[GreenKeys] 28 ASR Typing Reperforator Print Hammer Replacement

[Paul Heller]

Oh how I wish someone would be able to figure this out.  

George Hutchison got close. He may have made an engineering drawing of the thing. I believe he had a mold fabricated and was experimenting with different materials and hardeners. He was struggling with air bubbles in the finished product and was trying vacuum and pressure as a means to solve that problem. I understood that he had someone helping him who one day up and disappeared (as best I can recall). That person supposedly had a lot of knowledge of this kind of thing. 

In addition to finding/selecting the proper material to use, there is also the issue of how it slips on and stays on the metal hammer. 

Dave Tumey, who was a good friend of greenkeys and used to be quite active on this list at one time, engineering and had the 33/35 print hammers made.  Maybe he has some ideas.

I’d be happy to contribute $$ towards a solution, but not for any wild goose chases...

Paul


> On Jan 2, 2020, at 12:44 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
> 
> Oh, I was hoping that this was already a solved problem. Old rubber is a headache. It's also a problem in my vintage computing hobby, where it affects things like capstan rollers in tape drives. Out of curiosity, I've done some minimal study (i.e., looking at YouTube videos) about how rubber products like capstan rollers and platens are manufactured and refurbished. The process is understandable, but I have a sinking feeling that trying to procure a tiny amount of uncured rubber might be akin to calling up the regional water district and asking for a quotation for a cup of water.
> 
> Maybe it's time for me to try out elastomeric filament in my 3D printer. My best guess about the shape and dimensions of a 28 ASR reperf typing hammer seem like something that might lend itself to 3D printing, assuming that the available elastomeric filaments have suitable mechanical properties for this use. I know of at least one computer collector who has had some success in 3D printing replacement belts for small tape and diskette drives. But I don't know yet about the hardness of available filaments, or how well they would hold up in impact service like this.
> 
> If that won't work well, then I guess the next thing to try would be to get a chunk of suitable rubber and try grinding it to shape.
> 
> -- 
> Mark J. Blair, NF6X <nf6x at nf6x.net>
> http://www.nf6x.net/
> 
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