Helical gears tend to be the default choice in applications that are ideal for spur gears but have nonparallel shafts. Also, they are used in applications that require high speeds or high loading. And whatever the load or acceleration, they often provide smoother, quieter operation than spur gears.
Rack and pinion is useful to convert rotational motion to linear movement. A rack is straight tooth cut into one surface area of rectangular or cylindrical rod designed materials, and a pinion is usually a small cylindrical gear meshing with the rack. There are numerous ways to categorize gears. If the relative position of the gear shaft can be used, a rack and pinion belongs to the parallel shaft type.
I’ve a question about “pressuring” the Pinion in to the Rack to reduce backlash. I have read that the 
Helical Gear Rack larger the diameter of the pinion gear, the less likely it will “jam” or “stick into the rack, however the trade off may be the gear ratio boost. Also, the 20 degree pressure rack is preferable to the 14.5 degree pressure rack for this use. However, I can’t discover any information on “pressuring “helical racks.
Originally, and mostly due to the weight of our gantry, we had decided on bigger 34 frame motors, spinning in 25:1 gear boxes, with a 18T / 1.50” diameter “Helical Gear” pinion riding on a 26mm (1.02”) face width rack since supplied by Atlanta Drive. For the record, the motor plate is certainly bolted to two THK Linear rails with dual cars on each rail (yes, I know….overkill). I what then planning on pushing through to the engine plate with either an Air flow ram or a gas shock.
Do / should / can we still “pressure drive” the pinion up right into a Helical rack to help expand decrease the Backlash, and in doing so, what will be a good beginning force pressure.
Would the use of a gas pressure shock(s) work as efficiently as an Air ram? I like the idea of two smaller drive gas shocks that equivalent the total force needed as a redundant back-up system. I would rather not operate the air lines, and pressure regulators.
If the idea of pressuring the rack isn’t acceptable, would a “version” of a turn buckle type device that would be machined to the same size and shape of the gas shock/air ram function to change the pinion placement in to the rack (still using the slides)?
But the inclined angle of the teeth also causes sliding get in touch with between the teeth, which generates axial forces and heat, decreasing effectiveness. These axial forces perform a significant function in bearing selection for helical gears. Because the bearings have to withstand both radial and axial forces, helical gears require thrust or roller bearings, which are usually larger (and more expensive) than the simple bearings used in combination with spur gears. The axial forces vary compared to the magnitude of the tangent of the helix angle. Although bigger helix angles provide higher quickness and smoother motion, the helix angle is typically limited by 45 degrees due to the creation of axial forces.
The axial loads made by helical gears can be countered by using dual helical or herringbone gears. These plans have the appearance of two helical gears with reverse hands mounted back-to-back again, although in reality they are machined from the same gear. (The difference between your two designs is that double helical gears possess a groove in the middle, between the tooth, whereas herringbone gears do not.) This arrangement cancels out the axial forces on each group of teeth, so larger helix angles may be used. It also eliminates the necessity for thrust bearings.
Besides smoother movement, higher speed capacity, and less noise, another benefit that helical gears provide over spur gears is the ability to be utilized with either parallel or non-parallel (crossed) shafts. Helical gears with parallel shafts require the same helix position, but opposite hands (i.electronic. right-handed teeth vs. left-handed teeth).
When crossed helical gears are used, they could be of either the same or opposite hands. If the gears have the same hands, the sum of the helix angles should equivalent the angle between the shafts. The most common example of this are crossed helical gears with perpendicular (i.e. 90 degree) shafts. Both gears possess the same hands, and the sum of their helix angles equals 90 degrees. For configurations with opposing hands, the difference between helix angles should equivalent the angle between the shafts. Crossed helical gears provide flexibility in design, however the contact between the teeth is closer to point get in touch with than line contact, therefore they have lower drive features than parallel shaft styles.