Understanding the Advanced Mechanics of Helical Gear Rack

Helical gears are often the primary choice in applications suitable for spur gears but with non-parallel shafts. They are also preferred for high-speed or high-load applications. Regardless of the load or speed, Helical gears frequently provide smoother, quieter operation than spur gears.

Basics of Helical Gear Rack and Pinion

Rack and pinion are employed to convert rotational movement to linear motion. A rack is a straight tooth cut into one surface area of rectangular or cylindrical rod-shaped materials, while a pinion is a small cylindrical gear meshing with the rack. There are several ways to classify gears. When the relative position of the gear shaft is considered, a rack and pinion falls under the category of parallel shaft type.

Pressuring the Pinion into the Rack

One common query pertains to the concept of “pressuring” the Pinion into the Rack to reduce backlash. Information suggests that the larger the diameter of the pinion gear, the less likely it will “jam” or “stick” into the rack. However, this results in an increased gear ratio. The 20-degree pressure rack is preferable to the 14.5-degree pressure rack for this purpose. Despite these facts, there is limited information on “pressuring” helical racks.

Optimal Setup for Helical Gear

Originally, and predominantly due to the weight of our gantry, we had chosen larger 34 frame motors, twisting in 25:1 gear boxes, with an 18T / 1.50” diameter “Helical Gear” pinion riding on a 26mm (1.02”) face width rack as provided by Atlanta Drive. For the record, the motor plate is bolted to two THK Linear rails with dual cars on each rail. Then, the plan was to push up on the motor plate with either an Air ram or a gas shock.

Pressure Driving the Pinion

The question arises whether we can still “pressure drive” the pinion up into a Helical rack to help further reduce the Backlash, and if so, what would be an appropriate starting force pressure. Would the use of a gas pressure shock work as efficiently as an Air ram? The concept of using two smaller drive gas shocks with the same total pressure required as a backup system seems appealing. This eliminates the need to run air lines and pressure regulators.

If pressuring the rack is not feasible, a “version” of a turn buckle type device that would be machined to the same size and shape of the gas shock/air ram could work to adjust the pinion position into the rack (still using the slides).

Axial Forces and Heat Generation

The inclined angle of the teeth causes sliding contact between the teeth, generating axial forces and heat, which reduces efficiency. These axial forces play a significant role in bearing selection for helical gears. As the bearings must withstand both radial and axial forces, helical gears require thrust or roller bearings, which are larger and more expensive than the simple bearings used with spur gears. The axial forces vary in proportion to the magnitude of the tangent of the helix angle. Although larger helix angles provide higher speed and smoother motion, the helix angle is typically limited to 45 degrees due to the generation of axial forces.

Countering Axial Loads with Dual Helical or Herringbone Gears

The axial loads produced by helical gears can be countered with dual helical or herringbone gears. This arrangement cancels out the axial forces on each set of teeth, allowing for larger helix angles. It also eliminates the need for thrust bearings.

Advantages of Helical Gears

Besides smoother motion, higher speed capacity, and less noise, another advantage that helical gears offer over spur gears is their ability to be used with either parallel or non-parallel (crossed) shafts. When crossed helical gears are used, the sum or the difference of the helix angles should correspond to the angle between the shafts, providing flexibility in design.

Why Choose WLY for Your Helical Gear Rack Needs?

At WLY, we take pride in providing high-quality, durable, and reliable helical gears. Our gears are designed with precision and built to last, ensuring you get the most value for your investment. We offer competitive prices, superior customer service, and a wide range of products to meet your specific needs.

We encourage you to explore our range of products and see the difference that WLY can make for your applications. If you have any questions or need further information, don’t hesitate to contact us. We look forward to assisting you with all your gear needs!

Manufacturer

Common Questions About Helical Gear Rack

Q1: What is the advantage of using a larger diameter pinion gear?

A: A larger diameter pinion gear is less likely to “jam” or “stick” into the rack, resulting in smoother operation.

Q2: What type of bearings are required for helical gears?

A: Helical gears require thrust or roller bearings, as they must withstand both radial and axial forces.

Q3: Why are helical gears preferred for high-speed or high-load applications?

A: Helical gears provide smoother, quieter operation and are capable of handling higher speeds and loads compared to spur gears.

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