Dec 01, 2020, 11:37 am


New, New TardisBuilders!

Gear sizing question

Started by blixathecat, Oct 30, 2020, 09:57 pm

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I am working on K9's ears and have three 44T 5MM pinion gears, two of them attached to the bottom of the ears. I need to add two more gears of a smaller size (3MM) so they will cause the outer gears to rotate opposite (clockwise and counter-clockwise.)

I ordered two smaller 44T gears and did not think about it... well, 44T in 2MM doesn't exactly work.

So, what is the math to determine how to scale down a gear size and the teeth placement still match?  I thought I would ask before ordering another set.

(Photo shows the two smaller gears)

Davros Skaro

smaller gears need less teeth if you wish to keep them the same size to use with the bigger gears. I'm not sure on how to work out the ratio, so hopefully someone knows that part of your problem.
All the best with it too.



Thanks. Someone send me the quick math to reduce the size, but the key is to ensure I have the same pitch. I am using 32P gears.

Thanks to everyone who responded in the forum and to me directly.



Oooh...a K9 with working ears...*drool* 
"My dear Litefoot, I've got a lantern and a pair of waders, and possibly the most fearsome piece of hand artillery in all England. What could possibly go wrong?"
-The Doctor.


Can't wait to see those working ears, too!

My K-9 just sits there all day doin' nuthin'!

I can often feel his faceplate staring at me accusingly...

Good luck,