Attn Rebuilders: Pounding in machine

Posted by: Supply

Attn Rebuilders: Pounding in machine - 03/13/09 12:23 AM

Rebuilders -
I have been thinking about developing and building a simple pounding in machine. It would really be advantageous for a shop to have a machine that pounds every key about 20-30,000 times after regulation and first voicing, to stabilize the tuning, bring action and key felts to the state of compression they will eventually attain, pound in the voicing etc. Then fine regulate, tune and voice and you can send the piano out to the client and not have to worry about major changes in the first months of playing.

This is what factories do, and it makes real sense. Would there be a market for such a machine? What would it be worth to a rebuilding shop?
Posted by: Dale Fox

Re: Attn Rebuilders: Pounding in machine - 03/13/09 12:28 AM

I've been thinking of making my own. Mason & Hamlin has a nice machine based on a series of cams. Never gotten around to it to this point. I figure it would take me about two days of labor to build once I get the design on paper. Parts wouldn't be that big an expense. So it would have to cost less than the two days labor it would take to build myself????
Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 03/13/09 12:50 AM

I use a Playola that works great. I have a disk I play at night that pounds in the notes for 10 hours.
What I like is it also plays music during the day.
I have over 5000 songs on disks.

I paid $1,500 for a used one and felt it was worth every bit of that.
Posted by: rysowers

Re: Attn Rebuilders: Pounding in machine - 03/13/09 02:44 AM

I've thought about it for years! It's a great idea Jurgen.

Rod - do they still make Playolas?
Posted by: Gregor

Re: Attn Rebuilders: Pounding in machine - 03/13/09 05:46 AM

Okay, it´s not the same like a machine, but it helps to work all new felts (excepted the hammer felts)and leather with a hammer. Just pounding them with a hammer on the work bench.

Gregor
Posted by: Les Koltvedt

Re: Attn Rebuilders: Pounding in machine - 03/13/09 08:03 AM

Just bring your niece's and nephews under the age of five over, they always like to pound on mine when they visit.... grin ha
Posted by: UnrightTooner

Re: Attn Rebuilders: Pounding in machine - 03/13/09 08:24 AM

Anybody have a picture of one that piano manufactures use? All I can think of is that scene from Barbarella!
Posted by: S. Phillips

Re: Attn Rebuilders: Pounding in machine - 03/13/09 11:14 AM

Sign me up..

Sally
Posted by: Gregor

Re: Attn Rebuilders: Pounding in machine - 03/13/09 01:23 PM

Here is a video:

http://www.wendl-lung.com/jart/prj3/wend...rve-mode=active

Gregor
Posted by: UnrightTooner

Re: Attn Rebuilders: Pounding in machine - 03/13/09 01:38 PM

Thanks, Gregor!

Hey everyone, there is a model of an upright action with a true repetition lever on that site!
Posted by: Erus

Re: Attn Rebuilders: Pounding in machine - 03/13/09 01:46 PM

Here's the model mentioned by Jeff:



Do you think that action could be troublesome?
Posted by: Del

Re: Attn Rebuilders: Pounding in machine - 03/13/09 04:32 PM

Originally Posted By: Supply
Rebuilders -
This is what factories do, and it makes real sense. Would there be a market for such a machine? What would it be worth to a rebuilding shop?


I think so. I've been using one for about 15 years now.

ddf
Posted by: accordeur

Re: Attn Rebuilders: Pounding in machine - 03/13/09 05:37 PM

Unright or Erus,

You should really start a new thread with that action model. To me, it looks like it would be difficult to regulate, especially drop and let-off. I think the Fandrich action is simpler, easier to regulate and more elegant.
Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 03/13/09 08:36 PM

Originally Posted By: rysowers


Rod - do they still make Playolas?


Yep, PianoDisc makes them. Way to much money for what we need them for.
Posted by: Del

Re: Attn Rebuilders: Pounding in machine - 03/13/09 08:49 PM

Originally Posted By: Rod Verhnjak
Originally Posted By: rysowers


Rod - do they still make Playolas?


Yep, PianoDisc makes them. Way to much money for what we need them for.


They do?

ddf
Posted by: RoyP

Re: Attn Rebuilders: Pounding in machine - 03/13/09 10:05 PM

I believe it was a QRS product, not Pianodisc. I don't see it on the website currently.
Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 03/13/09 11:28 PM

Sorry I meant QRScrazy

http://www.pianosupply.com/playola/
Posted by: rysowers

Re: Attn Rebuilders: Pounding in machine - 03/14/09 01:29 AM

Yeah, $4200 is a chunk of change. You could hire a lot of child labor for that amount.
Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 03/14/09 01:50 AM

This one is for sale on ebay. Still $3,000.00



Posted by: Duane McGuire

Re: Attn Rebuilders: Pounding in machine - 03/15/09 08:42 AM

Jurgen, I'm certainly interested, but don't go into production for me! I am getting started at rebuilding, and expect to be full time when I retire from my current job in about 5 years. Anyway I'd think every rebuilder needs one. Priorities and money are the thing. I'd think that you need to come in at less than $1000 - $1500. More than that and this inventive crowd will probably be in the DIY camp. Just my guess.
Posted by: Supply

Re: Attn Rebuilders: Pounding in machine - 03/19/09 02:16 AM

Yes, I was thinking in that ball park.

If it is the floor model I visualize, it will need to have a certain amount of mass to keep it stable. Which means that shipping cost could stifle the sales potential for the machine.

Perhaps just produce blueprints for techs to build the machine or have it built for them locally?
Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 03/19/09 02:28 AM

Sorry my good friend but before you get into business.

You mean like this?



When built it looks like this.



And Sounds like this.

http://www.youtube.com/watch?v=2a_uTTMT30A&feature=player_embedded
Posted by: BDB

Re: Attn Rebuilders: Pounding in machine - 03/19/09 03:08 AM

Originally Posted By: Supply
Yes, I was thinking in that ball park.

If it is the floor model I visualize, it will need to have a certain amount of mass to keep it stable. Which means that shipping cost could stifle the sales potential for the machine.

Perhaps just produce blueprints for techs to build the machine or have it built for them locally?
Or leave a shelf or box that could be filled with sand or rocks.

Personally, I am not interested. If a part sticks, it will stick when it is pounded, so it will not wear in anyway.
Posted by: Supply

Re: Attn Rebuilders: Pounding in machine - 03/19/09 03:08 PM

Originally Posted By: BDB
.. If a part sticks, it will stick when it is pounded, so it will not wear in anyway.


It has nothing to do with sticking parts. If parts are sticking, your repair and regulation is incomplete. Finish doing that work before you hit the switch of the pounding machine.

Pounding machines are used to play all keys vigorously, usually about 20,000 times or so, after which a final regulation, voicing and of course tuning takes place. This will result in a piano that is much, much more stable in tuning, touch, and voicing after delivery.

I see that Rod has found a source for such a machine that I was not aware of. Thanks Rod!
Posted by: Bart Kinlein

Re: Attn Rebuilders: Pounding in machine - 03/19/09 03:37 PM

Quote:
And Sounds like this.


Pounder refrain

Kind of catchy. Reminds me of...

Never mind
grin
Posted by: Pianos & Pianos Mexico

Re: Attn Rebuilders: Pounding in machine - 01/20/13 05:28 AM

Hi! I´like to revive this post because Im restoring about 20 pianos for an institute, and after replace all felt and bulkskin from the action i have to regulate again about a month of use, but they don´t play all the keys and the compression on the felt is not even. Who wants to wait and regulate over and over

I have draw some ideas of a 2 lever pouding machine like the one on the video but to be place on top of the piano to avoid that big box. I haven´t build nothing yet,

I´ll love a electronic one with solenoids but still to expensive and more living in mexico, I have talk to a WN&G tech and they have design a pounder over the pianodisk system, the hardest part is to hold down the solenoids up side down with springs.

The playola is too old and for the price, the lx system is far less expensive than that and better,

Who has more ideas, pictures or drawings of your machines? I guess most if not all restorers should have one on the shop.

someone here has an old (but not to old) un-used pianodisk system or parts sitting around the shop getting dusty I´ll be interested

I´ll apreciate your comment

Thanks
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 01/20/13 09:08 AM

I learned to pound with 2 hand pounders, then a regulation pass is necessary. And earplugs
Keyboards are stabilized with a long lever that push on the underside of the pinblock and an adapted woodblock above the balance (als used to lower a key that is only a little high) balance punchings where ironed before installation, also , it does not make them so even but it helps.

Using first grade paper punching is also a must. The ones sold by Yamaha are good, not too sensitive to moisture and rigid enough.

The machine pounding is more efficient for the hammers and the action, but hand pounding can be firm , also on a new stringed piano you have to tune hard 4 times and that pound also , regulation passes and voicing are inserted between those tunings. I will pass the exact procedure.

So I always have think I need a machine, but can live without it.
I believe the machine pound not so hard, also , I asked how many strokes and had no precise answer, but even 10000 have been said to me too much.

Do someone know an exact range ?



Ps felted blocks in wood (leaded) are placed on the strings to avoid too much noise , it also make the pounding more efficient. (not anyone agree on this, but the noise is really too much, I also dont like to pound strong on bass strings)
Posted by: Supply

Re: Attn Rebuilders: Pounding in machine - 01/21/13 11:57 AM

The idea of the pounder is to effectively and quickly put the equivalent of 10, 20 or more hours of playing onto the new or re-built piano. In factories, this noisy process is done in sound insulated rooms. It seems they want the strings to resonate freely.
At two blows per second, a pounder can rack up 10,000 keystrokes for every key in short order (extended lunch break!).
This would be hard to beat pounding by hand.
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 01/21/13 01:15 PM

Sure Jurgen , at 7200 impact one hour, I dont compete...

Then :

I hit several times before regulation to check the jack alignment

Then after finishing regulation I do the first tuning with tough strike

After that I do the damper works – then a second tuning with hard strike

Then second regulation and pre-toning, after that a third tough tuning

After that the finish regulation, finish damper regulation and finish voicing.

Now if you have counted well – the amount is a little less than 10000 …..

The reason is that regulation stability comes with time and in the correct relation between strike power to strike amount.

Too much is not automatically better.

( I am just jealous wink
 


Posted by: Supply

Re: Attn Rebuilders: Pounding in machine - 01/21/13 02:06 PM

Originally Posted By: Kamin
...Too much is not automatically better.

( I am just jalous wink

...but not enough is automatically worse!... I kind of wish I had a pounder too...
Posted by: Silverwood Pianos

Re: Attn Rebuilders: Pounding in machine - 01/21/13 02:36 PM

Originally Posted By: Supply
I kind of wish I had a pounder too...


Like a 40 pounder?
Posted by: Pianos & Pianos Mexico

Re: Attn Rebuilders: Pounding in machine - 01/21/13 04:22 PM

I asume that no body owns this kind of machine machine? it really ironing is enough to break down a new action or restored one

But the thing here is to built one! now what will be better built it over a pianodisk or QRS, or have a mecanical one?
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 01/21/13 04:45 PM

Ironing ? only the balance punchings can be ironded , that is for better stability of keyboard leveling.

Ironing does not pound the hammers, I was talking of pounding them against the strings, or against a heavy wooden block , a bass hammer can be installed in a handle to make a one note pounder.
Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 01/21/13 07:36 PM

I still think this is the way to go. A playola from QRS

Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 01/21/13 07:42 PM

I know of one tech that uses a custom made (by him) fitting on the end of a electric Jig Saw. He holds it over
6 keys at a time and pulls the trigger.
Better than nothing and nothing is common.
Posted by: Ed Foote

Re: Attn Rebuilders: Pounding in machine - 01/22/13 11:19 AM

Originally Posted By: Rod Verhnjak
I still think this is the way to go. A playola from QRS



Not bad, good rhythm, but I think the lyrics could use some work...
Posted by: Minnesota Marty

Re: Attn Rebuilders: Pounding in machine - 01/22/13 03:54 PM

Is that the Philip Glass op. 106 1/2?
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 01/22/13 06:00 PM

Originally Posted By: Ed Foote
Originally Posted By: Rod Verhnjak
I still think this is the way to go. A playola from QRS



Not bad, good rhythm, but I think the lyrics could use some work...


The devil's staircase, by Ligeti

Posted by: Minnesota Marty

Re: Attn Rebuilders: Pounding in machine - 01/22/13 07:14 PM

I performed the Legiti on my senior recital. I wore shoes, however.
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 01/22/13 10:24 PM

There is no audience so the smell is not a problem (and the sound engineers
are safe in a protected room)..
Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 01/24/13 07:53 PM

If "you people" are still thinking about a POUNDER I was thinking I could build the prototype.
If anyone has ideas or rough sketches would be a good start.
I like to build with home made or surplus parts.
I started to put together an idea I had to see if it might work.



Posted by: Supply

Re: Attn Rebuilders: Pounding in machine - 01/24/13 08:56 PM

Instead of having 88 rotary cams, have 2 bars play the keys and then you only need one cam for the sharps and one for the naturals.

Instead of spring producing the downward force, use the weight of the metal bars. As well, simply pad the bar with felt where it meets the key - no springs needed there.
Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 01/24/13 09:28 PM

Hello Jurgen, I was thinking that pressing 56 keys at 60 grams is about 120lbs. yes a much simpler to accomplish and easier to build.
the idea I was thinking about would be 5 keys at a time would be 37 lbs but would entail much more work to build.
With 5 keys at a time the unit wouldn't have to be as big as the unit shown pounding the 56 whites then black keys
My shop is small and that unit is pretty big.
If that's what re-builders want than I am up to building a prototype of what re-builders are interested in.
Posted by: Supply

Re: Attn Rebuilders: Pounding in machine - 01/24/13 10:53 PM

Your math is off, by quite a lot. 52 keys (naturals) times 60 grams is about seven pounds.

But 60 g would not be enough - more like twice or three times that amount are needed. So now we are up to 20 lbs. Still no big deal, weight wise or mechanism wise. And in fact that is the way factories have done it for decades if not longer.
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 01/25/13 05:14 AM

I have the weight , or grms force necessary to play pianissimmo, somewhere.

I seem to recall that above 200 g/cm, the cinetic energy due to the action (catapult effect) begin to happen.

Action begin to be "efficient" with an impact, hence a certain speed, allowing compression of the wooden pieces, cloths and leathers being there to adbsorb the hardness of the impact on the key and on the centers. (for the fingers, and for the wear of parts)

THe thing is that keys have not to be pressed but impacted



Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 01/25/13 07:46 AM

Oops man was I off, I converted grams into ounces but forgot to divide by 16.
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 01/25/13 11:57 AM

Originally Posted By: Supply
Instead of having 88 rotary cams, have 2 bars play the keys and then you only need one cam for the sharps and one for the naturals.

Instead of spring producing the downward force, use the weight of the metal bars. As well, simply pad the bar with felt where it meets the key - no springs needed there.


Should be OK as soon as the bars are raised high enough above the keys

Yes individual is not necessary in my opinion.

Before then, the apprentice in the piano factories did take their shoes off, and dance on the keyboards to settle the regulation.

Or may be to get the grape fruit juice, I am not sure
Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 02/13/13 07:18 PM

Are you guys still thinking about a "Pounder"?

Well I've been building a prototype one to see if I can do it.

Goals are;

Keep cost at a minimal.

Make design simple but perform or function in the best possible with few moving parts.

I decided to make it in two halves, Top and Bottom. Maybe the bottom can be legs that fold up.

One thing I need to know before making the base.

On pianos is there a standard key height from floor to key-top or dose it vary and how much.

Will it need a timer to shut it off?

Will it need a counter?

It's almost ready for the first piano test as soon as the motor arrives.

Posted by: accordeur

Re: Attn Rebuilders: Pounding in machine - 02/13/13 07:53 PM

That is so cool!!!!
Posted by: Minnesota Marty

Re: Attn Rebuilders: Pounding in machine - 02/13/13 08:41 PM

The sound it will produce scares me!
Posted by: BDB

Re: Attn Rebuilders: Pounding in machine - 02/13/13 08:48 PM

Key heights vary, perhaps 4 or 5 inches.
Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 02/13/13 08:54 PM

4" to 5" wow more than I thought.

Any idea on floor to key-top say lowest to highest?

Right now the total drop per paddle is 1-1/8", 3/8" of that is depressing the key.

I set the weight of each paddle at about 12 lbs.

On first tests I found that 12 lbs. is not enough, well at least at a 5/8" drop

Also I used a high density 1/4" foam on the paddles and when it's pressed down on my piano I found that most of the center keys were not completely down.

Maybe a softer felt might fix this?
Posted by: BDB

Re: Attn Rebuilders: Pounding in machine - 02/13/13 09:01 PM

What you may be getting is deflection of the bars that you are using to press the keys. You probably need at least 3 to 4 ounces of pressure on each key. That would be a total of about 13 pounds for the white keys. That could cause the center of the bars to bend upwards quite a bit.
Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 02/13/13 09:38 PM

The paddles/bars are not bending it's that there's a slight dip in the center of my piano of about .020 thousandths of an inch.

I'm wondering if this will cause an uneven pounding?

Posted by: Supply

Re: Attn Rebuilders: Pounding in machine - 02/13/13 10:20 PM

Dan, I think you are making great progress, congratulations.
I would tend to look to a firmer felt instead of a softer foam for the "beater rails".

Dips in the key bed are a problem for sure, but the idea is to have this machine pound on a freshly regulated piano to pound in the regulation and voicing, so there would not be a dip. I am not sure how it would work for pianos that are regulated with a crowned key surface and corresponding key travel.

The height from the floor would have to be adjustable, plus/minus one inch. I think 4 or 5 inches is very, very extreme. A machine like this would mostly be used on very good pianos, and I doubt that the keyboard height varies by more than 1.5 - 2 inches on those. You only get really low keys on small spinets, and really high keys are indicative of someone having installed improper casters under the piano.
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 02/13/13 10:37 PM

Yes the basis looks appeealing. I suggest that the travel of the bar should be enough to absorb the 2 mm crown upward (max) that could be find in a dressed keyboard.

Shaped bars ?

Did you install lead or another mass in the wooden bars ?

I have seen numbers for mass and fall height that produce different force of stroke. (in the Pfeiffer book on the hammer)
Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 02/13/13 11:22 PM

Hello Supply,
At this point I haven't measured any pianos other than my own at 28-5/8" or 730mm

Hello Isaac,
Next I'll try more weight and if that doesn't work I'll try a softer foam.

I have a lot to learn about pianos. Is that typical to have a 2 mm crown?
Posted by: Rod Verhnjak

Re: Attn Rebuilders: Pounding in machine - 02/14/13 12:48 AM

Looking good!!!! thumb thumb thumb
Posted by: Olek

Re: Attn Rebuilders: Pounding in machine - 02/14/13 06:43 AM

Originally Posted By: woodfab
Hello Supply,
At this point I haven't measured any pianos other than my own at 28-5/8" or 730mm

Hello Isaac,
Next I'll try more weight and if that doesn't work I'll try a softer foam.

I have a lot to learn about pianos. Is that typical to have a 2 mm crown?


Hello, is a grams.cm mesasure useful for you ?

What noticed Pfeiffer is that it is not efficient enough to just put weights on the keys, even heavy one.
He conclude that the energy provided may begin to flex a little the action parts for the piano to be efficient.
SO there is an impact notion to take in account.
Hopefully the level at which this situation arise is not very high . it seem to be above 300 g.cm that the energy provided to the hammer is less absorbed .

(for instance with 100 and 200 grms.cm the action "ratio" is reflected in the hammer work, 100 grms >5.5% "rendering" (efficieny)
200 grms.cm > 4.5% , even less than the first
300 gms > 9.8 % there is a sudden raise in efficiency at some point.

300 g.cm is a 300 g mass falling free from 1 cm height (if I understand well, so a mass just layed on the key , the key have 10 cm dip)

600 g.cm would be the work done by the same mass at 1 cm from the key, (??) 200 g.cm gives a "p" nuance, which is not strong. (400 g =mF , on actions build before WWII)

He state that the foam must be sof enough to counte rthe initial resistance of the keys and avoid rebouds.

What Pfeiffer state is that the catapult effect arise above 200 g cm at the condition there is enough speed

I believe that a pounding machine may be strong enough to raise that point where the impact is not adsorbed much by the action cloths and wood resiliency. I doubt a softer foam will help in that matter but I seem to understand what you think, it could compress then release the energy, it seem difficult to setup and probably you will need even more mass then

When the piano is played we have a short impact very soon when raising in dynamics, then if we want to play stronger we need to accelerate even more once the compressed action is felt under the fingers , but sur the pianist use the "free fall" of its arm and forearm, (and shoulders )that makes a lot of weight

THe crown in keyboards is not always find, but the rules we use to straighten the keys with paper punching are flat, with 1mm crown, or 2mm crown.

I for one tend to use the 1 mm one when all parts are new, as the center of the keyboard is the first region that flattens,

When the piano have played enough and the cloths under the balance are compressed it can be dressed flat.

But Steinways, (for instance) induce a curved key level by construction. on grands about 2 mm , on verticals 1 mm.

It could be done for visual reasons as well.

Good job ! in the end that should be a height + weight question.

The sharps are more heavy to move very often

The keyboards are noy at a so wide range in heigh as 2.5 inches but this point may be secondary.

PS, when we say a keyboard have a 50 gms "down weight" that just mean that the parts move slowly up when that weight is installed on the key.
Schimmel state about a weight they use to verify the action is well regulated and that play all notes at ppp level - an octave range I believe, not sur ethey give the exact mass of the thing.
Playing p, or ppp is not helping a lot to break in an action, but too much is probably not good either. mF sound good to me (?)
Posted by: jim ialeggio

Re: Attn Rebuilders: Pounding in machine - 02/14/13 10:58 AM

Originally Posted By: woodfab
The paddles/bars are not bending it's that there's a slight dip in the center of my piano of about .020 thousandths of an inch.


I find in general it is quite difficult to evenly depress or clamp all the keys evenly across the 4ft plus width of the keyboard.

I liked your original idea which had dedicated cams...but in all jig development, working out these details is what eats most of the time...ask me, as a member of Jig Makers Anonymous, how I know. I'm on the 12 step recovery plan, but I'm afraid its not working smile

Jim Ialeggio
Posted by: woodfab

Re: Attn Rebuilders: Pounding in machine - 02/14/13 11:50 AM

Thanks guys for info an ideas.

Even when pressing down firmly with my hand in the center of the better bar with the high density foam I was unable to get all keys to bottom out.

The new motor arrives to today. I'll post some photos as soon as it's in.

By the way,what is the "12 step recovery plan"?
Posted by: Bill McKaig,RPT

Re: Attn Rebuilders: Pounding in machine - 02/14/13 01:21 PM

I built a pounder like this many years ago that worked on the same principal, pounding all the keys as a unit. I came to the same conclusion as Jim, individual pounders for each key would work better. I could never get even wear on all the keys.

It certainly made a lot of noise. I would cover the piano with blankets and leave the shop. Even standing in the driveway it made a terrible racket.

I looked for a long time to find one of those old player units that would sit above the keys. I never found one. I now use a different system that works well for me.
Posted by: jim ialeggio

Re: Attn Rebuilders: Pounding in machine - 02/14/13 03:36 PM

Originally Posted By: woodfab
By the way,what is the "12 step recovery plan"?


A dorky joke smirk

This escalates the construction, but how about having a dedicated spring and depressor for each key,mounted on your existing rails. The spring rate would match the force needed to depress the key, and each key would be pressed independently, by a the single cross arm??

Jim Ialeggio