How Do You Determine the Ratio Between Two Sets of Gears
When start diving into the gears' world, you may run across several terms: gear ratio and contact ratio. You do not have to know how to calculate gear ratio to cull the right one, as yous can observe it in the product description, simply understanding how information technology works will make your choice more than… calculated. Employ this article as your personal flashlight and y'all won't get lost.
To make it simple not only in word only besides visually, we tried to explain the whole stuff using Lego. Then, let'due south start, or every bit scuba divers say, let'southward get wet!
The Big Gears Family
Start there was the Wheel. And so came a Gear. Gears come up into play for i of the following reasons:
- to reverse the direction of rotation
- to keep the rotation synchronized
- to increase or decrease the speed of rotation
- to movement rotational move to a dissimilar axis
Humanity has known the gear systems (known as 'trains') since at least four ages BC in China, so the first invention may even be much older. During these 2,000 years, they developed and divided into numerous dynasties. Let's mention some of the near powerful representatives. Three big railroad train groups be based on the orientation of the gear axes:
I. Parallel Axes Trains: Where the teeth are parallel to the axis
one. Spur
When someone hears the word 'gear', in most cases, a elementary spur gear comes to their mind.
Spur type is applied in a wide range of industries and it is the easiest to find on the marketplace in all the sizes.
2. Helical
A cylindrical gear with helicoid teeth (they are at an bending to the axis of rotation of the gear) can handle more load force than spur i, but they are less efficient. During the move, there are sliding contacts between ii helical gears, which produce axial thrust of gear shafts and increased rut.
three. Rack and Pinion
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This is a linear gear (the rack) comprised with a spur gear (the pinion). Rotary driving of the pinion causes the linear movement of the rack. Driving the rack causes the pinion to rotate. This system is the simplest tool to convert rotary motion into linear motion and back. You can read more than on linear drives and its advantages here.
4. Internal Gears
This is another i with cylindrical shape, merely the teeth here are within the band. As a rule of thumb, these gears are found in planetary mechanisms. Thanks to this design, the vibrations and losses in planetary drives are minor. The rotational stability improves the reliability and repeatability of the movement. Planetary drives offer greater efficiency and accuracy than other systems.
II. Intersecting Axes Trains: Where the gear axis cross at a point
i. Bevel
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In a bevel gear, the shaft axes intersect. Normally, the angle between the shafts is 90 degrees, only the train exists with other angles too (except for 0 and 180 degrees). This angle flexibility lets the states widely apply the bevel organisation to alter the force direction. For example, from horizontal to vertical. According to the shape and the number of teeth, at that place are miter, spiral, and direct bevel gears.
III. Nonparallel Axes Systems:
1. Worm and Worm Wheels
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Worm train consists of a normal spur gear (worm wheel) and a gear with ane molar (the worm), but this i tooth is similar a screw thread. The movement of the wheel and the gear is a mixture of sliding and rolling actions. Sliding moves cause friction and heat that subtract the efficiency of the train up to 50%. At the same time, this type of meshing ensures very tranquility functioning, which makes worm suitable for usage in environments where noise should be minimized. Even if the efficiency is relatively low, worm trains provide very high reduction ratios.
two. Screw
The spiral railroad train is a pair of crossed helical gears that transmit movement and power between perpendicular but non-intersecting shafts. They practise non have a standard rolling motility during their interaction just a screw motion (that'south why screw).
Gear Ratio
Every mentioned train type has its strengths or weaknesses, only the master parameter of meshing gears still is the gear ratio. Since each part in the train has a unlike number of teeth, each of the gears rotates at a unlike speed. Gear ratio shows this departure.
Knowing a ratio in a robotic project is crucial for:
- Finding the rotational speed of drive gear.
- Reaching speed and torque balance. If the gear ratio is 1:i, the amount of torque is the same, and the speed is the same. With the ratio 1:iv, for example, you'll get less torque but more speed. With the ratio 4:1, you lot would cutting the speed but heave the torque.
- Optimal servo motor sizing. If the motor inertia is as well high relative to the load inertia, the motor is bigger, meaning that it was more than expensive than it'due south necessary to produce information technology, and the motor uses more than energy than needed for the awarding.
- Minimizing errors and increasing accuracy. An ideal gear ratio is the lowest inertia that can produce maximum acceleration without making the system unstable, overheated, or inaccurate.
How to Calculate Gear Ratio?
Permit's first with the simplest gear train with only two meshing gears. The starting time gear fastened to the motor shaft is chosen a "drive". The second attached to the load shaft gear is the "driven" one.
To summate the gear ratio:
- Count the number of teeth on each function. In our example, the smaller drive has 21 teeth and the driven has 28 teeth. Likewise, when we speak about spur type, the 1 with more than teeth is called the "gear" and the one with the fewer teeth is the "pinion".
- Divide the number of driven gear teeth past the number of drive gear teeth. In our example, it'due south 28/21 or 4 : iii. This gear ratio shows that the smaller commuter gear must plow 1,3 times to become the larger driven gear to brand one complete turn.
Now, stay calm and brace yourself: A high numerical gear ratio is called a "low gear". A low numerical gear ratio is a "high gear". Low gears cause fast dispatch and are suitable for smaller engines. High cause meliorate cruising and college top speed so they are applicable for more powerful engines.
But what if the system incorporates more than two elements? The intermediate gears or so-chosen "idlers'' are used to continue or to change the direction of rotation.
You can utilize the ratio formula to each pair of wheels, but you don't really need to do that. No thing how many idlers there are in the train, the final gear ratio is the ratio between the driver and the driven bike. For piece of cake calculation, you lot tin use this Lego Online ratio calculator.
Contact Ratio
Another of import parameter when choosing gears is the contact ratio. It represents the number of teeth meshing at the same time. If multiple teeth are in contact, the load is shared and the operational life of the mechanism is improved.
Knowing a contact ratio in a robotic project is crucial for:
- Torque: more than teeth in contact = the machinery transmits and withstands more torque.
- Stiffness: higher contact ratio = fewer stiffness variations. This ways less deflection of the teeth and manual errors.
- Accuracy: higher contact ratio = good accurateness, fewer mistakes, and a uniform manner of organization performance.
- Dissonance level: higher contact ratio = increased stiffness = reduced noise.
How to Calculate Contact Ratio?
Formulas for calculating the contact ratio volition depend on the gear type. Merely when considering all types in general, contact ratio consists of two components:
Radial contact ratio, εα + Overlap contact ratio, εβ (applied only for helical or spiral types).
More on calculating gear contact ratio you can read here and hither.
So, hopefully, y'all now know a flake more than well-nigh gears, information technology'due south differences and parameters, and tin easily dive deeper into the Big Ocean called "Motion Command''.
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