It’s about the rocks that don’t break – Steve and Fred would have been mates

D David

MetPlant 2017 – Metallurgical Plant Design and Operating Strategies – World’s Best Practice, 11-12 Sep 2017, Perth, Australia


Amongst those whose task it is to design tumbling mills and other comminution machines there is a religious divide between devotees of the Bond method and devotees of methods developed in more recent times. For a decade or so the issue was between the Bond power-based methods and the JKMRC Simulation based approach. The newest methodology to challenge the Bond world view is a power-based method developed by Steve Morrell. As the title suggests, this paper will take some liberty at concluding that Fred Bond and Steve Morrell are separated by history, but not by their approaches to their individual contributions to the science of comminution.

Another conclusion is that although it is good to have diversity of thought, the existing divisions are problematic for those of us signing public disclosure documents. If alternative design methods produce materially different outcomes for the one project then at least one of them is wrong. At some point the unsustainable argument may need to be put in a court that we metallurgists have two or more materially different design methods, each of which is correct! Perhaps a resolution is needed before this occurs?

The works of both Fred Bond and Steve Morrell are each directly related to their contemporary grinding mill design and operational environments. Both their approaches are empirical, borne of observing and measuring real world situations. Both worked with theories that preceded them, gathered their own data and then each saw shortfalls in the status quo.
Fred Bond was an escapee from revolution, a victim of The Great Depression, and claims to have nearly lost his life on a number of occasions during his early site-based experiences. Perhaps he was fortuitously rescued from himself when asked by Allis Chalmers to set up their rock testing lab in Milwaukie in 1930. Fred’s testing led him the conclusion that neither the Kick nor the Von Rittinger theories explained his measurements. His writings on the failings of the old theories caused a similar divide between devotees of old and new methods. After many years, much thought and plotting of data (the old way!) he came up with his now-famous equations (and his third theory) which have stood the test of time, certainly in the world of Bond-era machines.

Coming from England via African mines, Steve Morrell immersed himself into the comminution world of the JKMRC in Brisbane about a decade after Fred passed on. The JK had developed its SAG simulation framework using their own pendulum breakage tester, itself a derivative of the twin pendulum impact device invented by Bond decades earlier. At JKMRC Steve developed his authoritative Tumbling Mill Power equations and was involved in real world analysis of comminution problems on the global stage. Steve’s JK experience coincided with the demise of the rod mill, the rise of AG/SAG milling and rapid expansion in concentrator capacity.

Morrell left the JKMRC to pursue his own interests, which included ongoing consulting demanded by the comminution world. He then turned to investigating a growing list of discrepancies between the opinions of designers and theoreticians and the factual outcomes. The Morrell Method of design arose from a re-examination of ore testing, real world operating data and the glaring discrepancies between design and outcome.

The elements necessary for a relook at the world of rock breakage were in place.


CEEC acknowledges and thanks the Australasian Institute of Mining and Metallurgy and MetPlant convenors and organising committee for organising the MetPlant 2017 Conference.

Abstracts can be found at the AusIMM MetPlant conference website (

Full papers published in the Conference Proceedings can be purchased from the AusIMM website .