2026-07-22

Last modified: 2026-07-22 21:07:46

Keyboard Glockenspiel

To increase the key weighting from 12g by a factor of 4, I want to add about 36g of weight opposite the bit you press. Unfortunately that much in lead shot will not fit. Maybe 20g or so fits in the key, which I then taped in place and tested it out:

https://www.youtube.com/watch?v=Lye7HZBuT9c

The key return is much faster, and the key no longer bounces, so this is an improvement. But the hammer now bounces after returning. I tried putting foam on the underside of the shelf at the back of the case that the hammer lever rides on, but it didn't make much difference.

But in any event, I want a better way to attach the weights to the keys than filling them with lead shot. I am thinking cut out triangles or rectangles of thick steel and glue those in place.

The cavity in the key is like this:

Apparently randomly-packed lead spheres are actually slightly less dense than 100% solid steel. So replacing all these lead balls with solid steel would probably be a win. That's good to know, I was not previously aware of that.

So unless you have a particularly inconvenient shape to try to fill, you are better off buying like steel cylinders instead of lead shot.

The cavity is 9mm wide, 15mm across at the narrowest point. So I could buy 9mm thick 15mm wide steel and make rectangles? Or I think 20mm wide and make right-angled triangles? And potentially you'd want to trim the triangles to better fit the space, but I need 31 of them so I don't want to be doing too much work per one.

Another idea would be to machine a mould and melt the lead shot into it. Would that be efficient if doing it 31 times? Maybe!

How does this look as a mould cavity?

Imagine that cut out of aluminium, and capped off with a flat piece of aluminium, and lead poured in the top. Then wait for it to dry and snap off whatever is left in the sprue. I think just machine a bit of a funnel into the top and we're golden?

Does it need a second passageway for air to get out or is just one sufficient?

Does it need a draft angle? On balance I expect demoulding 31 of these with no draft angle will be easier than machining a draft angle.