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Topic: All Pull Changer Finger Question |
Joseph Meditz
From:
Sierra Vista, AZ
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Posted 27 Feb 2012 8:36 pm |
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With the changer apart I see that each raise/lower pair is like a scissor. My question is should it behave like a pair of ordinary scissors, meaning that when the changer fingers close should there be a little friction when the reach their closed position? Or should they move entirely freely?
Also, how close should the axle bearings be, i.e., how much play should there be between the changer fingers? Should they be as close as possible while allowing free movement or should there be some slop between them? If so, how much?
Thanks,
Joe |
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Bent Romnes
From:
London,Ontario, Canada
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Posted 28 Feb 2012 5:32 am
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Joe, An all-pull changer needs to move as freely as possible. The scissors have to move with the same amount of freedom in the total distance of their movement. This is decided by how tight the rivet is. It needs to be tight enough so that there is no, or hardly any slop. I use a very thin washer between the scissors , just a 2/1000" washer I cut from a shim. Then I don't use a rivet but a stainless Chicago screw, where I can control the amount of tightness more easily. That way the whole scissor parts ride on the washer without rubbing much against each other.
Same with the axle. Drill rod is perfectly sized to 1/2" say...I ream out the hole in the scissor with a reamer thereby getting the fit I am after.
_________________
BenRom Pedal Steel Guitars
https://www.facebook.com/groups/212050572323614/ |
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Tony Russell
From:
North of England
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Posted 28 Feb 2012 5:47 am
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Friction is bad. "Slop" is bad too, but friction is worse. Mechanisms need to be just free enough to move without jamming. From the wording of your post I think you guessed that already. I hope your question does not result from a problem? Good luck, Tony.  |
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Joseph Meditz
From:
Sierra Vista, AZ
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Posted 28 Feb 2012 6:24 pm
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Thanks for the replies. To free up the changer fingers I first tried 0000 steel wool and then 600 grit sand paper without much success.
When the scissor was closed it could be turned upside down without opening, and this is after the mechanism was completely clean. What I then did was bend them in my hands, or should I say, "re-form" the metal. It just took a little bit to free them all. The rivets were fine, actually just about perfect, hardly any play and free movement.
Joe |
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Joseph Meditz
From:
Sierra Vista, AZ
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Posted 28 Feb 2012 8:49 pm
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| Well, that tiny bit of bending caused interference with adjacent pulls. It appears OK now with good clearance and the scissors free, but I'll still fiddle around with it some more later this week to convince myself that everything is really OK. |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 29 Feb 2012 3:14 pm Re: All Pull Changer Finger Question
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| Joseph Meditz wrote: |
| With the changer apart I see that each raise/lower pair is like a scissor. My question is should it behave like a pair of ordinary scissors, meaning that when the changer fingers close should there be a little friction when the reach their closed position? |
No, because you're not cutting anything. Ordinary scissors exhibit that tendency because they are used to cut thin materials Or should they move entirely freely?
| Quote: |
| Also, how close should the axle bearings be, i.e., how much play should there be between the changer fingers? Should they be as close as possible while allowing free movement or should there be some slop between them? If so, how much? |
Ideally, there would be no slop and no friction. You can't get that, but you can get very close. You need a thou or two of clearance to keep things from binding up when they get hot. As the guitar is played, parts will eventually get looser on their own. Too much clearance in a new one or on a rebuild would mean that in a number of years, it may get pretty sloppy.
In the final analysis, though, a little slop is better than a little binding. 
Thanks,
Joe[/quote] |
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Joseph Meditz
From:
Sierra Vista, AZ
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Posted 29 Feb 2012 8:30 pm
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All that makes perfect sense.
I asked about the fingers since so as not to do something wrong. As it turned out,that tiny bit of bending to free up the fingers did cause problems with adjacent lower tuning nut flanges. Rather than put them back into scissor mode I belt sanded off a small amount of material on the sides of lower pull hole flanges.
There is a little wear on the axle which may have been exacerbated by the minor slop. If one could have zero play then the fingers would ride on the axle as squarely as possible.
I polished the axle a bit with 0000 steel wool. Still, I'll rotate the axle with its good side up when I install the changer as was mentioned recently. |
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