INTERNALGEAR CENTER DISTANCE

[ricec]

I HAVE AN INTERNAL GEAR WITH 104 TEETH AND A 14 TEETH PINNION.....CAN SOMEBODY TELL ME HOW TO CALCULATE THE DISTANCE AT WICH THE PINNION SHOULD BE??????
THANKS IN ADVANCE

 

[israelkk]

If the pinion is has a profile shift correction than you have a problem. Can you provide more information including Diametral Pitch or Module and the gears accuracy?

 

[ricec]

THE DIAMETRAL PITCH IS 3....

 

[israelkk]

Do you have the gears or you are now designing them?

 

[gearcutter]

A 14 teeth pinion with standard addendum will have “undercut” so there’s a good chance it has a plus addendum modification. If this is the case and the gear has no equivalent minus correction, then the standard calculation for hard mesh center distance, sum of the two P.C.D.s divided by two, can not be used because the operating pressure angle is no longer the same as the standard pressure angle. You need to have more information before the center distance can be worked out.

 

[gearcutter]

To clarify my previous post: The calcutation of centre distance I mentioned was for external spur gears. For standard internal spur gear and pinion center distance is P.C.D. of gear minus P.C.D. of pinion divided by two.

 

[scarecrow55]

go to this fellows site and try and get the internal gear program

http://uk.geocities.com/mikebull2001/green.html

 

[ricec]

I have the gears in my shop.

 

[israelkk]

You can either measure them using dimension over pins and from that calculate the actual pitch diameter. Or find where they were come from and ask for the blueprints or catalog.

 

[gearcutter]

Are the gears in reasonable condition? If they are then I can help you reverse engineer the set with a pair of verniers. Do you know how to take tangential span measurements with a vernier?

 

[diamondjim]

Normally the Center Distance for Internal
Gears Is:
(Gear pd - pinion pd)/2

or in terms of the Number of Teeth and
Diametral Pitch (Dp)Is:
(Ng - Np)/2 divided by the Dp

If the pinion and gear are both modified
the center distance will be as above.

If only the pinion has been modified the
equation is more complex. More than likely,
one or the other have been modified.
Pin readings using .500 diameter pins would
be helpful. It is often common to cut more
backlash in the internal gear like 2/3 of
the total back lash and 1/3 of the total
backlash on the pinion. A close approximation
will be to use the center distance as above
but add the modification of the pinion to it.
There is a slight difference because one is
a sin function and the other a tan function.

 

[diamondjim]

In my last post, you should subtract
the modification from the center distance
as a fatter tooth would move the pinion
in toward the gear centerline.

 

[ricec]

THANK YOU ALL FOR THE INFORMATION YOU HAVE PROVIDED, I BELIEVE THAT WITH ALL THIS HELP I WILL BE ABLE TO SOLVE THE PROBLEM.......BEST REGARDS