Rivets versus hooks

[alex_holden]

1 hour ago, Richard Mellish said:

You could avoid that by having something like the hook with flat faces but facing upwards, with the spring on the pad section of the lever pulling down, but that would be trickier to manufacture, particularly anchoring the spring to the action plate.

 

I think Dana Johnson's ingenious action is a bit like that:

http://www.kensingtonconcertinas.com/photo-album/lever-pivot-and-spring.html

[Richard Mellish]

8 minutes ago, alex_holden said:

 

I think Dana Johnson's ingenious action is a bit like that:

http://www.kensingtonconcertinas.com/photo-album/lever-pivot-and-spring.html

So it is! That looks pretty good to me and it deals very neatly with anchoring the spring. What are its disadvantages, if any?

[Dana Johnson]

 

On 10/14/2020 at 5:52 AM, alex_holden said:

With hook type actions, particularly on the shortest levers, they have a tendency to lift off the pivot point when you press the button quickly, leading to a slight delay in lifting the pad and a clicking sound as the lever comes back into contact with the pivot.

 

They also aren't as good at dealing with the side forces you get with levers that are cranked to go around an obstruction; in that case they tend to twist a bit when you press the button before they start to pivot, and the pad may not land flat on the board again when you release it. Sometimes notches wear in the sides of the lever over time, causing them to stick and not close reliably (Dave Elliott calls this "cranked lever syndrome").

 

Makers have come up with several different solutions to the problem of making a riveted action 'just tight enough'. The way I do it is to turn an accurate step in the shaft of the rivet so it can't go too far into the post and cause it to bind.

 

[Dana Johnson]

The wheatstone way Steve Dickinson showed be was to peen the rivet over tight, then invert it over a head sized shallow hole in the anvil and give the rivet a tap , causing it to release just enough to leave the lever free.  It was quick and easy.

Dana

[alex_holden]

9 hours ago, Dana Johnson said:

The wheatstone way Steve Dickinson showed be was to peen the rivet over tight, then invert it over a head sized shallow hole in the anvil and give the rivet a tap , causing it to release just enough to leave the lever free.  It was quick and easy.

Dana

 

I used to do something like that, but I learned the hard way that occasionally a rivet that was hammered tight then loose, will work itself back tight again after a few days of playing.

[Dana Johnson]

Re: Richard’s reference to my concertinas, my pivots have evolved over the last 25 years, as have my springs, but all had the same aspect of being a downward pulling spring between the pivot and the pad rather than the normal upward spring on the button side.  All get tested for about 4 million cycled to check for wear, which even then is negligible.  I like the down spring because it keeps the pivot in contact regardless of any button pressing ( referring to Alex’s comment on hook actions ), Is wear compensating  compared with rivets which can eventually wear their holes oblong causing clicking and reduces forces trying to pull the pivot out of the wood,  where the normal spring exerts more upward force on the pivot at rest, and sometimes after years can cause the pivots to start to pull out. The pivots are not as laterally secure as a rivet, but  the ease of working with the levers, pads and pivots separately instead of as a unit Is enough to outweigh the lateral issue for me, especially since the combination of guide hole in the action board and button bushing in the end plate keeps things nicely in line. The link is to the 4th version , where I am using the 6th version now, though they have only very minor changes in form since version 2.  The current spring is easier to preload and adjust (which is more difficult for the down spring than the traditional up spring.) and is also easier to install.

Dana