Brake blocks

Does anyone know the correct/best composition of iron and additives to make long lasting brake blocks? Our last few batches have worn very quickly even though the foundry have added chromium to the latest batch.

Nigel

 

I'm no expert on the subject but, back in my British Coal days a colleague did some investigation into variation of brake block wear and associated coefficient of friction for underground locos and found that a significant factor was where the foundry left the castings to cool. If they were left outside in the cold air rather than in the foundry itself a harder block ensued, even though the blocks had come from the same cast!

 

To an extend the ones with the best friction seem to be the ones that wear out quickest. What engine?

 

The loco in question is 'Triumph', a 2'6" gauge 0-6-2T which is a tad under 20 tons. The blocks always used to last a fair number of years but one batch last year did about 20 days service and left iron filings in areas we really wouldn't want them. The foundry did cast more sets free of charge but we're still not getting much more than about 500 to 600 miles out of them. The set on another loco have lasted at least 7 years with a similar yearly mileage - the trouble is the foundry that cast them has long closed down.

 

What grade of cast iron did you specify? I always go for BS1452 grade 14 and get acceptable wear and performance from them. I've never had to change any loco blocks for a good number of years, although the coaches do the majority of ther braking. Just looked in the LMA handbook and they specify BS 1452 grade 10!

 

I was just wandering, but what do the grades mean? Is BS1452 Grade 14 stronger/weaker or what, compared to BS1452 Grade 10?

 

I'm a little unsure of the grading but according to Foseco Ferrous Foundryman's Handbook; BS1452 was withdrawn and replaced with BS EN 1561 in 1997.
http://books.google.com/books?id=1BoUNF ... Yl34_X-rRI
But then again BS308 was replaced with BS8888.

 

Unfortunately I didn't specify a grade as the foundry led me to believe they had been supplying brakeblocks to another major railway for some time without any issues.

 

That may be so but everybody understands BS1452 grade 14. It's the same with BS970 EN steel nomenclature. They haven't been in the British Standards for years but most people still refer to the EN numbers.

 

And so do I, Steve. Ones efforts at precision can easily be mistaken for pedantry.

 

Yeah, me too Brian! Strange that the war time emergency number (Hence EN) is more easyly recognised than the technically correct BS, ISO or DIN standard number

 

Have been speaking to others on this subject. Representatives of a certain loco overhaul/hire organisation (no name as I can't speak for them) specify Grade 14 for newly turned tyres and Grade 17 for those that have been in service and work hardened. Basically, Grade 17 is slightly harder than grade 14. Don't know the Brinell number, though and I haven't got a copy of the standard to hand. I'd personally stick with grade 14 for all cases, though.