IBM Beamspring / Model-F Foam replacement

[Wodan]

Please excuse me for opening a new topic for this but I am currently facing the task of replacing the foam under the plate of one Beamspring keyboard and several Model-F keyboards. My plate restoration skills are quite decent by now but I am totally out of clues how to replace the rotten foam. I have seen some people briefly mention they replaced the foam under their plates but though it made sense to collect different methods of replacing the foam and various types and specs of materials used.

I made some experiments using a 1mm foamed rubber mat. Cut it to size and glued it to a IBM Bigfoot plate. Unfortunately, The spray-can glue is quite messy and I will be pretty busy cleaning up after it dried up. Looks ugly so far. In my disappointment about the outcome, I started looking at other solutions. I just happen to have a friends China-laser in the garage, some 30W cutting laser. This thing does wonders cutting foamed rubber mats and I thought about trying to design single barrel pads that can be individually attached to each barrel. Same thing for Beamsprings, just make a square cutout with a ~14mm hole in the center. Anyone tried that before? Curious of that provides enough stability ...

But that would GREATLY reduce the amount of work for me. Just put in a sheet of foam rubber and let the laser cut, repeat until enough cutouts are made.

What's the general preference when it comes to thickness? I tried some rubber rings around my Beamspring shells and found that 2.5mm seems to be a bit too tight but 1.5mm is still a little loose. Unfortunately, I just don't have any 2mm rubber O-rings that fit

Beamsprings to look like they could take an o-ring very well, might try and experiment a little with that.

Happy for any input I can get here, even if it's just links to existing guides that I must have missed.

[chzel]

Check my 3101 restoration Wodan, I used 70A orings, they kind of work, but are a bit too stiff and the middle rows are loose enough for the switches to turn a little. Softer ones would probably work better. I'm on my phone now so I can't link it, sorry.

[Wodan]

Can you remember the dimensions of the rings used?
Tried ordering a selection of o-rings with AROUND 14mm inner diameter and 2mm material diameter. 70A rings though, couldn't find anything softer ...

[chzel]

I used #15 orings, I had a bunch, we use them in paintball for the air tanks, I can't remember actual dimensions, but they are a pretty good fit (about 1,5mm thick).

[Wodan]

MHM really curious how ~2mm o-rings will perform. Feels like they should fit, I could even lock the switch in with 2.5mm rings ...

[fohat]

No experience with beam springs but plenty with Model Fs.

I have used 1/16" (1.5mm) "art foam" from the art supply store several times, and cut it by hand with a punch.

This foam is recommended for scrapbooking as "archival" and acid-free, so I feel pretty good about its longevity. It is very lightweight and fairly firm, but it will compress and bed down easily under pressure. I have never felt any need for glue, the assembly is very tight when you are finished and it will not be moving.

Once I used a soft 1mm neoprene foam (thanks, wcass) and it worked well, too, as well as making re-assembly easier.

[Hypersphere]

As you perhaps know, there have been a number of threads on these topics. In addition to whatever comes up here, you might also wish to consult the other threads. Here are a few examples. Note that the last one is about beam springs.

https://geekhack.org/index.php?topic=58814.0

workshop-f7/replacement-foam-in-ibm-model-f-t11657.html

keyboards-f2/replacement-foam-mat-for-i ... t8033.html

photos-f62/ibm-beamspring-3278-t8818.html

[Wodan]

Thanks so much for putting these links together Hypersphere!
Great material.

Here's finally some contribution by me. My focus is on individually cut pads for single switches. This works pretty well for Beamspring keyboards. After a little experimenting/adjusting of the laser, I was able to cut the material without burns:


Got several sheets of this black foam since I like this as a color:


These 4x5 patterns are the best I can do with this crappy laser. Any additional row/column will have such a bad laser beam focus that the cuts get bad.

One evening of cutting:


Fit on IBM Beamspring switch housings:


Fit in the plate is quite perfect. Snaps in with nearly no force required by sits firmly:

[seebart]

Great work Wodan, keep us updated!

[ramnes]

What kind of laser is that? Is it the same type of laser which cuts acrylic?

[Wodan]

Yup it's the same kind of laser you can use to cut acrylic. They are usually sold as engraving lasers.

Here's some more pics of the Model-F results:






They have a tiny overlap at the lower end. It does look okay when putting them into the plate but since this plate already has some foam replacement I can not check the PCB/Backplate fit. Maybe the 2mm foam is also a little too thick and I have to do tons of sheets with 1mm foam.

Good news though is that I spent some time tweaking the laser and I can finally cut more consistent in a much larger area. This means I can do as many as 60-70 cutouts per run which greatly reduces manual labor and thus means I can probably offer these cutouts for cheaper.

Also please be aware that I will make the CAD files public to anyone who wants to cut his own. The only reason why I am considering to offer these for sale is because I think there are still people with no proper laser access living in this world today. To cover my time/expenses for these cutouts, I will ask for a price if you want some of these cutouts.

The beamspring ones are ready for market, the Model-F ones are still in research until I have another keyboard prepares and waiting for replacement foam. Someone sell me a crappy near-death Model-F XT

[kekstee]

Hey Wodan: I went with this german offering of EPDM mats during my Model F restoration. Assembly was a pain, but I can't tell wether a different foam would have made it easier since it was the first and only one I put back together so far.

http://www.fugendichtband24.de/EPDM-Zel ... matten.htm

[fohat]

The foam is intended to compress considerably to "bed" the feet of the barrels. I use 1.5mm "art foam" that seems firm at first, but will actually compress without too much pressure.

At 2mm thick, yours would have made re-assembly quite difficult unless it was fairly soft.

[kekstee]

Yes, the foam is pretty soft. It worked well once I head enough clamps spread around the edges.