Contents
Does gear ratio have to be a whole number?
It should be fairly obvious that any gear can only have an integer number of teeth. Also for gears to mesh properly the tooth profile on all meshing gears needs to be similar if not identical.
Why spur gears are not preferred for high speed?
Spur gears generate too much noise when operated at high speeds. The wheel’s teeth experience a great amount of stress. They cannot be used for transferring energy over long distances. They are not as resilient when compared to other types of gears.
What is the minimum recommended contact ratio for spur gears?
The minimum acceptable contact ratio that recommended by spur gear manufacturers is 1.2. In general applications, contact ratios of spur gear systems around 1.5.
Which is better spur or helical gear?
Helical gears are capable of holding more load compared with spur gears, because the load is distributed across more teeth. Helical gears are more durable than spur gears because the load gets distributed across more teeth.
How do you increase contact ratio on gears?
Some ways that contact ratio is changed is through the modification of the tooth profile, i.e. addendum modification, decreasing the pressure angle for a longer line-of-action, or increase the number of teeth. Reducing backlash is one of the most effective ways to increase the contact ratio.
Which gear has the highest contact ratio?
Pairs of equal diameter gears, with equal addenda, have the highest contact ratio of any pair of gears with the same center distance.
Why are spur gear ratios not an integer number?
If the gear ratio were an integer number and a tooth was damaged, that tooth would wear on the same few opposing teeth until failure. A non integer ratio causes a damaged tooth to wear across all opposing gear teeth. This spreads the effective wear out, vice focusing it like an integer ratio would.
What’s the minimum number of teeth on a spur gear?
The pinion is made from a harder material than the wheel. A gear pair should be selected to have the highest number of teeth consistent with a suitable safety margin in strength and wear. The minimum number of teeth on a gear with a normal pressure angle of 20 desgrees is 18.
What is the efficiency of a spur gear?
A single spur gear is generally selected to have a ratio range of between 1:1 and 1:6 with a pitch line velocity up to 25 m/s. The spur gear has an operating efficiency of 98-99%.
What does it mean to have a gear ratio?
Gear Ratio’s can be difficult to understand, but with a fairly brief explanation I will attempt to make this often misunderstood equation VERY easy to grasp. Simply stated, a gear ratio is a numerical value that describes the relationship between two gears (a spur and pinion gear for our discussion).