Gear Backless Calculation

Kiln girth gear drives usually have a wide tolerance due to unavoidable kiln distortion. Tangent plates take some of the "play" out of the drive but it comes down to kiln alignment.

Contact the manufacturers.

If backlash is an issue, and if your system dimensions can accommodate it, you could consider an anti-backlash pinion. One way of doing this is to mount a second pinion in tandem with the first, with spring loading so that the pinion teeth "push apart" to fully occupy the spaces within the girth gear. This requires that the girth gear teeth are twice as wide as the pinion gear teeth. I don't know if this possible in your layout.

Hi Tornado

If you've seen a kiln girth gear in action it would horrify you as an engineer. The worse case I've ever seen the teeth were bottoming at one side of the gear and half engaged at the other. The gear and pinion were replaced eventually and the run out corrected with the tangent plates. The noise from them used to keep me awake at night in the workshop before they were fixed.

Ah, yes, elliptical gears....

No, I haven't seen a kiln of this type, and was only guessing.

Hello all friends, my quary for new girth gear and pinion not for old gear. I have new plant. supplier/menufacturer has not provide the data for alingment of pinion. Girth gear alignment has over. I have to go for pinion alignment according following data. girth gear moudule, PCD,No of teathe, need calculation formula/data for backlesse dimantion. How much backlesse are require? Pls a waited for good response.

The manufacturer will supply the information, it's in there own self interest. It would be unreasonable to expect an answer from a general engineering forum.

By the way you will find there is still run out on a new kiln install.

How much information do you have so far on this gear set? Diametral pitch, number of teeth in girth gear and pinion, tooth face width, pitch circle diameters of both gears, pinion rpm, torque to be transmitted (or hp/kw of drive), pressure angle, etc.?

Because of wide temperature variation, growth/shrinkage of the girth gear can be expected. The pinion may need to move accordingly. I would guess that this gear set would need to be relatively "sloppy", with a fairly large backlash. Maybe 0.050 inches (wild guess)? I doubt that there is any formula for this; more likely it is based roughly on practical experience.

How (and/or why) is the girth gear "spherical"? A drawing would also help.

It was not the right "guessing". Such gears can have diameters of several meters. The module can be up to 30 mm! So that the 0.05" clearance is very far from the possible range. The problem is quite complex for several reasons: - along the kiln temperature changes - load is not uniform so that the tube bends - rollers wear and the support shifts. Teeth are "spherical" (in fact barreled) in order to accept parallelism errors (deviations) between gear axes since even if the pinion has a more or less stable position the gear due to above mentioned factors is never parallel to pinion axis. Backlash should avoid any interference during function so that it has to be quite consistent. This cannot be indicated from the "shelf" it has to be determined according to real situation. I remember a case when the computation of the gears did not consider the starting transient the right way and the teeth were sheared!