[GreenKeys] 28 ASR Typing Reperforator Print Hammer Replacement

[Steve Garrison]

In the living room?

Mine is on the dining room table!

Steve G./N4TTY

-----Original Message-----
From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net> On Behalf Of Mark J. Blair
Sent: Friday, January 3, 2020 10:49 AM
To: GreenKeys Mailing List <greenkeys at mailman.qth.net>
Subject: Re: [GreenKeys] 28 ASR Typing Reperforator Print Hammer Replacement

> On Jan 2, 2020, at 7:46 PM, Hugh Pyle <hpyle at cabezal.com> wrote:
> 
> In my brief experience with PETG it’s quite brittle.  We’ve printed gaskets with elastomer, it works very nicely for that, and could make a good print-head hammer material I think.

Good to know. Thank you!


> On Jan 3, 2020, at 3:05 AM, Steve Garrison <steve.n4tty at gmail.com> wrote:
> 
> What about using a carbon fiber reinforced plastic in the 3D printer?
> 
> And doesn't the slot need a 3rd measurement as well as the orientation 
> and on what face of the solid?  If drawing from scratch and having 
> never seen one, a draftsman would need that information.
> 
> Or have I missed something here?

I'll try the resilient stuff first. I think I may already have a reel of Ninjaflex that I haven't gotten around to experimenting with. I've been poking around on the customer forum for my printer (a Makergear M2 dual-extruder) to learn about getting flex filament working well in it.

Yes, a draftsman who has never seen one would need a lot more than those dimensions. I've at least seen a line drawing, I can measure the spot where it goes on the metal arm to figure out the orientation of the 0.391" vs. 0.250" dimensions, I'll guess the slot location, and I'll just tweak the design and iterate until it works well. Those dimensions in the NSN (National Stock Number) description are far from a complete specification of the part, but I didn't expect to even have the external dimensions, let alone the slot size. I expected to have to guess everything from scratch.


> On Jan 3, 2020, at 4:56 AM, til128 at juno.com wrote:
> FWIW, yes, I believe the piece is offset to the high side and the top is curved to match the typewheel.

Thank you! I notice that the specified width of the hammer is 3x the mounting slot width, so I'll start by assuming that the bottom wall thickness is about the same as the two side wall thicknesses. I'll guess that the hammer face curvature should approximately match the typewheel diameter.

I don't know how long it'll be until I get this all dialed in... I'm very prone to being distracted by squirrels and hopping onto another project. Hopefully the disassembled 28 ASR in my living room will keep reminding me to get back onto this project. :)


--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/

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