Mechanical mystery of the A - A# -rod?

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Benjahmin
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Mechanical mystery of the A - A# -rod?

Post by Benjahmin » Sat Jul 03, 2010 2:25 pm

Hi Together !

There is a mechanical issue concerning the flute, which I had to deal with a lot as a repairsman, and now on my own flute as well, but for which I see no true reason:
I am talking about the lower end of the achsle for the A and A# Key.It mostly ends in a conical pin, which is inserted into the Pylon which also holds the upper end of the D,E,F,F# -
Key-component.

Now on quite a lot of Flutes, regardless of price, brand or model, this pin is actually too small, or the other way around : The bearing in the bulb of the pylon is too large.
The effect is, that the A# --or the Bb -- Trill key mounted on that end of the rod is seated loosely and likes to rattle (actually enlargening the bearing over time through this even more ), and of course that the complete rod might encounter angled movement causing the keys/pads to get unseated.

Most Flutemakers and repair-people cover this problem by adding a small piece of padskin between bearing and pin to make up for the difference in size and so get rid of the negative side- effects, similar as it is done in the Joint-angles of the lefthand - lowkeys of clarinets.( I've seen plastic used as well )
Well, in the clarinets and oboes, it makes sense, concerning the angled movement, but WHY does it have to be done on this special pin-connection, with nothing more than a simple circular movement around the achsis...like all other keys have just the same ?
Mechanically I truly see no reason, why this is done, what it is good for or what the advantage may be. Does ANYONE have an idea ??

There are different ways of solving this problem once and for all, one beeing a fillup with a two -component epoxy which will act as a permanent plastic bearing and simply won't wear off, or the more "orthodox" method of carefully forging and hammering the pylon at that side, until the inside bearing has the perfect fit, not needing any "washer" or buffer anymore to keep it snug and in exactly the right position.
I've been through a lot of different experiments to solve this, like soldering up the gap, trying Alumnium-foil and super -glue, most would work, but not last long, while the epoxy does a perfect job and the forging to size eliminates the cicumstances alltogether.I chose the last method after buying my own flute right away and never had to bother about the rest again.

Anyhow, I suppose this "Padskin-bearing" MUST have a good reason, since it is done so often and can't be related to a lack of technical "know how" or cheap production,
since it would be easier to just drill a bearing which fits in the first place ( like all the others ) instead of fitting in scraps of padskin later on into this special one. But to me personally it is a nuisance , since the padskin-filling mostly gets lost or destroyed every time the Flute is taken apart and needs to be replaced, which does certaily not give me the feeling of a ""solid and trustworthy" mechanism.

Can anyone tell the story about what it s good for? My former Boss didn't know, he just cursed those bearings as I did , and many flute-customers didn't even know, that they actually HAD padskin between their Rods.

Thanks for any serious suggestions !

Benjahmin

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JButky
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Re: Mechanical mystery of the A - A# -rod?

Post by JButky » Sat Jul 03, 2010 3:48 pm

Benjahmin wrote:Hi Together !

I am talking about the lower end of the achsle for the A and A# Key.It mostly ends in a conical pin, which is inserted into the Pylon which also holds the upper end of the D,E,F,F# -
Key-component.

Now on quite a lot of Flutes, regardless of price, brand or model, this pin is actually too small, or the other way around : The bearing in the bulb of the pylon is too large.
The effect is, that the A# --or the Bb -- Trill key mounted on that end of the rod is seated loosely and likes to rattle (actually enlargening the bearing over time through this even more ), and of course that the complete rod might encounter angled movement causing the keys/pads to get unseated.

Can anyone tell the story about what it s good for? My former Boss didn't know, he just cursed those bearings as I did , and many flute-customers didn't even know, that they actually HAD padskin between their Rods.

Thanks for any serious suggestions !

Benjahmin
Benjahmin,

I think you are referring to the king post bearing of which there are several types. The conical bearing (pivot bearing type) can exhibit wobble from excessive wear, rattle, and make regulating the 1-1 Bb combo near impossible.

The fit at the other end is very important for retarding the progress of this type of wear. If there are pivots they must be fit perfectly, pilots must have their tubing precisely fit to the posts. Poor fit with a conical pivot at the key post won't play right from the very start. Keeping the axles in a mechanically stable, precise manner is the key to prevention of this type of wear. If the bearing is still acceptable, refitting the other end to eliminate the wobble is the standard solution and very quick to do..

Quality of materials and accuracy of fit maintains even a pilot bearing style kingpost bearing. Usually when these wear, the most acceptable solution is to machine a new bearing and replace the old one.
Joe B

Benjahmin
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Post by Benjahmin » Mon Jul 05, 2010 2:48 am

@ JButky

Well yes, that goes along with what I've observed and stresses the neccessity of that Joint ( Kings-bearing it is called ?) to be precise and reliable just like all others .

Even more it keeps and puts up the question though: Why do NEW flutes already come up with a loose "Kings-Bearing" and the Padskin-fitting to start with ?
That was my actual question, since as You say, fitting a correct bearing is a possibility and thus could be done from the start on -- couldn't it ?
As I mentioned, it can't be a cheap-production factor, since highgraded expensive instruments will have it just the same !


Benjahmin

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JButky
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Post by JButky » Mon Jul 05, 2010 3:11 pm

Benjahmin wrote:@ JButky

Well yes, that goes along with what I've observed and stresses the neccessity of that Joint ( Kings-bearing it is called ?) to be precise and reliable just like all others .

Even more it keeps and puts up the question though: Why do NEW flutes already come up with a loose "Kings-Bearing" and the Padskin-fitting to start with ?
That was my actual question, since as You say, fitting a correct bearing is a possibility and thus could be done from the start on -- couldn't it ?
As I mentioned, it can't be a cheap-production factor, since highgraded expensive instruments will have it just the same !


Benjahmin
I have not seen padskin to account for a sloppy bearing here in the US on new flutes. I have seen some "repairs" on older flutes attempted this way, but I have not seen it on newer flutes.

I guess it is still a mystery...
Joe B

Benjahmin
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Post by Benjahmin » Tue Jul 06, 2010 10:22 pm

Hi Joe,

I had just prepared a private message to you, but now found out,that they are disabled on this board.

Don't want to call on brandnames here in "public", so I guess we'll have to leave it by that :wink:

Be happy anyhow, if You haven't been into the problem ! :P :P

Thanks for Your interst anyhow

Benjahmin

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JButky
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Post by JButky » Wed Jul 07, 2010 5:54 am

Benjahmin wrote:Hi Joe,

I had just prepared a private message to you, but now found out,that they are disabled on this board.

Don't want to call on brandnames here in "public", so I guess we'll have to leave it by that :wink:

Be happy anyhow, if You haven't been into the problem ! :P :P

Thanks for Your interst anyhow

Benjahmin
Check again...You'll find a working email link now :idea:
Joe B

Benjahmin
Posts: 29
Joined: Tue Jun 22, 2010 12:33 pm
Location: Ethiopia
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Post by Benjahmin » Wed Jul 07, 2010 2:16 pm

Joe,

That link seems quite complicated, needs installment of the programme first....but since You agreed to mailing, I sent it to the adress given in Your Profile, if it is not the same anyhow.



:wink:

Benjahmin

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