How do retractable buffers work?

[Railer]

Something that always played on my mind is how to the buffers retract when not needed and they can be be pulled out when standard coupling is used. Is it the case of a hydraulic piston is drained/ tapped off somewhere so the buffer can be pushed back when not needed and then the hydraulic piston is re pressurised when in normal use.

 

Is it the same for rolling stock Mk2/3s and for the push pull 201s.

[UP6936]

On a MK2 there is a saddle you put over the buffer shank when they are extended, to retract you just lift this off and push the buffer in by hand, and to extend them you do thr reverse of that

[Railer]

So there is no resistive force on the buffer at all until the saddle is fitted? Effectively the saddle provides all the resistive force to force the buffer to push back out.

[Lough Erne]

The buffer when retracted is sprung as it is against the inner buffer housing which provides the resistance force as it is mounted against a stop plate with the standard rubber and steel disc arrangement. When extended, the saddle is placed on the buffer shank and it effectively acts as an extension of the inner buffer housing and is again sprung as before.

 

Hope this makes sense.

[Railer]

Ok, I'm just wondering how a person can push a buffer back by hand and it stays back when I see locos getting pushed/bounced back from wagon buffers when they release the brakes. If they have the force to push a 100 ton loco back how can a person fully compress one by hand?

[Dhu Varren]

Here is a picture, and a drawing to illustrate the workings of a retractable buffer, in this case an LNER buffer.

 

[Railer]

Ah yes. I can see how that design works. Basically by turning the buffer head 90 degrees all tension is disengaged and it can be pushed back by hand and locked in place.

[Dhu Varren]

No, the buffer head is not turned. To retract, the saddle is removed, and the buffer head is pushed back till it contacts the sleeve, which is the sprung part of the buffer. The buffer shank slides inside the spring, and is not sprung itself. To extend, the buffer head is pulled out and the saddle is fitted between the head and the sprung sleeve. When the buffer is retracted, the saddle is hung on the hook to the right of the picture.