Gears all in a line--doesn't seem quite right

[TheTick]

I'm designing a gear train with multiple reduction stages (10:35 to 10:35 to 10:35 to 10:55). I have some flexibility in where the gears are placed.

My gut tells me it's best not to string the gears such that all the axles are all in a straight line. Any merit to that hunch?

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[MikeHalloran]

If the gearbox is split in the plane of the axles, machining of the bearing seats is simplified, or at least lends itself to a particular kind of milling machine.

Folding the gear meshes into ~a square vs a line makes the box more compact, maybe a little lighter, but more difficult to machine and more difficult to inspect.

If you're not pressed for space, I'd go with all the shafts in a single plane.



Mike Halloran
Pembroke Pines, FL, USA

 

[TheTick]

It's not a heavy-duty gear train. It's small plastic gears powered by a 3V motor in an appliance.

Usually I don't have room to make everything straight, so there's no question.

My hunch is based on something I saw in a toy. My kid have a gear set with magnetic bases for making gear trains on metal surfaces (e.g. refrigerators). The seem to jam up more if they're all in a straight line.

 

[MikeHalloran]

When toys had brass gears on steel axles, the pressed steel gear housings often took the shape of an extruded "U", with the axle bearing holes in a nice line, space permitting. I think it simplified the assembly tooling.

If, as in the extant case, you have the ability to move the gearsets around on a plane (cool toy), you have to properly space three axles to get the clearances right when the axles are aligned, whereas you only have to space two axles at a time if you place the gear passes at approximately right angles. Even if you just jam them together with zero clearance, the right angle arrangement allows them to sort of space themselves out a bit where the clearances and runouts add up in a bad way.




Mike Halloran
Pembroke Pines, FL, USA

 

[TheTick]

Thanks, Mike.