[CAUT] hammer line

[Mark Cramer]

You have my interest guys, with all this careful work.

 

However, what about the effects of uneven string-height on strike-line? A
capo cast or ground 3mm higher at one end is just as deadly as a gluing a
hammer on 3mm off line. And although a hammer offline by an 1/8th" (3mm)
would certainly catch your eye, a deviation in string height of 1/8" is not
all that uncommon. 

 

(I'm needing at least one person to agree that missing strike by a mm would
have "at least" as much impact as a shank that is .2g off target weight! :>)

 

The only two factory scale designers I've discussed this with assert that
the strike point is the first line they draw, and that it is most certainly
"straight." 

 

(my only other point of reference is a fairly vivid imagination, and I can't
"imagine" them drawing it any other way... can you?)

 

When the capo is curved, I've always believed (okay... assumed) that this
was a deliberate compensation designed around a straight strike-line, in
order to accommodate the arc and placement of the bridge, not to provide a
template for our hammer-line. (Correction welcomed)

 

In any case, I would want proof in the form of speaking length measurements
before going wavy with another hammer-line, having unglued/reglued my own
work onto "shortened" shanks more than once.   

 

Question #1:

 

So, if the strike line you set "by-ear" ends up being a little crooked, and
uneven string height is the culprit, why not vary the bore-length?

 

A wise and valued supplier who I turn to for pre-hungs when things get
"bizzy," will not do this for me. His claim being that moving mass further
in/out on the arc will have more detriment than anything I'm trying to
correct. 

 

(I trust his knowledge, but have to temper it with the reality that having
to graduate bore-lengths would also slow ($$$$) down his operation ;>)

 

Question #2:

 

So wouldn't moving the hammer in/out on the shank do exactly the same thing?

 

Question #3:

 

How does the Stanwood approach deal with moving the Sumo further in-out on
the see-saw?

 

Thanks all, I always appreciate your wisdom.

 

Mark Cramer,

Brandon University

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

 

 

    

 

-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Jon
Page
Sent: February 15, 2008 9:05 AM
To: caut at ptg.org
Subject: [CAUT] hammer line

 

I weigh shanks and separate them into piles to the .1 g.

Then I measure the height of the knuckle, measuring

the shank too (the shank width variance is negligible)

but the knuckles are not always pressed in the same.

So I further break down each weight pile into three groups:

low, med, hi.  I try to keep the variance within .010" (.25mm)

and set aside ones out of the 'window'.

 

I weigh the bored/tapered heads and plot their weights on a chart.

 

According to the hammer weight, I'll select the appropriate weight shank

to achieve as smooth of a SW curve as possible bearing in mind knuckle

height groupings to place the med's more central and the low's and hi's at

the extremes, screwing the shanks to the rail as I go.

 

Grouping like-height knuckles leaves a more even let off button line and

one less variable with note to note wippen/shank vertical placement

(I know there's a better word for this).

 

By assigning a specific weight shank to a hammer weight less SW adjustment

is needed at the end of the process, ie; if the hi bass weighs 9.5 and the
low

tenor weighs 9, using the same weight shanks will leave the .5 g difference.

But if you place a 1.7 g shank with the bass hammer and a 2g shank

with the tenor you will come out with 11.2 and 11, respectively.  Depending

on the availability of sizes, you can strive for the same weight or a 

.1g difference.

 

I then install the hammers and let dry, then remove them from the rail.

Next is to cut the shank protrusion off with a band saw and rough cut the
arc.

Cut all tails to a even length ( I order longer moldings to accommodate a

tapered bore) and sand the tails to a 3" arc. This produces a nice 

finished edge.

Arcing removes about .3g.

 

Now comes the final weigh off. Usually only 12 to 18 need addressing.

I precut the hammer leads so I only need to look at the graph to install the

appropriate lead. If material needs to be removed. I'll first look at 

the front side

of the cove to remove a few tenths with a Forstner bit.  I order sets
uncoved

as well; so as not to be hindered in the arcing process with a deep cove.
The

cove removes so little weight, it is not worth the effort in the 

scheme of things.

 

FInally, easing the rear edges and bottom of the tail with a file.
Reinstall.

-- 

 

Regards,

 

Jon Page

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