Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Attn Rebuilders: Pounding in machine

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.

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.

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.

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.

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

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

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

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.

That is so cool!!!!

The sound it will produce scares me!

Key heights vary, perhaps 4 or 5 inches.

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?

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.

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?

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.

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)

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?

Looking good!!!!

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 (?)

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

Jim Ialeggio