&SCR 'Atlantics' were fitted with air-brake only, and it was only after all three of these systems were incorporated as part of the Southern Railway in 1923 that the 'Atlantics' were additionally fitted with vacuum ejectors and accompanying equipment to standardise brakes on the Southern.

 

Tom, thanks for that really detailed insight into handling our new Atlantic, its almost as good as being on the footplate.
What I find amazing is that, until you mentioned it, I hadn't realised that 32424 will be working off 170 psi rather than the 200 of the original, but it makes so much sense, given the workload it will have, gradients it wasn't really designed for, and of course, boiler longevity.
And my god, it looked good heading up the Pullmans!

 

That's very interesting @Jamessquared, good to have another class two engine available as well as the 01; interesting though there are plenty of photos of them hauling well over that tonnage on the bluebell line, so the 200psi boiler must have made a difference, plus presumably these weren't stopping and starting all the time!

 

Yes, also the ruling grade is steeper now because of how the line approaching Imberhorne cutting was re-profiled back in 2013.

Tom

 

Don't forget that the boiler on 'Beachy Head' was an LNER built boiler for an Ivatt Atlantic which only had a working pressure of 170 psi.

 

I had not realised that. In a way it's a bit like the situation with the new-build County, though with better justification with a whole boiler being used. As new cylinders were needed for Beachy Head, could those not have been made a tad bigger?

 

As originally built, the H1 Atlantics had 18.5 x 26 (or 19 x 26) cylinders and 200psi unsuperheated boilers. The H2s as built had pressure reduced to 170psi, superheating and cylinders increased to 21 x 26 inches. That is essentially what we have.

Over time, the boilers of all the locos were bought up to 200 psi with superheating and it was in that form that Beachy Head was withdrawn - 21 x 26 cylinders (nominally), with a 200psi superheated boiler. I don't think new boilers were constructed, the pressure was raised simply by adjusting the safety valve settings - but that is much easier for the Southern Railway to have done in terms of approving their own modification. In the modern world, the provenance of the current boiler means it needs to run at its original design pressure.

Realistically, I think it is going to do everything we want. It will be able to take dining trains (Wealden Rambler and Golden Arrow); "B" services throughout the year, and "A" services off peak. About the only time we regularly run 6 coach trains would be the "A" services through the summer, and Santa trains - for which we have other options. Unlike many railways, we have always operated in an environment in which not all locos can haul all trains.

Tom

 

Interesting point