Inventor General Discussion

## Inventor General Discussion

Active Member
Posts: 10
Registered: ‎07-28-2005
Message 1 of 8 (1,355 Views)

# Rotation-Translation Constraint

1355 Views, 7 Replies
04-19-2006 06:46 PM
Hi all,

I have a Machine at work that operates on a rack and pinion. I have got an accurate measured model of the pinion but only a less accurate measurement of the rack (hard to access!!). I have modelled both parts and want to check if the number of teeth on the rack is correct over the distance in relation to the pinion teeth. Basically what i was wanting to do is to check in the assembly environment that my pinion of 18 (Addendum circle Dia 62.46mm) teeth is correct for my rack of 96 (910mm long) teeth. I have used the rotation-translation constraint but can't seem to figure out what the correct distance ratio to use to see if the rack is of accurate measurement!?

This will hopefully tell me if my number of teeth are correct for meshing with the pinion of 18 teeth. How do you work out an accurate ratio? Is this possible?

Any help appreciated?
*Howard Delano
Message 2 of 8 (1,355 Views)

# Re: Rotation-Translation Constraint

04-20-2006 05:36 AM in reply to: BARNUG
The rack will move a distance equal to the circumference of your pinion at
the pitch diameter for each revolution of the pinion.

wrote in message news:5148224@discussion.autodesk.com...
Hi all,

I have a Machine at work that operates on a rack and pinion. I have got an
accurate measured model of the pinion but only a less accurate measurement
of the rack (hard to access!!). I have modelled both parts and want to check
if the number of teeth on the rack is correct over the distance in relation
to the pinion teeth. Basically what i was wanting to do is to check in the
assembly environment that my pinion of 18 (Addendum circle Dia 62.46mm)
teeth is correct for my rack of
96 (910mm long) teeth. I have used the rotation-translation constraint but
can't seem to figure out what the correct distance ratio to use to see if
the rack is of accurate measurement!?

This will hopefully tell me if my number of teeth are correct for meshing
with the pinion of 18 teeth. How do you work out an accurate ratio? Is this
possible?

Any help appreciated?
Distinguished Contributor
Posts: 4,994
Registered: ‎12-12-2003
Message 3 of 8 (1,355 Views)

# Re: Rotation-Translation Constraint

04-20-2006 05:43 AM in reply to: BARNUG
If you can't figure out the ratio can you post the rack and pinion?
Active Member
Posts: 10
Registered: ‎07-28-2005
Message 4 of 8 (1,355 Views)

# Re: Rotation-Translation Constraint

04-20-2006 08:44 PM in reply to: BARNUG
Thanks Guys,

JD I have posted the file as an .iam, hope this is ok?

Bear in mind i have not modelled true gear teeth profiles as it is only an exercise to see if i have the correct length and teeth number for the rack in relation to the pinion.

I am using V10.

Cheers

B
Distinguished Contributor
Posts: 2,163
Registered: ‎10-10-2005
Message 5 of 8 (1,355 Views)

# Re: Rotation-Translation Constraint

04-21-2006 05:00 AM in reply to: BARNUG
"Bear in mind i have not modelled true gear teeth profiles as it is only an exercise to see if i have the correct length and teeth number for the rack in relation to the pinion."

P.D * Pi * # of Rev's=Rack Travel (min. length)
Distinguished Contributor
Posts: 2,163
Registered: ‎10-10-2005
Message 6 of 8 (1,355 Views)

# Re: Rotation-Translation Constraint

04-21-2006 05:25 AM in reply to: BARNUG

# of teeth on rack= # of pinion teeth * # of Rev's
*Expert Elite*
Posts: 27,983
Registered: ‎04-20-2006
Message 7 of 8 (1,355 Views)

# Re: Rotation-Translation Constraint

04-21-2006 05:29 AM in reply to: BARNUG
There is nothing in an assembly file other than links to the part files and assembly constraints. You need to include ipt files with the iam.
There is a rack and pinion in the samples folder that one of my students did a couple of years ago. Samples/models/assemblies/Arbor Press. Suppress the angle constraint on the pinion shaft. Isolate the pinion shaft and ram (rack). Suppress the rotational/translation constraint. Line up the teeth by eye. Unsuppress the rotational/translation constraint and move the ram.
The pitch diameter of the pinion was 1", therefore the circumference was PI. The student could have entered PI*1 as the ratio. I think he tried PI but didn't understand the units and ended up rounding off.
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Active Member
Posts: 10
Registered: ‎07-28-2005
Message 8 of 8 (1,355 Views)

# Re: Rotation-Translation Constraint

04-23-2006 04:27 PM in reply to: BARNUG
Thanks JD and the rest,

Got it sorted, the rack tooth profile is incorrectly measured as the pinion teeth do fall out of sync as the length increases over the revolutions.