deskthority

did you pull out all the keys before doing all that? Those create ~6.5kg force (closer to 8kg on F122) pulling the barrel plate away from backing. Removing that force makes the process way easier - like, you can chop all the rivets, then drill the barrel plate conveniently separated from everything ...

This thing can't just leave me alone..
Believe it or not, I found a SIMULATOR at https://phet.colorado.edu/sims/cheerpj/moving-man/latest/moving-man.html?simulation=moving-man and turns out the word I was looking for wasn't "energy", but "momentum" aka "amount of motion".

Distance: 8 meters ...

https://en.wikipedia.org/wiki/Work_(physics) says:
"The work is doubled either by lifting twice the weight the same distance or by lifting the same weight twice the distance." So we're both right - depending on what Wikipedia article we believe to be true :D

Why time doesn't appear in E = ∫ F(r ...

[*] The heavier doors have more friction at the hinges. You actually must put more energy to it to overcome bigger frictional energy losses.

You have no idea. That door's hinges are very smooth - you can move that heavy door with a single finger, but it will be a very slow movement.

I figured ...

@vvp what you say is logical.
But I'm still not convinced somehow: isn't same force applied for longer time results in more work done?
Like, when you plug in an iron, it consumes same wattage, but it definitely becomes warmer with every second passing (until thermostat kicks in) - so it's definitely ...

I found a solution to a spring sticking a wrong way.
The solution is a small hole at the top of the stem.
To fix the spring stuck in a wrong position, you unbend a paperclip, stick it about 10-12mm into the hole, and nudge the spring a little.
Then you remove the paperclip, and after 2-3 presses it ...

..so I printed a couple of gigantic, 880mg flippers: Those aren't that much louder if you hold the thing in your hand.
HOWEVER, should you press the assembly against the table and press the stem, there'll be absolute GUNSHOTS

Energy pumped into flippers depends only on the force at position r (F(r)) and the tiny position change (dr) over which the force is exerted: E = ∫ F(r) . dr
If two flippers differ in their mass only then the force must be different to result in different energy.
I kinda see heavier flippers ...

Printed GINORMOUS 320mg and 350mg flippers:

PXL_20260215_213435838.jpg

Boy, do those SLAP! Checkmate!
I think it's because heavier flipper spends more time in flight, so spring has time to pump more energy into it (a = F/m, higher m -> lower a -> longer travel time).
Seems like 5-degree are ...

Today I remembered that with 3D printing one doesn't need to drill into things to see what's inside - can just punch a hole in the model itself and print.
model_holes.jpg

So I now have a see-thru barrel and a see-thru stem.
PXL_20260215_020917354.jpg

Also I wanted to see what will happen if I ...

vvp wrote: 14 Feb 2026, 12:41 IBM keyboards do not have enough keys
viewtopic.php?p=502674#p502674

Easily doable.
In fact the more keys the better - larger number of switches drives cost per unit down.

..by experimenting with spring support length & angle I discovered a configuration which only clicks on the keypress - return trip is silent (unless you flick the key - this way stem hits the barrel on the way back with a pretty loud "thud" - but you need to be really intentional about it, even on ...

Quoted barrel and stem at protolabs.com

Stem:
up to 1000 copies: $6385 + $2.83/copy. 1000 shots = $9215 = $9.215/shot
20k - 1 cavity: $9580 + $1.35/copy, total $33780 = $1.689/shot
20k - 8 cavities: $49140 + $0.50/copy, total $59140 = $2.957/shot

Barrel:
up to 1000 copies: $7430 + $2.82/copy. 1000 ...

And so, I quickly designed some test flippers with varying degree of spring slant: 5 degree (varying spring support height), and 10 degree with default height.

flippers_galore.jpg

Results: (flipper - actuation point)
5° - 3.5mm
5°+0.5mm - 2.75mm
5°+1mm - 2mm
5°+1.5mm - 1.5mm (fails to reset)
10 ...

Printed!
printed!.jpg

It's moderately scratchy and moderately wobbly (kinda comparable to MX switches I have, may be tad more. Comparable to model F, actually).
It doesn't bind.
It doesn't click either. I mean it clicks outside of the barrel. It clicks when key is all the way down and flipper ...

The problem with these is that the head is smaller than the hole. So it would just slip through.

Washers to the rescue!

Also, depending on external diameter of the rivet stems, reaming the hole so that larger screw fits. But that's riskier, as you only have one chance - if the larger screw ...

attached dust sleeves to barrels relatively easily. Supporting wall came about 0.75mm thick - should be enough for people not explicitly trying to break the key, I guess. Increasing barrel diameter should provide more sturdiness - but can cause barrel to keycap contact.

dust_sleeve_up.jpg
dust ...

Turns out, using MX stabilizers is quite tricky with buckling spring mechanisms: barrel top is 0.6mm above the top plate and all the dust and bread crumbs will go straight under the flipper.

So one either needs to severely redesign key travel limiter or add dust caps to the stems.
Added dust caps ...

I'm slowly coming back from the 2025.
Still very tired but can do stuff for maybe an hour-two a day.
Here's what I found so far:
1) Brother model M and IBM model M stem internal cavities are identical - despite 5 mm length difference and significantly different stem appearance.
2) Buckling spring ...

I'd cut off the protruding part with a sharp knife - leaves space to later fasten those back later with a short self-tapping screw.

MG Chemicals 843AR.
I resin-printed a flipper, cured, and then painted as thinly as I could. Ideally, I think, would be to paint before curing and then covering with a thin layer of liquid resin, to prevent conductive stuff from flaking off.

They work. Printing from normal plastic and painting with silver conductive paint also works.

After a slight delay, I modelled and printed a first working Brother Buckling Spring unit (it's scratchy as hell because layers, but it clicks).

brother.jpg

It really looks like BBS is force-buckling: the stem pushes on the flipper, slightly rotating it, triggering buckling towards rotation ...

Some care needs to be taken pulling off keycaps - look at the photos of the switch stem to better understand which direction to pull.
Otherwise, beamspring is easier to assemble/disassemble than model F.

Also, beamspring is not protected from debris ingress - people used saran wrap for a membrane ...

I guess so - no other place to go, really. You should, however, remove all keycaps before attempting reassembly.

Can anyone give me hope of fixing this without taking the keyboard apart again? :roll:


I don't think so. But if you, when assembling it, lay the top plate not on the table, but on some supports that will leave barrels hanging, and use clamps like https://www.amazon.com/dp/B097P8L5TV (get the ...

Not saying the Classic or Hybrid were bad, they just didn't feel as tactile. It might just be how the rubber ages too. I've heard they stiffen with age and that probably affects the tactility. Of course my Hybrid didn't feel as tactile as my Classic. So, there are differences between their new ...

AndyJ wrote: 12 Mar 2025, 00:55 Actually, older (some 1920s-1930s) Cadillacs had pinstriping. So did some European luxury cars. All done by hand.

Yeah. Damn car dealers use them to bump the price $100-$200-whatever. Totally not worth the money but you literally can't opt out. This and painting tires black.

worst case you have a dead GPIO - in which case you'll likely need to replace controller. But yes, far more likely it's a bad solder joint.

Debris under the keys? Or inside the switches even?
My T420s lived thru 3 keyboards - all of them eventually stopped registering a key or two - and eventually cleaning them with canned air (CAREFUL, high-pressure air can rip off your keycaps!) stops working for some reason.

If laptop is still under ...