Years ago, it was expensive and very difficult to make spiral bevel gearboxes. And while the precision necessary to craft such beautiful and intricate pieces is still tricky, with the right attention to design and fabrication, it's much more doable.
In order to fully appreciate the many advantages of spiral bevel gearboxes, here is everything you need to know about spiral bevel gear design.
The most common form of this kind of gearbox is a differential, like that found in a car. That is a much more complicated design which allows each wheel to turn at different rates. It also relies on a pinion and ring gear assembly, where the driving and driven gears are very different in size. But the simplest form of a right angle gearbox uses the same elegant spiral bevel gear cut with gears much more similar in diameter and number of teeth.
The gears in a spiral bevel gear design are cut in a helix, which is very complicated and intricate. Before computer controlled machines, it took an expert machinist many hours to be able to craft gears like this from raw stock. The helical cut runs either clockwise (right hand) or counter-clockwise (left hand). For this reason, they always have designed, fabricated, and used in pairs. A gearbox, once fabricated, should be considered sealed.
The many advantages of this design:
- They are on-plane. The input and output shafts are at a perfect right angle to each other, not offset vertically. The alternative, a hollow bore helical gearbox, cannot provide this direct transfer of power at a right angle in the same plane. This allows a spiral bevel gearbox to simply turn a corner to deliver the power you need where you need it.
- They are precise. With less than half of a degree of backlash, there is little torque or power wasted in the slop of the gearbox. This is a feature of the intricate spiral bevel gear design which has to be made to very exacting specifications.
- They can easily be made into a three-way coupling. Power can be transmitted left, right, or in both directions with the same shafts. This makes for a handy way to split the power from one motor to operate several things at once, saving on motor cost and maintenance.
- They have a long life. Because of the tight tolerances in a spiral bevel gear design, there is very little wear between the teeth. This gives them a very long operating cycle with minimal maintenance other than basic lubrication.
For all these reasons, the modern spiral bevel gear design is very much the system of choice for transferring power at a right angle. Where they were once very difficult and expensive to machine, today they are the standard method of choice for any application where power must be turned at a right angle. They are definitely the state of the art for any application of turning force today.