Large Spur Gear and Pinion Problem
Large Spur Gear and Pinion Problem
(OP)
Hi Guys,
I'm designing a set of gear. My problem arise when my gear is very big, more than 2.5mtr diameter.
I have to keep my pinion around 120-150mm diameter. Velocity ratio will not effect my problem.
Force on teeth is very low as not much load to carry.
When i use standard pressure angle, 14.5 or 20 degree, it gives wrong value of base diameter and dedendum diameter.
It suppose to give a dedendum dia. smaller than base diameter but instead it is the other way.
So, then i try my stupid analysis to try make different pressure angle, i tried 6 degree, it gives quite reasonable value.
but when i try to plot the involute, it doesn't seem right.
I need someone expert here. Attached is the analysis i did (sheet 3).
I'm designing a set of gear. My problem arise when my gear is very big, more than 2.5mtr diameter.
I have to keep my pinion around 120-150mm diameter. Velocity ratio will not effect my problem.
Force on teeth is very low as not much load to carry.
When i use standard pressure angle, 14.5 or 20 degree, it gives wrong value of base diameter and dedendum diameter.
It suppose to give a dedendum dia. smaller than base diameter but instead it is the other way.
So, then i try my stupid analysis to try make different pressure angle, i tried 6 degree, it gives quite reasonable value.
but when i try to plot the involute, it doesn't seem right.
I need someone expert here. Attached is the analysis i did (sheet 3).





RE: Large Spur Gear and Pinion Problem
RE: Large Spur Gear and Pinion Problem
RE: Large Spur Gear and Pinion Problem
You need to go and research the reasons behind a phenomenon that occurs with involute gearing generally referred to as 'undercut'. Put basically; it's a function of the number of teeth and pressure angle and how these affect the diameters that you're talking about.
A quick search with Google reveals heaps of info.
That's a neat little spread sheet that you've come up with.
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
http://www.aussieweb.com.au/email.aspx?id=1194181
RE: Large Spur Gear and Pinion Problem
A simple formula
#teeth/diametral pitch=pitch diameter.
And as long as the true involute is above the base diameter. You are good.
And It is not necessary to have the root below that base diameter. I did not look at your data. But these are elementary gear subjects.
If know the basic center distance of the pair gears. You can reverse calculate to get the correct # of teeth.
Mfgenggear
RE: Large Spur Gear and Pinion Problem
RE: Large Spur Gear and Pinion Problem
As gearcutter noted, you will have undercutting with a 15T pinion unless you tweak your mesh geometry. One other option would be to go with a 20T pinion that would not undercut, plus a slightly different module and a 396T gear to maintain the same PCD.
Hope that helps.
Terry
RE: Large Spur Gear and Pinion Problem
Thanks a lot for your information.
Regards,
Conantar