Vacuum and air pump

[Ralph Lucey]

Hi. I am starting a rebuild of a Lachenal Anglo and need to build a valve sounding box. Can anyone advise where to buy a suitable pump to use. Im in the UK. Also any links to articles much appreciated. 

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[AndyNT]

Find a 'scrap' piano accordion and use the bellows from that to make a tuning table.

There are quite a few threads about homemade tuning tables over on the melodeon.net forum.

[Chris Ghent]

You could just have said “find a piano accordion…”

[alex_holden]

I made my first one from a set of 8-fold 6 1/4" concertina bellows (actually, they were the first bellows I ever made and they are still going strong). That works fine if you have access to some spare bellows or don't mind making a set from scratch.

 

Later on I made an electric tuning bench using one of these fans:

https://uk.rs-online.com/web/p/axial-fans/1810518

It needs a 12VDC power supply and a separate PWM logic signal to control the speed. Importantly, don't try to control the speed by PWMing the power because that will quickly kill the electronics inside the BLDC motor (guess how I learned that). It's a two stage fan, which gives a lot more static pressure than a single stage. You don't need much air flow to sound a free reed. My earlier experiments with much larger and noisier extractor-type single stage fans were a complete failure. To be honest, I'm using three stages in my tuning bench because I only blew up one of the motors in the first fan I bought, but I think two would probably be sufficient. I'm generating the PWM signal using a Raspberry Pi Pico and a potentiometer, which is total overkill but they are cheap and easy to use and I already had one on hand. I can supply the source code if it's useful.

 

It's very useful to have a Magnehelic vacuum gauge to help maintain a consistent playing pressure, particularly if you're using bellows. The one I use reads up to 500 Pascals and I usually tune at about 200 Pascals (the actual units are irrelevant as long as it has an appropriate range).

 

The reed frame holder is a separate issue, which I don't think I have completely solved yet. I'm planning to build some improved ones soon.

[Don Taylor]

I built a 'constant' pressure pump out of an old a/c hand-held vacuum cleaner and about 12' of shop-vac hose.  I controlled the pressure by using a router power tool controller to control the power to the vacuum cleaner.  All stuff that I already had on hand.  Plus duct tape - of course!

 

I needed a long length of hose so that I could run the vacuum cleaner in a separate room as the constant noise was very annoying.  The controller I kept on the bench with a long power cord back to the vacuum cleaner - I could then dial the pressure up or down as needed.

[Clive Thorne]

2 hours ago, Don Taylor said:

I built a 'constant' pressure pump out of an old a/c hand-held vacuum cleaner and about 12' of shop-vac hose.  I controlled the pressure by using a router power tool controller to control the power to the vacuum cleaner.  All stuff that I already had on hand.  Plus duct tape - of course!

 

I needed a long length of hose so that I could run the vacuum cleaner in a separate room as the constant noise was very annoying.  The controller I kept on the bench with a long power cord back to the vacuum cleaner - I could then dial the pressure up or down as needed.

Same here back in the day, except that it was constant speed, so I rgulated the pressure by having an adjustable "Bleed hole". Bloody noisy, as you say.

[Clive Thorne]

9 hours ago, alex_holden said:

The reed frame holder is a separate issue, which I don't think I have completely solved yet. I'm planning to build some improved ones soon.

What I used to do when I was doing tuning was to have a round hole adjacent to a fixed block of wood, and slide the whole Reed plate up against the block. Had the advantage of tuning the reed in situ, fitted into the reed plate and chamber that it would work in.

 

Obviously only worked for reeds around the periphery (which is all I ever needed), but I guess the interior once could be done with a simple hole in the face of the box.

 

[alex_holden]

13 hours ago, Clive Thorne said:

What I used to do when I was doing tuning was to have a round hole adjacent to a fixed block of wood, and slide the whole Reed plate up against the block. Had the advantage of tuning the reed in situ, fitted into the reed plate and chamber that it would work in.

 

Switchable suck/blow? Before I built my electric tuning bench I saw a video of one made by Scott Bellinger for tuning accordion reed blocks. You can't just reverse the fan direction when you want to switch between push and pull reeds, so it has a clever slide valve mechanism that reroutes the air port to the inlet or outlet of the fan. Not really necessary for the way I hold reeds because they always operate in suction mode, so I just copied the fan and didn't bother with a reversing valve on mine.

 

Here's the video:

 

A bit more information about it:

http://bellingersbuttonboxes.com/workshop/

[Clive Thorne]

8 hours ago, alex_holden said:

 

Switchable suck/blow? Before I built my electric tuning bench I saw a video of one made by Scott Bellinger for tuning accordion reed blocks. You can't just reverse the fan direction when you want to switch between push and pull reeds, so it has a clever slide valve mechanism that reroutes the air port to the inlet or outlet of the fan. Not really necessary for the way I hold reeds because they always operate in suction mode, so I just copied the fan and didn't bother with a reversing valve on mine.

 

Alex, nothing so sphisticated! It was an old cylinder type vacuum cleaner (if you're old enough to remember those), where you could plug the hose in the suck or blow sides. So I tended to tune a batch of suck reeds, then go into the next room to swap the hose over and then do a batch of blow reeds.