[TowerTalk] TIC plastic gears

[David Gilbert]

I've 3D printed knobs using 1/4" brass inserts with a set screw for the 
shaft.  The inserts are knurled on the outside and you use a soldering 
iron to get them hot enough to press into the shaft hole on the knob.  
It works very well, and you get a recessed set screw for a tight 
connection.  The downside for using it on a gear is that you need to 
have a small hole for the set screw, but if the gear is wide enough that 
might not matter.  It's possible, though, to get a very tight fit even 
without an insert.

55 teeth could be dicey to print on a 7/8" OD gear, but the precision of 
a good 3D printer is pretty amazing so it could be possible.  I use a 
modeling program called OpenSCAD and it creates 3D objects using code 
statements for geometric shapes, which makes it great for parts like this.

If N4TZ can send me some close up pictures with precise dimensions it 
might be fun to give it a try.  No promises, though.  The biggest 
concern I have would be getting the profile of the teeth correct.

I have an FDM printer (extrudes thin strings of melted plastic to build 
up layers) and I can print with either PLA or PETG.  PLA is harder but a 
bit more brittle.  PETG is more flexible, but it is tougher and seems to 
be more slippery.

To be clear, I have no intention of doing stuff like this for money ... 
nor for doing a lot of it.  This would simply be a one-off effort to 
help out a fellow ham in need.  Somebody could probably try to make a 
business out of it, and the material cost is peanuts, but I question 
whether the time spent making custom parts could generate a decent 
financial return.

73,
Dave   AB7E



On 1/6/2023 9:18 AM, john at kk9a.com wrote:
> Good luck with finding one. There are many gear suppliers online but buying
> a small quantity is challenging.  I would try McMaster-Carr.  Maybe another
> option is 3D printing if you have solid modeling software. Make sure that
> the plastic gear is tight against the rotating shaft to prevent slippage and
> wear.  I put a screw in the side of my housings to keep the potentiomenter
> bracket in position.  About a decade ago I needed a couple of the steel
> gears that fit on the 10mm windshield wiper motor shaft and was unable to
> purchase them, at least not for an affordable cost.  I wound up having to
> buy gear stock and machine them myself on a lathe.
>
> John KK9A
>
>
> Zivney, Terry N4TZ wrote:
>
> Does anyone know of a source for the small plastic gear that fits on the
> multi-turn pot inside the Tic-Gen ring rotor motor box? The one that lost
> some teeth
> had 55 teeth, was 7/8 inch OD and had a metal insert to fit the 1/4 inch
> shaft of the pot.  I have a replacement from the pot removed from a
> slave motor which didn't need the position indicator, but I would like
> to have a replacement for just in case.  These motors were late 1990's
> vintage, with the sheet metal box, and the 1022 size ring.
>
> I don't want to have to go to the external pot assembly TIC-Gen uses now.
>
> Terry N4TZ
>
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