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Topic: There is a question in here, just not sure how to ask it... |
Allan Munro
From:
Pennsylvania, USA and Scotland
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Posted 22 Aug 2009 9:50 pm |
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I am having a problem getting this in to words that I can understand - I hope it makes sense to someone else!!!
Right, here I go - the pedal goes down, it pulls on the vertical rod thingie which is attached to a bell crank on the cross rod thingie. (Come on people, why are so many of the parts called the 'thingie'? It makes it so difficult for someone new to this.) Then, the cross rod thingie pulls on another bell crank thingie which pulls on a horizontal rod attached to the wobulator dohickey which has the strings attached to it and tightens or loosens said string to effect the desired tension change.
Now I am getting to the meat of this - at this point it all comes to a halt at the correct tension under the control of that long nut sort of thingie on the end plate.
Question A) Have I got this sort of right so far?
Question B) If the answer to A is 'Yes' or even 'Yes, sort of' then how is it possible to have a single pedal control/change the tension of more than one string? It seems to me that multiple strings will reach tension at different times and with different amounts of movement being required. The result of this would seem to be that the first of multiple strings to come to the place set by its long nut thingie would bring the entire mechanism to a juddering halt which would then stop any further strings from continuing on to reach the new tuning required. I am guessing that there is a degree of slippage (I so love these technical words!) built into the system so the real question seems to be, where is it?
I am currently building a wobulator dohickey as an exercise but I have decided to rename it for simplicity, I just refer to it as a changer coz that's what it does.
Please excuse me if this question has been dealt with on here before and, if so, a reference to the previous thread would be great. I did try searching under 'wobulator' and 'thingie' with no real success.
Regards and thanks to all who make this forum such an amazing resource, Allan..... |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 22 Aug 2009 11:33 pm
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| Quote: |
| Question A) Have I got this sort of right so far? |
Yes, sort of 
| Quote: |
| Question B) If the answer to A is 'Yes' or even 'Yes, sort of' then how is it possible to have a single pedal control/change the tension of more than one string? |
The bell cranks on the cross shafts have several holes/positions at various distance from the cross shaft. Hinging up the horizontal rod close to the cross shaft gives short travel, while hinging it up further away from the cross shaft gives longer travel.
We use/choose these bell crank holes/positions so as to balance travel for various strings characteristics, taking into account how many half-tones each string should be raised or lowered, so they all can be tuned individually for correct tone with their respective nylon tuners pulling the changer fingers when the pedal is fully down.
We also make sure there's a little travel to spare - free-play - when the pedal is fully released, so all strings can return properly to true open tone. Getting enough free-play for rods with really short travel can be difficult, but it is essential to get this right for true open tone.
On a changer with several raise/lower holes to thread the horizontal rod through, we may also choose hole to balance the travel even further.
As we're usually dealing with bell cranks and changers with holes/attach-positions at fixed distances from the cross shafts and hinge-points, we can rarely ever get several strings in perfect balance with regard to start (pedal up), stop (pedal down) and travel-distance (in between). At some point we just say: "good enough", set the instrument up and start playing. |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 23 Aug 2009 7:19 am
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| The pedal is attached to the pedal rod, which is attached at the top to the cross-shaft crank, which turns the cross-shaft, which is attached to one or more bell-cranks, which can be attached at multiple slots to the pull rod, which runs horizontally to the changer finger, which is a jointed lever that rotates on the changer axle and pulls or releases the tension on the strings. The nylon hex nuts at the ends of the pull rods allow the pedal and lever stops to be individually tuned. That's the common terminology. Georg has explained pretty well how to balance the travel of the bell cranks and pull rods to time the multiple pulls together. |
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Brint Hannay
From:
Maryland, USA
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Posted 23 Aug 2009 9:01 am
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Re your question B:
It isn't the changer (wombulator) of any string reaching its tuned point that physically stops the movement of the pedal or lever. All the changer mechanisms, for whatever strings are moved by a given pedal, have room to spare. They don't hit anything when their tuned points are reached. There is a physical stop out at the cross shaft which is what stops the movement of all the mechanisms attached to that cross shaft, and thus to that pedal/lever. This is adjusted to allow the amount of travel required by the pull that needs the most. Other pulls, as mentioned, are set up via hole selection in the bell crank and changer to cause the timing of their travel to be as close to equal to that of the longest pull as possible.
There is a limit to how far the changer mechanisms can move before they do hit something, but only a few pulls one might want to try exceed that limit on most modern changers. For example, on most guitars, the changer can't move far enough to allow lowering the 3rd string (E9) from G# to F#, no matter what is done with the setup of the pull rod.
Last edited by Brint Hannay on 23 Aug 2009 1:48 pm; edited 2 times in total |
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Allan Munro
From:
Pennsylvania, USA and Scotland
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Posted 23 Aug 2009 12:19 pm
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As I said in my original post, this forum is an amazing resource and it is the members that make it so.
Many thanks to all who have responded to my badly worded questions. I have a much better grasp of what happens now.
As I said, I am building a version of a changer just as an exercise and to keep me off street corners and away from naughty ladies. I am half way considering building the complete changer now that I have a better grasp of what I am doing.
Again, thank you all for the information.
Regards, Allan..... |
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b0b
From:
Cloverdale, CA, USA
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Posted 23 Aug 2009 12:40 pm Re: There is a question in here, just not sure how to ask it
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| Allan Munro wrote: |
| Come on people, why are so many of the parts called the 'thingie'? It makes it so difficult for someone new to this. |
vertical rod thingie = pedal rod
bell crank thingie = bell crank (ding! one right)
cross rod thingie = cross bar
horizontal rod = pull rod
wobulator dohickey = changer finger
long nut sort of thingie = tuning nut
| Quote: |
| ... how is it possible to have a single pedal control/change the tension of more than one string? It seems to me that multiple strings will reach tension at different times and with different amounts of movement being required. The result of this would seem to be that the first of multiple strings to come to the place set by its long nut thingie would bring the entire mechanism to a juddering halt which would then stop any further strings from continuing on to reach the new tuning required. I am guessing that there is a degree of slippage (I so love these technical words!) built into the system so the real question seems to be, where is it? |
The "slippage" is in the small gap between the tuning nut and the changer finger. The size of that gap determines the point in the pedal travel where the system actually starts pulling on the string. Turning the tuning nut changes the size of the gap.
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Tony Prior
From:
Charlotte NC
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Posted 23 Aug 2009 12:50 pm
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the bell crank thingie and the wobulator thingie each have a series of holes for the cross rod thingie, this is how multiple strings can reach the same stopping point for travel, the "king wobulator developer" ( you) can select different holes in each of the Bell crank thingies and wobulator thingies so that that travel for different sized strings can be adjusted within the same pull, you know shorter travel vs longer travel based on the selected holes.
the original thingie inventors were pretty smart I would say and I would also contend that they ain't done with there smartness.
good luck with the wobulator
t
Last edited by Tony Prior on 23 Aug 2009 1:13 pm; edited 1 time in total |
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Stuart Legg
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Posted 23 Aug 2009 12:53 pm
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Allan, great question. It would be helpful if we had an exploded view of PSGs in general with the universal names attached.
One of the problems is that it is not like an auto where you can go to the parts store and look it up in a book.
When is the last time someone used a crank off a bell as a part for the PSG?
When does a rod become a shaft or visa versa?
A hole by any other name is still a hole.
Parts is parts.
Shouldn't it be an across shaft? |
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Tony Prior
From:
Charlotte NC
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Posted 23 Aug 2009 1:16 pm
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definition
Stuart, you are not that far off !
Bellcrank
http://wapedia.mobi/en/Bell_crank
A bell crank is a type of crank that changes motion around a 90 degree angle. The name comes from its first use, changing the vertical pull on a rope to a horizontal pull on the striker of a bell, used for calling staff in large houses or commercial establishments.
The bell crank consists of an "L" shaped crank pivoted where the two arms of the L meet. Moving rods (or ropes) are attached to the ends of the L arms. When one is pulled, the L rotates around the pivot point, pulling on the other arm.
Changing the length of the arms changes the mechanical advantage of the system. Many applications do not change the direction of motion, but instead to amplify a force "in line", which a bell crank can do in a limited space. There is a tradeoff between range of motion, linearity of motion, and size. The greater the angle traversed by the crank, the more non-linear the motion becomes (the more the motion ratio changes). |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 23 Aug 2009 2:06 pm
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| There are some moving diagrams of typical pedal steel mechanisms over on the Carter site. I believe they are mostly labelled as I did in my post above. Or if you simply flip your pedal steel over and follow the linkages from pedal to changer while reading my post, you will have it all. Just be sure to never rest the bare strings at the bridge on anything hard, which will gouge grooves in the top of the changer fingers. |
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Allan Munro
From:
Pennsylvania, USA and Scotland
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Posted 23 Aug 2009 8:51 pm
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Even more replies - outstanding!
I spent the evening on the other confuser with the cad program fired up and steam coming from every USB port. I think I may actually get some success at the end of the day thanks to you all.
David, I saw the moving GIFs on the carter site, they were very helpful and actually partly triggered my questions at the start of this thread since they show a single changer element.
If anyone else is interested in the subject at my very low level there is a wealth of information to be got from looking at patent applications.
A new question if I may - is there a source for those long nut sort of thingies - SORRY b0b, I meant to say 'tuning nuts' - and what is the thread detail?
Ta muchly y'all, Allan..... |
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b0b
From:
Cloverdale, CA, USA
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John Fabian
From:
Mesquite, Texas USA * R.I.P.
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Posted 24 Aug 2009 9:09 am
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| Pedal Steel Guitar Illustrated has all the terminology you are looking for. Just use the two image maps to find what you're looking for. |
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Allan Munro
From:
Pennsylvania, USA and Scotland
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Posted 24 Aug 2009 11:15 am
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Thanks for that b0b, I will be placing an order for some stuff later tonight.
And John, thanks to you too. That 'Ask Bud' website is another excellent resource for a total tyro like me. I really will try to stop using words like 'wobulator' real soon...
Regards, Allan..... |
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