Two stage spring

[ddrfraser1]

Ok an idea hit me when I was trying out heavier springs on a linear switch.

What if you had a spring with two weights? For example, 62g for the first half and as you press the switch you hit 70g. You would have the effect of tactile feedback (maybe?) while maintaining linear smoothness.

Is such a thing possible? Practical?

[Mr.Elli0t]

Maybe something like progressive springs?

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[fohat.digs]

This has been discussed several times before. Many people think that it would be a good idea, but that is usually done with gourd-shaped springs.

I don't think it has ever gone anywhere.

[ddrfraser1]

Who are the go to spring makers to get in touch with?

[Leslieann]

Who are the go to spring makers to get in touch with?

This isn't a call up and ask them to make it scenario, even if it was you'd still be looking at quite a lot of money (they won't do this for $20).
You need to figure out spring rates (diameter, thickness, material, coating) and figure out if that combination will even fit into a switch body without binding. Remember, switches were designed for a traditional switch, can they even accommodate something this shape?

Costs?
Springs alone, figure $2k plus. You will be disrupting a product line with low margins, so you will need to compensate for down time AND buy enough to make it worthwhile. If the springs don't fit you may need an entire switch redesign to make it work that can easily run up into high 5 figures, and that's assuming you can do the design work yourself and then hoping and praying it all works or can be adjusted without making an entire new mold because, oh god, those can get expensive really fast.

Then there is what comes next.
Few people will want a $70 set of springs or willing to spend $6 a piece on switches. That's IF you succeed, what happens if you do all of this and you don't like the results or worse it doesn't even work? You need to be willing to spend more to try and make it work or accept that you just spent a lot of money for nothing.

[ddrfraser1]

Who are the go to spring makers to get in touch with?

This isn't a call up and ask them to make it scenario, even if it was you'd still be looking at quite a lot of money (they won't do this for $20).
You need to figure out spring rates (diameter, thickness, material, coating) and figure out if that combination will even fit into a switch body without binding. Remember, switches were designed for a traditional switch, can they even accommodate something this shape?

Costs?
Springs alone, figure $2k plus. You will be disrupting a product line with low margins, so you will need to compensate for down time AND buy enough to make it worthwhile. If the springs don't fit you may need an entire switch redesign to make it work that can easily run up into high 5 figures, and that's assuming you can do the design work yourself and then hoping and praying it all works or can be adjusted without making an entire new mold because, oh god, those can get expensive really fast.

Then there is what comes next.
Few people will want a $70 set of springs or willing to spend $6 a piece on switches. That's IF you succeed, what happens if you do all of this and you don't like the results or worse it doesn't even work? You need to be willing to spend more to try and make it work or accept that you just spent a lot of money for nothing.

Sorry, you're right. We wouldn't want to ask questions and innovate would we. I'll just crawl back in my hole with the other noobs.

[Leslieann]

I never said it wasn't possible I simply stated the reality of the situation.

If you want to put forth the effort it's doable, maybe not practical, but doable, but it takes effort.
So far you're effort consists of asking others to do the work for you.

[Pylon]

From what I've read you can't do this with a constant-diameter (i.e. cylindrical spring), as two springs in series just acts as one spring. You have to have a conical or gourd-shaped spring, which current switch designs might not accommodate very well.

[Findecanor]

I don't think this is possible in a linear Cherry MX-like switch. The tactile MX Clear has an increase after actuation but that is because it has spring with sharp slope — and the spring's low force before actuation is masked by the tactile bump.

Vintage Tokai switches have a sharp increase of force at actuation, and then some travel. See this force graph that HaaTa made.
It's a very unique switch design, and not very durable. I have only tried them briefly on a keypad, but they felt quite weird there ... Would they feel different on a full-size keyboard?

There are a couple of announced near-linear switches that are supposed to have two-stage force. Neither would be compatible with Cherry MX other than the keycap stem and mounting plate.
* Cherry Viola.
* A Leopold foam-and-foil type, seen at trade shows. The feel is supposedly different from vintage foam-and-foil because of use of a different type of foam than what is in those vintage switches.

[ddrfraser1]

I never said it wasn't possible I simply stated the reality of the situation.

If you want to put forth the effort it's doable, maybe not practical, but doable, but it takes effort.
So far you're effort consists of asking others to do the work for you.

Huh? I never asked anyone to do anything for me other than point me in the right direction. It seems like you’ve got a chip on your shoulder for others who have done that in the past and I merely stepped in the crossfire. I think it’s important to facilitate an environment where people can ask questions even if they appear stupid at first glance or the topic has been done before.

Thanks to the others for the info. I’ll continue to look into it! 

[Maledicted]

SPRiT's website isn't always the most clear in its descriptions, so I'm not sure if progressive springs were still in the design process, or if the springs of the same weight, on literally the same page, are meant to already be early results of that testing. I know they're not conical, or gourd shaped in the case of Kailh springs, and I couldn't perceive anything approaching a progressive weighting in feel.

Leslieann just comes off as brusk/curt/blunt. That can easily be interpreted as condescending, or combative, without being able to hear tonality, see gestures and facial cues, etc. I don't think that that's the case. She just tries to make people consider all of the hurdles before they commit to something fairly daunting.

[ddrfraser1]

SPRiT's website isn't always the most clear in its descriptions, so I'm not sure if progressive springs were still in the design process, or if the springs of the same weight, on literally the same page, are meant to already be early results of that testing. I know they're not conical, or gourd shaped in the case of Kailh springs, and I couldn't perceive anything approaching a progressive weighting in feel.

Leslieann just comes off as brusk/curt/blunt. That can easily be interpreted as condescending, or combative, without being able to hear tonality, see gestures and facial cues, etc. I don't think that that's the case. She just tries to make people consider all of the hurdles before they commit to something fairly daunting.

I suppose we all need a healthy dose of reality now and again.
No hard feelings Leslieann 

[ddrfraser1]

Ok, progressive linear from key dot co. Just got the email. Is this the same as what I was thinking? If so, this will be the second time in two weeks I've wanted something and the keyboard gods have shone on me with favor 

If leslieann stomps on my joy, I'll cry 

[Leslieann]

Leslieann just comes off as brusk/curt/blunt. That can easily be interpreted as condescending, or combative, without being able to hear tonality, see gestures and facial cues, etc. I don't think that that's the case. She just tries to make people consider all of the hurdles before they commit to something fairly daunting.

I suppose we all need a healthy dose of reality now and again.
No hard feelings Leslieann 

That^
I've worked in too many industries where you say what needs to be said and be done (not to mention I'll ramble forever if I don't).
It wasn't intended as mean, sorry if I come off that way.



Speaking of rambling...
I've been thinking about this a bit and I'm convinced the gourd shape will not do what you want, that's a progressive spring, not two stage.
About the only way I can come up with to make it two stage is by having two very different rates and one will need to be almost fully compressed before the other even starts to compress. If the second half starts to compress at all before the other is done it will simply feel progressive.

Going from a 62 to 70gram spring is not quite what you think. Those are bottom out rates (Cherry measures at activation), a 62g may start at 40  and ramp to 62, while a 70 will start at say 45 and end at 70. Its actually going to lead to a less(!) progressive spring that starts at 40 (because of the the 62g) and ends at 70 (probably less since the spring will not be fully compressed) which is actually about what a Cherry red/blue/brown spring is. Note these are guesstimates on rates I did not verify them I'm just using them as an example to show what will happen.

What you need is a spring that starts at 40 and peaks at 60 (for the first half), then the second half starts at say 75 and ends at 90.
Something to note, if this transition happens in the wrong place on a clicky or tactile switch the feel could be obliterated by the switch itself, you may just want to focus on a linear switch but even then you need to find the right spring rates and position for it. I'd recommend modeling it in cad to try and get it as close to the activation point as possible, while you may think just transition at the mid point, that won't work as the first half completely compresses while the second will not and the transition will move, at least some, depending on the rates, being closer to the center when the rates are closer and further as they drift apart. Also, you can't just take a 62g spring winding and cut it in half and expect it to be 40-62g anymore, you removed half the coils, it's probably something more like 50-75g now.

Springs will mess with your head almost as bad as air pressure/volume calculations.


Edit:
You posted while I was working on this... Sorry. LOL
I hope the info helps though.