How does a differential created using a coupler ensure correct gear drive?

Garand · 2025-07-02T05:15:42+00:00

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Hello everyone,

I found a realise of vehicle differential using Coupler entity in a dual axle transmission model by MotionView Assembly Wizard, it looks like below:

As to my understanding, it distributes power from the input shaft between the two drive axles. To make it works correctly, the load torque should be defined on differential's sun gear (joint3 in figure), and rotation speed should on planet gear(joint 1 and 2).

However, my own model contains gears, and i want to make sure they have a correct drive relationship. Like figure below, I want G1 always works as drive gear. It is important in a Contact defined gear pair, for the side of drive affects the sideface of teeth in contact.

If I use the Coupler differential, rotation speed is defined on G2 side. Will it forces G2 to be drive gear? How can I ensure the drive gear is the gear I want at this situation?

Sincere thanks,

Garand

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GTT Adam

Hi @Garand,

The Gear and Coupler entity are both constraints in MotionView that influence the motion of two joints.

A Coupler requires the definition of two joints, and acts to ensure a motion ratio is applied between the joints.

A Gear acts the same way, except you also define a point of gear contact. Based on this point and the center of the joints, the radius of the gears will be determined.

Technically, there is no need to replace the Couplers in this differential model with Gears, as the transmission of power and gear ratios applied are exactly what is needed. If you really wanted to, the definition with Gears would be almost identical, with you needing to define extra points in order to give the Gears their sizes rather than just specifying the gear ratio, like in a Coupler.

More on Couplers https://help.altair.com/hwdesktop/hwx/topics/chapter_heads/couplers_r.htm?zoom_highlight=coupler

More on Gears https://help.altair.com/hwdesktop/hwx/topics/chapter_heads/gears_r.htm?zoom_highlight=gear

Hope this helps!

Adam Reid

Garand

Hello Adam，

Thank you for the reply. And apologize for the inaccuracies in my description.

I am not trying to use gears to replace a differential defined with Coupler. In fact, there is a real gear pair in my model, and is defined with Contact entity. What I concern is how to make gear teeth flank contact correctly.

As shown in the figure, when the drive gears are different, even if the rotation directions are the same, the contacting tooth surfaces are different. The red arrows in the figure mark the different contact surfaces.

I used to apply rotation speed on G1 and load torque on G2, it makes G1 drives G2, contact pattern is like the left one. But now I apply a Coupler differential, it force me to exchange the position of rotation speed and load torque (speed on G2 and torque on G1). According to my understanding, this will cause the drive wheel to change, leads to a contace pattern like the right one.

I wonder how can I make sure G1 is the drive gear even with torque on G1 and rotation on G2? In other words, in MotionView transmission, how is it determined who drives whom?

Best ragards,

Garand

GTT Adam

Hi @Garand ,

If you are using gear contacts for your differential, then what is the purpose of introducing a coupler? The transfer of power between G1 and G2 is already accomplished.

Are you able to share this model, to give more insight into your current issue?

Hope this helps!

Adam Reid

Orestis_YB

Hello @Garand,

as @GTT Adam said already, contacts define the transfer of power so coupler entity is not needed here. As for the drive gear, it'll be the one which has a motion defined on it. Motion constrain is stiff and it will be achieved no matter the opposing torque. If you want to continue with motion then set it to the desired drive gear otherwise you could use torques in both gears and the drive gear will be the one with the more torque applied to it.

Hope this helps!

Best regards,
Orestes