Effect of keyboard angle on tactility and spring

Learning and discussion Key switches
1

I’ve no idea if this is already known or even true but I am trying to figure out why a lightly tactile switch I had in Polaris feel less tactile in Tofu. Going the opposite direction, linear switch felt more taut and springy in Polaris.

My current theory is this: Tactility is higher in lower angled case. So Holy Panda in 5-degree Poker 3 case would feel more tactile than same switch in a 7-degree case. I think the effect, if real, would increase with higher difference in angle. If true, surprising part is how angle difference as low as 0.5 degree would make noticeable difference.

Maybe I’m just imagining the effect. If you have boards in a range of angles, please try testing how case angle affects switch feel.

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My basic physics knowledge tells me that there should be more force the more perpendicular you are to the switch.

image

I’m just going to go with this first response here (https://www.quora.com/How-much-pressure-can-a-finger-exert-Can-this-be-measured-in-lbs) and say we are going hard and poking the switch with the force of 47N.

If we take the example on the left where the switch is flat on, 47N of force would be applied downwards through the tactile event. The tactile legs of the stem would collide with the leaf of the stem with full force.

Now let’s take the chart on the right.

From (Numeracy, Maths and Statistics - Academic Skills Kit))
Let’s take this main chart;
image

If we apply that in the same fashion, we get

image
image334×536 19.3 KB

And if we follow the equation;

COS(AB)
B = Length of travel = 4mm
θ = 8 degree typing angle
A = Let’s say you are a soft typist and you only press down 2mm to reach actuation

Component in the down direction = Fcos(θ)
= 47 x cos(8)
= 47 x 0.9902
= 46.5394

So less force would travel down the shaft of the switch meaning less force would transfer to the tactile legs and leaf.

There force it would be less force I guess.

My physics is probably wrong somewhere, but it’s a slow day at work :stuck_out_tongue:

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So if it’s difference in angle of the bump then North-facing switches would then feel more tactile in higher angled cases? Going to try this after work.

Correct or not, thanks for that epic reply Galileo! :slight_smile:

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4

Afaik, no? A switch being north or south facing doesn’t change the angle of the stem in relation to the “ground” I think.

Theory is of course different than reality some times.

Some people would argue that they might think a more angled switch is more “tactile”. This argument could be supported by the fact that their finger strikes the stem at an angle, which means they aren’t able to put as much force behind the press. This means they would “feel” the tactile bump a lot more and consider this as an increase in tactility.

Conversely, someone who can hit the switch straight on every time may be putting a lot of energy into every hit completely overcoming the tactile bump without any issue and they might think the switch lacks tactility.

Physics is physics, but our reality is open to our interpretation and as far as I know, our meat digits aren’t the best measurement tools in relation to our feelings :stuck_out_tongue:

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Tested just now and confirmed. Switch facing doesn’t seem to affect tactility.

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I think there might be some sort of difference in force required to press down on the stem if angle of the switch is changed, as per @Manofinterests 's calculations. But that is just because now part of the force is being applied in a direction other than the direction of the stem’s movement and adds a friction force in the opposite direction of movement due to the stem rubbing against the housing. However, it shouldn’t affect the tactility, as that comes from the movement of the metal leaf inside the spring. Usually when a switch is made more tactile, it’s because the tactile bump is bigger. That causes more tactility because as it slides along the metal leaf, it causes the metal leaf to have to move away from its original position more. The metal leaf essentially acts like a spring, so moving it further causes a stronger restoring force. The feeling of tactility comes from building up that restoring force and then the sudden release as the stem slides past. Therefore, I don’t think changing the angle of the switch will change the tactility, because the metal leaf is still there, the same distance away from the stem’s tactile bump, providing that same restoring force. I think the only way to change tactility is to change the size of the tactile bump, the friction between the bump and the leaf (sandpaper tactile bumps anyone?), or change the material that the metal leaf is made of, which would change the spring constant. However, it does make me wonder now if using other metals for the metal leaf would provide for more variety of interesting tactile feelings switches…

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