Re: Roller Bearing advantage - busted


devansprr
 

Looks like it will take some concentration on my part to stop using "friction bearings". Meant Journal bearings. Busted. Correction below

--- In STMFC@..., "Dave Evans" <devans1@...> wrote:

--- In STMFC@..., "Mike Brock" <brockm@> wrote:

Well...what the hell...everyone else seems to have commented on some part of
this subject so why not me?

From The Steam Locomotive by Ralph Johnson, Chief Engineer of Baldwin
Locomotive Works, 1942, "Roughly it may be said , that the ratio of
resistance in starting a car equipped with roller bearings, as compared to
one equipped with solid bearings is eight to one in favor of the roller
bearing". "As the speed of the train increases the difference in frictional
resistance between the two types of bearings decreases rapidly, and above 10
mph the difference becomes very small. In cold weather the starting
resistance of a train with solid bearings is quite high and therefore the
acceleration of a train equipped with roller bearings is aided very
materially". " As a general propostion it may be stated that, by the use of
roller bearings, the journal friction will be reduced 50% at starting,
approximately 10% from 5 to 35 mph and nothing above 35 mph".

Reckon he knows anything?

What do I call non roller bearings? Depends upon how many beers I have
consumed.

Mike Brock
Mike,

I hope my latest post does not drive you beyond a six pack....

This seems like a good starting point for 1942. What surprised me from reviewing the car builder's cyclopedia was the immersion of roller bearings in oil. This would no doubt significantly increase the friction of roller bearings.

There has been significant progress in reducing roller bearing friction since then - not sure where things stood at the end of this group's era (1960), but roller bearing friction today, at speed, is much less than the JOURNAL bearings of old. Friction that results from trucks tracking through curves is also reduced (by a combination of better bearings and better truck geometries), such that the old curve compensation standard for laying out right of way may be out of date (note - this is a theory based on some analysis of a very complicated subject a few years ago that I am not going to get into again - not worth my time.)

One 2003 engineering report I have from a prototype truck manufacturer indicates that rolling resistance of modern freight car trucks on tangent track is only 1.8 pounds per ton of car weight - without any speed dependency. The increased car resistance with speed is now mostly aerodynamic. Tapered roller bearings have come a long way.

Dave Evans

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