35018 British India Line

So how do you identify the kinetic envelope from the sideways movement / oscillation that arises at different speed ranges ?

 

Thought NR had a fancy measuring device for agreeing gauging with loco's, have certainly seen it on Ian Riley's site, when they did FS.

 

More likely to get at the valves. I never did understand why Bulleids have outside admission valves, it must be harder to keep them steam tight

 

Outside admission valves are fine on original Bulleid Pacifics......

 

If you like uneven beats !

But yes without the valve glands at the ends of the cylinder block it does become easier to keep outside admission valves steam tight. It makes you wonder why they did not do a proper job and change them to inside admission when they rebuilt them. . .

 

Only if things aren't set up properly.

 

Because new cylinders would have been required.

 

Yes I know that, but they changed a great deal of other things why stop with a relatively minor thing (in those days) and go the whole hog and replace the outside cylinders as well. I guess we'll never know the real answer and we'll have to live with the odd weep now and again (and possibly more work repacking glands).

 

Not quite true. They changed things that were either visually or operationally prominent (cladding, reverser mechanism etc) but in terms of actual metal, very little changed - boiler, cab, frames, wheels, tender etc all retained. I’ve heard an estimate that more than 90% of the originals was unchanged. With regard cylinders, they worked without issue and were nowhere near life expired, so there was no financial case to change them when the motion could be adapted at the design stage to work with the original outside admission valve chests on the outside cylinders.

How “rebuilds” of locos are considered seems fraught with enthusiast prejudice. Lots of pre-grouping locos got new boilers of different design, maybe all sorts of other changes but are considered still to be the “original” work of their designer if they have sufficient popularity. Whereas Bulleid’s Pacific’s retained 90% of their original fabric, yet are considered a shocking waste, and any good points in the rebuilds are invariably ascribed to Jarvis! No-one talks about the Drummond Well Tanks that worked out their days at Wadebridge, but there’s far more Drummond (and Adams, and Maunsell) in them than Beattie, and far more Drummond in 30585 than there is Jarvis in 35018!

Tom

 

Because if you changed the valves to inside admission you would have to rearrange the steam and exhaust pipes and the valve gear. For inside admission the combination lever has the valve spindle pin below the radius rod pin, the opposite is true for outside admission. Apart from the combination lever the expansion link, eccentric rod, return crank and possibly the main crankpin would need to be changed. There may be alternative modern sealing arrangement which could reduce the maintenance required on the valve spindle glands. After all piston rod gland are often subject to the same pressures when the loco is working hard.

 

And as you've changed the inside cylinder AND the two outside cylinders don't you think the steam and exhaust passages (in the cylinders themselves) will be changed and then all you have to change is the main steam pipe(s?) which are after all replaceable items. As for the valve gear - I don't think there was a Return Crank in the original design however I don't know how much of the rest of the original gear was reused when rebuilt when those chains went into the scrap bin, perhaps others can answer.

 

All the valve gear must have been replaced because all three sets were between the frames

 

Yep that's what I thought too, although others may know more if any of it was reused.

 

Outside admission does give an advantage for the exhaust passage from the valve chest - which can be effectively larger and straighter to the blast pipe, minimising
back pressure which is well worth some trouble.
The cost of it is a gland at steam chest pressure which was accepted to reuse the original outside cylinders on the rebuilds.

Note: with traditional slide valves the glands all had full steam chest pressure on them.

 

Nice to see BIL on a test run today. Fingers crossed she has a trouble-free trip around the circuit with no leaks!

 

No such luck John , loads of steam coming from the fireman’s side

 

What, overheated fireman ?

 

Well, she made it to Hellifield GL 8 mins early, so I live in hope!

 

just looked at some photos taken this morning and posted on the light engine & tests thread, whilst there is clearly still leaks around the area of the RH cylinder its certainly not as bad, or doesnt appear to be as bad as in previous shots, something looks to be very difficult to get steam tight ,