On 5/4/2017 6:24 PM, Bald Eagle wrote:
> Stephen,
>
> What are you using to determine your gear tooth numbers?

You do ask awkward questions. ;-)

> Did you start from scratch, use existing plans, or some sort of gear train
> calculator?
>


Basically I use my fingers and integer arithmetic. Although a s/sheet 
helps. First you work out the final ratio which in that case was 28:1. 
28 revs of the earth in the same time that the Moon rotates once. (To 
keep the same face pointed towards the earth.) So it is number of teeth 
on the input gear to number of teeth on the output. But since I did not 
want to build all the bearings and supporting structure. I used a 
planetary gear chain. That uses specific ratios and diameters for the 
gears and I got them from this site: http://www.otvinta.com/index.html

After all that it was a wasted effort because it was indistinct and I 
might as well have use textures. So following the Animators guidelines I 
cheated and made sure that the gears meshed and no one would be able to 
tell it was not accurate. Smoke and mirrors. ;) The mind is easily fooled.

> (I have piles and piles of plastic gears - I was wondering about finding the
> best / approximately correct arrangement of the ones I have available.)
>
>
Best for what application? Remember when using compound gear chains the 
ratios are multiplied.
This is mostly from memory. I only did mechanical engineering at high 
school and that was a long time ago. So that is what I meant about doing 
it on my fingers. One step/gear at a time. ;-)
If I have not answered your question. Ask again.

-- 

Regards
     Stephen

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