Theory of hammer blow distance...

Posted by: johnlewisgrant

Theory of hammer blow distance... - 02/26/13 08:04 PM

Seem to be quite a few opinions on the issue. And obviously the impact of the distance between the hammer at rest and the lower face of the strings has a major impact on both the tone and the feel of the piano.

Are there any agreed on rules of thumb for the "ideal" or "preferred" distance for the modern grand? Is 4.5 to 4.7mm or, say, 1 3/4- 1 7/8 a good starting point? Does the bass deserve a little more distance than the treble? Or should everything be kept the same? Does more always translate into louder?
Posted by: Mark Cerisano, RPT

Re: Theory of hammer blow distance... - 02/26/13 09:36 PM

My humble opinion and experience is that it doesn't matter much.
Upright soft pedals move hammers closer to strings with little or no loss in power.
Keydip and let off are much more sensitive.
When looking to rob from elements of the regulation triangle, blow distance is always the first to go because the tone and response doesn't change much for even a decrease of 10mm IMHO and experience.
There are so many more elements that contribute to power. The elasticity of the shank, for example.
Posted by: Del

Re: Theory of hammer blow distance... - 02/27/13 01:33 AM

Originally Posted By: johnlewisgrant
Seem to be quite a few opinions on the issue. And obviously the impact of the distance between the hammer at rest and the lower face of the strings has a major impact on both the tone and the feel of the piano.

Are there any agreed on rules of thumb for the "ideal" or "preferred" distance for the modern grand? Is 4.5 to 4.7mm or, say, 1 3/4- 1 7/8 a good starting point? Does the bass deserve a little more distance than the treble? Or should everything be kept the same? Does more always translate into louder?

I’m not sure there is any particular “theory” about hammer blow distance.

The starting point is usually set by the physical parameters of the piano. In what we call the “modern” piano the distance from the bottom of the pinblock to the string plane it typically around 38 to 40 mm. Sometimes a little less or more. It’s about 6 to 8 mm from the top of the dropscrew down to the hammershank center. Plus there needs to be a little clearance between the bottom of the pinblock and the top of dropscrew. And, usually, we don’t want the hammer to rub against the bottom of the pinblock when the action is removed from, or replaced in, the action cavity.

Add this all up—and assuming you don’t want the hammershank to over-center at hammer impact—and you come up with a hammer blow of somewhere around 45 mm. Some pianos have a hammer blow specification of 48 mm but this is usually because there is more distance between the bottom of the pinblock and the string plane.

ddf
Posted by: BDB

Re: Theory of hammer blow distance... - 02/27/13 02:03 AM

An old Erard grand that I worked on must have had a blow distance of about 60-70 mm. So it has gotten considerably smaller since then.
Posted by: johnlewisgrant

Re: Theory of hammer blow distance... - 02/27/13 08:47 AM

Yes "theory" is a fancy word for "approaches to".

Anyhow, to put the discussion into some kind of context: I asked Hailun for specs on the 218. The "official" hammer blow distance for the 218 is "4.7mm" but "4.5mm" for a new piano (a little less than 1 3/4") but I quickly realized that these numbers were pretty theoretical.

For one thing, the strings of the middle section of the 218 (a3 to f#4) are NOT level, but actually slant down towards a3 from f#4! So a uniform hammer distance would have required the hammers in this range ALSO to slant down, which they did not. So the hammer drop in effect DECREASED towards the A3, by about 1-2mm (I haven't measured it exactly), by virtue of the fact that the hammers themselves were level. (That setting didn't make a lot of sense to me. One would think that the hammer drop should remain more or less constant in the trichords... Go figure.)

My new piano "out of the box" measured something like 4.4mm for the trichords and 4.6mm for the wound strings. After playing with the let-off, which to my taste, dramatically improved the feel of an already very nice instrument (I decreased it to the min I could get away with without bobbling), I noticed in passing that the hammer drop seemed a little shallow (small) for my taste (4.4mm in the trichord region; 4.6m in the bass).

I tried various different (increased) settings and found that 4.6 was a better sounding ballpark for me on the trichords, especially once I had decreased the let-off: I got a better tone and more dynamic range (without any doubt) in the trichords. The wound strings I set closer to 4.6-4.7mm.

So it seems to me anecdotally, that increasing the hammer distance has a huge impact on both tone and loudness. 4.7 was too loud and not enough control in the treb (trichords) 4.4 on the other hand was not enought "hit" or potential power, for want of a better word, when needed.

But you can't leave the let-off out of the equation.

The tight let-off seems to be important in the overall equation, since once the hammer blow distance is INCREASED (closer to "factory specs"), the let-off makes pp and quick repetition still easy to achieve. If I were merely to increase the blow distance, absent refining the let-off, it seems to me that pp and fast repetition might become much more difficult.

44mm (under 1 3/4") just seems a little too short a distance for hammer blow distance, at least in this case. Can I take that as a safe generalization about hammer blow distance, I wonder? Are there large grands out there that are routinely set at 4.4mm blow distance for the trichords? Are there professional pianists who insist on that kind of setting?

I ask because I'd be willing to experiment with the 4.4mm "limit" in the trichords if I thought it were something techs routinely did. Something tells me that it isn't.
Posted by: David Jenson

Re: Theory of hammer blow distance... - 02/27/13 10:05 AM

"The starting point is usually set by the physical parameters of the piano." Del

That's the key phrase! In setting up an action for regulation, I look at everything even including how much of the drop screw I want showing above the hammer flange. As I think about it, the amount of blow is about the last thing I pay any attention to except as to how it affects let-off, drop and aftertouch.

I suspect that reliable repetition, even checking, and durability of the regulation are more important than hammer blow esoterica to most of us.
Posted by: Mark Cerisano, RPT

Re: Theory of hammer blow distance... - 02/27/13 10:23 AM

Did you read my threads on the regulation triangle?

You are leaving a lot out of the equation.

For me, aftertouch needs to be appropriate and uniform, for great feel and expression. This is the key to proper regulation, IMHO. Also, keeping aftertouch as an ideal in your mind, allows you to more easily grasp the theory of how all the other elements relate to each other. (Only one other poster in this forum claims aftertouch is unnecessary for proper mechanical execution, but we are talking about feel here. Most technicians I know agree and agonize over aftertouch.)

Jack knuckle alignment must be uniform or all other specs will need to be uneven to some degree to achieve uniform aftertouch.

Keydip will affect all other elements of the triangle.

So, when you are monkeying around with hammer blow, of course you are setting the whole mechanism out of whack and you will get inefficient energy transfer which results in huge variations in tone.

In my course, I am very succinct in how I describe the way the action works and how to decide what to adjust.

In simplistic terms, you must have appropriate aftertouch for any combination of Blow/Dip/Letoff. Changing any one of these will affect aftertouch and requires that you adjust one of the other two to preserve aftertouch, assuming it was good before.

Finally, any technician will tell you that proper regulation and proper relation of the triangle elements has a dramatic affect on tone. After I do a regulation, I am always impressed by how much the tone has improved as well as the uniformness of the response.

I hope you have a better understanding now of the larger picture; if you want to get into the action and start changing settings, you understand now that you are incorrect if you make assumptions about the ideal settings for this or that without understanding how all the elements work together. I say this from experience; I have relearnt much more than I know due to my own incorrect assumptions. This is a humbling skill; individual knowledgeable technicians have a long history of broken assumptions IMHO, I know I do.

As simple as your understanding of regulation was entering into this thread, that is my understanding relative to many other concepts I catch a glimpse of now and then. Like shank stiffness, balance hole friction, downbearing, downweight, upweight, action geometry, etc. Understanding how all these elements and more relate is necessary, the more precise one wishes to regulate.

Good luck with your project. Use and understand the elements I, and others are presenting and you will have much greater success.

Do not dismiss the comments of other experienced technicians. For example, when Del Fandrich refuses to pin down an exact theory on hammer blow, and describes vague limitations like the height of the pinblock and nothing directly related to tone, you should have a pretty good idea that it is not as critical as you think it is, unless of course you don't know who he is.

I hope you do not find any impoliteness in the tone of my email. Truly, I am very excited about the thought of someone with a beginning understanding of regulation, suddenly grasping the weight of certain ideas and experiencing the effect of specific and understood adjustments on an action for themselves. I wish I could be there.

All the best.
Posted by: beethoven986

Re: Theory of hammer blow distance... - 02/27/13 01:38 PM

Originally Posted By: Mark Cerisano, RPT

For me, aftertouch needs to be appropriate and uniform, for great feel and expression. This is the key to proper regulation, IMHO. Also, keeping aftertouch as an ideal in your mind, allows you to more easily grasp the theory of how all the other elements relate to each other. (Only one other poster in this forum claims aftertouch is unnecessary for proper mechanical execution, but we are talking about feel here. Most technicians I know agree and agonize over aftertouch.).... In simplistic terms, you must have appropriate aftertouch for any combination of Blow/Dip/Letoff. Changing any one of these will affect aftertouch and requires that you adjust one of the other two to preserve aftertouch, assuming it was good before.


Absolutely 100% agree. Too little or too much and/or uneven aftertouch is annoying not only for techs, but also for pianists, even if they don't know it.
Posted by: Supply

Re: Theory of hammer blow distance... - 02/27/13 01:44 PM

Quote:
I noticed in passing that the hammer drop seemed a little shallow (small) for my taste (4.4mm in the trichord region; 4.6m in the bass).
I am not sure how anyone can measure tenths of a mm in drop. In any case, these measurements are close to twice what the drop should be in a properly regulated piano.

I suggest you bring in a technician to go over the regulation details.
Posted by: Withindale

Re: Theory of hammer blow distance... - 02/27/13 02:28 PM

"Is 4.5 to 4.7mm or, say, 1 3/4- 1 7/8 a good starting point?"

"I noticed in passing that the hammer drop seemed a little shallow (small) for my taste (4.4mm in the trichord region; 4.6m in the bass)."

Are the units here cm or mm, which measurements refer to blow and which to drop?
Posted by: beethoven986

Re: Theory of hammer blow distance... - 02/27/13 04:18 PM

Originally Posted By: Withindale
"Is 4.5 to 4.7mm or, say, 1 3/4- 1 7/8 a good starting point?"

"I noticed in passing that the hammer drop seemed a little shallow (small) for my taste (4.4mm in the trichord region; 4.6m in the bass)."

Are the units here cm or mm, which measurements refer to blow and which to drop?


For blow, it would be 4.5cm or 45mm. 4.5mm would be impossible, of course. Drop should be 1mm, maybe 2mm at most. I always set to 1mm. Anything more than 2mm is just... wrong.
Posted by: Withindale

Re: Theory of hammer blow distance... - 02/27/13 04:58 PM

Originally Posted By: beethoven986
Drop should be 1mm, maybe 2mm at most. I always set to 1mm. Anything more than 2mm is just... wrong.

Do you measure drop from the string or from the let off point? Reblitz suggests let off of 1.5mm plus drop of 1.5mm making a total drop height of 3mm (1/8") below the string.
Posted by: beethoven986

Re: Theory of hammer blow distance... - 02/27/13 05:05 PM

Originally Posted By: Withindale
Originally Posted By: beethoven986
Drop should be 1mm, maybe 2mm at most. I always set to 1mm. Anything more than 2mm is just... wrong.

Do you measure drop from the string or from the let off point?


From let off.
Posted by: Withindale

Re: Theory of hammer blow distance... - 02/27/13 05:16 PM

Originally Posted By: beethoven986
Originally Posted By: Withindale
Originally Posted By: beethoven986
Drop should be 1mm, maybe 2mm at most. I always set to 1mm. Anything more than 2mm is just... wrong.

Do you measure drop from the string or from the let off point?

From let off.

Now set aftertouch and you're done?
Posted by: Gene Nelson

Re: Theory of hammer blow distance... - 02/27/13 05:54 PM

Then there are those wonderful pianos where the string height decreases in a shallow arc across the capo section.
Some will regulate a straight hammer line and decrease key dip to compensate while others will maintain constant key dip and lower the hammer line to maintain blow distance.
Posted by: johnlewisgrant

Re: Theory of hammer blow distance... - 02/27/13 05:58 PM

Originally Posted By: Supply
Quote:
I noticed in passing that the hammer drop seemed a little shallow (small) for my taste (4.4mm in the trichord region; 4.6m in the bass).
I am not sure how anyone can measure tenths of a mm in drop. In any case, these measurements are close to twice what the drop should be in a properly regulated piano.

I suggest you bring in a technician to go over the regulation details.


Did I say "drop"!! I meant "blow distance"!! And not "mm" but of course "cm" (centimeters)!!

Sorry for the confusion.
Posted by: johnlewisgrant

Re: Theory of hammer blow distance... - 02/27/13 06:00 PM

Originally Posted By: Withindale
"Is 4.5 to 4.7mm or, say, 1 3/4- 1 7/8 a good starting point?"

"I noticed in passing that the hammer drop seemed a little shallow (small) for my taste (4.4mm in the trichord region; 4.6m in the bass)."

Are the units here cm or mm, which measurements refer to blow and which to drop?


Sorry. Centimeters!! (Not mm.) And I'm not talking about drop; I meant hammer blow distance! Typing faster than I ought to!!
Posted by: johnlewisgrant

Re: Theory of hammer blow distance... - 02/27/13 06:15 PM

Everything Mike says about the triangle nature of adjusting the hammer line makes perfect sense.

My question was really more about whether the Rebliztian suggestion that blow distance--for the modern concert grand--should sit ideally between 1 3/4" and 1 7/8" is still considered pretty accurate, these days. You hear reports of new grands having blow distances from the factory of 4.4 CM or less, which seems awful small!

Also, I suspect just from common sense, certainly not from any professional experience, that one would aim towards a greater blow distance (towards the 1 7/8) as long as let-off and after touch are preserved. Seems to me that one gets in this way both power and subtlety--if everything else is OK.

Now my piano is in a small room; so here's what I think might be an exception: if I push the blow distance to 1 7/8", this grand gets quite loud. Fine--great--in a concert hall; but not in a small room. So I'm playing with something in the range of 1 3/4".

A real discovery for me was the fact (as I said above) that the string height actually varies from section to section, and even within sections!! Sure, the wound strings will vary in thickness: that's obvious. But I had no idea that I couldn't just set the trichord hammer line smooth from top to bottom (although that's the way it came from the factory.)
Posted by: beethoven986

Re: Theory of hammer blow distance... - 02/27/13 06:49 PM

44mm is fine for blow, depending on your other regulation specs. In fact, that is more or less my default, but, I also set my key dip somewhat more shallow than some, I suspect.
Posted by: johnlewisgrant

Re: Theory of hammer blow distance... - 02/27/13 08:28 PM

Originally Posted By: beethoven986
44mm is fine for blow, depending on your other regulation specs. In fact, that is more or less my default, but, I also set my key dip somewhat more shallow than some, I suspect.


Thanks... that's exactly the sort of info I'm looking for.

JG
Posted by: Del

Re: Theory of hammer blow distance... - 02/27/13 09:26 PM

Originally Posted By: johnlewisgrant
My question was really more about whether the Rebliztian suggestion that blow distance--for the modern concert grand--should sit ideally between 1 3/4" and 1 7/8" is still considered pretty accurate, these days. You hear reports of new grands having blow distances from the factory of 4.4 CM or less, which seems awful small!

Many factories set blow distance some shallow knowing full well it is going to settle (increase) over time. There may also be some who specify a shorter blow distance for some mechanical or action ratio reason.

An example might be a piano with particularly heavy hammers that has been balanced with a relatively (numerically) low overall action ratio. By setting a slightly short blow distance they could still use a reasonable key stroke (i.e., not too deep) while still providing an adequate amount of key aftertouch.



Quote:
Also, I suspect just from common sense, certainly not from any professional experience, that one would aim towards a greater blow distance (towards the 1 7/8) as long as let-off and after touch are preserved. Seems to me that one gets in this way both power and subtlety--if everything else is OK.

Now my piano is in a small room; so here's what I think might be an exception: if I push the blow distance to 1 7/8", this grand gets quite loud. Fine--great--in a concert hall; but not in a small room. So I'm playing with something in the range of 1 3/4".

Generally small variations in hammer stroke—by themselves—do not have a great effect on the acoustical power produced by a piano. Assuming, of course, that the rest of the action parameters are regulated accordingly. If you really are hearing a significant variation in acoustical power—as opposed to a perceived difference—I’d be looking somewhere else to find out why.

Subtlety is achieved by making sure all of the various regulating parameters are precisely and correctly adjusted to balance with the chosen hammer blow distance.

There is nothing magical about this; it’s really just a matter of several different lever ratios working in synergy with each other. Unless you are prepared to modify the overall action ratio—Not advised unless something is screwed up in your action and you really, really know what you are doing!—then the appropriate hammer blow distance ends up being a compromise between the physical location of the hammer relative to the bottom of the pinblock and the rest rail (or cushions) at the back of the wippens and the desired amount of key travel and aftertouch.

In most pianos there is enough room to move the hammers a little closer to, or further away from the strings than is specified by the manufacturer. It is OK to experiment with this as long as you remember to compensate for the changes in hammer blow distance with suitable adjustments in key travel and aftertouch.

I suspect that if you fully re-regulate the action after changing the hammer blow distance you won’t find all that much difference in overall acoustical power. You will notice a change in how the action feels and this is often translated into a perception change in how the piano sounds.



Quote:
A real discovery for me was the fact (as I said above) that the string height actually varies from section to section, and even within sections!! Sure, the wound strings will vary in thickness: that's obvious. But I had no idea that I couldn't just set the trichord hammer line smooth from top to bottom (although that's the way it came from the factory.)

Yes, the string height, as measured from the keybed, can vary considerably from section-to-section as well as within a section. This is a function of how “flat” the casting patterns and molds are, how the string frame twists and warps as it cools and how it is machined and drilled. In theory modern string frames should be somewhat “flatter” than their predecessors because the machinery doing the cutting and drilling is now often NC (numerical) or CNC (computer/numerical) controlled. Many string frames are now cast with a little extra iron in critical areas and the milling/drilling machine simply hog their way through cutting off the excess and leaving the V-bars and agrafe drilling seats relatively flat. But, obviously, this is not always the case.

In terms of a piano’s performance a string frame would have to be wildly out of square before there would be any noticeable degradation of tone.

ddf
Posted by: Dave B

Re: Theory of hammer blow distance... - 02/27/13 10:04 PM

I'm surprised by Mark being the only one to mention key dip in relation to blow distance. Whenever I think through action mechanics, I try to keep in mind that the first act of mechanical movement is the arc of the fingers pushing on the key tops. I bring this up because of the relationship of the key dip to both the blow distance and the players hand.
Posted by: Del

Re: Theory of hammer blow distance... - 02/27/13 10:12 PM

Originally Posted By: Dave B
I'm surprised by Mark being the only one to mention key dip in relation to blow distance. Whenever I think through action mechanics, I try to keep in mind that the first act of mechanical movement is the arc of the fingers pushing on the key tops. I bring this up because of the relationship of the key dip to both the blow distance and the players hand.

Key travel and key dip are the same thing. I prefer the term key travel as being more descriptive of what is actually happening; i.e., there is a direct relationship between hammer travel and key travel. Key aftertouch is a part of the overall key travel. (But you knew that....)

ddf
Posted by: Withindale

Re: Theory of hammer blow distance... - 02/28/13 03:25 AM

Originally Posted By: Del
Subtlety is achieved by making sure all of the various regulating parameters are precisely and correctly adjusted to balance with the chosen hammer blow distance.

Quote:
Subtlety is achieved by making sure all of the various regulating parameters are precisely and correctly adjusted to balance with the chosen key travel.

Are these statements equivalent in practice?
Posted by: Del

Re: Theory of hammer blow distance... - 02/28/13 03:52 AM

Originally Posted By: Withindale
Originally Posted By: Del
Subtlety is achieved by making sure all of the various regulating parameters are precisely and correctly adjusted to balance with the chosen hammer blow distance.

Quote:
Subtlety is achieved by making sure all of the various regulating parameters are precisely and correctly adjusted to balance with the chosen hammer key travel.

Are these statements equivalent in practice?

Interesting question. Let's see if I understand it correctly, I would say yes except that there are usually more constraints on hammer travel than there are on key travel. That is, the maximum height of the hammer at rest is limited by the bottom of the pinblock and its minimum height is limited by the wippen and/or the shank rest rail. (Yes, that is adjustable but only within its own limits.)

So, if one wanted a particularly shallow (i.e., short) key stroke it may not be possible to shorten up the hammer travel enough and there may not be adequate aftertouch. Or, if one wanted a particularly deep (or long) keystroke it may not be possible to increase the hammer travel enough to accommodate.

On the other hand, it is usually possible to set the hammer travel anywhere within the physical limitations of the piano and still come up with a key travel setting that will work; i.e., one that will drive the hammer through its desired stroke and still have adequate travel left over for an appropriate aftertouch.

ddf
Posted by: Olek

Re: Theory of hammer blow distance... - 02/28/13 06:48 AM

There is something relative to hammer blow distance and that is the position of the knuckle and jack at rest, as well as at letoff moment.

SO the hammer blow allows for some variations but the range is not so large. (grand piano)

If the force actiing on the knuckle is pushing on its side too much the knuckle will deform even the wooden core can bend in time , and the knuckle on old pianos is often warped if not unglued, when the hammers have been filed a lot or if the "overblow" is very large (which is not uncommon on some brands)

WHile refining, indeed the stroke can be modified to change the touch or the tone (while it is sometime faster to change directly the key level)

The jack to knuckle relation is changing the dynamics of the shank on one side, and the suppleness of the keys on the other side.
We can use a range from a somewhat "hydrolic" keyboard, to a very springy one, just with variations in jack/knucle and aftertouch..