Keyboard axle removal via electricity

[Mr Mark]

My main instrument of choice is an older Hohner Tango IIB. I prefer the 80 bass simple 3/4 reed configuration (removed the piccolo in the bass) as I stand to play and am definitely a stroller where the instrument compliments my vocals as much as anything. I have rebuilt most components on the instrument and finely tuned things to where I am truly satisfied with the sound.

Except for the loudness of the keyboard. The main issue is the pressing of the keys, not the release, so I would like to add some felt under the keys. The problem is that the axle is really stuck. I have tried silicone spray between the keys soaking in (not too much, I'm afraid of swelling the wood!) and have gone so far as to buy one of those keyboard axle removal tools but the thing wont budge. I am only willing to twist so far because of course I do not want to shear the axle right off! I have to say, I have several accordions of this vintage (85+ years) and they all have the same issue, so it would be nice to have a solution for all.

It seems the only solution left is the electricity trick. I have done this before with moderate success, but found that the car battery method isn't ideal as the results are instantaneous - for better and for worse. While the rod came loose, it permanently stayed that way as the holes all got a tiny bit bigger resulting in a less than desirable amount of keyboard 'slop' (side to side rocking). This in turn meant the pallet had way too much movement and wouldn't settle back in the same place twice (causing leaks, notes to sound, and pallets flat out landing on top of each other). While I did find a solution of sorts (without reboring a larger sized rod as I do not have the capabilities) in paper hole reinforcements, this also proved to be less than ideal as with time they wear out or gum up.

So my thoughts are along the lines of a much more controllable electrical charge. The problem is I have no idea how I would accomplish this as I am not an electrician. It seems to me that a car battery is way overkill. Is there somehow a smaller sized battery that would be more appropriate? Something with a way to turn the juice up and or down? Something that doesn't require a tow truck once the jumper leads have fused to the axle rod and fried my car battery? Am I overthinking this (I already know yes and no )?

Thanks for indulging me.

 

[Dingo40]

So my thoughts are along the lines of a much more controllable electrical charge. The problem is I have no idea how I would accomplish this as I am not an electrician. It seems to me that a car battery is way overkill. Is there somehow a smaller sized battery that would be more appropriate? Something with a way to turn the juice up and or down? Something that doesn't require a tow truck once the jumper leads have fused to the axle rod and fried my car battery? Am I overthinking this (I already know yes and no )?

Thank you so much for sharing your experience with the "battery method " of axle removal and pointing out some of its pitfalls: very valuable .
I'm no electrician either, but seem to recall a gizmo called a "variable resistor" ("rheostat" ) you can insert in your circuit with which you can "dial" up or down the amount of current flowing through your axle, from zero to more than adequate in a controlled manner.
Perhaps, someone versed in applied electricity can explain how it can be done?

 

[JKJ]

It sounds like you could use a variable power supply to control the current - heat just enough to expand the rod in length but not enough to overheat the rod and damage the holes. A long, thin metal rod will expand proportionally, far more in length than in diameter. But my first question is exactly where do you think the rod is stuck?

A direct short from a car battery without current control could easily overheat the rod and even burn the wood in an instant. You could control the current by several methods but it seems to me that without a variable current power supply you would first need to carefully calculate the current needed. Given the material (steel?), the length, and the diameter of the rod any physics major (or physics teacher) can look up the expansion coefficient of the material and calculate the expansion at a given temperature and based on the estimated or measured resistance of the rod and calculate the current required for the desired expansion of the length vs diameter. The first trick would be to determine how much expansion is sufficient to break loose the rod without overheating. The second trick would be to find a useful controllable power source. The easiest thing might be to consult with a friendly local experienced science/materials/electrical/mechanical geek.

If it were me and I didn’t want to try to do the math I’d probably “sneak up on it”, try increasing the current by small amounts, perhaps monitoring the actual expansion (and temperature) with precision test equipment from my machine shop, then see of I could break the rod loose. If not, increase the current a little and try again. Unfortunately, a variable current digital power supply such as I have on my electronics bench can be expensive. (it can supply a wide range of current at a specified dc voltage) I know there are other controllable ways (using the proper resistors or ac power transformer /instead of a car battery) but I’d have to research them and do some experiments, or simply ask my friend Joe who knows everything there is to know about electricity and materials. Do you know any such geeks in your area?

I have no experience with this specific problem - is it possible that a directed transducer could provide enough sonic of ultrasonic vibration to break the rod loose without heat and without damaging the wood?

Have you asked a good accordion repair to to take a look at it?

 

[Dingo40]

wood?

Have you asked a good accordion repair to to take a look at it?

My understanding of the situation is that this would be a last ditch "in desperation " attempt to either break free or break, the technique being a rough trial by fire (literally) than science.
I think the main active principle is the action of heat on the swollen wood keybases. The heat induced expansion of the axle rod being more of a subsidiary effect. However, what would I know?
But this is a sudden death technique. Could a rheostat/variable resistor be used to tame the implementation?
I know some good accordion technicians would pass on such cases as being beyond help.

 

[Snoopz]

To significantly heat a solid steel rod of say 3mm diameter will need at least a couple of amperes of current. So you need a resistor that can handle this current without burning up itself. Suppose we only need a modest 5A of current, the resistor will still need to handle 5A * 12V = 60W. Load resistors able to handle 60W are not at all cheap and I doubt you’ll be able to get a variable resistor with this capability for less than a couple of hundred bucks.

If I were you, I’d try a local Makerspace or maybe a school for electricians or electrical engineers. They will be able to build something for you or maybe even have something on hand.

If you are handy with electronics or know someone who is, you could whip up one of several circuits that would do the trick. Either a Darlington current amplifier or since you only want to heat something, a pulsed current circuit would be my first experiments.

 

[Dingo40]

Either a Darlington current amplifier or since you only want to heat something, a pulsed current circuit would be my first experiments.

All this is Greek to me!

 

[debra]

...
...calculate the current required for the desired expansion of the length vs diameter. ...

Actually what you want is just the expansion in diameter, because it is a matter of putting pressure on the metal around the rod and then by shrinking due to cooling down get some wiggle room. The expansion in length is actually an unwanted side-effect because it may bend things you don't want to bend.

 

[debra]

The first error was the silicone spray. If you really want to use a lubricant it should be one that is intended to loosen up stuck bolts. WD40 may work but there are oils especially made to unstick stuck connections.
There are also specialized lubricants like Protek CLP. That one comes with a syringe that lets you position small drops of the lubricant on the metal connections without any of it getting on a wooden part (which happens with a spray can).

 

[PhiliGol]

Hi Mark

This is the kinda device you may be looking for - a (strong) lab power-supply.
It will let you control the current (and by that the power) flowing through the axle, causing a temperature-rise and the desired effect.
I didn't want to test it on one of my instruments also didn't quickly find a 2 or 3mm iron rod.
I had a 1mm on hand and cut it ca. half as long as an accordion axle.
By carefully cranking up the current you can nicely control the heat.
No problem to make it glow (you may see the smoke) and melt the isolation (OK it's just a 1mm, and its almost 120W flowing through this little rod).
Should you get hold of one please allow me 2 hints:
- make sure you have solid wiring and clamps (OK will be difficult to attach) from the power supply to the axle; else one of these will be glowing
- carefully adjust the current and/or voltage; once the iron starts to heat up it'll increase its resistance and by that dissipate more power which results in more heat (positive feedback)

A radio amateur (maybe even harder to find than accordionists ) or electronic tinkerer may help you out with such a device.
I should be able to deliver at least 20A / 10V.

Hope this helps - good luck getting it out of your Tango.

 

[jozz]

clamping a drill chuck on it and spinning doesn't work either?

 

[Snoopz]

I should be able to deliver at least 20A / 10V

most likely not something an electronics tinkerer has floating around, since these are quite costly in contrast to the 3/5A units you can get for less than 100€

 

[Scuromondo]

I do have a background in electronics, and I would not recommend dabbling with car batteries unless you really know what you are doing and are confident that you have adequate current limiting. Currents of only a couple hundred milliamperes can be lethal, and a car battery can easily deliver several hundred, if not a thousand, amperes.

 

[Pipemajor]

I have made a device out of a variable electric light switch to control the temp. on my soldering iron.
Works very well and very cheap, but that's for ac current. Don't know if it works on dc.

 

[Mr Mark]

The knowledge base here never ceases to amaze me.

The rod is brass and either 2.5 or 3 mm - I can't quite tell as access is limited. As to where it is stuck I am not sure, but it does not move AT
ALL. If I were to guess, the main stuck point would be at the chin end where it is buried and the only access would be to drill a hole. This thing has been in there 85 years so it could be stuck at any point along the way.

10A power supply units are readily affordable, 20A not so much. I see things like this and wonder if that might do the trick, or would it be underpowered https://www.amazon.ca/dp/B087TK6ZM2?ref=emc_s_m_5_i_atc&th=1 . I did think about the possibility of heating the rod with a soldering iron attached at one end (or both if I drill out the other end). I may tinker with this first although I'm not sure it will generate enough heat throughout the length of the rod. I do very much appreciate the experiment in the pictures!!! However have visions of myself being like that small electronics comedian always frying himself on social media . I think the key in this regard is gradually building up the juice until it works. A car battery is mega overkill (but a fun story to tell people) and I think I've resigned myself to live with the noise rather than suffer through sloppy keyboard action again if it came down to it.

I don't know too many folks with any kind of background like this. Perhaps time to broaden my social circles.

I might pick up some of that CLP with the needle applicator just because, however I think it will still be impossible to not get it onto the wood, at least in this case. But I would like to give that approach one more try before I start playing Frankenstein.

Will need to reread and digest some of this more, thanks for all the fantastic inputs!

 

[PhiliGol]

Hi Mark
I might be able to find a rod of brass later and do an experiment.
However as per my rough estimate 10A wouldn't be enough (20A neither) - that's why some came to the idea taking a car battery.
The diameter matters a lot as it factors in by square; also brass comes with ca. half the specific resistance over iron.
The axle will end up in single-digit mOhm (that's why wiring and clamps are important - they should come with even less mOhm).
Even if it was 10mOhm and you manage to dissipate 10A through the rod - that's only 1W.
You may be able to measure the temp-rise with a very precise instrument but presumably it won't (by far) not be enough to get the desired extension effect.

 

[colinm]

I have drilled a hole in the other end, that gives you the option of carefully tapping it in both directions.

 

[Dingo40]

Here's a relevant video:

 

[dak]

I do have a background in electronics, and I would not recommend dabbling with car batteries unless you really know what you are doing and are confident that you have adequate current limiting. Currents of only a couple hundred milliamperes can be lethal, and a car battery can easily deliver several hundred, if not a thousand, amperes.

That's kind of nonsensical since the category where a few milliamperes will kill are currents through the body, and a car battery does not have the voltage to cause such currents through a body. You can normally touch almost anything in a car without danger apart from the ignition circuits (which are high voltage). With your hands. But if you shortcircuit a battery with a metal tool, you are in for trouble. Dropping a spanner on truck battery contacts can end up melting the spanner to pieces and damaging other stuff in the process. If you connected the ground of your car battery first (never do that!) and then while connecting the other pole your spanner touches the already connected chassis of the car, really really bad things will happen. Not because of current running through your body but because of current running through the spanner.

Which gets us to the car battery on keyboard axle thing. Which can badly backfire depending on just the material of the axle.

 

[boxplayer4000]

Mr Mark:
I’m reading responses to your problem with interest. I’ve had mixed success, on some occasions been completely stumped, usually on very old instruments.
I recently had success in a repair to a split wooden frame supporting a PA keyboard (highlighted elsewhere on this forum). The key to the success was using a blunt nosed syringe to get glue to places which would otherwise have been inaccessible. While reading this thread I thought of the syringe. It’s needle is approx 2mm dia. so a hole drilled to allow its access is very small, unobtrusive and easily covered later if need be.
A carefully drilled hole will give direct access to the seized axle passing through its wooden supports. A liquid ‘lubricant’, such as WD40, would have the double benefit of lubrication and expanding the wood. I believe the expansion of the wood would temporary only and it it would soon resort to its previous form.
Just a thought.....

 

[Rosie C]

My main instrument of choice is an older Hohner Tango IIB. ... The problem is that the axle is really stuck.

I can't help with the problem, but I am having fun trying to visualise what's happening. Does the axle pass through a hole in each key? So if the axle was stuck within a key then either the key would be stuck, or the axle would rotate when the key was pressed? So the axle must be stuck at the far end? Or have I missed something...?