Alco 48 class loco pics

Pedro, others,
There were some major rolling coal miners strikes which really crippled the various coal fired industries, such as railways in NSW. There were 70 of the 120 55 class standard goods engines converted, and the 20 new Baldwin 59 class were built as oil burners. They were running Bunker C oil by memory, which is thick and heavy, not much better than crude, and had to be heated before it'd flow for refuelling. The crews preferred the oil to coal as their job became cleaner (no coal dust) and the fireman didn't have to shovel anything. Some of the lowly shunting engines were fired on wood during this period!
Coal infrastructure was much easier to maintain and of course being the fuel of choice since the start of the industrial revolution meant it was already widespread in place. So 18 of the 20 59 class were converted to coal and 16 of the 55 class converted back to coal, those that weren't converted were mothballed in case the striking restarted, then scrapped. The two oiler 59s are preserved at Thirlmere-they were used as steam generating plants at a loco depot till the diesel era was in full swing.
There was much more infrastructure set up for coal and it is still cheaper to run a steam loco on coal than fuel oil in Aus, but in the UK the price difference is not so apparent so some of the non-mainline preservation railways are converting to oil firing, such as the Ffestiniog in Wales.

EDIT: In respect to boiler maintenance and clagging up, the 55 and 59 boilers did show faster wear around the firebox tubeplate, as to unclag the oily muck the fireman would throw a handful of sand, or if available (unofficially of course) platform gravel, into the firebox, the grit/gravel would be sucked straight over the arch and through the tubes, wearing them away at the tubeplate.

Railroads in the USA had some very, very, big locos that were simply impractical to coal fire. Some were in the vicinity of 600-700 tons. Imagine the amount of coal they would have to carry to go any distance, and how frequently they would have to refill. Also fuel oil was cheap then. Oil companies had major marketing campaigns to get people to convert to oil heating so the companies could sell an otherwise almost useless product.

Not quite Brian,
Australia's biggest locos weighed 260 tonnes and were mechanically stoked, a bit short of an American Big Boy's 560 tonne weight, which was also mechanically stoked coal fired. The oil firing allowed for designs such as the SP cab forwards, but engines that size could be coal fired in a conventional arrangement.
Some US logging railways, with a seemingly abundant supply of waste firewood, were oil firing their (sub 20 tons) smaller engines-but part of that was bushfire safety.
The USA is a different case, both politically and physically. Virtually all US railroads were privately owned. The US was privately tapping their onshore oil reserves prolifically before AUS was/is. Its all the private ownership where the difference lies.

mechanically stoked---
any explanatory pics Mark?

and its amazing to think
3801
was half as big as the yank engines,,,:eek:

I'm no expert, but quite a few ,maybe the majority of mainline Yanky locos were "screw fed",imagine two small grain augers(very heavy duty!) together in a tube from the tender to loco,they would pulverise the coal so it was almost blown into the firebox.I'm sure there are pic's somewhere Pedro:D,but even looking at a screw fed loco,it's hard to see whats going on!.As for hand firing a Big-Boy,they say you couldn't do it going down hill with the regulator off and a good tail wind:eek:,theere are a couple of good docco's on these legendary giants!,they still have a couple of Challengers running in the states,that'd be good to see!
Cheeers Gregg;)

Yeah as 3 Gees said, mechanical stoking is by way of an auger, usually a small steam donkey engine drove it. Beneath the regular firebox door, there was another door that the coal was drawn through. Jets of steam were used to distribute the coal around the firebox grate. My recollection is it was only one auger not two, but haven't had to look at the big engines closely yet so not sure.
There was also a few experiments using pulverised coal, but that was less efficient than lump coal.

Best photos I have are pretty rubbish, this shows the donkey engine on an AD60 Garratt, and the hopper shape of the bunker
https://www.aulro.com/afvb/images/im...11/05/1487.jpg

mmmmm,you've got me thinking now:angel:,pretty sure I saw a drawing in a book about steam loco history,very detailed and full on book!!,and it was two screws???,I'm sure there were different types,but they are a bit of a mystery,either way,I bet the firemen loved them;),
Cheers Gregg;)