73096

73096 - Stick with your loco and don't let anyone try and put you off or bully you. Its your choice so go for it and help get the old girl running again.

Seeing as the loco was hired in from a third party (the one who must not be be named, i.e. the Prince of Darkness, architect of of all evil and the credit crunch..) I would guess that contractural requirements within the agreement would include cover for serious accident damage. I would hazard a guess that the one without a name is going to want his toy back in one piece and will be cranking his legal team up as we speak?

If it didn't - then he has 'beeped' up

 

A new Cylinder is surely going to be a 6 figure sum and take a year to complete.
The boiler by that time will have 1 year left and will need another 6 figure sum taking another 12 months to complete.
In addition to this it needs other expenditure.

Will the Mid Hants really get a good value return on maybe £250k worth of investment, with at most 3 years use before the engine is returned to the owner, who almost certainly will remove the engines from the line ?

Option 2 is to go all in now and do the boiler, wheels and cylinder now with an aim to be ready in 2010, and maybe get 4 years use from the engine, but it's still going to cost the same amount, just all in one go, again will this be good value for the MHR ?

Option 3 Though I hate to say it, it may be better for the Mid Hants to pay the owner for a new cylinder (if it's in their agreement to), retire the engine until the 2014 agreement ends and then release it to the owner.
At least with option 3, if there was enough support, people could start raising funds and be ready to make a bid to buy it if that became a possibilty ?

 

Is there any real need for that in trying to lower the tone again about a certain individual and just trying to add fuel to the fire. We have moved forward in time but yet theres still a few people out trying to turn it around to the same old argument everytime something crops up, please can we try and not let this drop into a free for all again!

 

Deleted

 

Whilst I agree that E.S. Cox said the above in his book, the cylinder drawing for the Class 5s (SL/DN-M 714) clearly states that the material is cast iron.

 

Err sorry Mr Shoddy but it is actually a statement of fact. Discussing whether the MHR repair the catastrophic damage is one thing but 73096 isn't actually their asset (it is the unspoken one as I understand and i purposely did not mention the unmentionable name to avoid accusations of critiscm or stirring) and as such I suspect he will want it back with two complete cylinders.

Every other major line gets put under the microscope of discussion but as soon as the MHR loco section gets mentioned someone always calls foul.

Bluebell puts up with a lot worse unwarranted stirring and critiscm than is here, most of it from the Hampshire direction.

 

I do wonder whether the steel shortages of the 1950s had something to do with this. Perhaps batch to which 73096 belonged had to have cast iron cylinders because that was all that was available.

I had the impression that there were only three sizes of cylinder casting; that a cylinder casting was chosen from the three by the relevant drawing office and bored out as appropriate.

Regards

Regards

 

This is going to sound slightly stupied.... 8-[


...whats a core plug?

 

Good question. There was a good explanation of it earlier. If it's not in this thread, then it will be in the MHR Gala thread. It's the way that the holes left by the pattern when making a hollow casting, such as a piston, are filled. A hollow piston is lighter and therefore more efficient than a solid one, but the manufacture is more complex and therefore more expensive...

 

The questions about the economics of the repairs and the terms of the loco agreement raised by martin butler, learningtobelost, Silverlink60014, Maunsell man, ADB968008 and others are all valid, and must be causing Colin Chambers (MHR Ltd managing director) and the denizens of Ropley Manor much anxiety at the moment. However, having stated the problem, there's nothing any of us can add without knowing the terms of the agreement, and that's not something that's going to be revealed in this kind of public forum. Hopefully, there will be some kind of public statement from the MHR about what has been decided, but I don't expect that for a month or two. It seems to me that the pure engineering will be easier to deal with than the "business" side.

 

Posted twice!

 

In order to save weight and so reduce the reciprocating mass and the need to balance it, the pistons are cast hollow with a big, empty space in the middle. In order to make this space, the pistons are cast around a 'core' of sand, shaped to conform to that of the required space. Once the molten metal has cooled around it, the sand must be removed, so a hole is drilled in the piston face to release it. The hole through which the core sand is removed is then filled by a plug, the core plug.

Very similar techniques are used in casting car engines, and you should, unless hidden under everything else, see pressed steel core plugs in the side (or front, depending on point of view) of a car engine. These are usually simply hammered into plain holes; those in a loco's piston are threaded and screwed into place.

 

Thank you for the quick replys.

 

"What's a core plug" ... in outline ...

A sand casting is made in a box that has two pieces, a top and a bottom. If you want to make a casting you also need a pattern. The pattern gives you the outside shape of the casting and it may be in two halves also. You fill the both halves of the box with sand with the pattern inside them. You then put the top half of the box on top of the bottom half with the pattern still in place and you fill the top half of the box with sand. The sand is tamped down hard. You then separate top and bottom halves of the box and remove the pattern. Put the two halves of the box back together and pour in the metal. When the metal has solidified remove the top box and tip up the bottom one on the foundry floor and the casting will fall out with any luck. This will give you a solid casting.

If you want a hollow casting as in the case of a box piston head you also need a core. This core will give you the inside shape of the casting. You go through much the same process as before but after removing then pattern you have to put, in the shape which the pattern has left in the sand, the core. Now the important bit here is that the core has to be located firmly so that the act of pouring the metal won't disturb it. To do this lugs are made to project from the core across the void left by the pattern into the sand. These lugs will leave holes in the finished casting. The holes will require, in the case of a box piston head, 'plugging' hence the term 'core plug'.

I hope the attached drawing, which comes from my copy of the 1962 edition of Chapman's Workshop Technology will help you to understand.

You will have to ask one of the team at Ropley just how the core plugs are secured into the piston on 73096, I can't help there, but you should remember I think that the engine is over fifty years old and I would doubt if this design feature was expected to last as long as that.

Regards

 

Thanks Columbine, great explanation. The diagrams really help a lot. Neither LMS2968 nor I were quite right...

Although it's a general metal-working/engineering technique, rather than something specific to locomotives, perhaps this should be posted in the "Locomotive Engineering M.I.C" forum, for future reference?

 

Not really, although we didn't go into that amount of detail. The holes left by the lugs will be as rough cast and will not accept a core plug. They must be drilled to a larger size and a core plug hammered in, or are tapped to accept a threaded plug. But you can't simply plug the rough cast hole!

The point is, the core plug is there to plug the hole left to release the sand core.

 

'LMS2968' is quite correct in saying that the location holes left by the core, ie the holes that require plugging, will require machining but it would need to be a little more sophisticated than just drilling it with a conventional two-fluted drill. In the workshop I worked in during my apprenticeship of long ago it was standard practice to machine a fine pitch screw thread on both plug and casting, but ... that application wasn't designed for working under conditions of high pressure and temperature steam.

I would agree with 'LMS2968' that an additional function of the core locating holes is to release the material that the core was made from, which I remember being a mixture of horse pooh and sand![attachment=0:yo4u87of]img005.jpg[/attachment:yo4u87of][attachment=1:yo4u87of]img004.jpg[/attachment:yo4u87of]

If you look at the two diagrams I have attached below you of a typical BR Standard cylinder, you will find that firstly the core is circular and doesn't include the centre of the box piston head and also that the core plug goes through the piston head from front to back. I'd be interested if Ian Riley could come in on this one and say just how the core plug was secured. Please Ian!!!

Regards

 

I can't see the MHR spending a substantial sum of money on 73096 with so little time to recoup that investment. I expect that they will get a new cyclinder made up for the loco and get the other bits of damage sorted before the agreement runs out in 2014.

Regards,

Dan

 

Well, looking at the drawing for the MN piston, which is also hollow, this shows it to be a screw in plug which is then "rivetted over".

Looks like that when new, the plug has a extension piece to allow it to be wound in, and you keep winding until this shears off, then you peen the head over which helps to fully 'engage' the threads and in theory should stop it from rattling free...

See here:
http://34058.fotopic.net/p57025303.html

I would imagine that the BR Std drawing says something along these lines...

 

I think the way they were fastened depended on the works they were at... As 73096's were threaded and then held in place with a keyway