Helical gears are often the default choice in applications that are suitable for spur gears but have nonparallel shafts. They are also utilized in applications that want high speeds or high loading. And regardless of the load or velocity, they often provide smoother, quieter operation than spur gears.
Rack and pinion is utilized to convert rotational movement to linear movement. A rack is straight tooth cut into one surface of rectangular or cylindrical rod shaped materials, and a pinion is certainly a small cylindrical gear meshing with the rack. There are various ways to categorize gears. If the relative placement of the gear shaft is used, a rack and pinion is one of the parallel shaft type.
I have a question about “pressuring” the Pinion into the Rack to lessen backlash. I’ve read that the bigger the diameter of the pinion equipment, the less likely it will “jam” or “stick into the rack, however the trade off is the gear ratio boost. Also, the 20 level pressure rack is preferable to the 14.5 level pressure rack for this use. Nevertheless, I can’t find any details 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 on a 26mm (1.02”) face width rack because supplied by Atlanta Drive. For the record, the electric motor plate can be bolted to two THK Linear rails with dual vehicles on each rail (yes, I understand….overkill). I what after that planning on pushing up on 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 further decrease the Backlash, and in doing this, what will be a good beginning 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 the same the total drive required as a redundant back-up system. I’d rather not operate 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 shape of the gas shock/air ram function to adjust the pinion placement into 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 performance. 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 need thrust or roller bearings, which are usually larger (and more costly) compared to 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 angle is typically limited to 45 degrees because of the creation of axial 
forces.
The axial loads produced by helical gears can be countered by using double helical or herringbone gears. These plans have the looks 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 your two designs is that double helical gears possess a groove in the centre, between the the teeth, whereas herringbone gears usually do not.) This arrangement cancels out the axial forces on each group of teeth, so bigger helix angles may be used. It also eliminates the need for thrust bearings.
Besides smoother movement, higher speed ability, and less sound, another benefit that helical gears provide over spur gears may be the ability to be used with either parallel or nonparallel (crossed) shafts. Helical gears with parallel shafts require the same helix angle, but opposing hands (i.electronic. right-handed teeth vs. left-handed teeth).
When crossed helical gears are used, they may be of possibly the same or opposite hands. If the gears possess the same hands, the sum of the helix angles should equivalent 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 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 the same the angle between your shafts. Crossed helical gears offer flexibility in design, however the contact between teeth is nearer to point contact than line contact, therefore they have lower pressure capabilities than parallel shaft styles.