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I want to mount a small engine on a shaft of a large engine and rotate them both in the same direction, will the RPMs be a sum of the their RPMs or will the resulting number be a multiplication?

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  • $\begingroup$ Probably either addition, or failure. Can you include a diagram? Are you attaching the body of the small engine to the output shaft of the large engine? Does it mind being spun around? $\endgroup$ – Jonathan R Swift Feb 8 '18 at 17:42
  • $\begingroup$ yeah thats the idea, to connect the output shaft of a large dc brushless engine to a custom mount which will hold tiny brushless engine and shaft of this small engine will rotate in the same direction.. $\endgroup$ – user2820052 Feb 8 '18 at 17:53
  • $\begingroup$ In which case, addition. How are you planning to get a reliable electrical connection to the smaller motor? And, what is the design constraint that means you need this setup? $\endgroup$ – Jonathan R Swift Feb 8 '18 at 17:55
  • $\begingroup$ I am trying to achieve extremely high rpms and I am hoping that the answer would be multiplication which would warrant further investigation as I believe this might be simpler than gears based solution for the angular velocity values that I am trying to achieve. The power would be transmitted either wirelesly or via brushed connection whichever would be easier at this stage. $\endgroup$ – user2820052 Feb 8 '18 at 18:00
  • $\begingroup$ It's definitely not multiplication! Imagine you had a motor spinning in your hand at 1000rpm, and you decided to turn it over once every 30 seconds (2rpm). Would the output shaft be spinning at 2000rpm, or 1002rpm? $\endgroup$ – Jonathan R Swift Feb 8 '18 at 18:04
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It's definitely not multiplication! Imagine you had a motor spinning in your hand at 1000rpm, and you decided to turn it over once every 30 seconds (2rpm). Would the output shaft be spinning at 2000rpm, or 1002rpm?

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