Bellows for Iron Smelting (the measurements!)

Recently I was asked by my friend Mark Pilgrim (interpreter at L'Anse aux Meadows NHSC) for the actual measurements of the iron smelting test bellows I built for the 'Vinland' series. This unit would also influence the theoretical design of the 'Icelandic/Hals' series.

'Smelt Test Bellows' - shown as part of the Icelandic furnace layout.

As it turns out, although there are some earlier postings here describing this test bellows, I never actually published any physical measurements of the unit.
I refer you to these past postings on Bellows Reconstruction : 
ONE / TWO / THREE / FOUR

Rough Design with measurements

Depending on the operator, this bellows has been found to produce air volumes in the range of 700 litres per minute.
In practice it has turned out that this unit, over the course of a smelt in one of our 'standard' furnaces (about 25-30 cm ID), produces air = burn rates a bit on the low side (more typically in the 12 - 14 minutes per 1.8 kg charcoal burned). The net result is usually lower yields, into the range of 20 % return.

In comparison, the same furnace, with identical ore - but with the higher volume electric blower, produces higher quality results. (Both in terms of bloom density and yields into the 25 - 30% range.)