Rack and pinion

[BobL]

Hi All;

 I have discuss adding the ability to generate rack and pinion gearing in Gearotic Motion with Art, but was wondering how important and relevant it would be for designers to have it offered?

[John S]

Well pinions are covered and the rack is just a straight sided gear of infinite PCD.
I think the question needs to be asked how would someone want / need to cut a rack ?

If it's from a top view, rack on it's side for EDM or end milling with small cutters then this is easily laid out in any simple CAD program, draw a tooth copy offset X times.

Not knowing how the program works would it be possible to create / store one tooth in a user defined format, DP or MOD and PA then extrude this X times ? The limitatio ns are still going to be physical unless using EDM because of getting a long enough cutter to do the width of the rack, which is now defined as depth but being small enough to get into the root. Possibly creating the age old problem, drawing something that can't be machined 

Here's one I did earlier     





John S.

[BobL]

Hi John;

 Thanks for the input. Nice work btw...I agree drawing something you can't cut is an issue and will always exist, but if it could be cut, wouldn't it be awesome? Rack's are just another one of these cases in my opinion which have many applicati ons and work very well but not so easy to come up with for most. Adding this feature could be just another one of those tools which could come in very handy at times. What if you were able to set a max cut size parameter within GM, let's say of your cnc or jig tool, then cut the rack in multiple peices using these limits to join them all togther which would eventuall y allow your final rack lenght? A simple dxf output could do I think. The issue of "long enough cutter" to cut rack may also be reduced if both tooth depth and size is known prior to generate rack and pinion, since rack and gear would be generated perfectly in GM. Anyway justa thought.. .

Cheers
Bob

[John S]

Interesti ng concept.
I tried doing a 1,000 tooth gear running with a 15 tooth pinion, the idea being that a rack is a gear of infinite diameter.
Well it barfed  I think a 1000 is too many

[BobL]

Hi John;

 Interesti ng thing is rack is a simple straight lines to cut to make tooth ,unlike gears.

Thanks
Bob

[ArtF]

John:

 Some examples of the 45 degree helicals. .

[BobL]

Art;

 Any pictures of the "U" shapes gears?

[kimvellore]

I have applicati ons to use some rack and pinion gears, please consider it to add to the list of things to do in GM.
Thanks
Kim

[BobL]

Hi Kim;

 Noted and on the list of future possibili ties.

Cheers
Bob

[danmauch]

 If you need it now you may want to try this. Create the spur gear that you plan to use. Then save it as a dxf file. Load the spur gear gear into a CAD program. I used Bobcad 21. Carefully select one tooth and one root. Delete the rest of the teeth and roots.  Then deterime the length by using the dimension ing feature of your CAD program. Select the tooth and root then in translate and increment s list the number of copies with the distance previousl y noted and then enter. You should then see all the teeth and roots lined up and then you should be able to create your G code from there.

Dan Mauch
www.camtr onics-cnc.com
low cost cases for gecko products.
Kits and assembled stepper and servo systems.

I have applicati ons to use some rack and pinion gears, please consider it to add to the list of things to do in GM.
Thanks
Kim

[John S]

Dan surely that will use the tooth shape as the shape of the rack ?
A rack is easy to draw, it's just straight sided with an included angle of twice the PA of the gear.

John S.

[David Edwards]

This feature would be particula rly nice if it could produce racks for non-circular gears, elliptica ls, imaginari es, etc.

[BobL]

David;


 The primary focus at the moment is set on clocks. I know there was some talk for racks in future but not sure when that will materiali ze at this point, especiall y for elliptica l's and imaginary . Thanks for posting your idea.

Cheers
Bob 

[ArtF]

Hi:

   A rack is possible for a noncirclu lar, but it would look very strange and the elliptica l or noncircul ar gear would only fit it a particula r angle
to start. Each tooth in a rack for a non-circular woudl be different as opposed to a spur which is simply as John explained, a PA angle to to tip on each tooth.

Art