Helical gears tend to be the default choice in applications that are ideal for spur gears but have non-Helical Gear Rack parallel shafts. Also, they are utilized in applications that want high speeds or high loading. And regardless of the load or swiftness, they generally 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 of rectangular or cylindrical rod formed materials, and a pinion can be a small cylindrical equipment meshing with the rack. There are plenty of ways to categorize gears. If the relative placement of the gear shaft is used, a rack and pinion belongs to the parallel shaft type.
I have a question regarding “pressuring” the Pinion in to the Rack to reduce backlash. I have read that the larger the diameter of the pinion equipment, the less likely it will “jam” or “stick into the rack, but the trade off may be the gear ratio increase. Also, the 20 degree pressure rack is better than the 14.5 degree pressure rack because of this use. However, I can’t find any info on “pressuring “helical racks.
Originally, and mostly due to the weight of our gantry, we’d decided on bigger 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 because given by Atlanta Drive. For the record, the engine plate is certainly bolted to two THK Linear rails with dual cars on each rail (yes, I know….overkill). I what after that planning on pushing up on the electric motor plate with either an Atmosphere ram or a gas shock.
Do / should / can we still “pressure drive” the pinion up right into a Helical rack to help expand reduce the Backlash, and in doing this, what will be a good starting force pressure.
Would the use of a gas pressure shock(s) are efficiently as an Air ram? I like the thought of two smaller power 
gas shocks that equal the total pressure required as a redundant back-up system. I would rather not run the air lines, and pressure regulators.
If the thought 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 form of the gas shock/air ram work to adapt the pinion placement into the rack (still using the slides)?
But the inclined angle of one’s teeth also causes sliding contact between your teeth, which produces axial forces and heat, decreasing performance. 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 require thrust or roller bearings, which are usually larger (and more costly) 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 bigger helix angles provide higher quickness and smoother motion, the helix position is typically limited to 45 degrees due to the creation of axial forces.
The axial loads made by helical gears could be countered by using double helical or herringbone gears. These arrangements have the appearance of two helical gears with opposite hands mounted back-to-back, although the truth is they are machined from the same gear. (The difference between the two designs is that dual helical gears possess a groove in the middle, between the teeth, whereas herringbone gears do not.) This set up cancels out the axial forces on each set of teeth, so larger helix angles may be used. It also eliminates the necessity for thrust bearings.
Besides smoother motion, higher speed capability, and less noise, another advantage that helical gears provide over spur gears is the ability to be used with either parallel or non-parallel (crossed) shafts. Helical gears with parallel shafts require the same helix position, but opposing hands (i.e. right-handed teeth versus. left-handed teeth).
When crossed helical gears are used, they may be of either the same or opposing hands. If the gears possess 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 have the same hand, and the sum of their helix angles equals 90 degrees. For configurations with opposite hands, the difference between helix angles should equivalent the angle between the shafts. Crossed helical gears offer flexibility in design, however the contact between the teeth is nearer to point contact than line contact, so they have lower power features than parallel shaft styles.