About Checking

[antares]

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Hello William R. Monroe,
According to me, it is as Paul outlines : the angle.

Basically, you need an angle of exactly 72=BA.
So first get yourself a small piece of carton and cut it into an angle=20=

of 72=BA.
Put this carton in back of the back checks and check the angle.
Usually, the angle is faulty and this is the main reason why hammers do=20=

not check right.
Secondly, if you go through the motion of drop, there should be a=20
distance of 2 mm between the underside of the hammer tail and the=20
upperside of the back check .
Lastly, if you have back checks with an underfelt under the leather,=20
the hammer should, normally speaking, check at half the distance of the=20=

underfelt.

Take especially care of the back check angles. This usually is enough=20
to solve the problem.

On 10-nov-04, at 16:15, Paul McCloud wrote:

> Hi, William:
> =A0=A0=A0=A0If your hammers don't find increased friction when you =
push them=20
> down into check,=A0your angles may not be correct.=A0 If you take a =
wedge=20
> shaped block and force it into a crack, you'd expect it to get tight,=20=

> right?=A0=A0=A0 The tail is arc-ed in a radius which is less than the =
radius=20
> of the hammer shank length, so that when the tail meets the backcheck,=20=

> it acts as a wedge.=A0 It's possible that the radius arc of your tails=20=

> is too long (you may need to sand a tighter curve into them).
> The backcheck is bent so that the tail will be caught in it.=A0 The=20
> movement of the keystick=A0is also in an arc which intersects the arc =
of=20
> the hammershank.=A0 The movement of the hammer and keystick and their=20=

> arcs causes them to meet and interfere with each other (a good=20
> thing!).=A0=A0 Where these two arcs intersect should be=A0around the =
middle=20
> of the backcheck head.=A0 The bottom of the backcheck should be closer=20=

> to the hammer, and the top should be farther away (this is your=20
> backcheck angle)=A0=A0This angle insures=A0that the tail finds more =
friction=20
> as it goes down into it.=A0 It sounds like your backcheck angle is=20
> insufficient to cause this to happen.=A0 See if you can angle the=20
> backcheck back a little, and regulate the backcheck height again,=20
> while making sure it's not rubbing on the tail on the way up.=A0
>  It's too bad we can't see the action up close.=A0 Sounds like a good=20=

> subject for a Guild meeting/demo.
> Hope this helps,
> =A0=A0=A0=A0Paul McCloud
> =A0=A0=A0=A0inSaneDiego
> =A0
> =A0
> ----- Original Message -----
>  From: William R. Monroe
> To: Pianotech
> Sent: 11/10/2004 6:15:31 AM
>  Subject: Re: About Checking
>
>
> Joe Garrett,
>  I have already bedded the keyframe, and double checked to make sure.
> =A0
> Tom,
> Already repaired the balance rail holes (Onesti system=A0- great =
tool!).
> =A0
> Joe Goss, and Paul,
> Rep Springs really don't seem too strong, they have definite rise, but=20=

> do not "jump-up" from check.=A0 I will try weakening them more, =
though,=20
> and see what that brings.]
> =A0
> Terry F,
> Double checked jack position, by bringing it out to the point of=20
> cheating, then just in enough to function, and no change (Drat!).
> =A0
> Paul,
> Great ideas.=A0 Checks are aligned, spaced, etc.=A0 I resurfaced them=20=

> prior to regulation.=A0 Checking occurs about 1/3 of the way into the=20=

> backcheck, and backcheck height is just about even or a little below=20=

> the backcheck tail at drop, checks do not rub on tails on the rise.=A0=20=

> The one thing=A0that is giving me concern is that when the hammer is =
in=20
> check and I push them further into check, it does not happen.=A0=A0I =
can=20
> push the hammer pretty much through the range of the backcheck=20
> without=A0much increase in friction.=A0 As as mentioned earlier, maybe =
the=20
> hammers being hung at a different angle are to blame (if indeed that=20=

> was done).=A0 I will be checking that, but any other thoughts on why =
the=20
> hammers won't go deeper into check?
> =A0
> Thanks everyone for your input!!!
> William R. Monroe
> Madison, WI
> Assoc.
> =A0
> =A0
> =A0
> ----- Original Message -----
>  From: Joe Garrett
> To: pianotech
> Sent: Tuesday, November 09, 2004 11:35 PM
> Subject: Re: About Checking
>
> William asked: "Also tried varying the backcheck height, which showed=20=

> no noticeable
> improvement with either higher or lower backchecks.=A0 Also tried=20
> changing the
> backcheck angle - again no improvement one way or the other, hammers=20=

> simply
> will not check on soft blows."
>
> Lost in Wisconsin:
> William R. Monroe
> Madison, WI
> =A0
> William,
> If you've tried all of that, then it has to be something you didn't=20
> try.<G> Have you checked to see if the keyframe is bedded properly?=20
> I've known that to mess up checking.
> Best Regards,
>
>
>
> Joe Garrett, R.P.T.
> Captain, Tool Police
> Squares R I
>
friendly greetings
from
Andr=E9 Oorebeek

"where Music is, no harm can be"

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