Changer axle

[12string]

Hi folks,

What is the best material for the changer axle, in order to reduce flxing as my 12 string might be suffering from this problem ( 8-10 cents cabinet drop). I used high tensile steel but it was easily cut with a hacksaw,

Stuart

[Bent]

Hi Stuart,
My opinion is that you need an axle that will break before it bends.
I have recently learned that the axle flexing was of concern to the builder of the Emmons PP. So he chose to use 9/16" case hardened drill rod or the equivalent of this accurately dimensioned steel. From what I also learned, he figured that he had disproved the axle bending as a reason for cab drop and blamed it on the cabinet flexing. Whatever the reason may be, I choose to eliminate THAT question by installing an axle that I know will not bend. So I recommend an axle of at least 1/2" diameter that has been heat treated to a hardness of Rockwell 50... a hardness very close to that of a drill bit.

[azureskys]

I use stainless steel 1/2 inch diameter with zero cab drop, it has a very high sheer strength and its not going to flex , if you cut that what you called tool steel bar with a hacksaw i kinda dought it was tool steel , tool steel will rust , stainless can be polished before installation and it wont rust . high speed steel is also a good material and chrome moly is good. Russ

[12string]

Russ,

Do you have anything between the changer and the axle, bush ,PTFE or suchlike,

Stuart

[azureskys]

I dont think you need a bushing there , the fingers are what moves in the changer however if you felt it should have a bushing by all means do it but i really dont think its neccessary, the fingers dont have a bushing they just ride on the shaft .I have an old sho bud and a MSA neither has a bushing on the axle or shaft.Some makers might do it but i cant see why.Just lube it good when you install the fingers and your set. Someone correct me if im wrong. Russ

[Bent]

As I also have learned lately, there should be no bushing there. It should only be the aluminum finger pivoting on the steel shaft. Also, there should be as thin a wall as possible on the finger around the axle hole. I was told 1/8" wall around the diameter is ideal. But I can't see a big disaster making it a bit thicker.
All this is for maximizing the sound and vibration transfer throughout the guitar.

[mac639]

No bushings for sure. I've thought some about the wall thickness. Probably 1/8" is good, but thicker likely won't make a difference either. I can never get too excited about the axle diameter. If you support a 4" piece of 3/8" regular steel rod on the ends and see how much force in the center it takes to bend it.......a whole lot! You could pull your car easily with it and it wouldn't bend. I don't think for a minute that the axle flexing has anything to do with "cabinet drop", even on a 12 string. If you've got it, it comes from something else in the train, bushings in the crossrods, slop in the axle housing, changer bolts not snug, keyhead moving, lots of things. Same goes for the cabinet itself. 3/4" maple top with 3/4" by 2+ inches (on edge) screwed and glued aprons on both sides. How can that bend even a bit?? I tried something one time. Supported a new guitar body on the ground a couple of inches only on one end. Drove my Hyundai front wheel up on it and measured the flex with a 36" straightedge. Only the tinyness of a crack of light in the center....maybe a couple of thousands, no more. Don't know what the weight was but probably in excess of 700 lbs.??
Sorry for the rambling. I've made guitars with a lot of drop....turned out to be just sloppy workmanship, fix the things you did wrong, and it's mostly gone! We worry too much. Just make a pretty cabinet out of GOOD wood, fasten your mechanical stuff to it as solid as possible....and enjoy your creation!
Mac

[Allan]

Mac, my hero... I am delighted to see that someone has actually done some useful tests on this subject. I have always stayed clear of the arguments on body drop as I had nothing practical to contribute. I simply felt that the effect that some people see was not correctly named. Body drop/cabinet drop - nah, I don't think so. I have built enough conventional (Spanish) guitars to know for sure that even the thin wood used there can resist amazing compression forces. My feelings on the subject are precisely the same as your own and I am really pleased to see it all backed up by your 'Hyundai Test'.
I get a bit hacked off when I see those l-o-n-g threads developing on the subject because they always seem to start with 'so I pressed this pedal and that string went flat therefor I have cabinet drop'. Then the thread is off and running. All that is true in the statement was the part before the word 'therefor'.

Ach, I need to stop before I get into another sermon!!! I just wanted to say that I agree with you, 100%, in what you said above. I could have done that in a single line!!!

[Georg]

Mac, Allan, please don't write all comments about "too weak changer axles contributes to detuning" off as nonsense that easily. Otherwise you may end up calling me a liar when I say that the original changer axle on my Dekley S10 bended measurable when tuning up and contributed audible and measurable to detuning when pushing pedals/levers...

I have no problem with anything else mentioned about possible causes for detuning in a construction in this or other threads or forums - weak constructions and bad assembling of parts are the usual suspects, IMO. One must recognize and fix and/or counteract them all if one wants a PSG with no detuning, but don't write off that changer axle completely in the process.

[mac639]

Georg....You may be entirely right in finding that the changer axle was indeed bending on your Dekley, I don't know. The one thing I do know is that a piece of steel rod supported at both ends and only about 3" or 3-1/2" between the ends takes a heck of a lot to bend it in the center since the distance between the supports is so small. If the distance was a foot or more, sure it would bend, and the longer the distance between supports the more it would bend with the same force applied. I'm no scientist or engineer but I'm just thinking of my youth and a clevis with a gap of about that size hooked on the plow or harrows. We'd have a couple of 1500 lb. Belgian horses pulling on it and it didn't break. And that was a clevis made by hand by our local blacksmith with his forge. Oh well, it's fun to talk about anyway.
Mac