Cut Off

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Tony Attwell
Posts: 46
Joined: 25 May 2007, 10:34
Location: Johannesburg, South Africa

Cut Off

Post by Tony Attwell »

What is the minimum cutoff that be applied to our locos, the 24, 19D and 15F?

I have noticed that that drivers make very few adjustments to this setting during the journey. In theory, this should be adjusted continuously to provide the most economical use of steam.

I have only heard of one instance some time ago where a driver controlled a GMA by adjusting the cut off instead of adjusting the regulator. However this control is fascillatated by the Hadfield type of reverser.

Any comments from those with footplate experience.

Regards, Tony Attwell
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John Ashworth
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Joined: 24 Jan 2007, 14:38
Location: Nairobi, Kenya
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Re: Cut Off

Post by John Ashworth »

In David Wardale's book he stresses that the locos should be driven using the cut off rather than the regulator. He wanted the regulator fully open, and he ordered the removal of the teeth that hold the regulator partially open, so that there were only teeth right at the beginning and right at the fully open position. Apparently it wasn't popular with drivers.

But, like Tony, I notice that most of our drivers now make more use of the regulator than they do the cut off.
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Brendon Anderson
Posts: 124
Joined: 03 Jun 2008, 14:55

Re: Cut Off

Post by Brendon Anderson »

The gradient profile of the line would also dictate how a locomotive is driven. For example on the uncompensated, 1 in 30 gradients here in Natal, you could not drive and control a locomotive using the reverser alone.

To reply to the first question question about what the possible minimum cut off is, 30% seems to be a common preference that I have witnessed from drivers over the years. For locomotives like the 15F and 19D this is quite acceptable, but when you look at short travel valved locos like USR's 3BR, 40 to 50% is necessary to ensure free steaming.

A few years ago, I watched John Hunt from North Yorkshire Moors Railway driving a Black Five at 10!
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