Parkinson’s gear tester- detailed explanation |The Mechanical post

Gears are the heart of almost all mechanical machines. There are different types of gears being used for various purposes all over the globe.    

Gears are complex to manufacture and during the manufacturing process, gears do develop some errors. A single defective gear can cause problems in the machine.  

Therefore, it is very important that gears must be tested properly to avoid any errors. Hence, in order to test the gears, the Parkinson’s gear tester is employed.  

Download your copy of the PDF on Parkinson’s gear tester at the end of the article.

What is Parkinson’s gear tester?

Parkinson’s gear tester is a testing device used to measure the variation in the center distance of two gears in mesh. It consists of a master gear and a gear to be tested. Both the gears are rotated, as the gears are rotated the center distance would vary.

If the variation is within acceptable limits, it is accepted or if the variation goes beyond the acceptable limit, the gear is rejected.   The variation between the gears indicates that there is an error in the sample gear.

There may be an error in the tooth profile or pitch circle diameter or due to other reasons.  

What is meant by tooth profile? What is pitch circle diameter? all these question answered along with different gear terms everything explained in this article on Gear terminology.

  Let’s check out the construction and working of the Parkinson’s gear tester.

Construction of parkinson gear tester:

1. The Parkinson’s gear tester consists of a solid base with 2 carriages one is fixed and the other is movable.
2. These two carriages are connected together via a spring.
3. Upon these two carriages, there are 2 spindles.
4. Upon the fixed carriage spindle, the master gear is fitted.
5. Upon the movable carriage spindle, the gear to be tested would be placed.
6. These two gears are such placed that they are in mesh with each other.( as shown in the figure).
7. Adial indicator’s plunger is in contact with the carriage. ( as show in the figure).

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Working of parkinson gear tester:

1. The master gear is rotated slowly thus, the gear to be tested also rotates as both are in mesh.
2. If any errors are present in the sample gear, it would cause the gear to move away from the center line of the spindle.
3. When this gear moves, the carriage on which it is mounted also moves with it.
4. Now the plunger of the dial gauge indicator which is in contact with the carriage would get pressed and will show deflection.
5. This deflection can be measured to check whether the gear must be accepted or not.

Nowadays there are electronic sensors are used to detect the motion of the carriage instead of the dial indicator.
These sensors record the motion and give an output in the form of a graph.
The circular graph shows the gear is satisfactory whereas the irregular graph shows that the gear has errors.   

The circular the graph is, the less is the error it has. As errors increase, the shape of the graph changes to irregular shapes.

Limitations of the Parkinson’s master gear :

• The base of the Parkinson’s gear tester must be kept firm, or else this could result in incorrect readings.
• Composite errors only can be found out. ie. individual errors cannot be pointed out.
• The results of the test depend mainly on the master gear, it is very important that the gear must be highly accurate.
• For different types of gears, different master gears are required.

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Till then keep learning!