D-Type Spring & Loop Action

In the 1930s a type of action with fewer components (cheaper to make and smaller) was often fitted to small budget-price grand pianos. The black and white photo shows a catalogue illustration of this type of action made by the UK piano action manufacturer Herrburger Brooks. Below it, is a photo I took of one of these actions recently. (The catalogue picture is of the bass end, my photo of the treble end).
For comparison, at the top is a full grand action, from a top quality action using some modern plastics materials.
As you can see, the D-Type Spring & Loop action is much simpler. The full grand piano action is subtle, and is designed to afford very fast “repetition”; the ability to repeat notes very quickly and reliably without letting the key all the way up. Dr. Brian Capleton in his excellent Piano Action Regulating, A Reference for Students and Professionals says of the D-Type Spring and Loop action that “The action is as much capable of sensitive repetition as the roller action, when it is well-regulated”.
Perhaps it depends on what is meant by “sensitive repetition”, but it’s difficult to see how such a cut-down design can function as sensitively as the full roller repetition action. If it did, why bother to make the more expensive actions? In any piano I’ve played or worked on which has a D-Type Spring & Loop Action, the action simply isn’t as good. It doesn’t have the same feel. Since these were generally fitted to cheaper pianos in which other design compromises were made, the general quality of these pianos is such that it’s not worth spending the money on the time necessary to fully re-regulate the action.