Rack & Spur Gear Mate

[MikeInSoCalif]

I have a rack and a spur gear that I would like to mate so as I push the rack along a channel, it will rotate the spur gear.

Is this Possible?

 

[Beggar]

Yep. Check out Gear under Advanced Mates.

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Bring back the HP-15

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[MikeInSoCalif]

As far as I understand, the gear mate can be used for mating gears that rotate around an axis. I have one round spur gear thats riding along a rack. The rack is straight, there for has no axis.

 

[MElam]

There is not a mate that will do this directly (see thread559-82916)

If there are not a lot of teeth, physical dynamics may work but can be a pain for this type of thing.

 

[Beggar]

I just made a simple rack (rectangular solid with a couple of teeth) & pinion (cylinder with one tooth) and the gear mate seems to work for me.

I mated the cylindrical surface of the pinion to the edge of one of the rack teeth and then selected my gear ratio.

Perhaps I'm missing something but it seems to be what you're looking for.

--------------------
Bring back the HP-15

http://www.hp15c.org

--------------------

 

[ShaggyPE]

What did you use as a gear ratio?

 

[Beggar]

I started with 1:1 and then fiddled around with 1:10, 10:1, 1:1000, & 1:10000.

It won't take anything greater than 1:10000

--------------------
Bring back the HP-15

http://www.hp15c.org

--------------------

 

[qwerty13]

Beggar,

The advanced mate does not work for rack/pinion in a realistic way. You can visualy see this by using a long rack and moving the rack to generate pinion rotation. It appers that the gear ratio is not consistent.
The only way to do it is to use equations to link the rack and the pinion.
Hope this helps

Emil Nicoara

 

[Drhinehart]

I am working on a gear and rack and was having the same problem with the gear mates not working on a linear movement with the rack.

My solution was to use the concept of a motion limiter and mate to a distance from a point on the rack to a point on the gear. As I move the rack the gear will turn accordingly keeping the same distance from point to point. Grant it this will only work with a partial turn, but I only needed 120 degrees of rotation on my gear. Maybe this will inspire another or better way of accomplishing this.

Hope it helps.


Dale

 

[Drhinehart]

Side note the motion part of it seems to work a lot better when you turn the gear rather than moving the rack. When I move the rack it looks real flaky, when I turn the gear and make the rack move it is a very smooth movement.

 

[JRBruce]

I too have had flaky results using physical dynamics.

If you don't mind cheating, one way of creating a convincing, if not technically accurate, rack & pinion mate is as follows:

-Sketch a pitch circle on the pinion, and a pitch line on the rack.
-Sketch an arc on the rack, tangent to the pitch line, with a radius of 10000 x the pinion pitch radius.
-In the assembly, create a couple of temporary mates to line-up the teeth, then suppress them.
-Then create a 10000:1 gear mate between the rack's arc sketch and the pinion's pitch circle.

obviously, the larger the arc radius on the rack, the more accurate the motion will be, but there seems to be a limit of 1000000mm.