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Durahl
(@durahl)
Trusted Member
Calculating Gears?

Greetings!

I'm currently in the process of converting a Display Stand Tamiya 1:16 Gepard 1A2 into a Full Option Model using 3rd Party Parts for both Electronics and Mechanics but since the model was already built ages ago some of the Mechanical parts can no more be incorporated into the model without either converting the Model back ( not gonna happen ) or making changes to how the Mechanicals get attached to it.

My current grief is the Turret Rotation System which normally would be driven by a motor whose output shaft would directly be connected to a Turret Axle driving it at a 1:1 ratio. The problem with this would be the cable loom that would, at some point, risk itself getting wrapped around the Axle which I'm not fond of.

Now... The Turret Ring I installed back then is actually a giant ball bearing with a ~246 Teeth Gear on the outside allowing for it to be actually driven from the outside instead of a center located Axle thus negating the problem but requiring some gearing since I cannot install another 246 Gear in the available space for a 1:1 ratio to happen using the same motor so I went with an 82 Gear one but this causes a 1:3 ratio if the motor would be directly connected to it.

From my limited understanding about gearing, I was able to come up with a 3:1 ratio solving that by adding another gear that should work out but maybe someone can confirm this?:
Black Ring = 246 Teeth
Green Cog = 11 ( 82 ) Teeth
Blue Sprocket = 33 Teeth

So there's basically a 1:3 ratio between the Green Cog ( 82 ) and the Black Ring ( 246 ) which gets negated by the 3:1 ratio between the Blue Sprocket ( 33 ) and Green Cog ( 11 ) but afaik the 1:3 ratio should not matter unless the Green Cog was the Sprocket which it is not so only the 3:1 ratio remains giving the Motor to Turret Ring again a 1:1 ratio as if the, not present, Ring Axle was directly connected to the Motor Axle, right?

Sorry the long post xD

Posted : 07/10/2019 1:27 pm
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(@)
Illustrious Member
RE: Calculating Gears?

Gear 1 (blue) spins once, Gear 2 (green?) spins 3 times, gear 3 (black) spins once.  Seems simple enough. Just don't ask me which direction gear 3 spins, I always failed that test.

 

33:11 : 82:246  or 3/1 * 1/3 = 1

This post was modified 2 years ago by --
Posted : 07/10/2019 10:27 pm
Durahl
(@durahl)
Trusted Member
Topic starter answered:
RE: Calculating Gears?
Posted by: @tim-m30

Just don't ask me which direction gear 3 spins,...

In my case - The same direction, the first one spins though not critical for me as it can easily be remedied by swapping the motor leads =)

After watching a YouTube Video on simulating Gears in Fusion 360 ( duh!? ) I was able to confirm both my own assumption and expectation that the Turret would also spin at the same RPM using the Gears like how it would do if it were directly attached by the motor shaft.

Posted : 08/10/2019 3:48 am
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(@)
Illustrious Member
RE: Calculating Gears?

As for direction, it's even odd. Even number of gears reverses spin, odd keeps spin. As a kid I tried to work through spin using arrows ... but the tests wanted you to do the simple odd-even count.

Posted : 08/10/2019 6:20 am
Talaminator
(@andrea-t)
Active Member
RE: Calculating Gears?

Check the free demo of "Gearotic Motion", it's an awesome software for gears calculations.

It will probably make your life easier in this case! 🙂

Posted : 09/10/2019 12:29 am
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