New Type Air Pump.

Now if they could produce a standard gauge version (as mentioned), it would solve a lot of problems regarding air braking on steam locos. More reliable, less obtrusive etc.

Steam Loco Design - Our Work - Steam Driven Air Pump

 

Im not sure you could have a standard type of air pump, cheifly because they are fitted in various nooks and crannies on different loco types, all of different dimensions.

6024 and Black Fives have them between the frames, 35028 has it in the back of the tender, 34067 and 70000 infront of the smokebox, 5029 on/though the left hand running plate, 6201 down by the bogie, etc etc.

Can see why a standard design would be desirable from a maintenence and reliability point of view, but it would have to be a pretty compact unit to fit the vast majority.

I suppose if intended for Mainline use, it would have to pass VAB and NR Approval as well in terms of performance.

 

I don't see how this is more reliable. Generally there is not much to go wrong with an air pump, the Westinghouse or the more common ex polish railways pumps used on most mainline locos here today are fine given the proper maintenance.

 

Some Loco's did have issues with the airbraking system years ago when it was relatively new, but to be honest, I think it's been quite a while since a Loco's air braking has thrown a tantrum out on the mainline now.

 

Haven't there been stories of footplate crew having to give an existing type air pump "a clout" to get it working again when it stopped?
I assume this newer pump uses more modern materials/seals etc then the existing types. Not sure of the operation though, whether you get the "chuff chuff" noise or not. Looks a smaller profile as well for easier fitting.

 

Westinghouse pumps can be prone to stopping, often at inconvenient moments. Unlike a failed vacuum ejector which would lead to a very rapid halt, the stored air pressure in the main reservoir is often enough to enable the train to get to a sensible place to stop for a sort-out.

Common causes of stoppages are lack of oil (top-up of cylinder oil fixes that), water carried over into valves or just failing to re-start after being governed out. In most cases a rap on the valve case will be enough to get things moving again.

 

I agree that where Locos have been air fitted for mainline work it is desirable to reduce the "panting" of the air pump. There are one or two places where the absence of the Westinghouse pant would simply not sound right i.e. the Isle of Wight where the sound of the westinghouse "panting" is almost a trade mark.

 

HI no good for mainline locos to small. fish7373 81c

 

HI just a point how many mainline lococs are fitted with westinghouse pumps. fish7373 81c

 

That maybe so with that particular pump, but Westinghouse pumps are at least 3 different sizes and no doubt the North American versions were even bigger. There is nothing to prevent the development of larger versions of the new design.

 

I have often thought a vane type compressor might work on steam locos.

Diiscuss?

Cheers Dave

 

Hi, interesting thought. It could be done but without going into detail, I think it would be unnecessarily complex and costly.

 

Well... not intending to go down too much of a tangential path, it wasn't unknown for steam wagons in the 1920s to have their hydraulic tipping gear powered by small centrifugal flow turbines. This would presumably produce a whirring sound, perhaps similar to a Stone's turbo generator. That rotary motion could presumably be translated into another centrifugal compressor.

I suppose ultimately, though, the Westinghouse is tried and true, and any new design would likely have to go through a lot of scrutiny to be used... and to what advantage?

 

A vane compressor would indeed need to be turbine driven as rotary compressors need to run at high speeds, not a huge problem on a steam locomotive and the Americans have used turbine driven boiler feed pumps with great success.

Problems are, a compressor must be regulated/controlled to ensure that it stops or is "unloaded" when demand falls. This can be done a few ways:
1) Suction un-loader valve
2) Inlet throttling
3) By-pass
4) Blow off

The last two methods are the most simple and straight forward, as they allow a compressor to run continually but at full load. Not ideal in this theoretical application as compressors run hot when they are on load, which ties in nicely with what I'm going to say next...
Vane type compressors rely on oil injection for lubrication but more to the point this must be cooled and filtered, which adds more complexity (reservoir, separator, pipework, cooling radiators & fans, etc)
So if you have a compressor working flat out continually you need a pretty serious cooling system to take care of the lube oil, not very practical on a steam locomotive. Of course you could have control where the compressor is off loaded and/or reduce its speed (the latter is how the steam driven reciprocating pumps work) but this would require a more elaborate system to control such parameters - yet more complexity!

If that could all be achieved sensibly then you would need to find a turbine suitable to drive such an affair and that would either involve a degree of engineering or investment but probably both.
Its not impossible but you hit the nail on the head in your last sentence.

 

I went down this very same road on here 3 years ago ..... http://railways.national-preservation.com/locomotive-engineering-m-i-c/16169-air-pump-failures.html

I got as far as looking for a supplier of rotary air pumps as used on modern MU stock but doubted there would be a sufficient market to make development worthwhile.

 

Hydrovane compressors would be the way if this was to ever become a reality.

 

Certainly used several of those on various jobs in the chemical industry - good compact and reliable m/c in my experience.

 

Have experience with these units through work myself. They are used already quite extensively in the transport sector, both rail and road. Very compact, even with all of the associated equipment, especially when compared to the piston type compressors EMD and GE put on the 66's/67's etc and the class 70 they are quite massive!

 

I'm afraid I had to smile at the objection on heat grounds as I run a Saab turbo, these turbos can run red hot and so use synthetic oil.

In it's simplest form the compressor raises pressure and as it reaches working pressure the steam valve is gradually closed and stays so until pressure drops.

Not many moving parts, got to be worth a look.

Cheers Dave