Hump Yards - The Booster Retarder
 

<<'booster-retarder' very interested in the Dowty system... how does it fair up to a clasp system and have you any idea which would be better on a very steep descent... (better start this as a new thread... so as not to hijack the original posters thread)>>

To tell you the truth I don't know a lot about the clasp system but this is what I do know about retarders.

I think the first time I heard about them, apart from mags, was on 'Tomorrow's World'..... high tech. For Dowty, it was the low technology of their business, but a big money earner - I visited their works in both England and South Africa on occasions.

As I understand it, both a retarder and booster-retarder need a gradient. Both types consist of a hydraulic, unpowered cylinder with a piston which is compressed as the wheel of the car passes. The retarders are placed horizontally outside each rail, there are 3-4 per meter of rail.

For an overspeed car, a booster retarder will absorb more energy as the wheel compresses the piston than it returns when the piston releases behind the wheel, for an underspeed car the piston will return more of the energy to the rear of the wheel so aiding the motion of the car; a retarder just absorbs enough energy to, in theory, maintain a top speed for the car descending the hump.

It's all in the shape of the piston head, I suppose! I can talk more about hump yards but this is a starter for the current thread.