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 planetary gear design (planet shaft torque) Post Reply Forum
 Posted by: isha_shukre ® isha_shukre, isha_shukre 11/08/2006, 03:26:01 Author Profile eMail author Edit HelloI 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 WattsThen 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

 Replies to this message

 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?

 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 EveryoneIn 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

 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