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Hmm, good question. That was the weight required for the key to begin moving down on its own just by sliding the weight from the neighboring key.

Retesting it with the tapping method shows 57.0g for the key to begin moving, but it stops due to friction after just a few mm. I'm sure a piano technician would come up with a more accurate measurement that my admittedly crude hack of stacking coins on a 3D-printed rubber block. Dynamic response, I'd think, would be another important factor in how a keyboard feels to play.

FWIW here's a graph of the Casio's dynamic key force here, about 2/3rd down the page:
Casio GP-510BP Page

Thanks Bravo Romeo for your excellent reply!
I intend on using an iPad with a piano app ( possibly Flowkey)

As you say connecting might be easier with the CLP 775 as it has Bluetooth….

But as you also say, connection using USB cables is straight forward with the 510…

Bluetooth MIDI can be added with a small and inexpensive piece of electronics.

There's e.g.

https://www.thomann.de/gb/yamaha_md_bt01_wireless_midi_adapter.htm

https://www.thomann.de/gb/quicco_sound_mi.1_ii_wireless_midi_adapter.htm

So, they connect to the 5-pin MIDI sockets on a digital piano and convert them from wired MIDI to MIDI over Bluetooth LE.

Thanks for the info on the retest. 57 is very good, and stopping after a few mm is expected. However (but don't take my word on this because I am no expert on these matters) the stopping of the key is not due to friction but to increased leverage weight (the force needed to raise the capstan increases as the fake hammer is raised). Friction should be constant along the key travel and equal on downweight and upweight. Friction does affect dynamic weight.

If I may bother you a bit more, would you be so kind to also measure upweight? In this case you force the key all the way down, put the coins at the front of the key, and then slowly remove the hand of the key and let it raise. The minimum weight of the coins needed to keep the key at the bottom is the upweight, and I believe that the difference between down and upweight is considered to be the friction (or maybe half of it... Not sure... Again, no expert...).

I believe upweight is measured not at the bottom but at the letoff. It is basically the reverse of measuring the down weight.

So you measure the weight to make a key go to the just before the escapement and then remove weight until it rises to the top. The difference is the friction as you stated.

Purdy: yes, you are absolutely correct, but afaik the casio GP actions don't have any plastic fake escapement like Kawai GF actions. In this case I think that having the upweight measured from the key bottom is more informative than having it from a random halfway point of the key travel. But the test can also be done in the traditional way and measure downweight, and then see how many coins need to be removed for the key to rise... It would be a good way to know how consistent is the friction along the 88 keys 😊. Not sure if it is worth the trouble...

Fair enough but then you should measure the weight to go all the way to the bottom and then the weight to go all the way to the top.

I believe you need to measure up and down weight from the same key position to measure friction.

Again, the weight to the bottom had already been measured by BravoRomeo: 67.4g... So, upweight measured from the bottom would give a friction value for the entire key travel, as you propose. But the value of friction is somehow useless in this action, since I don't think there is any hope of balancing the key. The value of static weight to start movement and he value of push back weight at the bottom are the relevant measurements in this case.

I interpreted this to mean it was not at the bottom.

I don’t believe balancing a key or changing the moment of inertia with a counterweight has anything to do with friction.

OK, so here's another GP-510 measurement, just Middle C again as I didn't have time to do any more keys.

Initial (requires tapping on the frame to get the key moving): 57g
Key balances after a couple mm descent. Now I believe it is more correct to call that balancing rather than friction, otherwise any further tapping should cause more movement, which it doesn't. The key stays put until you adjust the static weight.

At approximately 80% of travel, the key once again balances at 62.7g
To get it to start ascending from that point, requires removing weight, so about 46g remaining and tapping on the frame.

Static weight required to get the key to completely bottom out onto the felt bumper below is 119g.
Removing weight to 100g and the key begins to rise from that bottomed out point.

Couple of observations:
That roughly 70-80% start of additional resistance is noticeable at extremely slow key depress speeds, like when you are trying to depress a key without sounding. At normal playing speeds, I just don't feel it.

You don't have to fully depress the key to make a sound... at some halfway point even if you physically restrain the key from bottoming out, you can effectively throw the "hammer". You can also get a repeat without fully releasing the key.

So, there you have it. Take these measurements with a grain of salt - a piano technician I am not. I'd be very curious to see how that compares to my rebuilt C. Bechstein back home, but won't have the opportunity to check that until May.

Interesting and detailed measurements. Thanks.

Hello,

@BravoRomeo, Interesting information, nice and informative little report!

I have had a hunch for some time already that a Casio GP (speaking purely action-wise) could be a fine friend of mine. Your post reinforces that thought.

Cheers, thank you and happy playing,

HZ

You’re welcome. I learned something new with this exercise, so thanks!


Happy to help. I have been exploring the Pianoteq demo, which tickles my inner geek. Amazing simulation, really. Still, I keep coming back to the GP-510’s built in pianos.

Another thing I noticed with the built in pianos. The normal key release has a sort of soft bounce to it at the top of the stroke. This little bounce is perfectly in sync with the Key Off mechanics sound effect. I was listening on headphones and the illusion that the key was physically making a release noise in time with the little bounce was uncanny. I even took the headphones off to dounble-check… perhaps I’m easily amused.

Happy music to you as well!

So, according this Stu video:



it is best action behind Kawai Novus (32:50). So, the action is very very good.

I watched Stu's review earlier. I found the noted treble issue intriguing; I wonder if it's somehow related to the "aliquot resonance" feature, exclusive to 510. Stu made no mention of this?

In case OP/others are still deciding between the models, perhaps 510 owners can comment.

I have not noted the same on 310.

Perhaps it is the Casio GP’s lack of USB Audio interface that you mis-remembered as no Line Ins .... ?

Anyway, since OP intends to use an on-line piano-learning program via iPad to help his beginner’s journey, it may be important he knows the candidates he’s considering do or don’t support any one or more relevant features. At a minimum he’ll probably want a DP that does midi, either conventionally or by usb. GP510 has conventional midi ports plus USB - to host and to thumb drive - ports, has no USB audio, does have line-ins, line-outs, dual headphone jacks and has an LCD display & settings/operations control BUT does not support any smart-apps/graphical settings/operations control.

I can definitely hear what Stu is observing. It is a bright, punchy, ringing treble, and seems to only affect the Berlin / Bechstein sound. I just figured it was the sound they wanted and may be what the particular piano they modeled it from really sounded like.

I have found turning the Brilliance down to -2 under Settings > Effects helps tame the Berlin piano. Playing with the lid closed does, as well, but I like having the lid open for a more enveloping sound. Another way to tame the Berlin treble is to adjust the simulated Lid position to CLOSED, but physically leave the lid open... or hit the Berlin button a second time to access the Mellow version.

The other pianos, Hamburg, and Vienna, do not have this ringing treble effect, at least to my ears. I find myself playing the Hamburg more, lately.

No... It was really a case of faulty memory and not double checking before posting, something that I tend to always do and that drives me mad when others post misinformation without checking. This time it was me, and I am really sorry for that. To make it worse, I believe that I also said (from faulty memory, again...) that the GP310/510 used the Casio Chordana app. Turns out, the chordana app is only compatible with mid and low spec casio models. Go figure! And another mistaken info...

Looking back, I think the mix up could be with the lack of registrations of the GP310...

This is my reason why I don`t want Yamaha 7xx - the action is significantly heavy.

This was a nice topic as I looked into the action a bit more.

I’m not entirely sure what Casio was trying to say with these graphs.



Casio went through a lot of effort to produce an acoustic action without escapement And there are no counterweights but still a light static downweight.

Is the Casio graded?

In theory that should produce a very fast keyboard with good key return force and low moment of inertia in the key, I’m going to have to find one someday to play.