Re: CX 12 problems (correction)

[Nicolas Fouquet <bbhcfr@xxxxxxxx>]

Are you really sure that there is no spring on Vern's Harps???
I think I seen springs on these harmonicas, but I may be wrong.
 
Froggy

Snaruhn@xxxxxxx wrote:
Hi,

I should make a tiny correction concerning my post.

At the beginning I wrote:

<< Can we agree that the spring is that piece of wire which moves the slide back? 
<< There´s a coiled spring at the CX 12 and an "open" spring at all other chroms. >>

No, not at all chroms. Vern´s HFC (Hands-Free Chromatic) has no spring because
there´s no slide. Here the mpc is movable up and down and longitudinally.

Just to be correct.

Siegfried 








Thema: CX 12 problems 
Datum: 08.04.04 
An: harp-L@xxxxxxxxxx 
Kopie an: harp-L@xxxxxxxxxx 



Hi CX lovers,

before I comment Michelle´s and other posts on "CX 12 tight slide action" I´d liked 
to clarify what we are talking of. It concerns the term "spring" as used in chromatics only.

Can we agree that the spring is that piece of wire which moves the slide back? 
There´s a coiled spring at the CX 12 and an "open" spring at all other chroms. 

That thing which presses the CX comb against the mpc is called in Hohner´s
English catalogues "tension band" which I found to be an appropriate term. It consists
of elastic hardened steel. So, I name this thing also "spring band". But Michelle names 
it simply "spring", however, I think that this is reserved for the slide spring:

< .......that the CX spring is the weak point of the design. >

Though "band" and "plate" have several meanings, I consider this "thing" more a band 
than a plate. And "back plate" provokes again a debate how the different sides of a
harp should "correctly" be named. I know that a non-native is surely the last one who 
is called up to rack his brain about English word meanings. 

Little sidestep: I´m a steady guy and so, I finally found an American harp friend 
who was a teacher for English at the college and who confirmed that in former 
times the term "upside down" really meant "to turn the upper side down" (as I 
always had suspected) i.e. the harp mpc is then at the bottom. Nowadays it means
"to change the sides" = the slide and the high notes are then at the left.

(Hey, Bobbie, in case you read this, yeah, yeah, nothing is new on harp-L)
    
Indeed, it´s an issue how the harp should be oriented in space in order to name its sides.

When I say that the mpc is at the bottom after having turned the upper harp side down, 
it is obvious that my outgoing position is the harp standing upright on the table or 
in other words, the side with the holes is now in contact with the tabletop.

However, to speak of a "back plate" means a harp in playing position = the holes 
are at the front side which also means in front of me. 

Hmmmmh, in order to prevent this dilemma I suggest to avoid any terms pointing 
to the sides of a harp. OK, I hadn´t planned such a long palaver but it was necessary. 
See, that´s eg. the reason of many superfluous discussions because everybody has 
another understanding of one and the same thing.

Back to the tension or spring band of the CX 12. 

Michelle writes:

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
The reasoning you suggest for filing the edges sharp makes sense, but I think 
that doing so creates a new problem. .....I'm sure that machining the culprit 
sharp corners in the production of the instrument to a shape that would conform 
to the inside surface of the combat the key points of contact would cost several times
..............  This is a typical management decision made to cut manufacturer's cost........
.... filing the sharp corners round as you (and G) suggest is not
the answer to this manufacturing shortcoming.  The reason I say this is that once 
the stock spring is properly installed the sharp corners, though the
wrong shape, ~are~ spaced the appropriate distance apart so that the slide
is prevented from moving along its length.  That's the whole idea behind
making the comb slots half the full thickness of the spring in the first
place.  The "field modification" that you suggest makes the tabs more the
correct shape, but it narrows the distance between the points at either end
of the spring where they would otherwise contact the comb and prevent the
spring from moving longitudinally.  Filing the edges back even further
compounds this problem, in my view.  The result?  The modified CX becomes a
veritable hand grenade.  If ever there is a significant shock or the
instrument is dropped, the spring can be bumped or even move due to its own
interia.  Because there is nothing stopping the spring from moving in either
direction along its length, the spring can easily pop out, causing the
harmonica to explode!  (Please don't ask me how I discovered this.  :)
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Well, Michelle, notwithstanding that you typed "comb slot" instead of "cover slot"
or mixed one time the tension band with the slide 

< .....so that the slide is prevented from moving along its length....>,

I understand what you fear when the edges are filed back. However, unfortunately,
you didn´t tell us how you have discovered that the CX can explode like a hand 
grenade. 

I suppose that it is a theoretical explosion only because I assume that you don´t
have a CX 12 with filed band edges. But I assure you that it can´t happen because 
the pressure of the tension band is simply too high to move the band longitudinally 
quite alone. Believe me, you always have to press down one end to get the band free.
I just checked that again at all my CX 12. 

Of course, when a CX 12 drops to the ground, you have a grenade, not surely but likely.

Your advice to assemble or take apart a CX 12 always very carefully I can only underline
fullheartedly. Before I engage the tension band I check whether the slide moves properly.

At my CB chroms (B stands for brass) I provided a tolerance of 1 mm for shifting the 
comb there and back in its mpc guide to make it absolutely sure that the comb AND 
the slide are correctly placed.

Finally, to mention also this. In case, the pressure of the tension band is too high,
it´s possible and allowed to file back the band at its curved (convex) point or to 
rebend it a little.

CXfried   
  


     









		
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