Spur gears not running on pitch line
Spur gears not running on pitch line
(OP)
Many gear manufacturers say not to do this, but here is my problem.
I have 2 rolls in which paper is nipped between. The rolls need to be driven. We are currently using spur gears to drive them. Both rolls are the same diameter. The distance between the rolls is ajustable. How much can the center distance change before a new set of gears is needed? Is there a general rule of thumb? The rolls are small and the gears have been overdesigned by a actor of at least 5 to 1.
I have 2 rolls in which paper is nipped between. The rolls need to be driven. We are currently using spur gears to drive them. Both rolls are the same diameter. The distance between the rolls is ajustable. How much can the center distance change before a new set of gears is needed? Is there a general rule of thumb? The rolls are small and the gears have been overdesigned by a actor of at least 5 to 1.





RE: Spur gears not running on pitch line
RE: Spur gears not running on pitch line
Two things to watch out for:
Keep the shafts parallel
Don't overload the gears (since you have a 5:1 safety factor at standard center distance, you are probably o.k. in this regard).
RE: Spur gears not running on pitch line
The other thing you will want to do is bevel the top of the teeth so that you don't have a problem with the flat tops hitting each other and preventing meshing.
RE: Spur gears not running on pitch line
RE: Spur gears not running on pitch line
To have a lower angle (14'5ยบ) is a good solution for little loads.
RE: Spur gears not running on pitch line
(Ro^2-Rb^2)+(ro^2-rb^2)-C(sin D)
--------------------------------
Pc(cos D)
Ro=radius of outside diameter
Rb=radius of base circle
C=center distance
D=theta (? doesn't this change)
Pc=circular pitch
Thanks for your help, guys. If there is something easier for identical gears, I'm willing to hear it.
RE: Spur gears not running on pitch line
RE: Spur gears not running on pitch line
Evidentially the manufacturer doesn't have a website and here is all that I could locate on them.
The Slimb bearings are manufactured by Yorkshire Industries, Inc. Andover, Mass., and are of more fully disclosed in U.S. Pat. No. 3399582. ...
RE: Spur gears not running on pitch line
cos A' = Dt/Dr * cos A
Where:
Dt: Theorical pitch distance
Dr: Real distance between gears centers
A: theorical angle
A': Real pitch angle
RE: Spur gears not running on pitch line
As the others have said, you will be able to pull the gears further apart from each other. The limitation will be the reduction in your contact ratio and backlash. I would not go below 1.0 for a contact ratio.
You can check out my sight, as I have an online gear geometry calculator. This will allow you to input non standard center distances etc. This will show you all the details with respect to the gears as the center distance changes.
Check it out at www.donkersdesigns.com/gear calculation.html
www.donkersdesigns.com
RE: Spur gears not running on pitch line
Donkers,
When I input the gear data (on your web site) the contact ratio says NaN. Am I doing something wrong?
RE: Spur gears not running on pitch line
I agree that most gear books will tell you that a 1.4 or higher. But this is just a rule of thumb. In fact the higher the contact ratio the better if your designing for low noise. Like HCR gears of 2.0 or higher. I've seen many gear designs that are slightly less than 1.2 that have worked for many years. They are usually of the old stub tooth form.
As for inputing the numbers on the website. You may have gotten this return if your center distance or some other value was way off from the norm.
What were the value you put in?
www.donkersdesigns.com
RE: Spur gears not running on pitch line
I was making different tests this year to know exactly the influence of the center distance on the noise. The distance has not an important influence in the noise if you have a correct engagement. Then, if you respect a minimum clearance, and the minimum contact ratio of 1.0 you are not going to have problems without load. When you have load in the gearing then and, because of the deformation in the teeth head, you need to have a bigger one ratio (with 1.2 is enough). Of course, the endurance of the gearing is going to be reduced, but the noise and, with that noise, the smooth contact between gearings, is not going to change very much. In fact, is easier to have noise problems with low clearances than with low contact ratio. Is much more important to have a correct teeth geometry than to have an exact center distance.
RE: Spur gears not running on pitch line
Why are you concerned about backlash, it never of itself caused a problem. It my have allowed other problems to develop.