Neck scale / keyhead positioning

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na4it
Posts: 101
Joined: Wed Jan 02, 2013 12:26 pm

Neck scale / keyhead positioning

Post by na4it »

What are the advantages between the shorter (22.5") and longer (24.5") scales? I'm playing 22.5" scale, and it seems the higher notes are harder to hit accurately. Want to figure this out before I build one...

As for keyhead positioning, I've seen some "bar" type keyheads that are slanted with the tuners installed 90 degrees to the mounting bar, and some that are compensated by milling the bar so that the tuners are 90 degrees to the string. Comments please...
Scott Duckworth
E6 Rogue lap steel, D6 Regal RD-30MS squareneck reso-guitar,
Li'l Izzy, Zoom MS-50G Effects Pedal into a Berhinger mixer and Harbinger V2112 speaker(s).

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richard37066
Posts: 517
Joined: Sat Dec 11, 2010 11:44 am
Location: Gallatin, Tennessee, USA

Re: Neck scale / keyhead positioning

Post by richard37066 »

Scott -

I think that I can shed some light on your concerns although others may want to chime in with additional comments.

Re: - scale length. In order to raise a note by, say, half of a tone, the bar must be moved a certain percentage of the available scale length. On an open string, the available scale length is the scale length of the instrument. If the bar is at the twelfth fret, the available scale length is 1/2 the scale length of the instrument. In actuality, the representative distances are approximately 1.35" from the nut to the first fret and approximately 0.67" from the 12th to the 13th fret for a scale length of 24" in order to raise the appropriate note by 1/2 tone. At the 18th fret, the distance to the 19th fret is but 0.48". You might displace the bar at the first fret by some small amount and, perhaps, not hear the change in pitch. If, on the other hand, the bar is displaced by that same physical amount at the 12th or 18th fret, then the change in pitch would be quite noticeable and, probably, not acceptable. The bugaboo in all of this is a thing called "parallax". That is, your eyes may be looking at a fret quite high on the keyboard, but at an angle. The bar cannot be placed 'twixt the eye and the fret on a straight line but must be placed OVER the fret in order to have proper intonation. This tests the skill of the player over and over again. On the other hand - and to be rediculous - if you had a scale length of 10 FEET then the bar at the first fret could be off by a quarter of an inch and you probably wouldn't notice the difference in pitch. I'm certain that, intuitively, you know all of this so I'm just throwing things up in the air for your perusal. Both of my guitars have 24" scale lengths and I'm quite comfortable with that number.

As to the tuning machine mounting position in the keyhead, I'm certain that we've all seen both configurations. My personal preference is to have the shaft of the tuning machine at right angles to the string. The force on the shaft end is singular - that is - a bending moment of the shaft. When the tuning machine is mounted such that the shaft is at an angle to the string then an additional force - a tension moment - is applied to the shaft. Two forces acting upon the machine. Does this amount to a hill of beans? I don't know. I only feel more comfortable - from a mechanical point of view - with the shaft at right angles to the string.

Perhaps someone with intimate knowledge of tuning machines can shed some expertise on this.

Hope all of this helps.

Richard
na4it
Posts: 101
Joined: Wed Jan 02, 2013 12:26 pm

Re: Neck scale / keyhead positioning

Post by na4it »

Richard,
Thanks for both viewpoints. I do think I would like the 24" scale better, and I think the 90 degree positioning to the string is also better. As I've mentioned before, I plan to build a D8 console. And probably will go with 24" scale and the "stepped" keyhead like a lot of pedal steels have on them.

At some point in time, I would like to fool around with a bass console guitar. Never head one, just curious how it would sound. I suspect I better get really good on my string blocking technique for the bass!
Scott Duckworth
E6 Rogue lap steel, D6 Regal RD-30MS squareneck reso-guitar,
Li'l Izzy, Zoom MS-50G Effects Pedal into a Berhinger mixer and Harbinger V2112 speaker(s).

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mark63uni
Posts: 34
Joined: Mon Jan 14, 2013 12:26 pm
Location: New Brunswick, Canada

Re: Neck scale / keyhead positioning

Post by mark63uni »

Very helpful insight on the scale length, I never looked at it that way. I have a stand up bass I slap around a bit and I guess that explains why I can be off by a mile and still manage to hit the notes here and there!
Paul Lafountaine
Posts: 332
Joined: Sun Jan 23, 2011 5:06 am
Location: Northern Ontario

Re: Neck scale / keyhead positioning

Post by Paul Lafountaine »

Hey Scott,

Some folks prefer the shorter scale for bar slants 22.5". I have a lap steel here that I play with a 21" scale that I like for the ease of slants. Preference is up to the player though! I also have a lap with a 24" scale and I find slants a little more difficult. Just something to think about.

Paul
na4it
Posts: 101
Joined: Wed Jan 02, 2013 12:26 pm

Re: Neck scale / keyhead positioning

Post by na4it »

Mark, I always wanted a stand up bass! Never got there though...

Paul, thanks for the tip. Good consideration.

I'm thinking about building a cross between a Carvin D8 and a Termblay D6. I like the design of both, but like the front neck elevated like the D8 Carvin. I like the keyhead design of the Tremblay. I also like his design of the 8 string bridge. That's easy to reproduce.
Scott Duckworth
E6 Rogue lap steel, D6 Regal RD-30MS squareneck reso-guitar,
Li'l Izzy, Zoom MS-50G Effects Pedal into a Berhinger mixer and Harbinger V2112 speaker(s).

Amateur Radio Operator NA4IT (Extra)
http://www.qsl.net/na4it
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