2026-03-23

Last modified: 2026-03-23 16:30:57

Celesta

For the second revision:

• increase hammer spring thickness from 1mm to 2mm
• decrease pivot spring thickness from 2mm to 1mm
• add a "stop" feature for the hammer to come to rest against

Seems a lot better than before.

https://www.youtube.com/watch?v=5VinUtSnSzI

It wants a stop for the key to bottom out on, and it wants felt pads on both the key stop and the hammer stop, and then it wants a way to suspend a tone bar above it at an adjustable distance so I can see how it actually works. And then may want some rebound damping on the hammer to prevent multiple striking.

I tried making a tone bar to see how it would work:

That is mild steel flat bar, 5mm thick, 16mm wide, 97mm long, with 9mm mounting holes drilled ~22.4% of the way along, which is apparently where you're meant to do it because that's where the "nodes" are.

It is made to approximately the same dimensions as the adjacent red one, which is 99mm long although with curved ends, 2mm thick, 20mm wide.

My one is a much higher pitch than the original, which means to get lower notes it would need to be even longer.

But mine rings very nicely and with a very clear tone, I think this is a perfectly adequate material, just needs to be thinner probably.

Plausibly you could use this to make the upper notes out of thicker material and the lower notes out of thinner material, instead of having them all the same thickness and a crazy variation in length?

I was working on the basis of 125mm for the octave, because smaller is more convenient, but actually it may be preferable if I have a bit more space. The more typical suggestion was 165mm for the octave, which works out to 13.75mm per note. So maybe I try 12mm wide, 2mm thick steel flat bar and make the notes from that? How much will I need? Depends how many notes I want to make and what tones I want. So I guess just get a sample first.

Interestingly it looks like 3mm is about the minimum thickness you can easily find steel flat bar in. That's annoying.

Rapid Metals will cut 2mm sheet to size, but the minimum width is 15mm.

There is an eBay seller offering 25x 6-foot lengths of 12mm by 2mm steel strip for £60, but I don't want that much. I won't use that much in a lifetime.

It is possible to buy "ground flat stock" gauge plate in 10mm by 2mm, would that suffice? It is rather expensive at £28/metre in small quantities. Or I could get the 100 metres of 12mm strips for £60 which is 60p/metre. I am trying to convince the seller to rinse me on price but provide a smaller quantity, so that I don't have to pay £60.

Update: he has done it! I got a pack of 3 (instead of 25) for £20 instead of £60. Egg on my face if I need to go and order more though!