Helical gears tend to be the default choice in applications that are suitable for spur gears but have nonHelical Gear Rack parallel shafts. They are also used in applications that require high speeds or high loading. And regardless of the load or acceleration, they generally provide smoother, quieter procedure than spur gears.
Rack and pinion is utilized to convert rotational movement to linear motion. A rack is straight the teeth cut into one surface area of rectangular or cylindrical rod designed material, and 
a pinion is usually a small cylindrical gear meshing with the rack. There are many ways to categorize gears. If the relative placement of the apparatus shaft is used, a rack and pinion is one of the parallel shaft type.
I have a question regarding “pressuring” the Pinion into the Rack to reduce backlash. I have read that the larger the diameter of the pinion equipment, the less likely it is going to “jam” or “stick in to the rack, but the trade off is the gear ratio increase. Also, the 20 level pressure rack is better than the 14.5 degree pressure rack for this use. Nevertheless, I can’t find any info on “pressuring “helical racks.
Originally, and mostly due to the weight of our gantry, we’d decided on larger 34 frame motors, spinning in 25:1 gear boxes, with a 18T / 1.50” diameter “Helical Gear” pinion riding upon a 26mm (1.02”) face width rack since supplied by Atlanta Drive. For the record, the electric motor plate is usually bolted to two THK Linear rails with dual vehicles on each rail (yes, I know….overkill). I what after that planning on pushing up on the motor plate with either an Air ram or a gas shock.
Do / should / can we still “pressure drive” the pinion up into a Helical rack to help expand reduce the Backlash, and in doing this, what will be a good beginning force pressure.
Would the usage of a gas pressure shock(s) work as efficiently as an Air flow ram? I like the thought of two smaller drive gas shocks that equivalent the total force needed as a redundant back-up system. I’d rather not operate the air flow lines, and pressure regulators.
If the thought of pressuring the rack is not acceptable, would a “version” of a turn buckle type device that might be machined to the same size and form of the gas shock/air ram work to modify the pinion placement in to the rack (still using the slides)?
However the inclined angle of one’s teeth also causes sliding contact between your teeth, which generates axial forces and heat, decreasing effectiveness. These axial forces perform a significant role in bearing selection for helical gears. Because the bearings have to withstand both radial and axial forces, helical gears need thrust or roller bearings, which are typically 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 larger helix angles offer higher velocity and smoother motion, the helix position is typically limited to 45 degrees due to the creation of axial forces.
The axial loads produced 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, although in reality they are machined from the same equipment. (The difference between the two designs is that dual helical gears have a groove in the centre, between the teeth, whereas herringbone gears do not.) This set up cancels out the axial forces on each set of teeth, so bigger helix angles can be used. It also eliminates the necessity for thrust bearings.
Besides smoother movement, higher speed capability, and less sound, another advantage that helical gears provide more than spur gears may be the ability to be used with either parallel or non-parallel (crossed) shafts. Helical gears with parallel shafts need the same helix angle, but opposing hands (i.e. right-handed teeth vs. left-handed teeth).
When crossed helical gears are used, they could be of possibly the same or opposing hands. If the gears possess the same hands, the sum of the helix angles should equal the angle between the shafts. The most common example of this are crossed helical gears with perpendicular (i.e. 90 level) 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 teeth is closer to point contact than line contact, therefore they have lower drive features than parallel shaft styles.