Helical gears tend to be the default choice in applications that are suitable for spur gears but have nonparallel shafts. Also, they are used in applications that want high speeds or high loading. And regardless of the load or speed, they generally provide smoother, quieter operation than spur gears.
Rack and pinion is useful to convert rotational movement to linear movement. A rack is directly the teeth cut into one surface area of rectangular or cylindrical rod shaped material, and a pinion is a small cylindrical gear meshing with the rack. There are several methods to categorize gears. If the relative placement of the gear shaft is used, a rack and pinion belongs to the parallel shaft type.
I have a question regarding “pressuring” the Pinion into the Rack to reduce backlash. I’ve read that the bigger the diameter of the pinion gear, the less likely it will “jam” or “stick in to the rack, but the trade off may be the gear ratio boost. Also, the 20 degree pressure rack is preferable to the 14.5 degree pressure rack because of this use. Nevertheless, I can’t find any details 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 supplied by Atlanta Drive. For the record, the electric motor plate is definitely bolted to two THK Linear rails with dual cars 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 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) are efficiently as an Atmosphere ram? I like the idea of two smaller push gas shocks that the same the total push required as a redundant back-up system. I’d rather not run 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 would be machined to the same size and shape of the gas shock/air ram work to modify the pinion placement into the rack (still using the slides)?
But the inclined angle of the teeth also causes sliding contact between your teeth, which generates axial forces and heat, decreasing performance. These axial forces play a significant function in bearing selection for helical gears. As the bearings have to withstand both radial and axial forces, helical gears require 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 offer higher speed and smoother motion, the helix position is typically limited by 45 degrees because of the production of axial forces.
The axial loads made by helical gears can be countered by using dual helical or herringbone gears. These arrangements have the looks of two helical gears with opposite hands mounted back-to-back, although in reality they are machined from the same equipment. (The difference between the two styles is that dual helical gears possess a groove in the centre, between the the teeth, whereas herringbone gears 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 necessity for thrust bearings.
Besides smoother motion, higher speed capability, and less sound, another benefit that helical gears provide more than spur gears may be the ability to be used with either parallel or non-parallel (crossed) shafts. Helical gears with parallel Helical Gear Rack 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 either the same or reverse hands. If the gears possess the same hands, the sum of the helix angles should equivalent the angle between the shafts. The most common exemplory case of this are crossed helical gears with perpendicular (i.e. 90 level) shafts. Both gears possess the same hand, and the sum of their helix angles equals 90 degrees. For configurations with opposing hands, the difference between helix angles should the same the angle between the shafts. Crossed helical gears offer flexibility in design, however the contact between tooth is nearer to point get in touch with than line contact, so they have lower power features than parallel shaft styles.