Why not pull-release?

[Bent]

Is this the same system as on the old Sho-Buds?...where, on theraise, it pulled against a fulcrum like a knife edge, and on the lower it just had the string tension(coupled with a spring?) do the lowering? I think they had this on the rack and barrel system.

[Bill Ladd]

Is this the same system as on the old Sho-Buds?...

Bent -- My first PSG was pull-release. Worked like this:



The strings with both a raise and lower were a bit tricky to set up, but once done properly worked quite well. I've read that for more advanced copendents, this system is problematic.

edit -- on my drawing I wrote that initial tuning is done on the lower pull rod. I should clarify -- it is whatever pull rod which allows the lowering. Could be the upper or lower, but in my drawing it is the lower rod. And, heck, it probably should be referred to as a "release rod" anyway!

[Allan]

I just heard from Larry and it seems that I can go ahead and load the drawing I did earlier today. (Thanks Larry)

As you will see, this is just a sketch, no dimensions or anything technical. - A discussion document if you want to say anything?

[Bent]

Wow sweet and oh so simple!
Certainly not like the old Sho-Buds that I was thinking about.

[Bill Ladd]

Allan -- That's a killer animation. What a simple and brilliant mechanism. I'm a bt confused though as it looks to be an all-pull, not pull/release, yes?

[Allan]

Hi Bill.
Well, I didn't know what a pull/release was so I drew that up this morning as something to discuss in this thread.
I guess it is a form of all pull but without the 'scissors' that is generally used. I drew it with a simple single hole in each part but there is no reason not to put more in for adjustment. I haven't done the math so I don't know yet how much movement would be needed or how much pull could be gained from the lever arms as drawn. Like I say, just something to discuss at this stage.

Regards, Allan.....

[Bill Ladd]

I like it!

[Bent]

Allan, so this is just your 'artists conception" of a pull release?? If so, brilliant! If that's the way it can be built I can't see any reason for not being able to have 3 raises and lowers on the same string?

[Allan]

Thanks guys.

Bent, I have got enough feedback to take it to the next stage then. Do you think I should start a new thread? It's NOT a pull/release is it.

I will spend a bit of time over the next few days drawing out the complete linkage right back to the pedal/knee lever cross rod to see if I can get enough movement for what would be needed in the real world. I don't know enough mechanical engineering to work out what degree of 'push' would be needed to overcome the spring resistance or even what size of spring would be needed in the first place. I can, however work out how much angular rotation could be achieved from pressing a pedal.

I do need some information though. When you press a pedal down, how much vertical travel to you typically get? And, what is the largest amount of angular change in the finger for, say, a double change - up and down. I am assuming that a low (thicker) string needs a larger angle of rotation than a high (thinner) string?
I know that 'angular rotation' is not easy to measure so if anyone could give me the 'straight line' movement of the string from top dead center at the limits of the change I will resolve that to an angle before I start the calcs.

Regards to all, Allan.....

[Georg]

Allan, your "all-pull" is designed as a "pull-release" with a kind of "release-inverter". Same strengths/limitations as for a regular pull-release, and difficult/impossible to do split-tuning on.

Since it's a variant, it probably should be given its own 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.