RE: [Harp-L] Gapping & Embossing and the "three angle valve job"

[Blunt White <playharp@xxxxxxxxxxx>]

I believe aerodynamic drag plays a big part.  Reducing drag reduces resistance which makes the reed easier to move.  If I am doing a full rework I polish the reeds with a Shofo Brownie Point (dental polishing tool).  I note positive effects and in the long run less oxidation and stuff adheres to the reed.  A recent post mentioned waxing the reed plate around the slots to prevent windsavers from sticking.  I am going to try polishing the reed to an even smooter finish.   

 

It would be fun to have an engineering lab and the time to explore the effects of reducing air drag.  The formula 1 guys and bike racers chase drag.

 

Blunt 
 

 
> From: amaccana@xxxxxxxxxx
> To: Harp-L@xxxxxxxxxx
> Date: Thu, 14 Jan 2010 13:18:57 +0000
> CC: 
> Subject: [Harp-L] Gapping & Embossing and the "three angle valve job"
> 
> Car buffls and hot rodders will be aware that hogging out the inlet ports is
> the conventional starting point for extracting more power from a stock car
> engine.
> However two engineers published a paper in the Institution of Mechanical
> Engineers about fifty years ago where they established that merely rounding
> off the corners on the inlet valves and their seats - the so-called "three
> angle valvejob" substantially increased gas flow without any other
> enlargement of the ports - particularly at low lift.
> l think it was Rick Epping who remarked some months ago that Hohner found a
> noticable effect on performance of harmonica reeds caused by slight
> chamfering of the reeds. Of course the embossing process would also cause
> chamfering of the reed plates (corresponding to the valve seats in the
> automotive example)
> All this suggests that the benefits of the embossing process may indeed not
> be just about reducing the gap, but may be due to changing the nature of
> the gas flow in the gap when the reed is doing its thing.
> By the way another useful tip Rick Epping gave in this connection is that
> one of those old microfiche readers is a great tool for examining the gaps
> in a reed plate. If you come across one in a junk sale it might be
> worthwhile to speculate five bucks!
> Beannachtai
> Aongus Mac Cana
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