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Author Topic: Heating a keyboard axle  (Read 911 times)

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RogerT

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Heating a keyboard axle
« on: April 14, 2019, 09:13:32 AM »

So if I want to heat a keyboard axle, as per the John Reuther Accordion Repair manual, to help remove stuck axle, what battery is going to work?
I can get one of these for a few £ but will it have enough ampage to heat an axle? I kind of doubt it.
https://www.hardwarexpress.co.uk/np7-12-yuasa-12v-7ah-sealed-lead-acid-battery-722-p.asp?gclid=Cj0KCQjwtMvlBRDmARIsAEoQ8zQcDDuVWcVzsfqZKrsFJMvsasKBQIEOyjP21igFMb006eum8u9OZkYaAtmeEALw_wcB
Advice please. I'm not about to pay out for a new car battery which in the old days cost about £35 but run to three times that now. Perhaps I could get a used car battery from a friendly battery centre.

Lester

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Re: Heating a keyboard axle
« Reply #1 on: April 14, 2019, 09:23:23 AM »

The NP7 datasheet gives a max discharge of 75A so at 12V only 900W, an average car battery cold cranking current is ~500A so 6kW. Not sure how this helps but the little battery is seems less likely to work than a car battery.

Theo

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Re: Heating a keyboard axle
« Reply #2 on: April 14, 2019, 09:25:56 AM »

Trouble with a car battery is that it has little internal resistance so you need to control the current or the result will be melted ends of the axle rod.
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Theo Gibb - Gateshead UK

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RogerT

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Re: Heating a keyboard axle
« Reply #3 on: April 14, 2019, 09:28:27 AM »

How would I do that Theo? Some kind of potentiometer?

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Re: Heating a keyboard axle
« Reply #4 on: April 14, 2019, 09:43:36 AM »

How about a small welding plant,turned down low if you could clip a decent crocodile clip to the end of the axel
to avoid damage to the axel
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Theo

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Re: Heating a keyboard axle
« Reply #5 on: April 14, 2019, 09:49:25 AM »

It would be a good idea to experiment with a similar length and thickness of brass rod. I’d be inclined to try a 6v battery first, maybe a small motorcycle type.
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Winston Smith

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Re: Heating a keyboard axle
« Reply #6 on: April 14, 2019, 10:06:44 AM »

I've wondered about this since I first scrapped an old rubbishy melodeon over the very same question!
Like; how hot does the axle need to get? There would seem to be a bit of a conundrum here; as the metal axle will expand as it warms, just how will the heating loosen an axle which is seized in? If it's heated to glowing (to possibly loosen any corrosion) will it retain enough integral strength to allow it to be pulled out without breaking? Would it not also burn the inside of the holes through which it runs, requiring the holes to be reamed and a larger axle to be fitted?
The whole process seems to be fraught with a never ending catalogue of compounding problems! Or is it?
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Theo

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Re: Heating a keyboard axle
« Reply #7 on: April 14, 2019, 10:23:03 AM »

Whatever the theory anybody with experience of dismantling old mechanical things will know that carefully applied heat can make the difference between seized parts refusing to budge and becoming movable. It doesn’t have to be a very high temperature to help metal to wood to move.  The heat from a soldering iron can be enough to enable old wood screws to turn.  I guess a similar temperature would help to release the axle rod.
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malcolmbebb

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Re: Heating a keyboard axle
« Reply #8 on: April 14, 2019, 10:43:56 AM »

I believe Rees has a story about freeing an axle using a battery, which involved a great deal of smoke.
As the metal expands it pushes to slightly enlarge the hole, after which the metal traditionally contracts but the hole doesn’t.  I would be looking at a 100w soldering gun, which can be obtained quite cheaply, assuming that access to the axle permits, if a smaller iron didn’t work.
A suitable potentiometer would, I think, be hard to find and expensive, and an unsuitable one just wouldn’t work or might fry.
Welders are designed to give controllable high currents but rather seems like overkill. But could provide an entertaining photo opportunity. 
« Last Edit: April 14, 2019, 10:46:00 AM by malcolmbebb »
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Rees

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Re: Heating a keyboard axle
« Reply #9 on: April 14, 2019, 11:05:44 AM »

Yes, red wine spilled on an Oakwood keyboard. The wine travelled along the axle then dried out leaving the tannin.
Impossible to shift. The battery trick worked, that Oakwood was smoking!
Make sure that the leads are very firmly attached to each end of the axle to avoid sparking.
Connect to the battery for a few seconds only.
When the axle did eventually come out the wine tannin was extremely difficult to clean off.
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RogerT

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Re: Heating a keyboard axle
« Reply #10 on: April 14, 2019, 11:31:39 AM »

Right. I'll keep you posted on this. It seems to be a perennial problem that I somehow need to solve. But I will experiment first  (:) to avoid the axle behaving like an overloaded piece of fuse wire....

Psuggmog Volbenz

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Re: Heating a keyboard axle
« Reply #11 on: April 15, 2019, 09:11:57 AM »

A laboratory type DC power supply where one can vary both voltage and current would be more appropriate than a battery, charger or welder. A buck-boost Dc-DC controller with a DC power source would also work.
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george garside

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Re: Heating a keyboard axle
« Reply #12 on: April 15, 2019, 09:44:57 AM »

?? would an old controller from a Hornby or similar trainset do the trick  as it presumably varies the voltage??
george.
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Tone Dumb Greg

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Re: Heating a keyboard axle
« Reply #13 on: April 15, 2019, 11:57:53 AM »

?? would an old controller from a Hornby or similar trainset do the trick  as it presumably varies the voltage??
george.

I think the available current might not be of the right order.

I think where you started is the right idea. Old car batteries do do this job well. Doesn't matter if their a bit too knackered to be reliable in a car. They usually end up at the tip so, why not ask your friendly neighborhood mechanic to put something aside for you?
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Re: Heating a keyboard axle
« Reply #14 on: April 15, 2019, 12:07:20 PM »

There are some cheap enough rheostats available on eBay which might be the way to go.

SJ
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RogerT

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Re: Heating a keyboard axle
« Reply #15 on: April 15, 2019, 07:47:48 PM »

Well getting hold of a used car battery was easy. Called the local garage, yeah mate, we got a whole pile of 'em here...the farmers come for them...'elp yourself...you'll need to test em yourself. Indeed they do have a great stack of them, found one putting out 12v...got it on a trickle charger right now. More later.

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Re: Heating a keyboard axle
« Reply #16 on: April 15, 2019, 08:44:58 PM »

Be careful, Roger! I've had two spanners welded together through shorting out a 12 volt battery.
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Tone Dumb Greg

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Re: Heating a keyboard axle
« Reply #17 on: April 15, 2019, 11:03:05 PM »

Now you need something to control the current, as SJ says. Second hand heater fan control, or something. This is the point where you need more advice from someone who does this successfully. It worked on my box, but I don't know the details of how the fettler did it. Winston's warning sounds like a sensible one. I could ask, but I sure someone else will tell you first.
« Last Edit: April 15, 2019, 11:04:57 PM by Tone Dumb Greg »
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Greg Smith
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RogerT

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Re: Heating a keyboard axle
« Reply #18 on: April 16, 2019, 12:30:44 PM »

Yes, that works (without a rheostat or anything like thaf). I watched a couple videos of people setting wiring on fire with car batteries..so...WARNING...you need to be careful. I used jump leads which are heavy duty and not about to explode into flames. Anyway, I Just freed up a keyboard axle that I’d all but given up on. The tricky bit is to make a decent contact with the axle. I made a couple of brass contact plates to grab with the big jump lead clips. As advised by Rees, ensure arcing (if there is any) happens where you make the circuit, away away from the axle. I tested it first on length of 2mm brass wire and that heated up in about 3 to 4 seconds. I used a lump of wax to see how hot it'd got. I also have a volt meter to test I have a circuit before I apply the juice directly. And then, as Rees said, it was smokin' a tiny bit after a couple of seconds and that was enough.
« Last Edit: April 16, 2019, 12:32:46 PM by RogerT »
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Rees

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Re: Heating a keyboard axle
« Reply #19 on: April 16, 2019, 12:37:02 PM »

Well done Roger. What fun!
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