Replacement Foam Mat for IBM Model F Keyboards?

[Snufkin]

@wcass: Thanks for the F122 templates! I appreciate the larger all-on-one-sheet size. I can get them printed at a nearby FedEx office.

Let us know if you decide to make an XT template.

I've just been playing around with an XT that's been lying around for a few years. I wanted to get the keys cleaned, which meant dismantling it all to get the space bar out, which meant finding out that the foam was disintegrating, which led to stumbling across this thread. Printing a template seemed like a good idea compared to trying to cut through the top plate. I couldn't just spot one for the XT so I sketched out the attached one and printed it out over a couple of sheets of fanfold paper and used it to punch out a sheet of 3mm neoprene. It seems to match reality pretty well, the only things I'd change would be to move the tab holes a couple of mm further apart and use softer/thinner foam.

Top plate had gone a bit rusty, so I had to sand that back. Ended up more or less polishing it in the end, so decided to lacquer it rather than paint; I figure there should be as much visible metal as possible. Got it all back together just in time for the keyboard's 30th birthday.

Thanks to all for the comments on the foam in this thread, hope the template might be of use.

[wcass]

Jumbo file dump.

An XT template is in the previous thread from Snufkin.

Use 122-107-77 for all three of those models. Use at least A2 or C size paper for the "one page" version. Use A4 or Letter for the "two page" version. Do not shrink to fit. Not all holes and slots are valid for all models, so be selective.

The AT template is centered on B size paper (12" x 18"). It is just over 17" wide, so it will print OK if centered on 11x17 (tabloid) paper with the left and right edges being just off the edge of the paper. A3 paper might work, but left and right edge will be further out from the edges.

The Kishsaver template is centered on Legal size paper (8.5" x 14"). It is 12" wide, so it might print OK if centered on A4 paper with the left and right edges a few mm off the edge of the paper.

[chzel]

We love you!
Now off to find some proper foam! Art foam sucks!

[vivalarevolución]

Yeah, thanks wcass.

[Hypersphere]

@wcass: Thanks for the templates!

[Ellipse]

In my F77 (inner assembly built in 1990), IBM appears to have used 2 mm foam that has held up well (I checked in a few places with my caliper). Attached are some photos of the foam.

I'm not sure of the type of this foam or its durometer. Any ideas?

The 2 mm foam has compressed to ~1.15 mm in the center row, ~0.42 mm in the top row, and ~0.82 mm in the bottom row. The F77 barrels have almost no wiggle.

20150610_174032.jpg (264.85 KiB) Viewed 14930 times

20150610_174047.jpg (385.09 KiB) Viewed 14930 times

[dramsey]

That looks exactly like the foam in my Model F XT. I just assumed someone had already replaced it, since it looked virtually new.

My two Model F ATs both had white foam that had degraded badly. I guess we see evidence of IBM pinching pennies even back then. On the gripping hand, I had the fun of refurbishing the Mod F ATs. Now they're _my_ Model F ATs!

[faycheung]

Cheers you guys for all these resources!! I've got a 122 coming in soon with a great chance that the foam will disintegrate by then. Here's hoping it doesn't, but even if it does, I have great confidence I won't mess it up.

The units were a bit wonky (imperial , nothing difficult with a converter), but I now have a good idea on the dimensions should I need to replace the mat. I'm looking at 3mm thick neoprene, a bit thinner than 1/8", but should be alright. Thanks, I love DT.

[wcass]

3mm might be too thick - especially with a 122. Try to find 2mm (3/32"). Ellipse's example has 50-75% compression of 2mm at the edges - that would be 75-85% compression of 3mm foam. Neoprene comes in different firmness; look for foam that is very compressible.

[faycheung]

I couldn't find any silicone, and I'm not too confident of the durability of foam. I have options to choose between 2mm, 2.4mm and 3mm neoprene.

[fohat]

The primary function of the foam is to be a bedding material for the barrels to seat into.

Whatever particular you use, it will need to be able to compress to 1mm-2mm (1/16" or less) or you will have a heck of a time forcing it all back together.

I prefer a firmer foam and wrestling with clamps, but that does tend to dampen the final result somewhat.

[alh84001]

Lots of useful info here. Does anyone know the european names/counterparts of the products mentioned in this thread, especially those of McMaster-Carr? I'll go to Bauhaus tomorrow, but I'd like to be able to say more than "i need that white thin styrofoam thingy".

Has anyone considered using a rubber-dome mat for this? I have one from a rubber-dome M, and this would be a noble end for it. However, looking at it, it seems around 1/32" thick, which is to thin in the middle.

[fohat]

Has anyone considered using a rubber-dome mat for this? I have one from a rubber-dome M, and this would be a noble end for it. However, looking at it, it seems around 1/32" thick, which is to thin in the middle.

The M blanket is a padding and insulating layer. The new ones from Unicomp are extremely thin white latex, and are superior for adding "springiness" to a Model M, in my opinion.

The foam mat in a Model F serves and entirely different purpose. I believe that it is intended to compress and create a "form-fitting" bed for the barrels to seat themselves into.

And, as you say, it may end up compressed to different degrees at different points in the curvature. That is why I always add a couple of bolts somewhere near the center line, but that is just me.

[wcass]

Color doesn't matter. It needs to be between 2 and 2.5mm and relatively squishy. In Croatia, you might try these guys ...
http://www.tehnoguma-zg.hr
If they are near you, you could show them the old material and ask them to suggest a substitute.

Good Luck

[alh84001]

Damn wcass, how the heck did you google that out?! I didn't know what to actually search for.

They are some 5 minutes by car from me, and what is even better, near them is the shop I think will bend the plates. Thanks!

[fohat]

wcass, how the heck did you google that out?

Everybody knows that wcass is a wizard.

[hellothere]

Just wanted to mention that the above templates helped me out today. Not bad for a 4 year old thread.

[wcass]

As laser cutters and services become more ubiquitous, i really should publish the DXF files for these. I had some cut a while back by laser and was very pleased with the quality and price. I will put this on my "to do" list if you guys ask for it.

[SneakyRobb]

As laser cutters and services become more ubiquitous, i really should publish the DXF files for these. I had some cut a while back by laser and was very pleased with the quality and price. I will put this on my "to do" list if you guys ask for it.

Hi,

Would be interested in these dxf files for foam cutting. Need to track down the F AT ansi mod one currently.

Robb

[wcass]

If you use them, please review them so that i can correct any errors.

[Coeus]

Is EVA (Ethylene-vinyl acetate) suitable. I read earlier in the thread that art foam is fine but searching for that here in the UK suggests it may be a trademark and sold only in the USA. Over here I see craft foam much of which is described as EVA. If suitable the only other thing is to find it in big enough pieces - not A4 size.

[wcass]

Most "art foam" is in fact EVA. It is used a lot in cosplay circles because it is (often) colorful and easy to work with. It is sometimes a bit stiff for model F foam, but it worked for me.

[Wazrach]

Is EVA (Ethylene-vinyl acetate) suitable. I read earlier in the thread that art foam is fine but searching for that here in the UK suggests it may be a trademark and sold only in the USA. Over here I see craft foam much of which is described as EVA. If suitable the only other thing is to find it in big enough pieces - not A4 size.

I made a perfect mat with 2mm craft foam from Blackwell's in the UK. It is way too stiff and firm for most Models F, but will work in boards like the F122 where there's plenty of room to add bolts through the assembly. If you can get craft foam to compress sufficiently in a Model F, the result is extremely crisp and dense-sounding keys.

[TheNeonKnight]

Anyone have a DXF of the IBM F XT mat? I'd love to get one professionally cut.

[darkcruix]

Quick update - the DXF for the IBM F AT is showing the incorrect sizes - it should be 435 mm x 134 mm as far as I know. When I open the DXF (and also upload it for cutting) it gives me a 17mm x 5mm size (probably the conversion from inch to mm is causing the problem here). As I don't have AutoCAD to correct, it would be great, if someone could make a metric version out of it...

UPDATE: Converted it into PDF and into metric units. I used "Neoprene cellular rubber 2.0 mm black 435x134mm" from Snijlab.nl. I will report how they have turned out.

Model F AT-Model.pdf.zip

(10.78 KiB) Downloaded 339 times

A proper DXF would be much better - I tried to convert the units so that 1mm = 1unit, but I am unable to get it done in the trial version of AutocCAD I downloaded (me = too stupid to use AutoCAD).

[cakeanalytics]

Where can I get foam professionally cut, other than buying from Ellipse?
The laser cutting place i asked doesn't allow cutting polymer due to toxic fumes

[TheNeonKnight]

Where can I get foam professionally cut, other than buying from Ellipse?
The laser cutting place i asked doesn't allow cutting polymer due to toxic fumes

Ponoko should be able to do it if you have a .dxf

[darkcruix]

Where can I get foam professionally cut, other than buying from Ellipse?
The laser cutting place i asked doesn't allow cutting polymer due to toxic fumes

Ponoko should be able to do it if you have a .dxf

They are attached from @wcass a few posts above - woudl be great!

[wcass]

You can go onto Etsy and search for "EVA costume". Most of what you get will be for laser patterns - but you can PM them and ask who they recommend for materials and service.

[wcass]

I am pretty sure the documents are in "units". You should be able to select your unit value when you open the file. Also, any CAD software should be able to scale a drawing. If you are on Windows or Mac, DeltaCAD is "beginner friendly" and the free trial version is fully functional. After 45 days, you can uninstall/re-install and get another 45 days.