Designing a circular rack and pinion gear system motion linking?

[Anonymous]

Hello, 

I'm trying to model a special type on rack and pinion gear system where what is special is that the rack in not linear but circular(bigger rides on a circle off center from the pinion gear and much bigger than the pinion gear diameter pitch)

and I'm having problems with calculating the ration(in degrees) for the motion link between the rack and pinnion for confirming the model is right maybe I've got the pitch distance for the rack in the "pattern along path" wrong as well.

Here is the video I used to study how to design a normal rack and pinion system:

https://www.youtube.com/watch?v=khG4Zk5XZrw&t=0s&index=108&list=WL

And a picture of what I came with so far:

just to mention it's a design for a digital pedal controller for machines games ECT...

Couldn't find a proper product to replace it.

and a shareable link to this project: 

https://a360.co/2HcosYt

Thanks for your time.

[etfrench]

A curved rack is just a planetary gear   Unfortunately, Fusion 360 doesn't have a built-in way of creating one.

You may want to do a search on creating planetary gears in Fusion 360.

Attached are an stl and a dxf file for a Module 1.25 127t planetary gear.

[etfrench]

The forum doesn't seem to like attached stl or dxf

[davebYYPCU]

You have most of it set up, 

Edit Revolve 8 - Joint limits, minimum -10 degrees, Maximum 10 degrees, or similar....

(when typing in the numbers the rack moves to that position, adjust as suitable)

Animate model looked OK to me.

Might help....

[Anonymous]

Not sure wether the problem is with the animation or the pitch of the rack but when animation the gear meshes with the rack at some point sins once is probably rotating more than the other: 

[davebYYPCU]

A bit of both, 

The spacing in the rack pattern was correct, but you used the outside diameter of the tooth as the path, instead of the construction diameter - for want of a better description.  I think it is PCD but not sure on that.  Updated that.

I went back to the motion link, and figured it should be 24 deg and 6 deg per tooth, or 4:1, that did not animate correctly, I found that 24 deg and 5.6666 deg did animate correctly, (my numbers were 144 : 34 degrees in the preview)

While setting up the Screencast I got a surprise with the last body, becoming visible. 

It with the motor and switch becomes a rigid group, and that doesn't change the numbers in the rack.

File attached.

[chrisplyler]

The ratio you want for the motion link is the Pitch Diameter of one gear divided by the Pitch Diameter of the other gear.

[Anonymous]

I am also looking for designing a similar type of circular rack and pinion system where circular rack will be driving the pinion. I want to know how to calculate gear ratio for this system, and whether it can have a gear ratio of 50:1 or above?? Can someone please help me out. Thanking in advance

[davebYYPCU]

Gear ratio for 50 : 1, is 50:1.

pinion turns 50 times, rack turns once.

pinion has 10 teeth, rack has 500 teeth, etc.

Might help...

[Anonymous]

I want to design a rack and pinion for a stairlift with curved sections.

[etfrench]

GrabCad has a few curved rack and pinion models.  A spiral bevel gear might also work.

[Anonymous]

i need a rack and pinion for a stairlift
where the guide is not completely straight, but has a curve with a spiral.
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