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The D-Type Spring & Loop Grand Action

This is a very short Challen grand piano from the early 1930s. 

Piano makers offer a range at various price points to suit different budgets.  Small grands like this were the cheapest of a maker's grand piano range, in the UK industry.  The total area of the soundboard is smaller than, and the bass strings shorter than, a large upright piano.

"But at least it has a grand piano action, and grand actions are more sensitive than upright actions".  Well, not quite.  Thousands of small grands like this were fitted with a cut-down version of the grand piano action.  This saved both space and costs.

The cut-down version of a grand piano action is called the D-Type Spring & Loop action. Also sometimes called a Simplex action.

Here is how a modern grand piano action looks This is a three-note model, of a Herrburger Brooks action. They were a large piano action maker and sadly closed down in the 1990s.
The line drawing of a Herrburger Brooks grand piano action is from a 1980s copy of their catalogue (I am unsure whose intellectual property this is, as the company sadly went out of business years ago.)  This design has a 'single-wing' Repetition Spring.  The Renner actions commonly used now, have a slightly different design.

Compare the mechanism above with a D-Type Spring & Loop action:
And a line drawing of the D-Type Spring & Loop action, from the 1959 catalogue of piano supply house Fletcher & Newman (reproduced with kind permission):
I don't think I will be giving away important confidential business information if I tell you that the trade price in 1959 for a full grand piano action was £595, while the price for the D-Type Spring & Loop version was £381.

Obviously the D-Type Spring & Loop action has fewer components, therefore was cheaper to produce. 

Dr Brian Capleton in his excellent little book on piano action regulation says that the D-Type Spring & Loop action was capable of sensitive performance when correctly regulated.  But I don't see how it could compare in terms of sensitive repetition and dynamic control, with a properly regulated full grand action. 

The D-Type Spring & Loop action stopped being produced in, I believe, 1967, so even the newest of them is now over fifty years old.  Most pianos which have them, are much older than that, like the little Challen at the top of this page which is almost 90.

In the small grand pianos which had these actions, other cost savings were made, in terms of choice of timbers etc.  So the general quality of these pianos means that it simply isn't worth doing a lot of work on a worn D-Type action.  The normal lifespan of a piano is about sixty years before restoration is required. Restoration is generally only for high-end pianos. The little grands with D-Type Spring & Loop actions were budget pianos when new, and are simply not worth significant expenditure now.

Here is an old catalogue illustration of the D-Type:

They were produced in several variations. The Challen piano at the top has a left pedal mechanism that moves the hammers closer to the strings instead of the usual 'una corda' method of moving the action to the right.  Below, another photo of the Herrburger Brooks and underneath that, a similar action by another maker. No doubt various European piano action makers had their own versions of lower-cost grand actions.
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