Calcualtion of Gearbox Output Speed and Torque Conversation

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tigerdon Commentator Join Date: Jun 2011 Posts: 79	Calcualtion of Gearbox Output Speed and Torque Conversation 09/28/2012 6:21 AM
	Electric Motor with 980 rpm and 29.82kg.m torque output connected directly with the input shaft of the toothed gearbox hacing ratio of 166.7:1 What will be the output speed and torque at gearbox output shaft??? How to calculate the same? plz help
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Calcualtion of Gearbox output Speed and Torque Conversation 09/28/2012 6:48 AM
	Torque is provided by the load. All the above figures indicate is that the motor is capable of supplying ≈30kg.m before it stalls and possibly burns out. Is the gearbox a step-up or a step-down? Output rpms are 980*166.7 or 980/166.7 as appropriate. To what is it connected, and how does this load vary its torque requirement with rotation speed? Once these questions have answers, one might determine whether the motor is correctly sized or not for the application. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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tigerdon Commentator Join Date: Jun 2011 Posts: 79	#2 In reply to #1 Re: Calcualtion of Gearbox output Speed and Torque Conversation 09/28/2012 7:08 AM
	- Gearbox are of setp-down type. - Gearbox output shaft connected to rope drum of 652 PCD. x 3600 LG. and the rope end connected with the huck for lifting the 66000kg weight. This is the EOT crane having a capacity of 66T.
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Joshi Guru Join Date: Oct 2007 Location: India Posts: 1246 Good Answers: 34	#3 Re: Calculation of Gearbox Output Speed and Torque Conversation 09/28/2012 8:53 AM
	You need to do lot of reading HERE
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K_Fry Guru Join Date: Feb 2011 Location: Atlanta, GA Posts: 1053 Good Answers: 110	#4 Re: Calcualtion of Gearbox Output Speed and Torque Conversation 09/28/2012 10:12 AM
	The basic principal is that torque is multiplied by the gear ratio and speed is divided by the gear ratio. (In basic principal, power is equal at input and output.) However, in a gearbox with such a high ratio, efficiency should be considered. Nevertheless, if three straight-cut gear meshes are used, the efficiency will be about 90%. So the cable pull with the motor running at full load could be as high as 29.82 kg x 167 / .326 x .9 = 13748 kg. (.326 is the drum radius, I believe.) This is a long way short of 66T. Perhaps there is a gear reduction which you are missing? With no load, does the drum rotate at about 5.8 rpm? Actual motor torque will depend upon the load applied. __________________ Think big. Drive small.
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K_Fry Guru Join Date: Feb 2011 Location: Atlanta, GA Posts: 1053 Good Answers: 110	#5 Re: Calcualtion of Gearbox Output Speed and Torque Conversation 09/28/2012 10:43 AM
	If this relates to this post, then you can see that the motor would need to supply about 5 times its nameplate torque to lift 66,000 kg. Most motors will not tolerate this much overload for long (i.e seconds OK, minutes NOT OK). Adding an additional gear reduction of 5:1 would enable this motor to lift the load, but the lifting speed would be incredibly slow. However, if all this is true -- the apparent overload you are reporting, the drastically undersized motor, etc., then it sounds like the crane was not engineered. So you would not want to add a gear reduction, because the structure could fail, or the cable could part, the gearbox could fail, etc etc etc etc etc. I'd find a new crane vendor. __________________ Think big. Drive small.
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fixitorelse Guru Join Date: Aug 2010 Posts: 687 Good Answers: 21	#6 Re: Calcualtion of Gearbox Output Speed and Torque Conversation 10/09/2012 12:10 AM
	Pick up a copy of Machinery's Hand Book. This is a vary valuable tool for any engineer type. It can help you find what you seek.
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fixitorelse (1); Joshi (1); K_Fry (2); PWSlack (1); tigerdon (1)

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