Ideas for changing a diatonic harp tuning on the fly

[Brendan]

I watched your video. Nice work Dom - your test apparatus certainly demonstrates the potential to work well for instant, accurate retuning on the fly once it's fitted with a spring.

Regarding coverplate clearance, here are a couple of ideas:

1. Try putting a couple of spacers maybe 2-3mm thick at each end of the drawplate behind the central coverplate screw holes. This will tilt the lower cover away from the drawplate at the rear, whilst maintaining a good fit at the front in the reedplate groove.

2. To slim down the magnet holder, try replacing the grub screw/magnet combo just with strong small magnets with a good pressure fit in the slider part. Probably 2x2mm N52 will be fine. Then adjust them slightly in their settings to give the semitone down note shift when the slider is pushed in. Because they're fixed and always giving the same note drop, once you have the positions correct there should be no further need of adjustment, I assume.

As you say, the magnets have a limited range because the draw reeds rise too high when going beyond a semitone drop.

I wonder if Edvin's idea of attaching a micro magnet of opposing polarity on the reed might help, assuming it could be fixed well? Then your slider magnets would push the draw reeds down into the slot, instead of up away from it. But possibly that might close the reed gap too much, so it wouldn't play well...?

Roman's idea of actually moving micro magnets along the reeds from the middle to the tip to act as weights sounds great in theory, but it boggles the mind about how it could be achieved in practice! 🥴

It's a Quixotic task that is fun to observe for us looking on . I'm guessing in the end you'll find an alt-tuned half-valved 10-hole chromatic does the job so much more easily that it's worth the trade off in size, but I still hope you succeed!

[FingerSinger]

I have played with magnetic field + steel reeds (aka turboslide principle) and so far my conclusion is that i need to looks elsewhere for my “irish harp style” harmonica.
The problem is that it looks like it’s only possible to lower reed pitch down for about a semitone via magnetic field, while i want to retune from standart richter to paddy, which means 2 semitones.
So for now i have only 2 ideas - either 2 reeds per hole with some muting device (but that means some heavy surgery of the harp / comb) or using magnets as weights (but need to find the way to do it smoothly)

[dominico]

I'm guessing in the end you'll find an alt-tuned half-valved 10-hole chromatic does the job so much more easily that it's worth the trade off in size, but I still hope you succeed!

I'm guessing you may be right! I'm holding this Trochilus and it is barely bigger than a diatonic, and it surprised me how well it plays. If it weren't for the slide it would easily fit in a pocket. I'll do another post on it sometime soon.
But, oof, I go in that direction and that's a whole lot of reeds I'll have to retune...

[FingerSinger]

I was experimenting with micro magnets as weights and it works quite nicely.
I'm not sure I want to go this way due to possible danger of magnet swallowing though. They seem to hold quite firmly on the reeds, but still, as far as I know it's not at all desirable to have super strong micromagnet inside your body So just wanted to remind you - be careful with magnets!

[dominico]

The problem is that it looks like it’s only possible to lower reed pitch down for about a semitone via magnetic field, while i want to retune from standart richter to paddy, which means 2 semitones.
So for now i have only 2 ideas - either 2 reeds per hole with some muting device (but that means some heavy surgery of the harp / comb) or using magnets as weights (but need to find the way to do it smoothly)

I was experimenting with micro magnets as weights and it works quite nicely.
I'm not sure I want to go this way due to possible danger of magnet swallowing though. They seem to hold quite firmly on the reeds, but still, as far as I know it's not at all desirable to have super strong micromagnet inside your body So just wanted to remind you - be careful with magnets!

I thought I would give this a try today! Using them both as a weight and seeing what happens if I weight the reed with a repelling magnet to the "turboslide magnet".

But yes, I definitely don't want to swallow any of these small magnets

[dominico]

I was experimenting with micro magnets as weights and it works quite nicely.
I'm not sure I want to go this way due to possible danger of magnet swallowing though. They seem to hold quite firmly on the reeds, but still, as far as I know it's not at all desirable to have super strong micromagnet inside your body So just wanted to remind you - be careful with magnets!

I tried two quick experiments today: One of them was using 2mm x 1mm magnets as "weights" for the draw reeds, on the coverplate side so I don't accidentally swallow them It was actually very quick and easy to drop a magnet on and slide it around using my titanium tweezers to get the exact pitch I was looking for.
I marked the spot where the magnet sits with an engraver on the reedplate next to the reed.
I pulled it off, dropped it back on again, and had the pitch I was looking for again in just a few seconds. That was pretty cool! It may start doing this intead of blu-tak on Seydels, I'll carry one around for a week or so and see how it goes.
For the blow reeds, since they are riveted on the "hole side" of the reedplate, the 2mm magnet was just too wide to attach them from the coverplate side, I've ordered 1mm x 1mm we'll see how those do for the blow reeds.
So with the magnets, right now I can switch between normal, "dorian" and easy third tunings just by moving the magnets to their indexed spots on the reeds.

In the photo below on the draw 3 reed I've indexed two spots, the spot closer to the tip drops the reed a full tone, the spot below that one drops the reed a semitone

magnetindexdo.jpg (634.27 KiB) Viewed 92 times

The other thing I did was put a magnet on a reed and then put the opposite polarity magnet in the turboslide.
It raised the pitch!
This is very cool. Though it would require even more coverplate clearance than I currently have in order to further explore this idea as something practical.

Regarding the drawplate turboslide, I am making progress. Ultimately the standard coverplate clearance just isn't enough space to make everything work, but on the upside I created a 1mm spacer for the coverplate to sit on and that seems to be doing well.

capture.PNG (168.65 KiB) Viewed 92 times

I also found smaller set screws, 3mm x 3mm. If only I could find 3mm x 2mm that would be the bees' knees!

I've settled on using 2mm x 1mm magnets for the tuning. They are weaker than Jim's turboslide magnets, but I've found that they can at least lower the pitch by a semitone, and the pitch is more stable, with a natural and pleasant sounding timbre. I cannot tell that the pitch is being altered by a magnet, whereas with the stronger magnets you can tell rather easily by thier almost artificial sounding timbre.

I took a page from Jim Antaki's blowplate slider and created an integrated spring just using the natural elastic properties of the plastic I'm printing with, so that's one less component to have to source.

After looking closet at Brendan's overblow booster design I've decided that it is a better slider mechanism that what the original turboslide was doing. So my next slider iteration will look very much like a marriage between the overblow booster and Turboslide, but on the draw plate.
I'm currently drawing out the overall slider platform, which will ideally be usable for other projects as well in the future.

When I fix the draw slide in place it sounds very nice. I just need to get the tolerances tight enough for the slider to work predictably.

I may have to switch to the .2mm nozzle on my printer, rather than the standard .4mm. Prints will take longer and I will probably have to recallibrate my XY compensation, but I'm so close to a workable solution I can taste it

[triona]

Regarding the drawplate turboslide, I am making progress. Ultimately the standard coverplate clearance just isn't enough space to make everything work, but on the upside I created a 1mm spacer for the coverplate to sit on and that seems to be doing well.

Why not use the higher coverplates from the Seydel 1847 Classic Low? They leave about 2 mm more space above the reedplate. You ca buy them single as spare parts. If you only want to use one on the blow reed's side, you can fit two harmonicas with one pair of covers.


dear greetings
triona

[dominico]

Why not use the higher coverplates from the Seydel 1847 Classic Low? They leave about 2 mm more space above the reedplate. You ca buy them single as spare parts. If you only want to use one on the blow reed's side, you can fit two harmonicas with one pair of covers.


dear greetings
triona

Yes! This would very much work. I forgot you mentioned they are bigger. This is why I should post my updates more often, you all give me good feedback.
I might have to speak with a Seydel rep though, looks like the replacement covers are 30 bucks a pop if I buy them individually.

[dominico]

No printing right now due to a thunderstorm and shakey power.

I'll give it a print in the morning, but I think we are getting somewhere with the dual draw and blow turboslide design.

The "integrated plastic spring" worked, but I thought it might be more fun (and not subject to eventual material stress failure) to have the slider spring mechanism work through magnetic repulsion. So we will give that a go in the morning when I can print again.

turbodurboslide.png (209.87 KiB) Viewed 85 times

Regarding the "magnets as an even quicker alternative to blu tak" its only been one day but I've carried the thing around in my pocket and played a bunch and the magnets haven't budged. I'll keep carrying it and see what happens.

[triona]

I might have to speak with a Seydel rep though, looks like the replacement covers are 30 bucks a pop if I buy them individually.

I know that they are not cheap. But it seems they cost twice as much in the US than in Germany - not including salestax. And there are 5-packs for 100$ as well. They are not even listed in the online shop. But I know that they are available. I have already bought a couple of them to upgrade my old low harps from the days before there were the higher covers. But if you only replace the bottom coverplate where the draw reeds are, it is only half the costs. Or you might try to print them as well?

Indeed, we have the same problem here when buying something from the US - and from UK as well since new.


dear greetings
triona