Duysen Grand Update

[Richard Brekne]

Hi list... just in case anyone is interested in this project of mine, I
thought I might describe my observations so far as they might be
instructive to others on my same path, and interesting for those who may
have already tread this way.

I started scratching my head almost at once when I started to line up the
spread. Nothing added up. And ratios measure by length or by weight seemed
just plain wacky compared to what I have been able to find in old journal
reprints, and information provided with the Standwood kit.

Examples... alligning the spread to the existing magic line results in the
jack center to be about 5 mm behind (wide spread) of the perpendicular to
the hammer shank at the knuckle core. Alligning the spread to conform to
this "perpendicular rule" results in the magic line to be about 2 mm low of
the present point of contact for the capstand and whippen cushion.

My key ratio is rather high on this thing so I have concluded that it has
to be moved in. At present its about .60 and I want it down to at least .55
This means moveing both the whippen and the capstan towards the front about
10-12 mm, which also means that the magic line calls for an even lower
contact point. So the whippen cushions are going to need to be a bit
longer. At present they are 15 mm including the felt, and I will replace
with 20 mm. My objective is to get as close to the 9.0 gram Whippen Balance
Weight Stanwood specifies as I can. (Key Ratio times the Whippen Radius
Weight), and at the same time insure that the Key ratio lifts the whippen
just enough at a 10 mm key dip so that the jack just clears the knuckle at
lettoff / drop when these are at their proper adjustments.

Another thing I bumped into on this thing is what seems to be a long hammer
shank ratio. The shank is 132 mm from centerpin to center molding, with the
center to knuckle at 16.8 This pushes the shank ration close to 8  (7.86~
to 1). This seems a bit high, but I havent thought through what this means
yet... grin.

All in all, it looks like to me that this action was set up origionally in
a pretty helter skelter fashion. I have a hard time imagining what criteria
they use to set the spread, but it seems like they had a balance pin
position, and simply pushed the whippen to a position where you could draw
a line straight through the bottom middle of the whippen cushion to the
center pin of the whippen flange, and put the capstan right underneath the
whippen middle line. Who knows..

Anyways.. your comments are welcome appreciated for sure.. This is my first
attempt at all this, and I feel definately like I am way out on a pretty
thin branch.. If worst comes to worst... I suppose I will have to eat this
one big time... grin.

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway