Placing gears PD tangent

[SherpaDoug]

I need to place several gears in mesh in a gearbox. I don't really need to model the gear teeth, but they are commercial gears and I would prefer to use the manufacturer's STEP models if I can. I could also model them as simple disks. But is there an easy can I use Assembly Constraints to place the gears tangent by their pitch diameters and not their overall diameters, but still visibly showing the overall diameters?

 

[oldfox]

If I were going to do that for "eye candy" then I would just make the simple disks as you mention. I would make the OD equal to the PD.
Then align 2 gears with the offset being equal to the C-C distance of the 2 shafts.

 

[JST]

I usually do the PD as disk diameter, plus a thin ring to show the OD to be sure of clearances etc.

Then you can do tangent OD to ARRIVE AT the C-C distance, if you are at the "layout stage". You know that regardless of clearances, etc, you want the PDs to be tangent.

 

[Lew_Merrick]

SherpaDoug -- What I typically do is to create the gear (using WizoScript) as my "Base Configuration" and create an appropriate "Pitch Diameter Configuration" to use to verify my set-up. Does this give you ideas?

 

[bigseb]

But is there an easy can I use Assembly Constraints to place the gears tangent by their pitch diameters and not their overall diameters, but still visibly showing the overall diameters?

No. There are workarounds (creating a small rim on PD, using axis to align) but these require a bit more work.

 

[Jimpulse]

In case it wasnt clear from Sebastian's post, you can "show reference geometry" for both gears and then do an alignment constraint between the Axises (Axi ??) of each gear that is equal to the pitch diameter. This doesnt require the creation of any new features on the parts.
Unless I'm missing your intent/needs, It seem pretty easy.
-jimpulse

 

[dwc]

I usually make the entire geartrain with thin disks of the primitive diameter, make them tangent and place them as needed. Then for prettyness the real gears are constrained to the train-disks and the disks hidden.
Don

 

[SherpaDoug]

Thanks guys, lots of ideas to work with. I wanted to make sure I was not missing an obvious solution. I am an Electrical engineer and 3D drafting of gear trains is way on the edge of my skill set.

 

[drof34]

The pitch dia of the two gears in mesh together should be added together and then divided by 2 which is the center distance between said gears. This should be equivalent to making the two PCs tangent to each other.