[GreenKeys] gears

[Stan Voynick]

Larry,

  I don't think this is talking about me, although it sounds *so* familiar because I've doing something very similar for my Model 28 TD.  

  When I acquired it, it had 67 WPM gears, and I have not been successful at finding 60 WPM gears to install, so I designed a gearset in a CAD program, and had them 3D printed in "Nylon 12"  I just received the newly printed gears just this week, and did a first test run a couple nights ago.

  I've attached a photo of the original gears (67 WPM, ratio  11:49) next to my new 3D printed gears I just received a few days ago (60 WPM, ratio 18:88.)  I've got some other photos of them as I installed and tested them in my M28 TD; maybe I'll throw those up on a blog page or something if anyone's interested (I know Steve Campbell is!)

  Here's a link to video of a test run (1:45 long); there are some additional technical details in the video description if anyone's interested.

https://youtu.be/mo6j4bXJ5v4  

   The M28 TD is a good application for 3D printed gears, as (a) that's a fairly low-torque mechanism, (b) looking at that driven gear, for a given amount of torque required to drive its intermediate shaft, the driven gear has a relatively large radius (in the world of TTY machines) so this further reduces the circumferential tooth forces between the two gears, and (c) this gearset is a helical tooth design on parallel shafts, which is a fairly "easy" application, compared with a 90° drive application like the motor-to-mainshaft gearset on a M15, for example.  That's a higher-torque shaft, with a smaller-radius driven gear, and the gearset is essentially a worm-drive which acts with a lot of "slip" between the gear-tooth surfaces. (Probably why that gearset is a metal pinion against a fiber/composite driven gear.)  I don't know if I would try a nylon gearset in that location...

   This has been a fun experiment.  Will they last for years?  Months?  Weeks, even?  Who knows - but I can say with pride that they have served me me well for a number of MINUTES now, and they're still going strong! 

73,
- Stan
WB7RPG

> On 01/20/2023 4:26 PM PST Lawrence Godek <lawrenceg94 at gmail.com> wrote:
> 
>  
> I was listening to a fellow on 40M AM the other morning and he was 
> addressing some gears that his QSO partner was getting made. He uses a 
> 100W laser machine and does some excellent work.  I wonder if he could 
> cut some 60 wpm gear sets and would be glad to talk with him about it 
> the next time i hear him on the air.  What was the material that those 
> white gears were made from?  Some kind of plastic or fiber?  He 
> mentioned making gears from something similar.  apparently he is some 
> sort of Machinist and lives about 250 miles NW of me.  But would it be 
> worth the exercise to see if he could do it?  Make both the big and 
> small motor pinion as he was mentioning that the gear he was fabricating 
> had quite fine teeth on it.
> 
> I can't remember his call sign for some reason, maybe i'll hear him on 
> the air again as he had a booming signal into my QTH.
> 
> Larry W0OGH
> 
> 
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