Helical gears tend to be the default choice in applications that are suitable for spur gears but have non-parallel shafts. Also, they are utilized in applications that require high speeds or high loading. And whatever the load or swiftness, they generally provide smoother, quieter procedure than spur gears.
Rack and pinion is useful to convert rotational movement to linear movement. A rack is straight teeth cut into one surface area of rectangular or cylindrical rod shaped material, and a pinion is definitely a small cylindrical gear meshing with the rack. There are several ways to categorize gears. If the relative position of the apparatus shaft can be used, a rack and pinion is one of the parallel shaft type.
I have a question regarding “pressuring” the Pinion in to the Rack to reduce backlash. I’ve read that the larger the diameter of the pinion gear, the less likely it is going to “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 level pressure rack for this use. Nevertheless, I can’t find any information on “pressuring “helical racks.
Originally, and mostly due to the weight of our gantry, we had decided on larger 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 given by Atlanta Drive. For the record, the electric motor plate is certainly bolted to two THK Linear rails with dual vehicles 
on each rail (yes, I understand….overkill). I what after that planning on pushing through to the motor plate with either an Air flow ram or a gas shock.
Do / Helical Gear Rack should / can we still “pressure drive” the pinion up right into a Helical rack to help expand decrease the Backlash, and in doing this, what would be a good beginning force pressure.
Would the utilization of a gas pressure shock(s) work as efficiently as an Atmosphere ram? I like the thought of two smaller force gas shocks that equivalent the total drive needed as a redundant back-up system. I would rather not operate the surroundings 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 shape of the gas shock/air ram work to adapt the pinion placement in to the rack (still using the slides)?
However the inclined angle of the teeth also causes sliding contact between your teeth, which generates axial forces and heat, decreasing performance. These axial forces perform a significant function in bearing selection for helical gears. Because the bearings have to endure both radial and axial forces, helical gears need 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 larger helix angles provide higher velocity and smoother motion, the helix position is typically limited to 45 degrees due to the production of axial forces.
The axial loads produced by helical gears could be countered by using dual helical or herringbone gears. These arrangements have the appearance of two helical gears with opposing hands mounted back-to-back, although in reality they are machined from the same equipment. (The difference between the two designs is that double helical gears have a groove in the middle, between the teeth, whereas herringbone gears usually do not.) This set up cancels out the axial forces on each group of teeth, so bigger 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 more than spur gears may be the ability to be utilized with either parallel or non-parallel (crossed) shafts. Helical gears with parallel shafts require the same helix angle, but reverse hands (i.e. right-handed teeth vs. left-handed teeth).
When crossed helical gears are used, they could be of either the same or opposing hands. If the gears have the same hands, the sum of the helix angles should equivalent the angle between your shafts. The most common example of this are crossed helical gears with perpendicular (i.e. 90 level) shafts. Both gears have the same hands, and the sum of their helix angles equals 90 degrees. For configurations with opposite hands, the difference between helix angles should the same the angle between the shafts. Crossed helical gears offer flexibility in design, but the contact between teeth is closer to point contact than line contact, so they have lower push capabilities than parallel shaft designs.