Helical gears are often the default choice in applications that are ideal for spur gears but have nonparallel shafts. Also, they are used in applications that want high speeds or high loading. And whatever the load or acceleration, they generally provide smoother, quieter procedure than spur gears.
Rack and pinion is utilized to convert rotational motion to linear movement. A rack is straight the teeth cut into one surface of rectangular or cylindrical rod formed material, and a pinion is definitely a small cylindrical equipment meshing with the rack. There are various ways to categorize gears. If the relative placement of the gear shaft can be used, a rack and pinion belongs to the parallel shaft type.
I have a question about “pressuring” the Pinion into the Rack to lessen backlash. I’ve read that the larger the diameter of the pinion gear, the less likely it is going to “jam” or “stick in to the rack, however 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. However, I can’t discover any info 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 upon a 26mm (1.02”) face width rack since given by Atlanta Drive. For the record, the engine plate can be bolted to two THK Linear rails with dual vehicles on each rail (yes, I understand….overkill). I what then planning on pushing up on the electric motor plate with either an Air flow ram or a gas shock.
Do / should / may we still “pressure drive” the pinion up right into a Helical rack to further decrease the Backlash, and in doing this, what would be a good beginning force pressure.
Would the use of a gas pressure shock(s) work as efficiently as an Air ram? I like the thought of two smaller force gas shocks that the same the total power needed as a redundant back-up system. I would rather not operate the air lines, and pressure regulators.
If the idea 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 adapt 
the pinion placement into the rack (still using the slides)?
However 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 play a significant function 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 in combination with spur gears. The axial forces vary in proportion to the magnitude of the tangent of the helix angle. Although larger helix angles provide higher acceleration and smoother motion, the helix position is typically limited to 45 degrees because of the production of axial forces.
The axial loads produced by helical gears could be countered by using dual helical or herringbone gears. These plans have the appearance of two helical gears with opposite hands mounted back-to-back, although in reality they are machined from the same gear. (The difference between your two designs is that double helical gears have a groove in the centre, between the the teeth, whereas herringbone gears do not.) This arrangement cancels out the axial forces on each set of teeth, so bigger helix angles can be used. It also eliminates the need for thrust bearings.
Besides smoother movement, higher speed ability, 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 need the same helix angle, but opposite hands (i.electronic. right-handed teeth versus. left-handed teeth).
When Helical Gear Rack 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 equivalent the angle between the shafts. The most typical 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 the same the angle between the shafts. Crossed helical gears offer flexibility in design, but the contact between tooth is nearer to point get in touch with than line contact, therefore they have lower pressure capabilities than parallel shaft styles.