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planetary gear design (planet shaft torque)
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Posted by: isha_shukre isha_shukre, isha_shukre

11/08/2006, 03:26:01

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Hello

I was trying to do the bearing calculation for planetary gear

box (carrier, 3 planets, ring and sun). For computing the torqe in planet gear shaft do

I need to consider the planet RPM or (Planet + carrier).

Say Sun has 22 teeth, planet has 27 teeth, Ring has 77 teeth,normal module is 1, pressure angle of 20 deg. & helix angle is 0 deg. RPM of sun is 1200 and power to be transmitted is 500 Watts

Then by doing simple calculation we can find carrier will have 266.67 RPM. But for

planet I think it should be 493.83 RPM but I find in some refrence its given

(493.83+266.67)=760.5 RPM.

For computing torque in planet shaft T=P/w, do we need to use w=493.83 or 760.5. Because using the value of 760.5 will give significant reduction in torque compared to 493.83.

Another thing I tried to compute radial and tangetial force on the planet gear

corresponding to the two possible planet torques torques mentioned above. If I take the

planet speed of 493.83 rpm the planet torque comes to be 3.22 Nm and corresponding

tangential force = 120 N and radial force = 43N, which is same on the sun gear

considering contribution due to individual planet.

Can anybody please help me in understanding for computing the torque inplanet shaft do

I need to consider RPM of 493.83 or 760.5?

Thanks in advance
ISHA








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Re: planetary gear design (planet shaft torque) Smile
Re: planetary gear design (planet shaft torque) -- isha_shukre Post Reply Top of thread Forum
Posted by: cakub

11/15/2006, 17:11:21

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I could give you right formulae if I knew more info. Such planetary rearbox can operate in three modes. 1)Sun gear is stationary=doesn't rotate, 2)Carrier is stationary=doesn't roatate, or 3)Ring is stationary=doesn't rotate.
Which one is youyr case? What is input and what is output?







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Re: Re: planetary gear design (planet shaft torque)
Re: Re: planetary gear design (planet shaft torque) -- cakub Post Reply Top of thread Forum
Posted by: isha_shukre

11/23/2006, 00:13:55

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Hello Everyone

In my case ring is stationary.

But I have a more basic question. In simple planetary gear system where
-->carrier is an input shaft
-->sun is output shaft
-->ring is stationary (internal gera)
-->and planet is rotating on bearing OD and bearing ID is stationary. Bearing ID is mounted on pins which are pressfit in carrier.

In this particular configuration will planet shaft carry any torque? Planet is in between ring and sun and is free to rotate about its own axis.
I think plant is just a means of transfering tangential load but plant shaft itself wont carry any torque.

Can anyone please clarify this doubt?

Thanks
ISHA
Student, India








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Re: planetary gear design (planet shaft torque)
Re: planetary gear design (planet shaft torque) -- isha_shukre Post Reply Top of thread Forum
Posted by: zekeman

11/10/2006, 09:31:21

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how do you get 77 teeth in ring?
I get 22+2*27=76. Also your rpms should be:
sun 1200
planet 1849
carrier 480







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