Changer Stability

Fred Shannon · Post by **Fred Shannon** » 24 Jun 2008 5:11 pm

One of the threads being discussed almost violently has some information in it that has me very confused (not a hard thing to do at my age.) Tommy Young stated that he installed the screws in the changer to keep the "back of the changer" from coming up when the pedals are mashed. His rationale is this causes a detuning on older guitars because of the stress that has been applied to the aluminum over the years. I have had instances on some guitars that indicate the changer stability may be in question, but for the life of me I can't see how the back of the changer can raise. I usually fixed the problem by a good cleaning, lubrication and string change. I guess I just don't thoroughly understand the pressures placed on a changer when the pedals are being activated. I wish someone would take the time and explain to an old phart how this action can be done. Especially true where the changer is mounted in cast aluminum. I just can't fathom the action. thanks in advance.

phred

James Collett · Post by **James Collett** » 24 Jun 2008 7:58 pm

Just as confused as you are Phred!

admin · Post by **b0b** » 24 Jun 2008 8:21 pm

Consider the stress applied through the main axle onto the parts that hold it in place. John Fabian's animations might help you to visualize it:

http://www.steelguitar.com/steelmap/maptop/changer.htm

I think that the lowering movements are the ones that might apply upward force on the changer near the endplate. I've never actually seen this happen on any of my guitars. Seems that it might be a very rare problem.

Brint Hannay · Post by **Brint Hannay** » 24 Jun 2008 8:58 pm

Without in any way endorsing, seconding, refuting, or debunking Tommy's concept--

I believe the guitar with reference to which this was said by Tommy is a pre-Royal Precision Mullen. I have a pre-RP Mullen (1994--I love it, it's an absolutely wonderful guitar). While I have never disassembled the changer area of the Mullen to know the details of its construction:

Unlike, for example, the Sho-Buds I have (all wood-necks with the changer housing/tailpiece being one single large hunk of aluminum), or the Williams and GFI I also have (which both have aluminum necks with "cut-tail" construction) the changer on the Mullen is a discrete unit that emerges from a completely-surrounding cutout in the aluminum neck just as the pickup does. This makes it impossible to know without disassembly the nature and dimensions of the changer housing and the details of its attachment, as it lies underneath the neck surface.

I have no intention of disassembling mine just to find out, but perhaps someone who has disassembled one (or assembled one!) could shed light on this matter.

I might add FWIW that my Mullen has tuning accuracy and stability of both open strings and mechanisms that equals or exceeds any other guitar I've owned.

(b0b, I would think it would be the raises, if anything--increasing string pull on the "front" (toward the nut) side of the changer would be more likely to pull up on the rear side, wouldn't it?)

Fred Shannon · Post by **Fred Shannon** » 25 Jun 2008 3:51 am

Yeh Brint, I'm not questioning Tommy's reasoning, I just dont understand whether it's the tensioning of the string or the pressure from the pull rod that can cause the event. I can see the possibility of the back raising if the axle block screws/bolts are not properly torqued, but if they are I don't for the life of me see how the mechanism can raise when the pedals are activated.

b0b I looked at Carter's presentations, as you suggested, but dense as I am I guess, I still fail to see how it can happen. I've had the detuning happen on different makes of guitars. My old Mullen was not, to my memory, guilty of the "crime". It was probably one of the most stable of all the guitars that went through here. Thanks for the input folks.

phred

Post by **b0b** » 25 Jun 2008 5:55 am

I can't figure it out either.

Brint Hannay · Post by **Brint Hannay** » 25 Jun 2008 6:00 am

Phred, I am just another person trying to understand how this would be, like you. This is what Tommy said:

on """SOME"""" of the older MULLEN guitars they didn't put anything to hold the back of the changer down at all

I am highly skeptical of the accuracy of this statement, but a) for the reason stated in my previous post, it's not possible by simple observation without disassembly to determine the accuracy of what he says about the design of the Mullen changer, and b) I do not have substantial knowledge or experience in mechanical matters such as the flexibility characteristics of metals to evaluate the validity of his theory even if the physical facts are as he says.

Mike Mantey of Mullen posted this on the subject:

Your suggestion that the changer is failing over time from the use of the changer is ridiculous. That changer has the same integrity it did on day one. For your information there are screws in the back of the changer. They go all the way through the body, end plates, and changer.

David Wiggins · Post by **David Wiggins** » 25 Jun 2008 7:00 am

Hi All, To me,the comment about pulling the back out of the guitar, is a bit of an over statment! I think that the writer is on about play in say a lower screw, even if you are not lowering that string. This will allow the finger, when moving to raise the string tone, to move in an arc. The lower is not bound tight in the end plate.Just as you would with a ZB guitar. Hope this helps.
Best regards to all.
Dave Wiggins.

Fred Shannon · Post by **Fred Shannon** » 25 Jun 2008 7:03 am

Well then if what Mike says is true, "For your information there are screws in the back of the changer. They go all the way through the body, end plates, and changer," then why the need for more screws. Maybe the others came out or something. And for all the Tommy Young supporters, this is not picking on Tommy. We just have legitimate questions.

Phred

Mike Mantey · Post by **Mike Mantey** » 25 Jun 2008 7:35 am

There are the screws actually bolts, socket head cap screws that go all the way from the bottom of the guitar through to the changer. If you look on the bottom of your Mullen under the leg sockets, you should see them. They are black.

Now the changer still could be flexing (possibly) a little bit, due to the extreme loads pulled on them. I guarantee this cannot be seen with your eyes, only measured with a dial indicator. You could have a thousand screws in there and it would still flex, if not at the changer then somewhere else, there is no way to totally eliminate it. Like I said you can't see it nor should you be able to hear it.

The statement that the changer fatigues due to stress over time is not true. The only thing is the screws may loosen over time and may need to be tightened. The wood also expands and contracts a lot and can cause the screws to loosen, so if you find these screws on your guitar, go ahead and sock them down.

I speak for the Mullen guitar only.

Bent Romnes · Post by **Bent Romnes** » 25 Jun 2008 7:39 am

Would this thing be settled by someone actually loosening the screws holding the changer to see what happens?
Edited:
Mike got in just ahead of me. Of course you're correct Mike.
The only way the changer can lift is if the bolts holding it come loose.If so, then simply re-tighten the bolts.

Brint Hannay · Post by **Brint Hannay** » 25 Jun 2008 8:43 am

Mike, I was hoping you'd chime in here. I just looked under my guitar and found the bolts you described--I just didn't know where to look before.

If the bolts loosened up, obviously the solution to that would be just to tighten them down--no added screws required.

That only leaves the theoretical possibility that the metal might flex between the bolts, which are at the bass end and treble end of the rear of the changer. But a) can it?, b) enough to matter?, c) if it does flex, is there any fatigue factor that would result in a change of flexibility over time, thus requiring a "fix"?

Seems dubious, IMO.

admin · Post by **b0b** » 25 Jun 2008 9:14 am

Mike, were some early Mullen made without those bolts?

Mike Mantey · Post by **Mike Mantey** » 25 Jun 2008 9:55 am

b0b, nope.

Fred Shannon · Post by **Fred Shannon** » 25 Jun 2008 10:01 am

Well, with Mike's answer to b0b's last question and because there were screws/bolts there, then my original question is answered to my satisfaction.

Thanks, you guys for a very informative thread. Gee, and with no butt whacking. Ain't it amazing when truly interested folks can converse in a friendly manner. Love it.

Mike especially thanks to you for the summarization. And b0b i was aware of the Carter schematics before but I had forgotten them. I bet a lot of newer folks to the guitar would enjoy them also.

If no one else has further questions then we can shoot this horse dead and close it. Now I can look at the other threads with a more knowledgeable outlook on what transpired.

phred