Idea: Extra springs to increase Topre switch force

[coolbho3k]

I did the foam silencing mod on my HHKB Pro 2 yesterday. Cutting out the disks took forever... When I was doing the space bar I had an idea.

The space bar has an extra spring around the switch to change the feel. I read about swapping domes from a 55g RF board, but then I thought what if I put springs on the other keys as well?

Instead of buying a new keyboard and gutting it for 55g domes, which would cost $200+ and force me to sacrifice a nice RF (or leave it with Frankenstein mix of 45/55g domes, not quite variable force...), I thought that maybe I could buy similarly sized 10 gram springs and put them over the switch just like the spring on the space bar. I know it won't feel exactly the same because the force the spring exerts will be different throughout.

Anyone know if this idea has been tried before? I tried searching for 10 gram weighted springs online and I haven't been able to find anything suitable.

[SpAmRaY]

People have tried this but I don't think anyone did it on more than a couple keys.

[coolbho3k]

People have tried this but I don't think anyone did it on more than a couple keys.

I just found this post:

https://geekhack.org/index.php?topic=48597.0

Seems like people have had the idea, but the problem is sourcing springs that fit. I'm willing to bet you could grab suitable springs from somewhere. The question is how to find them.

[SpAmRaY]

I've got some old keytronic boards with springs I think might fit but they are in storage.

[coolbho3k]

I've got some old keytronic boards with springs I think might fit but they are in storage.

Seems like people think they have to be an exact fit. The diameter has to cover the Topre switch, no more no less. Ideally I'd like to find a bulk supplier of springs that would replicate the force curve of a real 55g Topre switch as closely as possible.

[coolbho3k]

Just realized that I could probably cut much longer springs to size as well. They just have to be the right diameter. Now to revisit elementary physics to figure out forces and measure the spring around the spacebar.

[Oobly]

I doubt you'll be able to get it to feel the same. Springs tend to have linear force curves, although you can make a dual rate spring, but it's tricky. Rubber domes have an s-shaped force curve. Since the difference between 45g and 55g Topre is in the domes, I don't think you'll be able to approximate the curve well enough for it to feel similar.

Worth a try, though, even if you do just end up with a new switch feeling, that's interesting enough to do it, IMHO Topre don't have enough mods to change the feeling.

[coolbho3k]

I doubt you'll be able to get it to feel the same. Springs tend to have linear force curves, although you can make a dual rate spring, but it's tricky. Rubber domes have an s-shaped force curve. Since the difference between 45g and 55g Topre is in the domes, I don't think you'll be able to approximate the curve well enough for it to feel similar.

Worth a try, though, even if you do just end up with a new switch feeling, that's interesting enough to do it, IMHO Topre don't have enough mods to change the feeling.

Of course you could never get it to feel exactly the same.

My other idea was maybe heat or chemically treating the 45g domes or something to make them stiffer... but I don't think anyone but Topre knows what goes into making these things and I'm not willing to risk any of my precious domes.

[Melvang]

Just realized that I could probably cut much longer springs to size as well. They just have to be the right diameter. Now to revisit elementary physics to figure out forces and measure the spring around the spacebar.

The problem with this is going to be cutting the springs close enough in length to not notice differences in weight.  Plus you probably need capped ends to keep the end of the spring from poking through the domes.

[Oobly]

How about just doubling or tripling up the springs under the domes? Hopefully the capacitive sensing wouldn't be affected too much.