BR Standard class 6 No. 72010 'Hengist' and Clan Discussion Thread

Regarding the casting of new cylinders, I wonder what experience there is out there of using SG iron for cylinders?
If SGI was used for the pistons as well that should remove the need for liners as well. But what about the wear in the bores?

Things are progressing with the project, watch the website.

 

Unless my memory is playing tricks did'nt Duke Of G have her cylinders made from SG Iron . . . .

{For those that dont know SG iron is much stronger than cast iron due to the additives effect on the grapite with in the structure - in simple terms turns the 'flakes' of graphite into spheres} Metallurgy for beginers leason over . . .

 

And the quality is better controlled. Do,nt know about SG running against SG though............

 

Also of course is Meehanite to be considered........

 

Pardon?

Regards

 

Yes sorry was,nt thinking. www.meehanite.org should tell you all about this process. It is used for high quality castings.

 

Spelling lessons to follow .-)

 

Web site just updated with news of progress with the new cylinders. I understand SGI is proposed for the castings, let's hope it has a better durability than other grey iron castings which have failed lately.
Seems like the message is, 'Hengist project' is coming to a railway near you, watch out for it!!

 

No question about that, it is better. Much finer grain and easier to machine, just a tad more expensive.

 

That's interesting news given that the drawing shows the casting to be made out of steel with a cast iron liner fitted. Mind you, some of the cast irons these days are top quality and far easier to cast than steel.

 

Apparently, casting steel for such a complicated form is rather difficult nowadays, difficulty = cost, SG iron can be cast easier and give as good a structure as the steel, without the cost of the liner. Add an SGI piston and the correct steel piston rings and job's a good un! So the man who knows says anyway.

 

All things considered, SG Iron is probably the best material for the job. Unlike traditional cast irons, it is quite ductile. I don't know about Tornado, but 71000's replacement cylinders were SG Iron.

 

Before going too far down the road of proposing the use of SG Iron instead of steel with grey iron liners has anyone confirmed the self lubrication properties of SG Iron is comparable with that of regular Grey (flake) Iron castings? Until that is confirmed I must advise a degree of caution.

 

Perhaps one of the Mid Hants crew on here could find out what is the material spec of 73096's new cylinder.

 

Steve, were they lined, do you know?

 

No idea but I can't see why they should be.

 

My understanding is that SG is much better self lubricating than grey flake because the graphite is held as nodules rather than flakes.
The information is that liners would not be required with SGI as it is hard enough and has enough lubrication built in(?).
Liners were only required with cast iron because of the dodgy quality of the cast iron.

 

Thanks for the input. In that case it makes sense to go with SGI. That information also fills another gap in my knowledge of metallurgy.

 

Liners were fitted in cast iron cylinders when, after re-boring, the bore of the cylinder became larger than acceptable limits. Cylinders would not be made of "dodgy quality" cast iron for obvious reasons.
The spec given on some drawings is Cast Iron (Cylinder Quality). This also applies to cylinder end covers.

 

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Which doesn't explain why 76079 had a liner from new. The truth is it had a dodgy quality casting!