# Factor of Adhesion



## CSXfoamer1997 (Jan 7, 2019)

Factor of Adhesion is the weight of a locomotive (in lbs) divided by the tractive effort (in lbf). But that is on dry rail.

How much does adhesion typically decrease on oh say wet rail, snowy rail, and icy rail?

For instance, the GE AC6000CW has a factor of adhesion of 2.35 on dry rail.


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## cirdan (Feb 6, 2019)

50% loss is easily possible.

Under extreme conditions up to 90% can be lost.

On modern software-controlled locomotives, the leading axle or truck can be controlled to slip slightly faster than the other axles so as to "clean" the surface of the rail, and thus partially restore adhesion.


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## CSXfoamer1997 (Feb 6, 2019)

cirdan said:


> 50% loss is easily possible.
> 
> Under extreme conditions up to 90% can be lost.
> 
> On modern software-controlled locomotives, the leading axle or truck can be controlled to slip slightly faster than the other axles so as to "clean" the surface of the rail, and thus partially restore adhesion.


Hmm. That's interesting!

Btw, what is the difference between the Factor Of Adhesion and the Rail Coefficient? I was asking, because I read that the Dry Rail Coefficient can be as high as 0.78.


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## cirdan (Feb 7, 2019)

Not 100% sure here, but I think it's a question of definition.

Factor of adhesion is weight (well, I think mass actually?) divided by tractive effort.

Rail coefficient is the inverse, so tractive effort divided by weight


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## TinCan782 (Feb 7, 2019)

Related to this discussion...

_*Getting a Grip on Friction Management*_

https://www.rtands.com/track-maintenance/friction-management-railroad/


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## cpotisch (Feb 7, 2019)

cirdan said:


> Factor﻿ of adhesion is weight (well, I thi﻿nk mass actually?) divided by tractiv﻿e effort.


It is actually weight, not mass. Weight is just mass times acceleration (in this case gravity), so is just the force down. The mass itself is irrelevant when calculating the factor of adhesion or rail coefficient.


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## cirdan (Feb 8, 2019)

cpotisch said:


> It is actually weight, not mass. Weight is just mass times acceleration (in this case gravity), so is just the force down. The mass itself is irrelevant when calculating the factor of adhesion or rail coefficient.


Yes, of course. Obvious really, when I think about it.


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