How is the function of" Differential" achieved in Railway Engines/Coaches(like motor vehicles)?

Question

How is the function of" Differential" achieved in Railway Engines/Coaches(like motor vehicles)?

Answer 1

To add to the answers above, the latest locomotives from EMD and General Electric have self-steering radial trucks.

In self-steering trucks such as the 3-axle HTCR trucks used on EMD locomotives since the SD70 series, each of the three wheelsets in the truck can independently swivel to follow curves in the track.

Answer 2

There is no differential. The axles are solid, and the wheels turn in dead sync with each other.  Yes, on sharp curves this causes wheel chirp and scuff, and other sounds too as the flanges hit the side of the rail.

What happens on broad curves?  There's a slight taper on the wheel tread,

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so that as the wheel drifts left of center on the track, the left wheel is turning on a larger diameter, and the right wheel is turning on a smaller diameter.  This makes the axle want to "turn right" back to center.  That's why trains self-center on the track, and you rarely hear a flange hit the side of the rail except in a sharp curve.

Answer 3

The wheels are tapered across the tread.

The taper allows for the wheels to turn at slightly different speeds when traversing the curve, since the outside wheel must cover a slightly longer distance than the inside wheel. This taper also allows for keeping the wheel/truck tracking correctly when on straight rail as well, reducing excessive lateral movement, called truck 'hunting'.

Even so, there is still 'flange bind'.  So to help, where there is curvature of any great degree, there are lubricators at each end of the curve, with underground reservoirs, that automatically lubricate the flanges of the wheels as they pass over them.  The flange activates a mechanical pump that greases the the flange with the curve grease in the reservoir.

Answer 4

I think Hoghead explains it best, the wheels are on a solid axle so a diferential of speed as in your vehicle does not exist. Curves on a railroad are never as tight as in a roadway. Still, a stiff 3 axle truck on a 10 degree curve does a lot of grinding and groaning.

Answer 5

there are no differentials on locomotives.... the diesel engine sends the power to a traction motor that turns the wheels...

Answer 6

Not too sure about Hoghead's last paragraph, the flange bind lubricators and all, but the first part of his answer is spot on.  Locomotives and rolling stock do not have differentials, they have solid axles and the wheels and axles turn at the same rate.

Answer 7

If you are refering to the differential in the drivetrain, the electric drive motor is attached to a gear case through which the trains axle passes. In some cases the axle has a gear on it which meshes with the idler gear which meshes with the motor gear. In other cases the motor gear meshes with the axle gear alone. Each axle has a motor and gearcase.