Roller Bearing vs. Friction Bearing

Friction bearings required oil, and had brass bearing blocks, with cotton wadding that would catch fire when oil was low, aka: a hotbox
They had lids that were lifted up to add oil to the journals. Teams of oiler men were once employed on incoming trains to a yard, to open, oil, and close journal lids.

Some friction bearing truck sideframes were retrofitted to be roller bearing trucks.

Today almost all trucks are new roller bearing type.
 
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cascaderailroad said:
Friction bearings required oil, and had brass bearing blocks, with cotton wadding that would catch fire when oil was low, aka: a hotbox

Today almost all trucks are new roller bearing type.
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I'm not sure if they were actually brass, dunno if they could really take the weight. And I would rephrase that last line to say ALL. Journal (friction) bearings have been banned from interchange service for many years now. (think manufacture stopped in 1960s, but service permitted until 1975ish?????) May also be reason why steam services may not be popular with Class 1 RRs (ie, potential for shearing off axle). However, hotboxes DO occur with roller bearings, there was an awful one in Canada within the last 20 years. Shouldn't really happen because they are sealed against contaminants, but something got in, jammed the rollers, burned through the grease and heated the axle end to well over 1000* F.
 
Interesting. I'm still trying to figure out why the temperature is so critical with friction or roller type bearings. What could ultimately happen?
 
An axle can burn off ... if a bearing, or hotbox gets blue hot !

I once saw a wheel that had its hand brakes on, and after dozens of miles it was blue hot, smoking the roller bearing grease ... touch a stick to he wheel tread, and it ignites ... so hot it would take your fingers clean off !
 
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cascaderailroad said:
An axle can burn off snip....snip
so hot it would take your fingers clean off !
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So true. In the days when axle boxes had to be topped up regularly the greasers would always check the heat of the axle boxes before opening them. Just by putting a hand close to the axle box but not actually touching it.

Bill69

p.s. The bearings were actually made of phosphor bronze not brass. (from Wikipedia)" These alloys are notable for their toughness, strength, low coefficient of friction, and fine grain. The phosphorus also improves the fluidity of the molten metal and thereby improves the castability, and improves mechanical properties by cleaning up the grain boundaries."

Bill69
 
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Friction bearings are also known as plain bearings and are white metal, Australia still has allot of stock with plain bearings, they can still take allot of weight, some wagons built in 1920s could take 60 tons and run at 50mph, plain bearings also roll easier than roller bearings at slow speeds, and the opposite at higher speeds, roller bearings keep momentum while plain bearings create lots of drag.

Cheers.
 
A third name is solid bearings. The term "friction bearings" was coined by a roller bearing manufacturer to promote their product. Of course all bearings have to deal with friction.
 
Azervich said:
Friction bearings are also known as plain bearings and are white metal, Australia still has allot of stock with plain bearings, they can still take allot of weight, some wagons built in 1920s could take 60 tons and run at 50mph, plain bearings also roll easier than roller bearings at slow speeds, and the opposite at higher speeds, roller bearings keep momentum while plain bearings create lots of drag.

Cheers.
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Interesting, remember reading in old Trains mag that during WW2, the ACL put roller-bearings on "captive" cars in phosphate service. It was stated that they were a nusciance, because after they had been set out, if the brakes weren't set, the slightest breath of wind would set them rolling! Completely unlike friction bearings, which have a certain amount of "stick" due to the nature of physics (sliding [stationary] friction takes more force to overcome than rolling friction, but once you "break out" of stationary sliding friction, the active sliding friction requires much less force to fight)
 
If you consider the mechanics, a whitemetal or bronze bearing is metal to metal when stationary but once it is rotating it is supported by a film of lubricant. A roller bearing has little or no 'stiction' effect but when rolling there is rolling resistance due to the minute deformation of the rollers and housings under pressure.

Peter
 
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