Introducing the GASKET-VALVE System

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EdvinW
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Joined: Tue Jun 05, 2018 6:02 pm
Location: Sweden

Re: Introducing the GASKET-VALVE System

Post by EdvinW » Thu Jul 04, 2019 9:35 pm

Brendan wrote:
Tue Jul 02, 2019 8:06 am
Good news bad news on the Gasket-Valves, it seems!

Glad you like yours Edvin, but sorry to hear you're having issues Lizzy. What do you mean by the valves sounding?
I'm overall happy with my purchase, and I hope to buy more after some more experimenting with how to best make use of them and how to eliminate the aforementioned sounds.

The worst sound is a kind of "bubbling" sound, or a fluttering, which happens when I blow. The valve is lifted by the wind and partly covers the blow reed, instead of covering the draw reed slot as it should.

I've tried to mount the bottom plate with the valves but leave the top plate off, and when I blow through the hole the valve indeed lifts from it's place. During normal operation preasure builds up when you blow into a hole, pushing the valve closed. If the flow through the chamber is large compared to the pressure, it might be enough to lift the valve. Once a valve has been lifted the valve easily gets bent while flapping so that it remains more or less lifted from the draw plate even when the hole is not in use. This makes the valve even more suseptable to lifting and fluttering, propelling a vicious circle. Placing a fluttering gasket-valve sheet on a falt surface, the valves are clearly lifted.

HOW TO FIX IT:
I've done two things which seem to eliminate the fluttering.

The most straight forward one is to simply bend down the valves so that they point downwards instead. I start to fold them at their base, but stop before an actual fold is formed. There is room for some experimenting here. Maybe it would be better to place the fold/bend some distance into the valve, or do some more complex reshaping, but simply bending at the base seems to work. It might be possible to actually make a fold along all of the sheet; the pressure from the comb should keep it in place anyway,
but I haven't dared to try with one of my sheets.

I've also regapped the harps to have smaller gaps on the blow reeds than I typically prefer. This reduces the amount of air that escape through the blow reed slot when attacking the note. I reason that as this raises the pressure/airflow ratio the valve should be less prone to lift.

Lizzy wrote:
Mon Jul 01, 2019 8:56 pm
Actually, some of my gasket-valves sounds too, and i have done it after the recomendations . The valves to Seydel session are worst. Several of them sounds. Seydel favorite valves are better but still have a couple of holes sounding. I have done the process to fit them a couple of times over again but so far i have not managed to make them silent. :roll:
This is my experience as well. My Lee Oskars did flutter a bit, but trying to check the aligning a few times and regapping them as outlined above was enough to fix it. I think there might be something with the positioning of the screw holes in the SSS model that wrinkles the sheet ever so slightly, which in turn lifts the tips of the valve. I'm not sure though, there might also be some difference in the factory gapping between the models.

There is another more benign sound as well: a slight buzzing that some times sound even when the setup otherwise works fine. To some extent this can be reduced by adjusting the positioning of the sheet and regapping, but I haven't managed to eliminate it completely.
Edvin Wedin

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Brendan
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Re: Introducing the GASKET-VALVE System

Post by Brendan » Sat Aug 10, 2019 3:36 pm

Thanks for the helpful feedback Edvin and others.

For riveted reed harps, it helps to sand the draw reed flat. However since that's beyond the skills of most players I've started to add rivet holes in the Gasket-valves, allowing the rivet stubs to poke through and ensure they lay flat on stock reedplates. The Seydel GVs will be next to get this feature.

I'm surprised at reports of the valves lifting, as they should come with a very slight curve towards the reedplate, giving them a propensity to lay flat. That could be down to distortion from protruding rivet ends perhaps.

I'm finding the Gasket-valves in my harps very reliable, so am a bit surprised and concerned some of you are reporting issues. I'm heartened by the fact that since we started selling them, there have been very few complaints - so most users must be happy. But improvements are always possible, and I'll try to make tweaks to get them more 'slap in and forget'.

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