Later Generation Alps Feel Worse Due To An Actuator Leaf Change.

[dr-lipschitz]

Hypothesis
I don't see it documented anywhere, but the shape of the actuator leaf is different in newer Alps. This is what is causing newer generations of alps switches to feel less refined. Before I go into more detail here, first some background:

Background
There are numerous well documented changes to alps switches overtime:

• the removal of lube, coinciding with a change to smoother plastic for the sliders

• the removal of slits in the top (pine vs bamboo)

• the change in color and length of the switch plate

of these, only (1) has any affect on the switch feel, but that doesn't explain the whole story. Anyone whose used different generations of alps switches can feel there is something else going on.

The Changes

green_vs_yellow_force_curve.png (508.09 KiB) Viewed 7 times

long grey switch plate from SKCM undamped cream on the left, short white switchplate from
NOS SKCM White Pine on the right

actuation_leaf_change_side.jpg (1.68 MiB) Viewed 7 times

long grey switch plate in back, short white switch plate in front.

from these images you can clearly see that the second fold in the actuator leaf spring came later in the newer switch plate. This results in the older actuator having longer "feet", and the newer one having a longer "legs". I don't have the tools to test, but i'd estimate the difference is between .3 mm and .5 mm. The total vertical and depth displacement remain roughly the same.

This should result in the force curve of the first switch reaching its local maximum peak force first, since the slider passes the legs earlier. Indeed, if we look at the force curves HaaTa measured for SKCL Green (older) and SKCL Yellow (newer) Alps, we can see exactly this:

actuation_leaf_change_front.jpg (3.5 MiB) Viewed 7 times

In this graph we see the green switch peaking about .3mm earlier, which aligns with the observed difference in leg length. We also see that the force drop is lower in the yellow alps, but that can be explained by a higher spring rate in the coil spring.

Conjecture: Why Does The Earlier Peak Feel Better?

I think this feels better to us because it flattens out the total force curve earlier in the press. This makes it feel the fatigue of actuating the switch for a shorter portion of the press, and a longer portion of the press feeling satisfied as the slider bottoms out. This is all my personal conjecture though.

Theory: Why Did Alps Make This Change?

The change to the switch plate actuator likely aligns with the same time alps switched to a smoother plastic and stopped using a lubricant. The change may have been necessary to reduce scratchiness as simply changing the plastic didn't fully alleviate the loss of lubrication.

By making the actuator leaf's foot shorter, the amount of distance the slider spends rubbing against the foot decreases, giving less time to feel scratchiness. By making the leg longer, the moment arm is increased which also reduces the max frictional force felt in the first place.