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Simulation Question

3 REPLIES 3
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Message 1 of 4
Anonymous
168 Views, 3 Replies

Simulation Question

I have a motor with a 66:1 gearbox attached to it, and wanted to do
some simulations with applying a torque to the output shaft of the
motor to see how the assembly behaves.

Running into one problem though, and that is that I can't seem to find
a way to tell the dynamic simulation the releationship between the
output shaft of the motor and the output shaft of the gearbox.

In the standard assembly I can do this just fine with the rotation
constraint, but in the simulation there doesn't appear to be such a
constraint.

I also tried to convert the assembly constraint and I get the
following error from DS: The type of joint obtained by mates
translating is unknown!

So, is there any way for me to tell DS the gear ratio of the two
shafts without actually modelling the internals of the gearbox?

Thanks,
3 REPLIES 3
Message 2 of 4
Anonymous
in reply to: Anonymous

Just a question, and of course I have not seen the assembly, but do you
really need simulation for this? If it's just torque and speed, some quick
hand calcs should give you what you need.

I just would not want you spending a lot of time on simulation when a pen
and paper would be quicker.

--
Sean Dotson, PE
RND Automation & Engineering
www.RNDautomation.com
www.mcadforums.com


"Stephan Rose" wrote in message
news:5471441@discussion.autodesk.com...
I have a motor with a 66:1 gearbox attached to it, and wanted to do
some simulations with applying a torque to the output shaft of the
motor to see how the assembly behaves.

Running into one problem though, and that is that I can't seem to find
a way to tell the dynamic simulation the releationship between the
output shaft of the motor and the output shaft of the gearbox.

In the standard assembly I can do this just fine with the rotation
constraint, but in the simulation there doesn't appear to be such a
constraint.

I also tried to convert the assembly constraint and I get the
following error from DS: The type of joint obtained by mates
translating is unknown!

So, is there any way for me to tell DS the gear ratio of the two
shafts without actually modelling the internals of the gearbox?

Thanks,
Message 3 of 4
Josh_Petitt
in reply to: Anonymous

yeah, what Sean said. Instead of putting the driving torque and velocity on the motor shaft in the simulation, drive the output shaft of your gearbox. You know the torque will be amplified and the velocity reduced by your gear ratio. In a simulation of a gearbox, the driveshaft and gears can be modelled as a series of very stiff springs with masses. However if you don't know the internals of the gearbox, for low frequency analysis, you can assume that the gearbox is a perfectly rigid set of ideal gears (i.e. no backlash, frictionless motion tranfer).
Message 4 of 4
Anonymous
in reply to: Anonymous

Hi Stephen,

As far as a "rolling" relationships go in DS, you are correct, it is
different than the Assembly Motion Constraint. As you know in constraints,
you define the ratio. In DS, the ratio is defined by the geometry itself.

To create an equivalent relationship to an assembly motion constraint, you
can use the Rolling Cylinder on Cylinder Joint. The belt joint is also
similar in the fact that it too uses the geometry itself to define the ratio
relationship.

...I hope this clears things up a bit...

Cheers, -Hugh

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