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geekhack Community => Keyboards => Topic started by: Jixr on Tue, 29 October 2013, 14:04:40

Title: progressive springs
Post by: Jixr on Tue, 29 October 2013, 14:04:40: Surely i'm not the first person to think of this, but does anyone know of anyone who's found a progressive spring to put in a switch?

basically start off as light as reds and then it feel more like blacks the further down you push, that would be a perfect switch spring for me.
in reds or blues that spring would be awesome.

ideas, comments, thoughts?
Title: Re: progressive springs
Post by: esoomenona on Tue, 29 October 2013, 14:07:19: Have you ever tried MY switches?
Title: Re: progressive springs
Post by: Jixr on Tue, 29 October 2013, 14:09:58: just to make myself clear
Title: Re: progressive springs
Post by: esoomenona on Tue, 29 October 2013, 14:19:34: Hmm... Would stretching out a portion of a spring have the same effect?
Title: Re: progressive springs
Post by: fohat.digs on Tue, 29 October 2013, 14:23:23: I think that almost everybody would like a spring that was soft at the top and stiff at the bottom.

There must be some realistic reason that it isn't feasible.
Title: Re: progressive springs
Post by: Jixr on Tue, 29 October 2013, 14:32:52: i'm sure there are springs out there that would work, but you would just need to find them, and needing 80+ springs could be expensive. compared to standard springs which can be had for around $10
Title: Re: progressive springs
Post by: Hellmark on Tue, 29 October 2013, 14:38:25: I think sourcing them, and making sure things are consistent is the hardest part.
Title: Re: progressive springs
Post by: CPTBadAss on Tue, 29 October 2013, 14:44:05: Ok, my Team Lead at work was a former Automotive industry mechanical engineer. They have lots of springs. I asked him why this wouldn't work. This post is about to get engineering-y.

It can be done, but not with the current constant spring diameter. Or in other words, this won't work:

(http://geekhack.org/index.php?action=dlattach;topic=50254.0;attach=41574;image)

Why? You have two springs in series which means the spring constant will even out. It won't have two separate feelings, it will just blend into one weight that we'll call XX g. You can see the equivalent spring rate formulas here (http://en.wikipedia.org/wiki/Series_and_parallel_springs#Formulas).

Now what can be done is if you have a Topre like spring where the diameter of the spiral is variable (aka "beehive" spring). Like this picture from Baldux on DT (http://deskthority.net/marketplace-f11/topre-key-switch-spares-housing-rubber-dome-spring-screw-t2833.html):

(http://i47.tinypic.com/21bwi8.jpg)

Either that or make the actual gauge of the wire variable (thinner or thicker wire) could get you what you want. I bet that either the beehive or variable wire gauge springs aren't cheap and we'd have to figure out how to fit them in an MX switch without binding.

Hope this helps a little.
Title: Re: progressive springs
Post by: IvanIvanovich on Tue, 29 October 2013, 14:46:21: Even if dual stage isn't possible, I don't see why can't make custom spring like clear but say 25% lighter. I also would love such a spring.
Title: Re: progressive springs
Post by: TheSoulhunter on Wed, 30 October 2013, 00:00:22: Dual stage is possible!

You can get springs in different lengths (perhaps cutting works as well)
Combined with...
You can interweave springs (putting one into another)
Title: Re: progressive springs
Post by: fohat.digs on Wed, 30 October 2013, 08:13:06: Quote from: TheSoulhunter on Wed, 30 October 2013, 00:00:22
You can interweave springs (putting one into another)

It would be awesome to have an extremely light spring that got very stiff immediately below the actuation point!
Title: Re: progressive springs
Post by: Jixr on Wed, 30 October 2013, 09:02:37: Quote from: TheSoulhunter on Wed, 30 October 2013, 00:00:22
Dual stage is possible!

You can get springs in different lengths (perhaps cutting works as well)
Combined with...
You can interweave springs (putting one into another)

Yeah, that may work.
though cutting springs and everything would lead to many uneven key spring rates.
Title: Re: progressive springs
Post by: metalliqaz on Wed, 30 October 2013, 09:09:26: Quote from: CPTBadAss on Tue, 29 October 2013, 14:44:05
Ok, my Team Lead at work was a former Automotive industry mechanical engineer. They have lots of springs. I asked him why this wouldn't work. This post is about to get engineering-y.

It can be done, but not with the current constant spring diameter. Or in other words, this won't work:

Show Image
(http://geekhack.org/index.php?action=dlattach;topic=50254.0;attach=41574;image)

Why? You have two springs in series which means the spring constant will even out. It won't have two separate feelings, it will just blend into one weight that we'll call XX g. You can see the equivalent spring rate formulas here (http://en.wikipedia.org/wiki/Series_and_parallel_springs#Formulas).

Now what can be done is if you have a Topre like spring where the diameter of the spiral is variable (aka "beehive" spring). Like this picture from Baldux on DT (http://deskthority.net/marketplace-f11/topre-key-switch-spares-housing-rubber-dome-spring-screw-t2833.html):

Show Image
(http://i47.tinypic.com/21bwi8.jpg)

Either that or make the actual gauge change of the wire could get you what you want. I bet that either the beehive or variable wire gauge springs aren't cheap and we'd have to figure out how to fit them in an MX switch without binding.

Hope this helps a little.

See, this is why it's good to have a Mech E. around. :)
Title: Re: progressive springs
Post by: kolonelkadat on Wed, 30 October 2013, 09:16:40: Quote from: fohat.digs on Wed, 30 October 2013, 08:13:06
It would be awesome to have an extremely light spring that got very stiff immediately below the actuation point!
thats a simple matter of adding more turns per unit length to the spring. this way the spring becomes fully compressed sooner.
Title: Re: progressive springs
Post by: dorkvader on Wed, 30 October 2013, 18:41:06: don't OKI gourd springs already do this?
(http://patentimages.storage.googleapis.com/pages/US4927990-1.png)

The tactile one does for sure (look at the force curve slope before and after the tactile / hysteresis point.
http://patentimages.storage.googleapis.com/pages/US4927990-2.png
I think the non tactile one might as well. Also, making the tactile bump in the wall larger will result in a sharp rise in the force required (so it's a stop point for like half the spring)

If you look at the force graph above and imagine the little bump that stops the spring to go all the way to the keywell floor, the switch travel will effectively stop at 5(c) in the below image, making the spring rate change. You could balance the switch by having a single wide "hoop" instead of an eccentric spring with a single "notch" sticking out. The "hoop" could make contact with the entire keywell diameter and it should be very stable.

http://patentimages.storage.googleapis.com/pages/US4927990-3.png

So in short: this sort-of exists, and we can difinately make more with 3D printing and custom would springs. It woludn't be easy though.
Title: Re: progressive springs
Post by: CPTBadAss on Wed, 30 October 2013, 18:46:10: Right so like I said, there'd have to be a variable diameter.