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 whatever the load or swiftness, they generally provide smoother, quieter procedure than spur gears.
Rack and pinion is utilized to convert rotational motion to linear motion. A rack is directly teeth cut into one surface area of rectangular or cylindrical rod designed material, and a pinion is usually a small cylindrical equipment meshing with the rack. There are plenty of methods 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 regarding “pressuring” the Pinion into the Rack to lessen backlash. I’ve read that the larger the diameter of the pinion equipment, the less likely it will “jam” or “stick in to the rack, but the trade off is the gear ratio boost. Also, the 20 degree pressure rack is better than the 14.5 level pressure rack for this use. Nevertheless, I can’t find any info on “pressuring “helical racks.
Originally, and Helical Gear Rack mostly due to the weight of our gantry, we had 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 since supplied by Atlanta Drive. For the record, the engine plate is usually bolted to two THK Linear rails with dual cars on each rail (yes, I understand….overkill). I what after that planning on pushing through to the motor plate with either an Air ram or a gas shock.
Do / should / can we still “pressure drive” the pinion up 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 idea of two smaller pressure gas shocks that equal the total push needed as a redundant back-up system. I’d rather not run the air flow lines, and pressure regulators.
If the idea 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 produces axial forces and heat, decreasing efficiency. These axial forces play a significant function in bearing selection for helical gears. Because the bearings have to endure both radial and axial forces, helical gears need thrust or roller bearings, which are typically larger (and more costly) than 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 bigger helix angles provide 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 dual helical or herringbone gears. These arrangements have the appearance of two helical gears with reverse hands mounted back-to-back again, although the truth is they are machined from the same equipment. (The difference between the two designs is that dual helical gears possess a groove in the middle, between the the teeth, whereas herringbone gears do not.) This set up cancels out the axial forces on each group of teeth, so larger helix angles may be used. It also eliminates the necessity for thrust bearings.
Besides smoother motion, higher speed ability, and less noise, another advantage that helical gears provide over spur gears may be the ability to be used with either parallel or non-parallel (crossed) shafts. Helical gears with parallel shafts require the same helix position, but reverse hands (i.e. right-handed teeth versus. left-handed teeth).
When crossed helical gears are used, they can be of either the same or opposing hands. If the gears possess the same hands, the sum of the helix angles should the same the angle between your shafts. The most common example 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 reverse 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 contact than line contact, therefore they have lower pressure capabilities than parallel shaft styles.