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Post new topic Aluminum Blocks on Pull Rods ??? (Sierra U12)
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Author Topic:  Aluminum Blocks on Pull Rods ??? (Sierra U12)
Adam Derstine


From:
Indiana, USA
Post Posted 2 Dec 2017 5:10 pm     Reply with quote

So I bought a nice red Sierra Universal (from some weird guy named Damir??) and I'm working on getting it set up. I understand most of what I have to do, I think, and I've been over it with a luthier friend.

However, there are a few rectangular aluminum pieces with set screws that join pull rods on the same string, and I don't know what they're for. (some kind of tempering for when a string is already being pulled? or are the blocks a way to overcome the fact that there can only be two raises and two lowers on each string with this changer?) I'm sure someone here knows... also, will I have to use them on my new setup?

You can see the square blocks, about the size of a postage stamps in the pictures below. The copedent on this guitar is BIZARRE! There's no third string change at all (B lever doesn't raise the G# to A). I'm going to build a pretty standard U12, stripping it down to nothing and adding in three pedals to get my mind wrapped around this 80 pound beast.

Any help would be very much appreciated. I'm having fun with this and actually looking forward to working on the guitar.





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Jerry Overstreet


From:
Louisville Ky
Post Posted 2 Dec 2017 5:29 pm     Reply with quote

Yes, they are for adding another pull. You can go to http://steelguitar.com/manuals.html and download the Sierra manual. Look under the CHANGER paragraph for the explanation and description.

There is a diagram further down in the manual on another page as well.

Here is some info as used from an MSA source.
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Adam Derstine


From:
Indiana, USA
Post Posted 3 Dec 2017 5:28 am     Reply with quote

Unfortunately, I don't think that's exactly it.

I looked closer and all the rods that go to one of those blocks keep going on to the changer, so it doesn't seem that it's a way to add more pulls... and I don't understand why the blocks do what they do.

For example, when the 5th string is raised with the 5th lever, one of those blocks pulls on a rod that pulls on the rod that raises the 5th string with the 3rd lever. But it's set up so that the reverse doesn't happen when you pull the 3rd lever.

I imagine this is some kind of tempering help, but to me it seems that it would just make tuning harder because whenever you hit the 5th lever you're pulling two rods to accomplish the raise. Or since it's the same change does that mean you only need to tune one?
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Tim Herman


From:
Alberta, Canada
Post Posted 3 Dec 2017 5:39 am     Reply with quote

Is it possible those blocks are for timing your pulls?
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Jon Light


From:
Saugerties, NY
Post Posted 3 Dec 2017 5:51 am     Reply with quote

.
.

I don't have the time to study on this. I've never been underneath a Sierra so I don't want to throw guesses out there. But this is out of the manual.

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Jerry Overstreet


From:
Louisville Ky
Post Posted 3 Dec 2017 6:07 am     Reply with quote

Jon's diagram shows the function I described above in the Sierra manual I referred to.

I've owned 2 Sierras, and have used this a few times.

Can't really tell from the photos the entire run of the rods and mechanisms, up to the changer.

If they're not there for adding pulls, I don't know what other function they would provide....unless they are extending pull rods that are just too short.
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Tony Glassman


From:
The Great Northwest
Post Posted 3 Dec 2017 10:05 am     Reply with quote

It's a way to get a triple raise out of a double raise changer. The block
(called a "slave "unit by Don Christiansen -then owner of Sierra) allowed a third poor pull rod to piggyback on another pullrod.

Note that the pull rod without changer spacers cannot activate the changer by itself. However When you move the bell crank connected to that rod, it pulls a collar up against the block which then pushes another pull rod that does have changer spacers, and thus the desired pitch change is made.

Each rod can be tuned independently.
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Adam Derstine


From:
Indiana, USA
Post Posted 3 Dec 2017 10:30 am     Reply with quote

Yeah, that's it.

The part I was missing and still don't 100% understand is what that extra raise or lower is attached to that makes it tunable but not really a pull... it's attached to the changer somehow. I need to figure that out.

Thanks for helping me with this, everyone!
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Tony Glassman


From:
The Great Northwest
Post Posted 3 Dec 2017 1:00 pm     Reply with quote

Ok..........for example - you want to have a vertical lever that raises the 4th string E-->F# but also keep pedal C . So that means your wanting to raise that string 3 times: ( pedal C, E-->F knee lever and the new E-->F# vertical lever.

Using John Light's diagram: there is aluminum block "Y" thru which pass 2 pull rods. One has a collar labeled "x" so call that pullrod-x and the other has collar "z", so call it pullrod-z

Pullrod-z (which has changer spacers) operates like all the other Sierra pullrods and is tuned by turning the brass hex head. This drives the pullrod into (or out of) the plastic barrel on the bellcrank allowing tuning of the change.

Pullrod-x has no spacers but still threads into a bell crank plastic barrel. When you turn the tuning hex, it changes the point at which collar-x impacts block "Y" by adjusting the rod depth into the plastic barrel.

When you "mash" a pedal or KL with pullrod-x: collar-x will impact block "Y" which will then impact collar-Z and drive pullrod-z forward against the changer to effect the pitch change desired.

If you loosen the hex on pullrod-x, it lengthens the distance between the impact point collar-x and block Y, so it moves the changer finger less. Tightening does just the opposite.

So tuning pullrod-x does not directly act on the changer. It indirectly does so, via block-Y and pullrod-z.

Hope that makes some kind of sense!
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Adam Derstine


From:
Indiana, USA
Post Posted 4 Dec 2017 12:04 pm     Reply with quote

Believe it or not, that's actually crystal clear. The X Y Z thing cleared it up for me. Thanks so much!

Now I just have to wait until tomorrow when the guy at North County steel is in the office so I can order rods and a few cranks (maybe a LK Raise?) and get to work on this thing in earnest. One question I was going to ask him - does anyone have a rodding diagram for this guitar? I think it's all stuff I can figure out, but probably with a lot fewer steps if I'm starting from a solid starting point.
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Lane Gray


From:
Topeka, KS
Post Posted 4 Dec 2017 5:01 pm     Reply with quote

If I were to want to add more pulls to a Sierra, I would add Sho-Bud barrels to the rods.
BUT you'd have to tune the barrel-tuned changes first, since tuning those would knock the nylon-tuned changes out.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects
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Tony Glassman


From:
The Great Northwest
Post Posted 4 Dec 2017 7:09 pm     Reply with quote

Lane Gray wrote:
If I were to want to add more pulls to a Sierra, I would add Sho-Bud barrels to the rods.
BUT you'd have to tune the barrel-tuned changes first, since tuning those would knock the nylon-tuned changes out.


Lane, what would the advantage be of using ShoBud barrels be? The Sierra block fix allows you to tune both changes at the end plate independent of each other.
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Lane Gray


From:
Topeka, KS
Post Posted 5 Dec 2017 12:09 am     Reply with quote

In the case of a universal, the B and G# strings will want 4 raises.
And, as I've not seen this block thing in action, I'm not understanding its operation.
From my perspective, the solution I understand is vastly preferable to the one I don't.
Perhaps I'm just funny that way.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects
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