I have used GearGen written by Thomas Anagnostou with great success generating bevel gears up to about 24 in. in diameter. The design for the current iteration of the project requires a larger diameter bevel gear; the pitch diameter is now in the neighborhood of 51.20 inches. Given the 45:1 gear ratio and the 400 tooth limit in GearGen, I’m afraid that the pinion hasn’t enough teeth to take the stresses imposed.
Can GearGen be modified to handle such a large diameter, small tooth design? If not, is there another script that can? The link below is to a quick and dirty representation of what I’m working on.
That’s my understanding also. The force on a tooth depends on the torque divided by the pitch circle, not the size and number of teeth. Stresses will be lower with larger and wider teeth. However vibration/noise may be greater with larger teeth.
More on tooth strength (from the article “Guerrilla guide to CNC machining”) :
“In general, low pressure angles result in quiet-running, precise gears that are easy to machine due to generous clearances - but will be weaker, and have more pronounced undercuts. High pressure angles result in thicker tooth profiles which need to be machined with smaller tools, and can be more noisy and prone to backlash and slippage - but also survive a lot more abuse.”
Another consideration in gear design is to select a ratio which results in the all the teeth on one gear eventually meshing will all the teeth on the other gear. With a ratio of 45:1 and gears with 8 and 360 teeth, each tooth on the large gear will mesh with only 1 of the 8 teeth on the small gear, and each tooth on the small gear will mesh with only 45 of the 360 teeth on the large gear. That means if a tooth is damaged or a slightly different shape the wear will be be concentrated on a few teeth.
A better choice (if the ratio does not have to be exactly 45:1 would be to use 8 and 359 teeth with a ratio of 44.875, or 8 and 361 teeth with a ratio of 45.125. With either of those combination all teeth on the small gear will eventually mesh with all teeth on the large gear and vice-versa.