73096

Looking at the pics on the website, you may well be right, if it came out the back side of the piston. Does anyone know?
Daniel

 

In a PM to another poster I put forward the following scenario (pure speculation on my behalf, but a possibility):
If it was a simple hydraulic explosion then the force on the piston would be evenly distributed and unlikely to buckle the rod to that extent. I'm wondering if there has been a hydraulic lock on the back stroke, which has pushed out the core plug towards the front of the piston. The plug is certainly missing from the 6 o'clock position on the rear side and seemingly in place but damaged on the front side of the piston from the photos published.
It's similar but not quite the same as your theory. Being much closer to the action than me, I'm sure that you have better access to all the facts. I have only seen the posted photos and video and a 450 mile return trip to look at the evidence isn't really worth thinking about.
With reference to our previous posts, is this speculating or an interesting discussion? I think that it is the latter and worth carrying on in a sensible manner until the official conclusion is known. Just the Sherlock Holmes in me.

 

Just adding another question to the puzzle. On most of the photos the bits of the cylinder show fresh clean fractures. That is, except the photo of 17th March which is of the front cylinder cover attached to the cylinder remains and the front draincock. At the lower left of the cylinder remains is a distinct area of red rust on the fracture face. Any opinions on this?

 

I picked up on the back cover going first yesterday:

It just seems odd to me that the core plug could come loose so quickly and move that far (remember - this is secured with a thread) without some prior warning that it was occurring.

Regards,

Dan

 

Hi all does anyone know if owning groups or loco owners have taken there BR standard locos or other LMS locos out of service to check the core plugs in their locos? Or would they wait until their locos require a piston exam?

 

As it is a known problem I would hope that loco owners/railways routinely check the core plugs on P & V exams. If not, I would hope that a specific exam has been carried out by now and that it is added to the check list.

 

I do, believe me. I did however misinterpret your post a bit.

 

my 2pence worth in the armchair engineers stakes.
Core plug works loose, loose enough to begin striking cylinder cover leaving witness marks. one each hammer the thread is stripped a little excacerbating the situation. eventualy thread is stripped, this would only reqire plug to come out enough to touch cyl. cover, plus pitch of thread, on power stroke plug is blown out in one go. plug falls to bottom of cylinder and is trapped between piston at end of stroke and rear cylinder cover. rear cylinder cover pushed off pushing it out of alignment causing piston to drop breaking through bottom of cylinder at rearwhich is already damaged by cly. cover being pushed off. on subsequent forward stroke lowered piston takes out rest if cylinder by ploughing through it, requiring considerable force as piston attacks cylinder end on. This results in bending of piston rod. It may have been worth noting where the various parts were found to give an indication of the sequence of events. ~I realise latter may be difficult due to the forces involved scattering debris.
It may be interesting to note whether the cavity side thread on front of piston is also stripped, it should be .
rog

 

Some years ago, I seem to remember a similar thing happening to 7325 the GWR Collett Mogul on the SVR (although not as drastic). I think that was caused by a core plug coming loose. If I'm correct, this problem can also occur on GWR locos.

 

48773; the 8F resident on the SVR suffered in a similar manner too. Fortunately both engines' cylinders were repairable with "metal locking".

 

A question - Once a new Cylinder has been made for the loco; won't this have to be pressure tested? And ongoing tests after this?

 

Won't go into details here, but the article on page 15 of the latest issue of Steam Railway(361) makes interesting reading.

 

Yes, seems to suggest that hydraulicing was a contributing cause of the failure.

Regards,

Dan

 

Can someone explain whay hydraulicing id please?.

Thanks
Chris

 

There are three states of matter:

1 Solid - definite shape, definite volume
2 Liquid - indefinite shape, definite volume
3 Gas - indefinite shape, indefinite volume

In simple terms, this means that a litre (or gallon) of liquid, such as water, will always occupy that volume - or space - even though it changes its shape. A litre of a gas, such as steam, will expand to fill the available space, or contract as the volume decreases (although with a change of pressure). So if a piston approaches the end of its stroke with steam trapped between it and the cylinder cover, the steam will contract to allow it, albeit with a pressure increase. If though there is water in that space, and once the water has been pushed to fill all the space, any further movement of the piston will try to reduce the volume of the water. This cannot happen, so the space must either expand (blow off the cylinder cover) or the piston must stop. At very slow speeds, the piston might well stop moving once the water is fully distributed within the space and there is nowhere alse for it to go; this is known as 'hydraulicking'.

 

You certainly learn something new every day....

 

But if you are aspiring footplate crew it should not be that new! Hydraulicking is one of an engineman's greatest worries.

There does seem to be an emerging opinion on the ultimate cause of this mishap. Whether it is right, I don't know.

 

It is not. In my various discussions with the "management", it has been confirmed that it did not happen.

 

The new LH cylinder for 34027 was hydraulically tested before fitting to the frames.