Bahamas

If anyone is able to help by buying from our online shop every thing helps, we're a registered Charity run by volunteers so any funds raised go towards helping the Jubilee return.... if you've not read the new book yet the reviews speak for themselves, worth a look !

Shop - The Bahamas Locomotive Society

 

I’ve just read in the latest KWVR mag that as part of the overhaul the loco will be fitted with air brakes.

 

Technically fitted with an air pump and combined brake valve for working air braked trains, the engine and tender will still be steam braked. I understand that the air pump will be located out of sight between the frames rather than under the driver’s seat as with 4871 and 5212. A sensible decision IMHO to future proof it as I’m sure the time will come when vacuum brakes are banned from the big railway.

 

Thanks for the detail.

 

We also have a Facebook page with pictures showing progress on the overhaul..

And of course a shop Shop - The Bahamas Locomotive Society any income from sales or donations helps with the overhaul or why not join us?

 

Out of interest, why do you think this? Granted the experience with Vacuum brakes is becoming more limited, but that is different from a ban? Surely as long as a train can be demonstrated to be stopped effectively, the method is not really a huge concern to railway inspectors. Not sure anyone has ever doubted the effectiveness of vacuum brakes.
Only air braked stock being available is probably more pressing than a vacuum ban - hence this work to Bahamas which will make it a very useful loco.

 

Vacuum brakes certainly are effective, less complicated and easier to maintain than a two pipe air system although less efficient as the maximum braking force is limited to atmospheric pressure, about 15psi I think. The air brake train pipe is charged to 72.5 PSI ( 5 bar ). I could be wrong but the problem is if anything goes wrong on an unassisted steam tour where is the nearest vacuum braked rescue locomotive? When Bahamas went over Shap a diesel loco was one block behind it but to do that regularly would be rather expensive.

 

That is a fact John, certainly seems to have been a concern over the last 10 years but it must be getting on 30 years since last there were any dual braked diesel locos active, apart from those operated by WC and more latterly VT of course.
Perhaps the consequences of a train stranded in section have become more onerous so precautions need to be greater?

 

The different air / vacuum (air pressure in reverse) are compensated by the use of bigger cylinders for a vacuum system so equalising the brake effort. A vacuum brake can be just as effective as an air system although slower acting, hence the need for vacuum experience. Ultimately, the effectiveness of the brake is the adhesion between the wheel and the rail, not the means of application.

 

I didn’t know that, I’ve always assumed that the faster action was because of the additional brake pressure

 

You either run it a block behind or put it on the back, still need to staff and fuel it.
This is no different for the last 20 years though, which is when EWS withdrew their last dual braked locos. Both West Coast and VT risk assess trips and act accordingly - Shap trips used to be unassisted due to the proximity of Carnforth and dual braked diesels.
I dont see any directive coming from HMRI on this anytime soon though.

 

The two systems work on very different principles and the mass of air to be moved in a vacuum system is much greater than in an air system, so it requires more time to, for instance, fill and drain a cylinder. Look tat the thickness of an air hose, which has to withstand about five times the pressure, and a vacuum hose and you'll see what I mean. There is far less air movement with the pressure system than the vacuum.

 

Maybe it isn’t which is why I used the term future proof

 

As I understand it, with two pipe air, one pipe acts as a ‘brake controller’ along the length of the train, and via the ‘triple valves’ actuates the brakes on each vehicle, these are then recharged from local reservoirs.
With vac, air is admitted and removed from the loco only, so it takes longer for pressure to rise along the length of the train and apply the brake, and vice versa to release the brakes on each.
This could be total rubbish as I’m trying to recall my Black Book knowledge from 50 years ago, so please feel free to put me right.

 

Nothing wrong with your memory, Sheff!

 

The vacuum brake is about as fail safe as a brake can be unlike an air brake as the triple valve or distributor can fail to operate. It relies on the fact that there are multiple distributors on a train and multiple failure is highly unlikely. Both systems are susceptible to freezing weather conditions, though, hence the need to make regular applications in freezing weather.

 

Modern air brake systems use a more sophisticated distributor valve allowing gradual brake release and a faster emergency application.
I’m not a driver and stand to be corrected but I would think the operation is a lot more smooth than a vac brake, to keep the latter at a steady level of vacuum during braking the driver will be fiddling with the brake valve all the time. Air brakes have set positions, initial, full service and emergency. When coupling up it will be set on overcharge that serves the same function as pulling the strings on the vacuum system.

 

Is there a reason its being placed in the frames rather than in a more accessible location, the pump on 46100 is behind the smoke deflector IIRC and so accessible but it seems odd (no doubt there is a perfectly valid and sensible reason) to place it where its hard to get to (for maintenance and fault without a pit) and there is also inside motion which you don't have on a 5?

 

Aesthetics I would imagine as much as anything. No smoke deflectors on a jub so it would certainly spoil the elegant lines. 6201 has the pump on the outside but below the running plate at the front LHS so it is visible but not prominent. As John has said 44871 and 45212 are below the drivers seat, quite unobtrusively, whereas 45407 has it between the frames. Not sure about 45231, 61306 and 34046? Eddystone is like Tangmere, by the smokebox LHS.
Incidentally when 34067 was initially restored the pump was inside the casing but after a couple of issues it was deemed to be overheating and the VAB insisted it was relocated to a better ventilated spot. I know the guys who initially installed it weren't happy with the instruction because they felt there was an issue with the pump that wasn't to do with overheating.

 

I’m a member of the society but not a party to the decision. I assume it’s so it isn’t visible, 45407 has the pump between the frames but for the other two Black 5s Ian Riley fitted it under the driver’s seat just protruding below the cab side sheet. I assume that’s because of easier access and not being subject to excessive heat. Originally Tangmere’s pump was hidden behind the boiler casing but later moved to the front. The authorities now don’t like a full boiler pressure steam connection between engine and tender in any new fitting so hiding it away in the back of the tender like Clan Line is no longer an option.