Gear Sizing - So that two different size cylinders have matched surfac 1

[EngMark007]

Gear Sizing - So that two different size cylinders have matched surface speeds

I have an application where I need to size gears for a set of cylinders with different diameters, and the surface speeds of the cylinders need to match.

Does the ratio between gears have to equal the ratio between pitch diameters?

This is our first application where the diameters of the cylinders are different. For our application, we need to be able to adjust the space between the cylinders, so we typically subtract .010 from the pitch diameter. Since the pitch diameters are the same, the ratio between the pitch diameters will equal the gear ratio. But when I follow this for cylinders with different diameters, the ratios are no longer the same.

Here is some other information:
Helical Gears
Ratio between the cylinders - 1.200 (22.776 & 27.3312)
Pressure Angle - 20 deg.
Normal diametrical pitch - 8

Thanks,

 

[PeteDB]

The ratio of the number of teeth on the gears determines how much one gear rotates with respect to the other. Changing the center distance changes the operating pitch diameters. The ratio of the operating pitch diameters will still equal the gear ratio.

 

[hydtools]

Are you comparing the cylinder diameters or piston areas for speed comparison? For a given flow input cylinder speeds vary by the piston area or the diameter squared.

Ted

 

[EngMark007]

Cylinder diameters.

 

[Compositepro]

Your gear tooth ratio must equal the cylinder diameter ratios. You can always use four gears instead of two to couple two rotating cylinders (rollers might be a better term). With a four gear arrangement you do not have to match the pitch diameter of the gears with the cylinder diameter and the gears stay in proper mesh even when the gap between the rollers changes.