Confused about Leverage/Rodding/Bell Cranks?

[Bob Snelgrove]

I'm doing some changes to my Franklin and read a bunch of posts about bell cranks and rodding etc. Seemed like contradictions but probably just me.

If a knee lever moves and hits the stop, will every hole in the B/C move the rod the same distance, just take less or more effort but more movement to get to same place?

If you want a softer, smoother feel would you use a hole or slot closer to the cross shaft or further?

That's a good start

thx

bob

[Jon Light (deceased)]

If a knee lever moves and hits the stop, will every hole in the B/C move the rod the same distance, just take less or more effort but more movement to get to same place?
bob

Nope. They are all pivoting around the axis of the cross shaft. The ones closer to the shaft have less linear movement, relative to the changer; the ones farther from the shaft have more.

If you want a softer, smoother feel would you use a hole or slot closer to the cross shaft or further?
bob

For softer, smoother, lighter feel you use hole or slot closer to the shaft. AND you increase the travel at the lever stop (or start) because you are now getting less linear rod movement

For quicker, shorter lever movement you move to the outer bellcrank holes. You get more linear rod movement and as a result you can shorten the lever stops. The feel will be stiffer.

[Bob Snelgrove]

Thanks, Jon

I'm seeing it now.

What about the changer holes (Franklin has 3)

bob

[Jon Light (deceased)]

What about the changer holes (Franklin has 3)

The farther away from the string -- from the top surface of the changer -- the less string movement you get from a given amount of rod movement. So the changer hole closest to the floor (of a standing-up guitar) will yield the easiest feeling pull but will require a longer pedal or lever movement to get the same amount of pitch change as the shorter, stiffer pull you'd get in a changer hole closer to the top of the guitar.

You can think of the cross shafts and the axle of the changer as being essentially the same -- pivot points for a circular motion. But they are opposite from one another in terms of one being upside down from the other.

[Bob Snelgrove]

Thanks, Jon

Very helpful

bob

[Chris Templeton]

Between string gauges and tension, wound and unwound strings, I've found that I make priorities in travel and throws.
When the F#- G# change, on the first string, gained popularity, via Paul Franklin, It became my priority with picking my leverage for that string.
F#-G# is some serious travel with the finger and older changer systems can't handle the travel unless there are some modifications.
There is also the "squeeze factor. Do you want sound of the pedal/knee change to sound slower as it changes
or as quick as possible?

[Bob Snelgrove]

Between string gauges and tension, wound and unwound strings, I've found that I make priorities in travel and throws.
When the F#- G# change, on the first string, gained popularity, via Paul Franklin, It became my priority with picking my leverage for that string.
F#-G# is some serious travel with the finger and older changer systems can't handle the travel unless there are some modifications.
There is also the "squeeze factor. Do you want sound of the pedal/knee change to sound slower as it changes
or as quick as possible?

That was the change that I was struggling with

bob

[Andrew Frost]

That's a great description Jon.
Timing separate pulls is another interesting thing. I think I'm getting the hang of it...
Recognizing that if one is getting a head start on the others, and creating an unwanted bump, it needs a 'steeper' pull. It can then be 'relaxed' so they all start (and end) together.

[Bob Snelgrove]

That's a great description Jon.
Timing separate pulls is another interesting thing. I think I'm getting the hang of it...
Recognizing that if one is getting a head start on the others, and creating an unwanted bump, it needs a 'steeper' pull. It can then be 'relaxed' so they all start (and end) together.

So further from the cross shaft to have it start later?

[Bobby D. Jones]

There are rules of physics working in a steel a guitar, We have to deal with, And live with.

The smaller the string, The farther the string has to travel to reach same note, Than a larger string, Or larger cored string has to travel.

The smaller string must travel farther with less pressure to reach note. A Larger string takes less travel, But requires more pressure to reach same note.

Tune the smaller string first, To raise or lower note required. Adjust any stops for smaller string, The larger string will tune to note in the confines of smaller strings stops, By moving pull rod in holes of changer and bell crank.

Example: When setting up E9th, 3rd and 6th string. Setup pull G# to A on 3rd string and adjust stops, Larger 6th solid string will now tune G# to A, Within the confines of the smaller 3rd string's stops. By moving pull rod in bell crank and changer holes.
CAUTION, With a wound 6th string the process may have to be reversed. Because of smaller core wire in wound 6th string.

[Bob Snelgrove]

There are rules of physics working in a steel a guitar, We have to deal with, And live with.

The smaller the string, The farther the string has to travel to reach same note, Than a larger string, Or larger cored string has to travel.

The smaller string must travel farther with less pressure to reach note. A Larger string takes less travel, But requires more pressure to reach same note.

Tune the smaller string first, To raise or lower note required. Adjust any stops for smaller string, The larger string will tune to note in the confines of smaller strings stops, By moving pull rod in holes of changer and bell crank.

Example: When setting up E9th, 3rd and 6th string. Setup pull G# to A on 3rd string and adjust stops, Larger 6th solid string will now tune G# to A, Within the confines of the smaller 3rd string's stops. By moving pull rod in bell crank and changer holes.
CAUTION, With a wound 6th string the process may have to be reversed. Because of smaller core wire in wound 6th string.

That's helpful, Bobby.

It doesn't matter if it's a raise or lower, if you have 5 pulls on 1 lever, start with the smallest gauge string, adjust the stop, and all others ( raise or lower) will fall in the confines of that stop?

Edit: What if the smallest string is only a 1/2 note change and a larger string is a whole note?

[Al Carey]

This is great stuff guys, and something I’ve tried to comprehend for a long time…

[Dale Rottacker]

The farther away from the string -- from the top surface of the changer -- the less string movement you get from a given amount of rod movement. So the changer hole closest to the floor (of a standing-up guitar) will yield the easiest feeling pull but will require a longer pedal or lever movement to get the same amount of pitch change as the shorter, stiffer pull you'd get in a changer hole closer to the top of the guitar.

You can think of the cross shafts and the axle of the changer as being essentially the same -- pivot points for a circular motion. But they are opposite from one another in terms of one being upside down from the other.

Jon, every manufacturer should be hiring you to write their manuals, from rodding charts to probably split screw setups as well. (I'm guessing on the split screws) Your bell-crank & changer explanations, are the clearest best described visuals I've ever read. You painted pictures and used words even this dumby could understand with clarity.

[Jon Light (deceased)]

Dale -- that's kind of you to say. When I succeed in getting an idea across, it's because I edited it 73 times, fretting about every little possible misinterpretation and confusion -- my own, included. When we are talking about shorter throw but also about shorter pull, it can get your head spinning and failure to see how someone might misread what you are writing causes all sorts of problems.

[Roger Rettig]

Jon:

Your 'Overtuning' sticky is a much-visited thread.

This is a different, but no less important, topic. It's not for me to say, but I'd think that your remarks on this thread should become a 'sticky' of their own.

Of course, it would mean you having to edit (maybe not 73 times), but could we impose on your kindness just one more time?

I'm learning these principles by trial-and-error but still don't have it in my grasp (especially timing pulls).

You're a big asset to our community - thank you!

[Andrew Frost]

Bob, yes - if one pull is out of the gate before the other(s), and creating an unwanted bump/hiccup, then moving that pull away from the crossrod will 'empower' the pull a bit more and then allow you to loosen the corresponding nylon hex nut at the changer end. It can then start later and smoothly synch with other changes on that pedal/lever.

[Bob Snelgrove]

What if the smallest string is only a 1/2 note change and a larger string is a whole note?

[Bob Snelgrove]

Bob, yes - if one pull is out of the gate before the other(s), and creating an unwanted bump/hiccup, then moving that pull away from the crossrod will 'empower' the pull a bit more and then allow you to loosen the corresponding nylon hex nut at the changer end. It can then start later and smoothly synch with other changes on that pedal/lever.

So, you would adjust the early pull slacker rather than the later pull tighter?

[Tucker Jackson]

If your only concern is the timing of the two pulls (rather than the total throw distance, or how stiff or loose it feels), you could go either way to get those pulls synced up.

But an overly-long throw or stiffness may also be an issue for you, so it might be a good time to post this even though its been well described above. Sometimes, it's easier to grasp with a picture:

[Dale Rottacker]

Dale -- that's kind of you to say. When I succeed in getting an idea across, it's because I edited it 73 times, fretting about every little possible misinterpretation and confusion -- my own, included. When we are talking about shorter throw but also about shorter pull, it can get your head spinning and failure to see how someone might misread what you are writing causes all sorts of problems.

I feel ya Jon ... Communication is NOT my Super Power. Finding the right word or phrase in real time is often an exercise in both futility and frustration. Writing something out 73 times is my preferred method. I need to revise, rethink, re-examine and massage it till I'm happy with it and even then, may only get my point across in my own mind.

And Tucker I like you're visual ... Icing on the cake for me, when my mind isn't quite getting the verbal clues as clearly as I like. You and Jon could make a good team.

[Roger Rettig]

Both Jon and Tucker have saved my bacon more than once!! I keep their correspondence handy.

I've just ordered the new workbench from Ross Shafer; I should have got one years ago but I never foresaw me working under one of these things!

Thanks to everyone who's been so helpful here on the Forum.

[Andrew Frost]

I'm learning these principles by trial-and-error

Same, Roger. The forum here is a much appreciated source of info.

Another interesting factor is the string tension...

What if the smallest string is only a 1/2 note change and a larger string is a whole note?

If you had a small string but very little tension on it, ie super light gauge, it will require less travel. So this runs a little counter to the 'small sting = more travel' general rule of thumb at times.

To get a feel for this, try tuning your 3 G# down a whole tone at the keyhead.
You effectively now have a very light gauge F#. Notice that the half tone raise on B pedal will throw it way more than a half tone. The string size didn't change but the tension is reduced when tuned down to F# so requires less travel up or down.
Conversely, if you tuned string 8 E up to F#, hypothetically, and then engaged the half tone lower, It would not make it down all the way.
If I'm misguided here at all I trust someone will chime in
The balancing of pull requirements is just as much about tension than string size.

[Tucker Jackson]

That's an interesting experiment you did.

It proved something, but maybe not the useable rule intended because it's an apples and oranges thing. It proved that less tension means less required travel... but that's mostly observable when comparing two tensions on one string gauge. So, on one given gauge, we can say less tension means less travel.

Good, but there are a few issues. First, this phenomenon doesn't much enter into the situation here of trying to time pulls. I know you weren't suggesting this, but we don't get to take one gauge and twist the tuning key to change it's pitch to achieve the better travel length or syncing we're after The pitch we're shooting for is fixed. Therefore, if we're going to take the less-traveled route and try to time pulls using different strings (rather than a change at the bellcrank), only the gauge and it's associated tension can be swapped out. To change one is to change both, so two sides of the same coin.

I don't think we can draw a universal conclusion from the experiment that says "less tension means less travel." That may be true when comparing two tensions on one string where the core size isn't changing, but it is NOT true if we get to expand out and compare strings of different gauges, because the differing core size kicks in and complicates things as a whole new overriding variable. Put a thinner string up against a thicker string pulling to the same pitch, and the thinner will always require more travel, even though it is under less tension. I don't understand the metallurgy behind 'why,' but gauge matters more than does tension level in terms of how much distance is required to stretch it, say, a half-step up in pitch. That's why it's good to focus on string gauge rather than the tension calculator when messing with strings to time pulls. Really, don't mess with strings. Bellcrank changes are where it's at...

[Andrew Frost]

Yes, duly noted and well said Tucker.

I hear what you're saying about leaving the string gauges alone. This simple realization about tensions, though, can help if one needs just that extra bit of travel when the bellcrank, changer and pedal stop are maxed out.
A lighter gauge string might get where you need it to go, or provide a touch of tuning 'headroom' so to speak...
But then, I question this myself because in my head I'm thinking exactly what you have outlined here, that smaller strings will need more travel...