This is a new thread since the pull release thread had gone way off subject. My bad!
I asked for some guidance on angular offset to achieve raise and lower pitches. Georg suggested a change of 1/4" for a change from G# to A on the 4th string in a E9th set up. I have made a drawing with this in mind. I made the drawing as a lower but a 1/4" is a 1/4" in this case anyhow. As you will see, the angular change is in the approximate order of 38 degs. I never realised that a changer had to move that much to achieve a half tone variation - seems excessive to me. I am thinking here of some of these new changers available that provide for four half tones - how on earth do they do that?
Anyhow, if this 1/4" requirement for a half tone is accurate then the entire concept illustrated in my original animation is a non starter. Here is the drawing, you will see what I mean...
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Allan.....
Only nuts eat squirrels. Keep yer tools sharp! That way you can use more of your strength guiding them AWAY from your body rather than forcing the cut!!!
Allan, Those are some nice clear drawings you are producing there.
However, somewhere along the line numbers got messed up. I know, because I did a test for Georg back in July...remember Georg?
Georg writes in the other thread:
For a typical E9 copedant, expect the longest travel on 4th string raise - G# to A on a .011 gauge. 4 mm travel should do there, but better provide around 6 mm or 1/4 inch for raise and at least that much for lower. The wound strings will normally need much shorter travel than the thin 4th string for the same pitch-change, since their plain core is what take up tension and they aren't tuned very high.
First, it is obvious we are talking about he 3rd string here, not the 4th (no biggie)
My test showed that in order to pull the .011G# to A plus 20 cents, took 0.1505" (3.83mm) of linear pull. This is just under 5/32"
This results in quite a bit less swing for your finger.
During my testing, I also arrived at another fact: The string that takes the longest linear pull is when you lower the .011 G# to F#. The .022W G# to F# came in a close 2nd as I remember ( I don't have the figures for those ones handy at the moment)
http://benrom.com/
21 BenRom pedal steel guitars, a Nash 112 and a 1967 TOS Milling machine with many cutters making one hell of a mess on the floor.
OK, thanks Bent. Here is another drawing then. I hope the colors show up OK but if not it should be easy enough to grasp based on the numbers in the table.
You are right, as you will see, the difference in angular rotation is significant using your number in the calculation.
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Allan.....
Only nuts eat squirrels. Keep yer tools sharp! That way you can use more of your strength guiding them AWAY from your body rather than forcing the cut!!!
Yes, of course I meant the 3d string, and yes, I used Bent's numbers from back in July. I've done some rough checks of those numbers and found them to go well with the travel measured on my own steel.
Actually: on my steel the travel needed for a half-tone raise (and a little extra) of 3d string was a little less than Bent's numbers, but some "allowance" for different string types and gauges is needed and that's where my larger numbers come in.
Some important factors: the outer diameter of the bridge-rollers is 7/8 inch on my steel - same as a quite "standard" bar. Much less and the strings will bend too much when operated and break too easily, while a much larger diameter will tend to cause string-buzz.
Some steels do have bridge-rollers with a much larger diameter - I've seen pictures of some with 1 to 1 1/2 inch diameter - and what looks like even more, which works well mechanically since the rotation is smaller for a given raise/lower and the strings aren't bended much when raised and lowered, but I'm not sure how well they work with regard to string-buzz.
The length of the raise-finger - down to where it is stopped/held in neutral by the lower-finger - should be much shorter to allow for enough rotation for lowering. This means the raise-finger has to be designed differently so it doesn't collide at the wrong point with the lower-finger when lowering while still be reasonably long for tunable raise. This is probably the most serious "show-stopper" for your design-idea at the moment.
Strings that are under high tension, like the 3d, need a bit less travel for lowering than for raise.
Some steels can barely raise and lower those strings far enough for a standard E9 copedent, while others can raise and lower 2-3 full notes as long as the strings can take it. Many steels can't handle the G# to F# lowering of 3d string and most steels don't even have that lowering.
You have to decide how much raise and lower that's necessary, and allow for slight variations in string-gauges.
Bent, Georg raises a good point here. I had thought of it but didn't realize how significant it could be. What is the diam. (or radius) at the top of your fingers? (bridge rollers)
I am going to go and plug that new info from Georg into my little spread sheet and my CAD prog. New drawing on the way soon.
Allan.....
Only nuts eat squirrels. Keep yer tools sharp! That way you can use more of your strength guiding them AWAY from your body rather than forcing the cut!!!
New drawing:
Again, a worthwhile difference. OK, I am back in the game! I will work with a one inch diam. bridge roller and make another, more considered drawing over the next day or two.
This is at 7/8"
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And here at 1"
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Thanks again Georg.
Allan.....
Only nuts eat squirrels. Keep yer tools sharp! That way you can use more of your strength guiding them AWAY from your body rather than forcing the cut!!!
Richard, your measurements seem quite realistic for that E to F#. The travel/angle is indeed quite small for raise/lower of most strings.
Travel (string-stretch) for raise/lower is the same for same strings/notes on all changer-systems, only offset some by whether it's a keyless or a regular keyhead steel with the extra string lengths. Thus, a marker-pen line across all bridge-rollers can be used to eyeball the actual travel. Pretty small movement for most strings.
One has to allow for some extra travel, or else there won't be enough to go on if one wants to experiment with different string types/gauges.
The only strings I've had some real problems with are the E9 3d string full note lower (which isn't used on most steels), as that's quite a travel, and also the raise and lower of the low G# and E strings on extended E9, that barely travel at all and therefore are difficult to tune/balance. These "extremes" should be no worse to handle on a pull-release than on an all-pull.
IMO, Allan's design is very well suited for discussions and sorting measurements and problems, but I'm not sure if it can outperform a regular pull-release because of the way it splits raise and lower on two axles. Will be difficult to keep those two axles and the neutral-stopper perfectly aligned under stress without building a very rigid and somewhat heavy changer-frame, which goes somewhat against the "simplicity" goal I think he has in mind.
Georg,
I agree with you that I too can see no advantage at all in making a pull-release finger in two halves, it will only add unnecessary complications.
There will still be slack needed in the raise rod, and having an extra pivot could have impilcations regarding cabinet drop/axle flex, and loss of tone
I've just measured the total movement of the 4th string (0.014") on my pull-release Denley, with a 3/4" diameter changer finger, and a regular keyhead.
From Eb to F#, the finger rotates a fraction more than 10 degrees, which equates to just over 1/16" travel at the circumference.
