Geartrain Doubt.... How to select the number of teeth given other specifications

[ANSAN]

TL;DR Summary

Doubt in Gear...!!

Hai all,

I need to get to know how a Gear pair teeth numbers are selected.

Details : Power = 300KW, N1=2950, N2=816.5 , i=3.62, Helix angle = 35deg, Pressure angle = 20deg.

I need to know how to select a Gear pair teeth for this input?

Knowing a gear set should have common Module to transmit velocity.

Is there any method to select Gear teeth w.r.t power to be transmitted?

Thanks.

 

[Lnewqban]

Welcome ANSAN!

You will need to find some flexibility for that transmission ratio of N2/N1, since matching numbers of teeth is going to prove difficult.
You also need to determine the diameters of your shafts, the material of your gears, any dimensional restrictions of your machine shop, and the physical available space for your lubrication casing.
Then, you will need to follow design recommendations of a good Machinery's Handbook for machine shop.

 

[berkeman]

Summary:: Doubt in Gear...!

I need to know how to select a Gear pair teeth for this input?

Hi @ANSAN -- Is this question for schoolwork? Or for a DIY project maybe?

 

[Baluncore]

Ratio 2950 / 816.5 = 3.613 so it will requires only a single gear pair.
How accurate must the ratio be?
How long must the gearbox last?

Too few teeth = undercut = weaker teeth. Too many teeth = a big heavy gearbox.
Calculate tooth ratios that are close.
01 : 3.61298224127373 ratio required
pinion : bull gear teeth
15 : 54.19473361910594
16 : 57.80771586037967
17 : 61.42069810165339
18 : 65.03368034292713 ≈ 2*3*3 : 5*13 close ratio, no common factors = hunting tooth.
19 : 68.64666258420085
20 : 72.25964482547458
21 : 75.87262706674831
22 : 79.48560930802204
23 : 83.09859154929578 ≈ 23 : 83 primes
24 : 86.7115737905695
25 : 90.32455603184323
26 : 93.93753827311696
27 : 97.55052051439068
28 : 101.1635027556644
29 : 104.7764849969382
30 : 108.3894672382119
31 : 112.0024494794856 ≈ prime : 7 * 2^n, but big.
32 : 115.6154317207593

Next determine the torque from kW and RPM.
Then strength needed of one tooth.
Then module and width of gear wheel.
N1=2950, N2=816.5 are both positive but a gear pair will reverse so one will become negative.

 

[ANSAN]

Welcome ANSAN!

You will need to find some flexibility for that transmission ratio of N2/N1, since matching numbers of teeth is going to prove difficult.
You also need to determine the diameters of your shafts, the material of your gears, any dimensional restrictions of your machine shop, and the physical available space for your lubrication casing.
Then, you will need to follow design recommendations of a good Machinery's Handbook for machine shop.

Thanks for your feedback and Guidance, more helpful.

 

[ANSAN]

Hi @ANSAN -- Is this question for schoolwork? Or for a DIY project maybe?

Thanks for your feedback, just a DIY.

 

[ANSAN]

Ratio 2950 / 816.5 = 3.613 so it will requires only a single gear pair.
How accurate must the ratio be?
How long must the gearbox last?

Too few teeth = undercut = weaker teeth. Too many teeth = a big heavy gearbox.
Calculate tooth ratios that are close.
01 : 3.61298224127373 ratio required
pinion : bull gear teeth
15 : 54.19473361910594
16 : 57.80771586037967
17 : 61.42069810165339
18 : 65.03368034292713 ≈ 2*3*3 : 5*13 close ratio, no common factors = hunting tooth.
19 : 68.64666258420085
20 : 72.25964482547458
21 : 75.87262706674831
22 : 79.48560930802204
23 : 83.09859154929578 ≈ 23 : 83 primes
24 : 86.7115737905695
25 : 90.32455603184323
26 : 93.93753827311696
27 : 97.55052051439068
28 : 101.1635027556644
29 : 104.7764849969382
30 : 108.3894672382119
31 : 112.0024494794856 ≈ prime : 7 * 2^n, but big.
32 : 115.6154317207593

Next determine the torque from kW and RPM.
Then strength needed of one tooth.
Then module and width of gear wheel.
N1=2950, N2=816.5 are both positive but a gear pair will reverse so one will become negative.

Thanks a lot for your fine reply.
Since iam learning the art of Gearbox, need some guidance in your feedback,

1. How you choose these - 3 Gear teeth pair?
18 : 65.03368034292713 ≈ 2*3*3 : 5*13 close ratio, no common factors = hunting tooth.
since its 18:65, no even numbers, so no hunting gear possible i think.
23 : 83.09859154929578 ≈ 23 : 83 primes
31 : 112.0024494794856 ≈ prime : 7 * 2^n, but big.

Pl. guide for selecting proper Gear teeth pair.
Thanks in advance.

 

[Baluncore]

The 18:65 ratio is close to what you need. It is a two gear pair.
18 teeth = 2*3*3;
65 teeth = 5*13;
There are no prime factor shared by the two gears.

When two meshed gear wheels do not share a common factor it is said to have a “hunting tooth”. Each and every tooth on one gear hunts out and contacts every tooth on the other gear. That means the teeth wear evenly and there is less noise. Take a look at the tooth counts and ratios found in automobile final drive differential gears.

To obtain an integer gear ratio, and still have a hunting tooth, you can use an idler gear with no common factor, between the two gears. Alternatively, a chain or a stepped belt with the number of links having no common factor with either of the two sprockets.

If the tooth count is high, the individual teeth do not contact very often, but they must all be just as strong. So minimise the number of teeth to make the gears smaller, but avoid undercutting.

31:112 gives a very close ratio, but it is a big and heavy solution.
You can factorise the numbers.