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#1 varney

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Posted 15 March 2010 - 07:54 AM

Are my eyes going funny, or is Bob Tedrow's assistant using a D'Addario gauge .017 steel string to cut springs from here:

http://hmi.homewood....pringbender.MOV

?????

#2 Dana Johnson

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Posted 16 March 2010 - 05:34 AM

Are my eyes going funny, or is Bob Tedrow's assistant using a D'Addario gauge .017 steel string to cut springs from here:

http://hmi.homewood....pringbender.MOV

?????

If he is, it is the most expensive way to buy the stuff. You can get a pound of the same thing for the price of a set of strings. First time I've seen a gear reduction for the job :blink:
Dana

#3 Bob Tedrow

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Posted 16 March 2010 - 06:48 AM

Lately I prefer .016"

#4 varney

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Posted 16 March 2010 - 08:53 AM

Very good, Bob!

As I play bouzouki mainly I've always felt there must be some use I could put my old strings to when they come off the instrument. Now I've found one!

I would have thought steel string of gauges .016/.017 would be too light to make lever springs, but I've never tried out a new concertina by Bob or any of the other top guys, so I'm assuming the super fast action must ( in part ) be down to very light springs....?

The springs on my Lachenals are pretty hefty and no doubt contribute to it's sluggish response. Would you or Dana recommend replacing these with handmade ones as demonstrated in the workshop movie, or are the Lachenal levers going to be a problem for springs that light?

Michael.
PS Dana - where can I buy string steel of the kind you spoke about?

#5 Bob Tedrow

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Posted 16 March 2010 - 06:09 PM

.016 steel music wire is a light as I can use without peril of blowing the pads off the tone holes on vigorous compression of the bellows. The levers/posts/rivets have to be carefully set with no binding, pads firm and very flat. Padboard smooth and flat as well. Bushings not too tight and the button/lever/aperture/bushing just right. Posts must be installed carefully and perpindicular to the action board. Button holes in the top concentric with their corresponding entry in the actionboard.

That conquered, .016 wire works pretty well.

#6 varney

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Posted 17 March 2010 - 08:32 AM

Thanks Bob,
I'm thinking that amount of work would hardly make changing the springs worthwhile!

The more I think about it the more it becomes obvious that I really need to start from scratch with this Lachenal - pads, valves, bushings, air leak, new bellows etc before even deciding if the springs need replacing. Grappling with an air leak on one side is the wrong time to even think of lighter springs.

As I'm currently travelling in the states it's really the wrong time to take the instrument apart and strip it down so the overhaul will have to wait until I get home and have my better metal-ended Lach to play while this other one is worked on.

#7 Dana Johnson

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Posted 17 March 2010 - 08:56 PM

Thanks Bob,
I'm thinking that amount of work would hardly make changing the springs worthwhile!

The more I think about it the more it becomes obvious that I really need to start from scratch with this Lachenal - pads, valves, bushings, air leak, new bellows etc before even deciding if the springs need replacing. Grappling with an air leak on one side is the wrong time to even think of lighter springs.

As I'm currently travelling in the states it's really the wrong time to take the instrument apart and strip it down so the overhaul will have to wait until I get home and have my better metal-ended Lach to play while this other one is worked on.

I prefer stainless spring wire to the regular steel music wire, but both make equally good springs. I get mine from MSC industrial supply corp, but there are other places frequented by hammer dulcimer makers and the like that supply music wire in 1/4 lb. to 1 lb. rolls. Both a lot more than you'd need for one concertina. ( a couple used guitar strings or something the like of the proper gage would probably be nearly enough. Most older instruments and a lot of new ones have brass or phosphor bronze springs which appear a lot thicker than the steel, but that is because the metal is naturally less stiff than steel and needs the extra thickness to make up for it.
Noting that you seem to have bailed on the idea of re-springing your concertina, ( sensible ) the"weight" of a spring, or the force it exerts when deflected, is a function of a lot more than the wire gage. fewer coils of this type of spring ( a torsion spring ) means a stiffer spring that builds it's force faster as it is squeezed. More coils makes a lighter spring that has a more constant tension. Larger coils mean a lighter spring, but longer spring life ( there is a minimum coil diameter for any wire gage and metal type that will give decent spring life ). What ever Bob is doing ( taking into account all these factors ) works for his concertinas. Other wire Material/ gage / coil diameter / number of turns, combinations will also work and give a similar effect. A good spring design takes into account the space available, the deflection characteristics you are looking for and makes choices on the wire type and size, and number of coils etc. from there. You can do this by experiment or calculation depending on your bent or by copying someone else's spring that works ( the easy way ) but buying replacement springs is probably the best way since they are readily available.
All that information above is just for those who might think about making their own instruments and get to make their own choices about what they are after. Designing stuff can be fun, but if you can design a spring that will last essentially indefinitely instead of only a few thousand deflections ( a surprisingly small amount of playing ) why not do it. A great resource for all this stuff is the Machinery's Handbook, though these days I'm sure it is all available on line . Heck, there's probably an App for it.
Dana

#8 Frank Edgley

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Posted 18 March 2010 - 07:24 AM

Your Lachenal probably does use a heavier gauge than what Bob, Dana & I use. That's because of the design of the Lachenal mechanism. Because Lachenal did not use a riveted action, but a variation of a hook action, the spring must be used to provide tension to raise the button (and keep the pad in contact with the action board), and also keep the mechanism arm tight up against the fulcrum. Tha arm has a bend right where it passes through the fulcrum, so a separate tensioner spring can't be used. Therefore, one spring, fairly close to the fulcrum, and a bit further away from the button, than ideal, must be used. In order to get enough tension on the button, and thus to the pad to hold it down on the action board, they used a bit heavier spring. Years ago, when I only did repair, I found that Colin's replacement springs didn't seem to have enough tension. The Lachenal design was not the best.

#9 Henrik Müller

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Posted 18 March 2010 - 08:22 AM

...
so I'm assuming the super fast action must ( in part ) be down to very light springs....?
...

I had an idea for a long time that fast action = light springs.
I've had to revise that; they may be featherlight to press, but the other part of the
sequence - closing - must also be fast (and "convincing").

Last year, I changed my (originally steel wire) springs to (heavier) spring brass.
That was better, but I still need to adjust some of them - still too light.

Of course there are individual taste in feel, but light can be too light.

/Henrik

#10 Kautilya

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Posted 18 March 2010 - 09:52 PM

[quote name='Henrik Müller' date='18 March 2010 - 01:22 PM' timestamp='1268918547' post='110020']
[quote name='varney' date='16 March 2010 - 02:53 PM' timestamp='1268747638' post='109952']...

/Henrik
[/quote]
So much useful and helpful information. I now realise too late, after installing the same model in the centre picture following, that I had found a Chinese solution that was slightly overengineered...
Judging by the official quote from the great leader tho, it must have been a spring machine maker for MASSed bands

http://www.anchorchain-china.com/

Edited by Kautilya, 18 March 2010 - 09:54 PM.


#11 Rod

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Posted 19 March 2010 - 03:33 AM

...
so I'm assuming the super fast action must ( in part ) be down to very light springs....?
...

I had an idea for a long time that fast action = light springs.
I've had to revise that; they may be featherlight to press, but the other part of the
sequence - closing - must also be fast (and "convincing").

Last year, I changed my (originally steel wire) springs to (heavier) spring brass.
That was better, but I still need to adjust some of them - still too light.

Of course there are individual taste in feel, but light can be too light.

/Henrik



Make do and mend. I cannot be the only one who has used an adapted safety pin in an emergency. They come in all shapes and sizes with ready made coils and can do a perfectly adequate long-lasting job !

#12 Chris Ghent

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Posted 19 March 2010 - 05:47 AM

Be careful using safety pin based springs long term. I have worked on two concertinas with safety pin repairs and in both cases the pivot was coming out of the action board. The nearest safety pin is typically not weak enough to do the job. Great fix to get you back in the session though.

Chris




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