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I have replaced several broken brass springs in Lachnel 32159, with springs cut from some brass safety pins which I came across in an old sewing box once. They happened to be just the right gauge, and the circular bend is ready made! All I had to do was to add the hook and root to them. Tension was just right compared to the other buttons (very light, making it very easy to play fast stuff...)

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  • 1 month later...

 

The rest (making the rectangaluar bend for the bottom end and shaping the pan for the lever end) is very straightforward and can be customized depending on the exact spring you need to fit. Remember that the more coils or the smaller diameter of the coils, the stronger the spring.

 

Thanks for the input, John, it got me on a couple of right tracks!

 

Small correction, given equal size coils, more coils yields a softer spring since the deflection is spread over more wire length. You are correct that smaller coils has the opposite effect. Coils below a certain minimum diameter will create compression failures in the wire that will cause substantially reduced spring life. More coils produce a more constant resistance over the total deflection of the lever. I find three coils preferable to two and use a wire gage that gives me the button pressure between 50-60 grams. More coils just makes too much offset between the spring legs.

Dana

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Can't remember the last time I had to replace a spring since I started applying the very occasional and tiniest drop of thin oil to all the spring coils. This takes care of any possible slight metal-to-metal friction within tight coils and ensures smooth operation. Certainly does no harm.

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Phosphor bronze, what Dave said. Lovely stuff, I use 24thou. A spring jig can be as simple as; take a round piece of wood about 150mm long about the thickness of a shovel handle. Place a 4" nail in the centre of the end and cut it off about 6mm high. Place a brad 15mm from it and cut it off at about 2mm. Bend the foot that will go into the actionboard onto the wire ( a longer piece of wire, as someone said), and then clip this around the brad and take three turns around the 4" nail keeping the free end of the wire very low, below the edge of the wood if possible. Judge the end point by how spread you want the arms of the spring. Form the lever cradle with a pair of pliers. Cut from the stock.

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Thanks for the correction, Dana, of course you are right. Will edit the misleading posting asap.

@All: I stand defeated. corrected.* One does not need tension to coil springs which I had a chance to see in practice when I visited David Robertson last summer. He uses a low tech jig like the ones depicted in this thread and makes perfect springs with just a pair of pliers, the jig and wire, nothing else...

 

 

* as well as meta-corrected... :blink:

Edited by Ruediger R. Asche
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In a pinch, you can make very serviceable spring by using small or medium sized BRASS (not brass plated) safety pins. They are not as stiff as steel ones. The coil is already there as well as the sharp end. You may wish to pull off the other end, which will give you more material to form the hook. You can increase or decrease the tension by putting needle-nosed pliers into the coil and either increasing or decreasing the angle between the arms.

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that gives me the button pressure between 50-60 grams.

Do you measure button pressure with the ends on or off?

 

I guess what I am really asking is if the button bushings should be set up so that they offer little or no significant resistance or should they be a good seal in which case they would add some friction and increase the button pressure.

 

All of my concertinas are set up so that the bushings add another 30-50 grams to the button pressure when the ends are in place. I don't find that ~100 grams of button pressure feels particularly hard, but I have never known anything lighter.

 

Maybe I should 'iron' the button bushings to reduce friction?

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I measure the button pressure on the lever without the end on so I can adjust the spring. I don't find MY bushings add appreciably, but this depends a great deal on the hole size in the bushing plate and the thickness of the woven felt. I have a little dial 0-100gm force gage that I soldered a piece of wire with a forked end to rest over the lever at the point the button will be. I often do a check when the end is on later. I would not go lighter than 50 gms. And think 100 would be the most I would think is still workable. You can get used to a lot, but I find too much pressure makes a long playing session painful, especially with small of very rounded buttons. I don't agree with someone's earlier statement that lightness equates with speed. I have had a couple nice Jeffries. One set at around 40 grams and the other around 60. It was easier to get nice crisp ornaments on he latter because the extra tension assisted me in getting my fingers up quickly, which matters just as much as how fast you can put them down. Someone with smaller hands and more delicate gingers might find the lower end suited them. The important thing is that the pressure needs to be high enough not to slow the pads to be pushed up by playing air pressure, so you are limited by the area of your largest pad hole since all the buttons want to feel the same.

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  • 9 months later...

 

 

Does anyone have a cool solution figured out or has details about the type of device Bob uses - ie how is the wire clamped to it so that one can still release the entire thing after coiling?

Here's my spring winder, loosely inspired by Bob's video:

https://www.holdenconcertinas.com/?p=831

 

This is brilliant, Alex, thanks for keeping up with the thread as well as sharing your thoughts and technology! :-)

 

Thanks!

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Springs can also be salvaged from old accordions and reused. I got some from a local accordion repairman, cut them down and they worked well. The main thing is to get the wire gauge that will fit into the existing hole. Only tools needed were a wire cutter and needle-nose pliers.

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The important thing is that the pressure needs to be high enough not to slow the pads to be pushed up by playing air pressure, so you are limited by the area of your largest pad hole since all the buttons want to feel the same.

This remark inspires a related issue. This slowing down is present only on push and the opposite happens on pull. The importance of spring tension for sealing likewise is important firstly on push. On pull the pads seal more or less passively. In consequence the calibration of ideal spring force needs to be carried out on push and as Dana said is related to the pad hole area ( and partly to the pad area since the pad lift has to be large enough so that the mantle-shaped opening area between pad and hole becomes larger than the hole area in order not to obstruct the air flow through the hole)

 

Now another thought comes in...Baritones for example by many causes are "slower" than similar trebles models. Reed dynamics is one factor..but... Since the (lowest necessary) spring force is limited by the largest pad holes you expect the possible problems ( among them "slow action" ) related to a too light spring force to be present in the low range firstly. If the spring force is merely at the limit you would expect a significant difference in "speed" capacity on push and pull. Do you? Some experience from this would be interesting to hear !

 

At least in theory fast and energetic playing is expected to be more efficient on pull than on push particularly when playing in the low keyboard range.

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I should read my own posts more carefully! I usually express myself more clearly. I intended to say that you need a certain minimum spring tension to keep your pads sealed on the largest diameter pad holes. For the sake of an even feeling keyboard, that minimum applies to all buttons whether they require it or not.

In practice, I believe the mass of the action is low enough not to materially effect the velocity of closure in the acceptable button pressure range. While bellows pressure will lift pads with a weak spring, it is not like you get a great gust of wind as a result. It is only in the last few thousandths of an inch that the pressure can hold the pad aloft. However, the mass of fingers is quite large, and the pad can close only as fast as the finger can be removed. Higher spring tension acts as an assist to your muscles in lifting your fingers. I find students often have lazy fingers and produce sloppy ornaments as a result. For quick ornaments like rolls and crans, fast finger motion is essential. In this case, the finger tip should move in an arc across the button, depressing it enough to sound at the center of the arc and coming off the button at the end to allow the button to pop up unobstructed.

Dana

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