Do you really need rollers?

Jim West · Posted 22 Jan 2005 9:06 am

After seeing the pics of Ed Packards new Sierra I had to ask myself the question, "Do you really need rollers on the nut?". As some (most?) of you know Ed's new ax has the changer/tuners on the left and a solid bridge on the right. This guitar will prove if you really need rollers for the strings. I have looked very closely while actuating pedals and have never been able to see the roller move on my guitar and have never been fully convinced that they are needed.

Comments?

Jim Palenscar · From: Oceanside, Calif, USA

Only on keyed guitars (IMHO)

Dave Zirbel · From: Sebastopol, CA USA

The GFI keyless guitars do not have rollers.

Dave

ed packard · From: Show Low AZ

Jim & Jim;
Here is what convinced me to do away with them:

My string length (ball to termination) is 31.5". My playable string length (nut to bridge) is 29.730".

My 11 gauge string (the worst case) stretches about 0.020" (measured) at the tuner/changer when raised a halftone.

The sting stretch at the termination is 0.0000" = zero; so we have 0.020" of stretch distributed along about 30" of string.

The "roller" = rod in this case, is 1.0" from the string termination; could be less if wanted.

So we have one 1 part in 31.5 string stretch at the rod/nut/roller tangent point (where it touches the string.) 0.020 string stretch divided by the 31.5" string length gives 0.0006" of stretch seen at the nut/roller/rod, or if you want to divide by the 30" it gives 0.0007", ..in any case, less than 0.001". I would suggest that the coefficient of friction of the rod is less that the coefficient of stiction for a roller on a shaft (with or without grease/nicotine tar deposits etc.).

Lets say that the string moved 0.001" at the nut/bridge/roller and did not return; what would the effect be upon pitch? Run the calc for an 11 gauge string 29.730" long, and 29.731"long at 28 pounds tension. These results indicated that the roller is not needed.

I am busy running out the pitch shift (commonly called cabinet drop) for the BEAST as b0b calls it). The common E9 check is with
P1P2 activated and string 4 = E change measured. I get 3 cents on this 31.5" total string length for both P1P2, 2C for P1, and 2C for P2, ..I can live with that. There is no noticeable change when I stand on the pedals (more weight), ..more on these + sustain/tone measurements later.

The tuner used is the Peterson VS-II. My Korg DT-1 was too ambiguous so I upgraded.

Wait till you see what we bring to the Texas show!!!!

Bill Ford · From: Graniteville SC Aiken

My first pedal steel was a Fender 400, then a single 12 with an all pull(Sho Bud type )changer. I always kept a small can of 3in1 oil to put on the bridge, they stayed in tune a lot better if a small amount of oil was kept on the bridge. I still keep the rollers oiled on my new S12.

Bill

Dave Grafe · From: Hudson River Valley NY

I once had a Maverick. No Rollers. Strings broke often and always at the nut.

Later I bought a Pro I. Gots Rollers. Strings break once in a while and always at the bridge.

Guess which arrangement I like....

[This message was edited by Dave Grafe on 23 January 2005 at 12:20 AM.]

Roy Ayres · From: Riverview, Florida, USA, R.I.P.

My Excel has rollers at the nut. I see no reason for them as far as changes in string tension resulting from the changer -- but I would hate to try to tune it at the left end with a wound string dragging across a fixed nut at a steep angle.

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Dennis Detweiler · From: Solon, Iowa, US

My first pedal steel was a no pedal stand up Fender with a puller conversion mounted on the pickup end of the guitar. And no rollers. I broke strings constantly at both ends.

So, is tuning easier and string return pitch more accurate and consistent without rollers on this new model? Maybe pullers at both ends, like Zane's guitar is the way to go? Strings slapping you in both sides of your face.

DD

Per Berner · From: Skovde, Sweden

This just occured to me: Has anyone tried a graphite nut on a pedal steel? That works fine on Strat-style guitars; never broke a string on mine.

--------------------
Emmons Legrande II D10 8+5, Sho-Bud Pro III Custom SD10 4+5, Goodrich 120, Peavey Nashville 1000

ed packard · From: Show Low AZ

A little arith' based as shown above will show that instruments using standard key type tuning systems will have a lot of string travel over the roller area because the strings are 6" beyond the roller and on a 24.25" or so scale = more string travel at the roller per halftone of stretch = rollers are nice, ..the question is what size?. The PSTL system has less than 1.0" beyond the nut/rod = why rollers?

Re fat wound strings, ..my string 14 is a 95 gauge, ..S/B a 112 (if I can find one). Notice that most of the string stretch motion is at the end away from the nut (unlike the key tuner type construction). With the key type tuners the string stretch motion is over the nut/roller = rollers are nice. With the PSTL system, the fat string windings are NOT dragged over the nut = no jumps/skips/lack of smoothness while tuning, or activating changes.

The rod on the instrument in the pictures is brass. We will try that for a while and see what happens. My zirconia rod did not make it in time for the assembly. Graphite, teflon coated, or other low coefficient of friction material would work fine as less than 0.001" of changer motion over the rod/nut is not likely to saw into the rod. Drill rod is another possible material. Tone is the issue at the rod, not wear.

There are no steep string bend angles in the PSTL system at either end.

Keyed (long string stretch beyond the roller/nut) and keyless (short string stretch beyond the nut/rod) present two very different scenarios re the roller issue.

Check it out at the Dallas show.

David Doggett · Posted 25 Jan 2005 2:58 pm

I also had an early Maverick with no rollers. I didn't notice the string breakage so much, but you could here the wound strings scratching as you pulled them - skritch, skritch. The guitar had a very solid sound, like a lap steel. I put a ShoBud Pro key head on it with rollers. The scratching was gone, and the sound was different - more sustain and harmonics. There was a definite new ringing sound, even when using the bar with fingers down behind it. It sounded almost like I had added reverb.

I agree with Ed that shorter string length behind the nut or bridge means less string travel, and less need for a roller to stop the scratching. But many people claim that longer string length behind the nut or bridge means better sustain. There is a physical rational for that.

As the string vibrates from bridge to nut, it must flex at the bridge or nut if the string is fixed a short distance from the bridge or nut. This flexing causes internal friction and dampens the harmonics and sustain. If there is some length behind the nut or bridge allowing some vibration back there, then the string has to bend less. As it vibrates in one direction in front of the bridge or nut, it is free to vibrate in the opposite direction behind the bridge or nut, causing less flexing at the bridge or nut. The longer the length behind the bridge or nut, the better. Putting the bridge or nut at a harmonic node would have a big effect on tone (not necessarily good), but maybe only with the open string.

Proponents of keyless heads maintain that the bar and bar hand should eliminate any effect of the length behind the nut. This does not seem to be the experience of many players. There is an easy test for this. Take a keyhead steel guitar and put all the same guage strings on it, tuned to the same pitch. Listen to the difference in the strings with a short length behind the nut, and ones with a long distance. Try it with and without the bar and bar hand. I've never tried this myself, but I'd sure want to before I invested in making or buying a keyless guitar with short string length behind the nut.

I've always been intrigued by the precision of keyless heads for tuning. But except to make the guitar more compact, there seems to be no particular need to make the string length behind the nut so short. The test above might help determine the optimum string length behind the nut. A keyless head would have a distinct advantage in getting all the strings at or very near that optimum length.

ed packard · From: Show Low AZ

DD; The wheels are turning, ..that is good.
Re your proposed experiment, ..how about just using the same gauge of string at the middle of the keyhead, and at the end, Then excite each individualy and see if there is a big difference in .....

I don't find a global definition for sustain.
By frequency Spectrum Analyzer measurement I find that the higher harmonics of the string fall off before the fundamental; so it becomes a matter of amplitude at frequency(s) vs time. I measure at 0, 2, 4, 8 seconds for that purpose.

Re the shirtness of string beyond the nut: The same argument should be applied to the shortness of string beyond the changer contact point, which is in the case of the keyhead instruments about zero re vibration, and this portion of the string is on the non bar side = vibrating portion of the string providing the signal to the pickup.

String stiffness plays a roll in both the effect of clamping (terminating) and in harmonic content.

Just by coincidence, I happen to be profiling the BEAST today re its sustain and harmonic content, body coupling and "all that jazz".

Line the different makes up at the Dallas show and we can have a tone/sustain shoot out complete with SA et al.

David Doggett · Posted 25 Jan 2005 5:13 pm

Ed, you are right. You can do the keyhead experiment just putting a single string on one of the middle posts, and another on either the highest or lowest post. You are also right that most changers have zero string length beyond the changer-bridge (I believe the Excell does). And since that end is not blocked by the bar hand, it should be more critical.

Your comment about the harmonics reminds me about another recent discussion about harmonics with horns or organ pipes. The same applies to strings. If the pipe or string is "closed" at one end (the pipe has no taper, like a clarinet, or the string is fixed at it's very end), then you get only even or odd harmonics (I forget which). If it is "open" (tapered like a sax, or the string merely pivots at the nut and has substantial string length behind the nut?), then you get both even and odd harmonics. That seems worth exploring. A sax sounds way better than a clarinet.

Good luck with your thinking and testing on this stuff. Some day I gotta get down to Dallas, but I don't know if it will be this year.

Per Berner · From: Skovde, Sweden

Ed, it would be VERY interesting to hear the difference in sound between the different bridge rod materials on your new horn. Like a few soundclips of a simple phrase played at the same amp settings, to hear how they affect tone and sustain.

--------------------
Emmons Legrande II D10 8+5, Sho-Bud Pro III Custom SD10 4+5, Goodrich 120, Peavey Nashville 1000

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