Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum weak repetition lever springs?

If I understand it correctly, after striking a key and keeping it down, the hammer rebounds and its tail is caught by the backcheck. If the depressed key is partially raised, the backcheck releases the hammer tail and the repetition lever should lift the hammer back to the drop position. This raising of the hammer by the repetition lever should neither be too sluggish or too jumpy.

In my piano's action, this does not happen, i.e., the hammer isn't lifted by the repetition lever on its own accord after the hammer tail is visibly not in contact anymore with the back check. The lifting can be effected either by 'helping along' the repetition lever by a gentle upward nudge by my finger, or by giving the key a gentle push downward (and therefore letting the jack nudge the knuckle's side upward).

So, are my repetition springs lacking tension?

They are lacking tension sufficient to overcome the friction and weight, yes. Excessive of either will need more spring.
There might also be terrible regulation and the drop is set far too low or the hammer is checking too high for the drop to actually affect it.
Regards,

The drop is ok but I feel that the hammer is checking too low. I suspect that the strip of restraining material that was placed between the hammer tails and backchecks during shipping maybe bent the backchecks a teeny weeny bit backwards. I'll check again.

I always like to go to the source when determining these things. Looking for proper speed of hammer rise is good, but don't forget the reason why you are trying to set the spring tension; for good repetition. So, can you play a note rapidly with two fingers of opposite hands, or the 4-3-2-3-4-3-2 pattern of the same hand?
Proper repetition spring tension has a window. Not strong enough and you cannot play single notes fast. Too stronge and soft notes will double strike, given that you have 1/16" letoff and 1/8" drop. Without this close letoff and drop, you may not get double striking notes, but at some point, you begin to feel a bump in the key as the hammer rises too abruptly.

Regulation must be correct too. That is, the hammers must be at the right height on the hammer rest rail. If they are to low, raising the hammers will also increase the speed of repetition. Make sure they are at the proper height. Could also be a gunk build up in the repetition slot interfering with it. Or, just weak springs.

Thanks for all the tips.

What are the chances of weak springs and gunk in a brand new piano though? Seems like it just needs a good regulation.

I'm with Jerry, likely that the hammer line is too low, very common in new pianos. The backchecks themselves are unlikely to have moved during shipping. Hammer to string distance should be about 45mm as a starting point.

Or the pinning is too tight on the hammer flanges as Ed mentioned.

Considering the high humidity location (Philippines) I would check for key pin and center pin friction first, before touching anything.

Yes as said Jurgen, in high humidity and on a new action, the first idea I would try is to moisten with 10 to 30% alcohol/water the flanges, so to "ream" the bushings a little.

the centres get stuck and locked with the moisture, then will free themselves a little once dry (it takes 8 hours usually)

lubrification later,once the pinning is in the accepted range.

Indeed that have to be done by a technician as different centers have different friction range, the solutions used may be more or les strong- the main problem is to have to wait.

The keys also are possibly too tight and have to be adjusted to the pins.

Once the centers have been fitted well they may not cause further problems

So, i checked.

Hammer travel distance is spot on at 45 mm.

Checking distance is 13 mm, which is also acceptable as Hailun specs suggest 12 mm.

Let-off and drop are 1.5 and 3 mm respectively.

Humidity is mostly in the 60's although it hovered at 85 the past couple of days due to a weather disturbance.

Yes, I can play trills just fine. Repeated notes using 4-3-2 fingers of one hand can be *definitely* played better on this action than the Yamaha U2 I previously owned.

But I'm just thinking that I may be missing something if the rep lever doesn't rise on its own when released by back check. I'm imagining how *much* easier it would be to do repeated notes. :-)

the spring only "sustain" the hammer at normal speed, with a short checking distance it is possible that the raise is barely noticed..

the pinning on those actions is sensitive to moisture, I was said ( a little more than others).

so the pinning have to be tested anyway.

Going by how the action feels, I think there is a bit of key and balance rail pin friction. But just a little bit. I could tell how the action has become a little bit heavier now compared to when it was right out of the crate. It may just be in my mind though.

But how could pin friction, if any, affect lifting of the hammer to drop position by the rep lever?

Regarding flange pin friction, I'd rather take the current situation over messing with these action pins with lubrication, reaming, easing or what not. Too much trouble and potential for disaster (because I'm not a technician).

The only lubrication I've ever done so far is to put a little talcum powder on the keybed guide rail pins and action return spring to make the una corda pedal lighter to operate.

Maybe so. The usual generic checking distance is 16 mm, am I right? But for Hailun grands it is 12 mm. My piano is at 13 mm.

High checking mean better repetition (and less strength when playing strong the high checking may be used to lessen the impact noise and favor the opening of the tone)

The hammer motion is less noticed as the spring is less compressed. it should be visible anyway, just when the key is barely released, as when you let the key go lower it is soon putting the hammer at 12 mm.

Possibly you release too much the pressure, or too fast, to see the hammer raise easily.

talcum, rubbed on the keybed, and tallow or similar , on the guide pins (talcum will not do much there)

if your technician is at ease with regulations he will find what is wrong.

Possibly he will need to ease the keys.

Also if the moisture have thickened the back cloth on the key frame, you have n,ow less key dip , and the hammers have a little less travel distance (if the hammers are not lining well the cloth have grow due to moisture)

if you have 60% and high temperature, the moisture is high, what counts is the amount of moisture in the parts, so the 60% HR does not give the complete information, it should be related to temperature.

A piano can stand 60% in a medium/low temperature, but the strings will oxyde a little faster, a "string cover" see (http://edwardsstringcovers.com/) could be installed then to make an humidity barrier.
Correcting the moisture in the room if possible is probably the best thing to do if the moisture is at fault)


Test the action feel (keyboard friction) with the sustain pedal engaged, notice if the keys are returning fast without the dampers weight help.

if the keys are sluggish, chances are that the centers are also a little stiff.

I am in touch with a colleague who works on those actions in music schools, he stated that the spring humidity is making the centers slow (it happens on all pianos, at different levels depending of the wood and the quality of the center cloth)

Thank you, Kamin, for all the tips.

May I give you an update on this.

I did a regulation. Followed the sequence in Reblitz but didn't do the bedding the keyframe and adjusting the glide bolts.

Taking detailed measurements this time, I was surprised to find out that the hammer to string distance of the bass was at 45 mm while tenor break up to treble was at 40 mm. So I lowered the concerned hammers to 45 mm.

Other measurements and alignments were ok so I left them alone. Checking distance was 15 mm, not 13 mm as I earlier stated.

So, when it came to adjusting the repetition spring tension, I made a device out of stiff wire so I could depress the spring, swing it out of its groove, adjust the tension, and put it back in the groove. I found that the springs didn't have sufficient push on the levers so that the hammers would rise. On release from the backcheck, the hammers didn't even wink a bit. So I adjusted the tension just enough so that the hammer would slowly but surely rise, without feeling a bump in the key. It took me five freaking hours just on the springs alone!! I went to bed at midnight, but not before I played the action.

The repetition is definitely better, but I noticed an increase in touchweight. Is this a trade off for having better repetition? Sigh...

Changing the spring tension will not change the touchweight, which is the amount of force necessary to get the key to start moving, but it will change the weight at other points in the key's travel. Even using the damper pedal will do that.

So it's all in my mind, then! Either that or I was so tired after doing the surgery! At any rate, I do perceive a slight increase in firmness of the action. Not sluggishness, but firmness in a good way. I've played it for a couple of hours now and I'm beginning to like it better than when it was lighter. It seems I make fewer mistakes and I can feel a definite feedback from the keys.

Oh, there's one note that strikes double on light playing, but I can fix that later.

So, all is well.