Questions about gummy mount

Learning and discussion
1

Hi,
I have a few questions about gummy mount.

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(image from Google)

  1. how is the comparision between gummy mount and true gasket mount? lets say true gasket is 10 points then how many points do gummy mount get?
  2. how do I calculate the necessary perimeter of the gasket used for gummy mount? is it something like the red line in the following pic:
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  3. how many mounting posts are enough? maybe 6 or 8?
  4. what is the ideal stiffness of the gasket? I heard there are 30a, 50a, 70a? (I’m not sure about the unit)

Thank you for reading.

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2

1 continuous mounting point that goes around the perimeter of your switches

You’ll need to measure and buy a size smaller to accommodate for stretch.

technically as few as 4 could be enough, but 4,6, or 8 is preferential

this is preferential, best to buy several and find out which you like the most

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3

thank you for the reply :grinning:

I also think the same so I would try to provide different stiffness gaskets to the user if possible.

4

So for the size of the oring, the cross section or I guess thickness will be the distance between the plate and the pcb or 1/8".

Next, measure from the outermost edges of switch cutouts on the plate, the left side of the left most switch, the right side of the right most switch etc. make a rectangle out of those measurements, and take the perimeter of that rectangle. With that perimeter, divide it by pi to get the inner diameter of the o’ring size you would need, it won’t be exact though so always round down so the oring will stretch to fit.

With all this said though, I’ve never tested this method IRL, though people that have did come to similar conclusions.

As one last note, the name “gasket” mount came from the giant oring style mount, I’m guessing the name was because orings are usually used as water proofing gaskets or seals in pipes, engines and even phones. Therefore gummy oring is the “true” gasket mount while isolation strip mount tried to mimic gasket mount but became more popular and stole it’s name it appears.

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5

I don’t have to ton to add, but I will give you some additional thoughts.

how do I calculate the necessary perimeter of the gasket used for gummy mount? is it something like the red line in the following pic:

Keep in mind that softer materials will stretch a lot more. I bought a 30A o-ring for my 60, and I was able to get it a little bit smaller than my 50A one.

  1. what is the ideal stiffness of the gasket? I heard there are 30a, 50a, 70a? (I’m not sure about the unit)

I have tested 50a and 30a. 50 is surprisingly stiff for my tastes. I was using a tray mount 60 with POM plate and the center standoffs in the case removed. 50a seemed to give me roughly the same amount of flex as the tray mount. Tt was just uniform flex/bounce rather than middle focused. For my tastes, 30a offered the amount of bounce and flex I perceived that I would get from gummy mount.

Are you looking to do this for the KBD8x? I can source the gummy o-ring size I was recommended and came with the board that I bought second hand. I briefly tried gummy o-ring mount in the KBD8x, but went back to standard burger-mount (top mount) as I felt if afforded more flex.

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:open_mouth: I didn’t know this
thanks for the info.

I actually want to design a board with Top-mount and Gummy mount combined (user can choose which to use)
thanks for the info, I guess I should focus on the 30a. :+1: