# Spur gear transmission

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1. Nov 24, 2016

### maths85

Hello.

I need to calculate spur gear transmissions.
I need a bit of guidance for the first steps.
The data is the next:
n= 1000 rev/min
Mt torque= 28.65 Nm
i transmission ratio= 4
P load in the shaft= 3kW

I am a bit lost to star selecting the material (depending the load and work conditions).
The strees of the transmissions and the module of the gears.

I understand that I need to check the material in a catalogue of materials. But honestly I am lost trying to select the right one and fail at the beginning of my calculation of gears.

Later on when I have to calculate the module, which date should I set as I random number, the number of teeth then I will be able to calculate the module later.

Thank you.

2. Nov 25, 2016

### Baluncore

3. Nov 25, 2016

### maths85

Thank you Baluncore. Do you know where could I find information of the material selection process ?

4. Nov 26, 2016

### Baluncore

Material selection will be decided by things like corrosion, lubrication and loads. You must be able to economically cut, finish, and then if possible, harden a gear.
The gears, shafts, bearings and enclosure must be compatible materials that will not encourage electrochemical corrosion.

Start your calculations with a minimum of 19 teeth on the pinion and 75 on the bull gear which gives a ratio of 3.947. Those tooth counts have no common factors and so will give a “hunting tooth” that wears evenly since every tooth on the pinion will meet every tooth on the bull gear.
20 : 81 = 4.05 is also possible since 20=2*2*5 and 81=3*3*3*3 have no common factors.