Helical gears tend to be the default choice in applications that are ideal for spur gears but have non-parallel shafts. They are also used in applications that require high speeds or high loading. And regardless of the load or acceleration, they often provide smoother, quieter procedure than spur gears.
Rack and pinion is utilized to convert rotational motion to linear motion. A rack is directly tooth cut into one surface of rectangular or cylindrical rod formed material, and a pinion is a small cylindrical equipment meshing with the rack. There are various methods to categorize gears. If the relative position 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 lessen backlash. I have read that the bigger 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 boost. Also, the 20 level pressure rack is preferable to the 14.5 degree pressure rack for this use. Nevertheless, I can’t find any info on “pressuring “helical racks.
Originally, and mostly because of 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 as given by Atlanta Drive. For the record, the engine plate is bolted to two THK Linear rails with dual vehicles on each rail (yes, I understand….overkill). I what then planning on 
pushing through to the motor plate with either an Surroundings ram or a gas shock.
Do / should / may we still “pressure drive” the pinion up into a Helical rack to further reduce the Backlash, and in doing this, what would be a good starting force pressure.
Would the use of a gas pressure shock(s) work as efficiently as an Atmosphere ram? I like the thought of two smaller power gas shocks that equivalent the total drive needed as a redundant back-up system. I’d rather not operate the surroundings 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 modify the pinion placement in to the rack (still using the slides)?
But the inclined angle of one’s teeth also causes sliding contact between your teeth, which creates 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 typically larger (and more expensive) compared to the simple bearings used with spur gears. The axial forces vary compared to the magnitude of the tangent of the helix angle. Helical Gear Rack Although bigger helix angles offer higher velocity and smoother motion, the helix angle is typically limited to 45 degrees because of the production of axial forces.
The axial loads made by helical gears could be countered by using double helical or herringbone gears. These arrangements have the looks of two helical gears with opposite hands mounted back-to-back, although the truth is they are machined from the same equipment. (The difference between the two designs is that double helical gears possess a groove in the middle, between the the teeth, whereas herringbone gears usually do not.) This arrangement cancels out the axial forces on each set of teeth, so larger helix angles can be used. It also eliminates the need for thrust bearings.
Besides smoother movement, 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 need the same helix position, but reverse hands (i.electronic. 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 have got the same hands, the sum of the helix angles should equal the angle between the shafts. The most typical exemplory case 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 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 tooth is nearer to point contact than line contact, so they have lower push capabilities than parallel shaft designs.