Proper places to measure speaking length

[Delwin D Fandrich]

David,

I don't know about any books or articles, but...

The procedure I recommend is as follows. The idea is to measure the exact
speaking length. That is the length of wire that actually vibrates in response
to a hammer blow. From a design standpoint, this is from the centerline of the
front termination on the plate to the centerline of the back termination on the
bridge.

Through the agraffe section this can be taken from the center of the agraffe to
the center of the speaking side bridge pin. I recommend using a Stanley tape
measure that is marked off in decimal inches and mm (the part number escapes me
right now, if you need to know I can get it for you). For rescaling work it is
accurate enough to hook the end of the tape over the agraffe and read to the
front edge of the bridge pin. If the agraffes are abnormally wide you can
compensate by subtracting an appropriate amount from your reading.

Through the Capo-d-astro bar/V-bar section it can be a bit trickier. Starting at
C-88, I use a thin 150 mm steel rule (made by Mitutoyo -- again, I can get you
the part number if you need it) that I have beveled slightly on one end. I slide
this beveled end along the strings to the V-bar, getting as close to the actual
string/V-bar intersection as possible. I then read the length at the center of
the bridge pin. When the speaking length gets to be longer than 150 mm, I switch
to an 18"/450 mm rule. This one is a bit wider than my 150 mm rule, but at this
point it is quite usable. Again, work the end of the rule as far in to the
juncture of the string and V-bar as possible and read to the center of the
bridge pin.

Wire diameters are measured with a micrometer. On wrapped strings you'll need to
measure both the diameter of the string core and the overall diameter of the
wrapped section. Often old strings have a healthy buildup of rust and general
corrosion. Check under the dampers on the steel strings, they're often somewhat
cleaner there. You may have to clean off a short section to get a reliable
reading. To save time, think ahead. Remember that, unless there is at least one
individually tied string in the unison, unisons will be paired. That is, the
same wire size will have been used for two consecutive unisons. It is only
necessary to measure one string of each pair.

That should do it. Remember that this is not rocket science. Accuracy and
consistency are important, but there is some tolerance allowed. For string
lengths I suggest reading to the nearest mm through the agraffe section and to
the nearest half-mm through the V-bar section.

As to whether to use decimal inches or metric, the choice is yours. My scaling
program is set up for string lengths in mm and wire diameters in decimal
inches.  String lengths in decimal inches are also acceptable. Fractions should
have gone out with square grands. Neither I nor my computer works with them.

If you have other specific questions on the process, please don't hesitate...

Regards,

Del

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Vanderhoofven wrote:

> Very sorry to be asking a beginnerish type question, but what is the proper
> place to measure speaking length?  Can you suggest the title of a book or
> an article that would have good information on where to measure?
>
> Thanks!
>
> David Vanderhoofven
> MSSC
> Cottey College