Steel Guitar Builder

I think Richard wants some form of endurance testing of changers to see what materials, lubrication-mix and what-not that works best/worst. Would be interesting, but don't forget the time-aspect. Some deterioration just takes time no matter the load and repetition-frequency, so better rig up parallel sets of changers that can be allowed to run for months and even years driven by the same geared motor.

Also, be prepared to change strings quite often, and make notes of what brands that do well and not so well. May get a lot of useful information out of the right endurance test rig.

Bent -

Georg has it right. I was a bit skimpy in my description of the experiment. The only question left in my mind is how many cycles do you let this thing go through before you tear it down and look for wear? At one revolution per second that amounts to 86,400 cycles in a 24-hour period. How many years of playing does that equate to? Don't have the foggiest. At that rate, ya might want to give it a shot of lube every morning right after ya have yer coffee.

I jest, my friend, but it WOULD make for a very interesting experiment. At the risk of taking you away from your miller and interrupting your building process I might also suggest changing the materials used for finger and axle. Measure each carefully before the stress test!

Richard

Richard, Good suggestion. I'll keep it in the back of my mind. Maybe when I have a slow week after the building of my existing project, I will check my local surplus store ..I am sure I saw a geared motor there with some sort of eccentric on it.

Bent -

We're certainly not intending to turn you into our personal "lab rat" but, when time permits we'd be interested in your findings!

Richard

Bent, Richard, remember that a rolling stone gather no moss.

If corrosion contributes to wear - which I personally am pretty sure it does, around the clock "playing" won't reveal that factor in years. Short bursts of intense "playing" with long periods of "rest" in between over a couple of months, will reveal a lot more of what really goes on in a real PSG.

So if such a rig is set up, I suggest using a timer and only let the rig "play" for a few hours by day and "rest" by night.

Georg -

I, and others, have essentially posed the corrosion question but no one has come up with firm answers as to the mechanism. Is it galvanic? Chemical? I certainly don't know.

Your point suggesting that things be given a "rest" is well taken. Let things "cook" for awhile and see what happens.

Richard

richard37066 wrote: Is it galvanic? Chemical? I certainly don't know.
Richard

Hi Richard, I don't know either. But if I may hazzard a guess, I think it could be a combination of what Gary said regarding electricity and incompatibility AND me using the wrong oil which created an environment for accelerated corrosion and galling.
I don't have very much to go on but 2 things: The Emmons PP I referred to, which had the axle galled - worse than mine, and the fingers were essentially fine
Lord know what all was used of oil in that one thru the last 35 years or so.
And... many people swear by the Triflo lube and they haven't reported bad wear like this happening. So from that I take it that Triflo works a lot better than ATF.
But sure. Let's give it a rest - no sense pursuing my unscientific tests on this item any further. New oils are being tried as we speak and we'll see how they perform.

It occurs to me that IF the question is what is the best lube then a wear testing procedure would be in order. If, on the other hand, the question is how do you prevent galling then I personally think the best result would come from using a material for the changer finger other than aluminum. Even if you use an aluminum finger and hard anodized aluminum axle you still have the strings in contact with the changer and steel, nickel, or stainless steel strings all would result in aluminum being the sacrificial anode. As far as I know (which is far from a lot) there is no lube that will prevent this from happening. Perhaps a little galling is just a practical reality for our instrument when we use aluminum for changer fingers. On the other hand stainless steel might be a good choice for both finger and axle alike. Maybe chrome plated brass (a la Bent)? Just my thoughts at this point.

Check the Periodic Table if you want to know what works best together. Maybe we should add some "better" sacrificial material a place it won't hurt, to save vital parts?

Back in my days as electrician we used what we called "CopAl" connections between copper and aluminum cables outdoors, as direct couplings corroded away in no time.
I think the connection material is known as "COPALUM", but ain't sure. Besides, there's a difference between really tight connections for cables running a few hundred Amps, and the somewhat loose connections in a changer. Different materials too.


Anyway, for a test-rig I simply meant to let the materials rest between runs - give them time to corrode. I did not mean to let such a project rest altogether, as there are not all that many alternatives if we really want to find out what's going on and what to do about it.

In my own construction I will use steel against steel (same type) and next to no lubrication on friction points, so may not see a problem. Would still be good to see some results of a test-rig.

LushPyle has a point. One of the three things necessary for galvanic corrosion is the use of two DISSIMILAR metals. For changer fingers, I'll take the stainless any day - with a stainless axle - and for reasons which I've expressed elsewhere.

As to galling and out-and-out abrasive wear, surface finish seems to be the prime concern even with the use of a superior lubricant.

Hard anodizing of aluminum seems to produce a molecular change to a depth of .001" below the surface with an additional .001" of material added to the surface. My understanding is that, since the base material is softer, there is the opportunity for cracking of the anodizing layer. This doesn't sound too appealing although I'm uncertain as to the ramifications of this cracking over time.

Richard