Tornado

link?

 

Gordon The Big Engine would do it for me if we're being daft.

You can't re-use a name though really imo, it has to be a brand new name, for a brand new loco.

Logically, following on from Tornado, it has to be Typhoon. And as far as I know, that name's not taken by any big engines.

 

2001! Yes please and in original condition, poppet valves and all. None too keen on the wedge nose unless it's A4 style with full streamlining.

 

The Romney, Hythe and Dymchurch has a loco called Typhoon......

 

hence 'big'

 

Yep, would be good - Although I get the feeling that they would need to get permission for this? Mind you the RHDR would get a good deal out of it - So you could have a valid point/idea there!!! \/ =D>

 

No, you wouldn't want it in original condition, honestly.

For a start, the Lentz rotary cam valve gear was most unsatisfactory. The scroll cams and rollers suffered from very heavy wear and so were replaced with stepped cams offering 12, 18, 35, 45 and 75 per cent settings in forward gear and 35 and 75 per cent in reverse. In addition the clearance volumes were high and even after some modifications the outside cylinders were in excess of 3% higher than the outside cylinders of 2002. The inside cylinder clearance volumes were, at 14.35% front and 14.05% rear, nearly double those found on Earl Marischal.

You could put Caprotti gear on in place of the Lentz since the LNER was making good progress with the application of this gear on the B3 class ex-GC 4 cylinder 4-6-0s before the outbreak of WW2.

Modern thinking is in favour of lightweight, multi-ring piston valves since these give much reduced leakage losses. They are also far more robust than cam gears - remember what happened to 71000.

Then there is the thorny subject of the double swing link pony truck. A version of the truck fitted as a modification to the V2 class could well provide a solution but the crank axle would probably require a re-design and if you are going to do that you might as well go all the way and Zara, Krauss-Helmholtz or Carrelo the whole front end.

You would end up with a quite reasonable performer though it would not be very faithful to the original. I don't believe that a slavish copy of the original would be approved today in light of the problems faced by the class so there is no way around that.

The design looks good but it is what lies beneath that matters.

 

I wouldn't disagree with any of that. For those of us who've forgotten, or never knew, could you just give us a refresher on clearance volumes and their importance please?

 

I should have expanded on my first post. Obviously you wouldn't want the poppet valves 100% as original but with the benefit of later experience with such things, particularly 71000, then a very reliable and flexible system could be fitted.

 

Thanks Sheff, but are you sure about this? I've actually tried doing this in the early hours but the submission got lost in the ether.


The clearance volume is that which lies between piston and cylinder cover when at dead centre plus the volume of the steam passageways including the valve ports. It is usually expressed as a percentage of the swept volume. An ideal engine would have no clearance volume but that is purely theoretical. Clearance volume causes incomplete expansion losses and so it should be kept to a minimum, idealy 5 or 6 percent. The higher the working pressure the heavier the loss but thermodynamicaly you want high pressures and temperatures.

You also want minimum pressure loss between superheater and cylinder and so desire to have large valves with a substantial port area. This has the effect of enlarging the clearance volume. It is possible to modify a piston valve by means of vanes and diffusers (streamlining) so that it functions as though it were a normal valve of nearly twice the diameter. Some locomotives have been designed with 2 moderate diameter valves rather than one large one - excess clearance volume is that bad. You are trying to achieve a high level of internal streamlining for the gas flow along with a minimum clearance volume.

The piston can be fitted with what Porta refers to as a brim. This is shaped to follow the outline of the cylinder end or cover but your chassis and motion design needs to be very good, with low wear characteristics, in order for these to work safely without piston hitting cylinder cover.

Clearance volumes are less of a problem in compound expansion locomotives than they are with simple expansion.

The clearance volume is filled during the compression stage, using a small quantity of expanded steam not expelled as exhaust, to a level where, at the point of admission, the pressure in the cylinder is the same as the steam chest pressure, which in turn should be the same as the boiler/superheater pressure.

There, tried again. Will that do?

 

I can't remember the what and when but I attended a lecture on suspension and wheel/rail interface a couple of years ago. The guy giving it was obviously an enthusiast, as well as being professionally involved with vehicle stabilty and he had 'run' a P2 through their computer programs. The results showed why you wouldn't want to perpetuate the design and why there would be great resistance to any idea of running such a thing on today's railway. As a vehicle, it was a pretty poor.

 

Thanks - that's what I thought. I'd have called it "dead volume" I guess.

The 5AT team intends to use the twin piston valve idea, though I fancied poppet valves. I can see now why they may be right. I do like the "tune-ability" that poppets give you though.

 

Thank you Sheff, I'm glad that was good enough - I was a bit concerned.

I understand why poppet valves appeal but the leakage past them as everything expands is very significant. Chapelon carried out leakage tests and was very surprised.

You can do some very interesting things with other forms of valve gear. One of the American railway companies, Denver and Rio Grand if I remember correctly, had an extra mechanism or refinement on some of its locomotives which allowed the crew to vary the lead. Very useful as long as you are trained how to use it.

The steam locomotive, it looks so simple but it certainly isn't.

 

Edinburgh trip thread

viewtopic.php?f=36&t=18248

 

I spotted comment #1 in this Edinburgh Evening News story about the Auld reekie, and had to rip into him:

http://edinburghnews.scotsman.com/lates ... jp#3801896

Feel free to rip into me for any bs I may have written there, it's all my personal opinion of course :lol:

And please, no thanks are required for the free advertising of the forum [-X

 

Archive of the post in case they decide to pull it

http://www.webcitation.org/query?url=ht ... 2009-02-28

 

Yes, it looks like the EEN did pull it. I can't view it at present

Thanks for the archive link =D>

 

How much steel have they cut so far?

 

None as yet. See here for more info .... http://www.5at.co.uk/

 

Back up now it seems?