
planetary gear design (planet shaft torque)  
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Posted by: isha_shukre ^{®} isha_shukre, isha_shukre 11/08/2006, 03:26:01 Author Profile eMail author Edit 
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

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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: cakub ^{®} 11/15/2006, 17:11:21 Author Profile eMail author Edit 
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 Author Profile eMail author Edit 
Hello Everyone In my case ring is stationary. But I have a more basic question. In simple planetary gear system where
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.
Can anyone please clarify this doubt? Thanks

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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 Author Profile eMail author Edit 
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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