Helical gears are often the default choice in applications that are ideal for spur gears but have nonparallel shafts. They are also used in applications that want high speeds or high loading. And whatever the load or rate, 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 designed material, 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 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 have 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 boost. 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 details on “pressuring “helical racks.
Originally, and mostly because of the weight of our gantry, we’d 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 supplied by Atlanta Drive. For the record, the engine plate is certainly bolted to two THK Linear rails with dual vehicles on each rail (yes, I know….overkill). I what after that 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 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 Air flow ram? I like the idea of two smaller force gas shocks that equivalent the total power needed as a redundant back-up system. I would rather not operate the air flow 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 adjust the pinion placement in to the rack (still using the slides)?
However the inclined angle of the teeth also causes sliding contact between the teeth, which creates axial forces and heat, decreasing performance. These axial forces play a significant role in bearing selection for helical gears. As 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 with spur gears. The axial forces vary in proportion to the magnitude of the tangent of the helix angle. Although bigger helix angles offer higher swiftness and Helical Gear Rack 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 the two styles is that double helical gears possess a groove in the middle, between the the teeth, whereas herringbone gears do not.) This arrangement cancels out the axial forces on each set of teeth, so larger helix angles may 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 more than 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 reverse hands (i.e. right-handed teeth versus. left-handed teeth).
When crossed helical gears are used, they could be of possibly the same or opposite hands. If the gears have 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 level) 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 the teeth is nearer to point get in touch with than line contact, so they have lower force capabilities than parallel shaft styles.