modeling of helical gear pair

[sudhir.patyal]

Design parameters
Number of teeth of the pinion, 1 N 17
Number of teeth of the gear, 2 N 77
Module, m 5.08 mm
Driving side pressure angle, d

 

[jbuckl]

Dear Sudhir,


Although your requirement is not clear, it looks like you might be having trouble modeling a helical gear pair?


From your profile it looks like you may be trying to model them in Catia.


This forum is for Pro-Engineer; 'Pro-E' is quite straight-forward to make gear models with.


What is your actual requirement?


Regards


Jbuckl

 

[sudhir.patyal]

u can see properly they are different gear


this is a only picture file it is not a model i can send a this picture for your understand


direction of teeth different in both gear so we need such type gear model


so we need such type of two gear


hope u are make such type of gear


what ever it is given that we need such type of gear

 

[Asho Pulsar]

Hey patyal,


Ohh damn, why the s'''t you created one more same topic again. Dont u know how to reply back? Still your requirement is not clear...


Ask questions like I need to model this helical gear pair or How to model this pair?
Edited by: Asho Pulsar

 

[sudhir.patyal]

how to mdel this pair?

 

[SRINIVASANIYER1]

Dear Sudhir,


In the case of a helical gear, RH gear will always mate with a LH gear where the axes are parallel.


Search the forum for "how to model gear teeth" to get the procedure for generating teeth cross section.


As the name suggests, use Helix to generate the profile.


Before starting with the modeling.... it would be helpful if you could read about gears. From the specifications above it appears that your gear is is not the regular 20 deg pressure angle gear. Your module too is not a standard.


Also check out if the module specified is the Normal module or the Axial module.


Study of GEARS is absolutely necessary before you can proceed further.

 

[jbuckl]

[url]http://www.mcadcentral.com/proe/files/gallery.asp?action=vie wimage&categoryid=11&text=&imageid=367&box=& amp;shownew[/url]=





Be careful with accuracy:-


your requirements are not accurate:-Radius of the worm pitch cylinder, rw 98 mm


All the best

 

[[-Skint-]]

Dear Sudhir.


Please only use this Thread to post & reply until you have your answers. Creating numerous threads only makes the forum worse and the search facility even less useful. We are all happy to help when & if possible.


A good starting point may be the Part files that can be downloaded from this site. There is a Helical Gear model to be found here :


[url]http://www.mcadcentral.com/proe/files/gallery.asp?categoryid =11[/url]


Hope that helps. Try searching google too, there is plenty of information available on Helical Gears.


Good Luck.

 

[SRINIVASANIYER1]

Sudhir,


Further to my reply, the following Study material are suggested...


1. http://en.wikipedia.org/wiki/Helical_gear#Helical_gears


2. Theory of Machines.... by Ballanay [since you are in India] (chapter on Gears..)


3. CMTI handbook: will give you a good insight on both S0 and S1 gear correction


4. BIS standards on gears (if your company is subscribing to BIS, you can recommend the same. http://www.bis.org.in/bis/start.htmsearch on gears on title.


5. PSG design data...


6. Machine Design M.F. Spotts


A deep study of the above is recommended, to understand what you are doing... Yes it is always easy to download a model, change parameters.... easy.... But you will not be complete.


Good luck !!!
Edited by: SRINIVASANIYER1

 

[jbuckl]

"As the name suggests, use Helix to generate the profile.2


Srini, correct me if Im wrong, but isnt it actually the tooth contact that is helical?


If the toothfollowed down a helix, how could it be cut?


This is why the term 'helix angle' is used, and an angle is only available for straight lines.


The helical contact teeth are cut along a helix angle (0 degrees =spur)


The helix angle in the gear geometry = gear blank to rack/hobber angle.


Btw, I think that tooth contact analysis from this thread is a long way off yet......

 

[SRINIVASANIYER1]

jbuckl,


When you cut a spur with a hob, [the hob is like a worm. hence has a lead angle] it is set at an angle = the lead angle of the hob for ZERO helix angle or Spur gear (ofcourse hand ofhob matters).


For a Helical gear, depending on Whether it is RH or LH, the Hob is set considering the HOB angle + Helix angle (Being an algebraic sum / difference).


While cutting the teeth, be it a Hob or a Gear shaper, Both the Job and the cutter rotate (Slightly different in case of a Fellow's Gear shaper using a RACK cutter)


Because of this action, the generated profile is a pure involute (like unwinding a thread from the base circle)


Though the theoretical contact between two gears is a straight line, the manufacturing errors (though within tolerance) prevents this, resulting in excessive toothwear at the two faces). Precisely for this reason, gears are crowned meaning a relief is given at the two faces of the gear to keep the contact in the center. Gears are thus DESIGNED for WEAR (Hertzian stress or contact stresses prevail) and CHECKED for STRENGTH (Standard Lewis equation for beam strength).


For proper gear design, it is also important that the contact ratios for a PAIR are > 1. I genarally followa value of 1.2 ~ 1.4. meaning that at any point of time, MORE THAN one teeth is in contact or plainly put, BEFOREa teeth, leaves the mating, another tooth gets engages with the gearing.


Ah ... yes...When it comes to modeling in Proe, it all depends on the Final Intent. If the intent is Mechanism only, then the teeth NEED NOT BE MODELLED.