Key Pressure!?

[conzertino]

I noticed that the pressure to actually press down a key differs a lot from instrument to instrument and - unfortunately - often even within one instrument.

So I made myself a usesful little device to measure that pressure. By bending the springs the pressure can be adjusted...

 

 

On some of my favourite players the pressure is as low as 40 g, on some others well above 100 g.

If the pressure is to low, the tightness suffers, if it is too high, it is no fun to play.

 

Any ideas or experiences?? Is there a diffrence between ES and anglo?? If so, why?

[Geoff Wooff]

I have a similar gauge ( bought at an antique/ junk tools dealer in a flea market) and modified it with a small block of cork fixed to the lever, so as not to scratch anything being tested. I like a button pressure of between 60 and 70 g. on my EC's though I also have one where the buttons need 100 g. to start depression. I do not have any problems with this change of pressure on my EC's.

 

With an English Concertina the fulcrum points of the action levers are reasonably in a central position, length wise... so the downward force on the pallet will be similar to that needed to press the key... but some levers on Anglos and Duets can have their pivot points a long way from the central position which might affect the spring pressure requirements.

 

I have measured the button pressure on two accordions that I play regularly , both have very constant spring pressure over their range... but one instrument will start opening its pallets at 50 g and the other takes 100g.... changing from one to the other is not a problem generally , only where rapid ornamentation practiced at one return pressure is transfered to the other box!

Edited August 3, 2017 by Geoff Wooff

[Bruce McCaskey]

I have an interest in being able to measure button pressure.

 

It seems to me that you want more than just sufficient pressure to keep the pad from leaking. A little extra pressure makes the difference between a soft close and an abrupt interruption of air flow. The latter, in my opinion, is essential to supporting crisp cuts and other ornamentation. On the other hand, too much button pressure and it's more of a challenge (when playing fast) to depress the button sufficiently to ensure that the reed actually sounds.

 

How about some more information about this pressure messing device? What is it called if one were to go looking to purchase such a thing?

[Chris Ghent]

I have an identical device to the one in the picture though my vertical return is a little different. I'm away from home so can't tell you the brand but they are expensive. You can make a cheap device which will do the same in many ways. The easiest I have heard, suggested by David Hornett recently, is to put the end on an electronic scale and push the button slowly while watching the readout. Another, suggested by Geoff Crabb some time ago, is to get a longish bolt weighing less than your target weight and a bunch of washers. Hold the bolt vertically on the button and let slip the washers one at a time until the button moves. Bolt weight plus washer weight x number of washers = button pressure.

[Chris Ghent]

Might just add, I find the minimum button pressure can be found by starting on the longest lever and finding what weight will hold it's pad closed under reasonable bellows pressure. Shorter levers should all have less trouble staying shut.

 

Minimum pressure is not everyone's favourite, someone was telling me it makes for a slow returning button, limiting your playing speed.

[Geoff Wooff]

Bruce,

 

I think the device I use, very similar to the one shown in Robbie's picture, is a hand held progressive spring pressure indicator used for setting mechanical Relays or the like. Perhaps these are not used much these days as I'd imagine electronic switches replace the old fashioned leaf spring Relays . As Chris says, they may be expensive tools to purchase new but can be found at government 'surplus' sales and the like. Perhaps every telephone engineer had one in their tool kit?

 

Mine has the black 'crackle' finish paint on the all metal body and the maker's name CARPO ( made in France) on the dial and came in a small wooden box. It reads from 0- 175 grames. If I see another , whilst I scour the flea markets for useful items, I will surely liberate it.

 

PS ; a quick search on a classified adverts website and I found another, which goes from 0 - 50g, the seller says it is used for setting the springs in a typewriter.... for sale in its box for 15 euros! Another that will measure to 150g , the seller says it is for weighing letters, for 20 euros.

 

PPS; found at least 3 for sale on line ( in France) that will measure 0- 150 grams.... prices range from 15 to 30 euros plus postage. I'm sure you will find these locally.

Edited August 4, 2017 by Geoff Wooff

[Don Taylor]

Somebody in China is making new ones that look very much like the one in Robbie's picture. There are several sellers on eBay listing the 0-100gm version for about us$35.

 

For example: http://www.ebay.com/itm/262699247208

 

If this is what Robbie's bought then perhaps he could comment on its quality and accuracy.

[conzertino]

Don, this is exactly the one, which I ordered from China. It does a good job.

I have found some buttons with a higher pressure than 100g, but as I set them to about 60g, it works!

I had experimented with other contraptions before using two tubes and a spring or metal bars with different weights, but this one works best.

The holes at the ends are useful as they hold the keys in position when ends are off.

Edited August 5, 2017 by conzertino

[Chris Ghent]

Cheap! About a quarter of what I paid for mine. Very similar looking so maybe a knockoff?

[Bruce McCaskey]

I've found a few "Force Gauges" online that are similar. Thanks for the insights.

[alex_holden]

I just picked up this Swiss one made by Correx. It has a handy second needle that records the peak force. The 125g reading is from a heavily-sprung cheap German instrument that happens to be sitting on my desk at the moment.