topic Re: Epicyclic Gear Verification/Measurement Failure, Needing Help Please? in 3D Part & Assembly Design

Epicyclic Gear Verification/Measurement Failure, Needing Help Please?

cadkins — Sun, 13 Dec 2020 10:08:42 GMT

Hi,I'm doing a standard planetary gear system analysis (pictured), however when verifying the results I find my planetary gear speed is coming up as 378 deg/sec when by hand calculations it should be 270 deg/sec. However what I did notice while writing this is that the given answer

Re: Epicyclic Gear Verification/Measurement Failure, Needing Help Please?

TomD.inPDX — Sun, 08 Mar 2015 19:02:57 GMT

I think you answered your own question.

The velocity of any of the 3 axes, (stationary, input and output) is measures at the sun gear's axis.

What you are seeing is the planetary axis which is over-driven in this arrangement.

Here is a good formula and calculator site for this.

http://www.torcbrain.de/uebersetzungsrechner-planetengetriebe/?lang=en

Re: Epicyclic Gear Verification/Measurement Failure, Needing Help Please?

TomD.inPDX — Sun, 08 Mar 2015 21:13:37 GMT

I come up with 378 as well on the hand calculation.

Input to planet:ratio 3:2

Back rotation on the ring: 108 = 0.3*360

360 input to planet = 540 (360*1.5) - if stationary

cycles along the input is 0.7 (1 rotation - 0.3 back rotation)

540*.7=378

I'm no math wiz, but if I input this in my planetary system, I'm pretty sure that is what I get.

A quick test is to put a servo motor to each axis and confirm visually.

Re: Epicyclic Gear Verification/Measurement Failure, Needing Help Please?

cadkins — Mon, 09 Mar 2015 11:22:54 GMT

Thank you.

See the 0.3 you have, is that from the website you linked in the previous message where the ratio= 1 + Nring/Nsun = 1 + 42/18 = 3.333

-> so 360/3.333 = 108

or is it to do with 12/42?

Re: Epicyclic Gear Verification/Measurement Failure, Needing Help Please?

TomD.inPDX — Mon, 09 Mar 2015 16:06:07 GMT

It was from the inverse of the 3.3333... 1/3.333333...Essentially the 108 was also given in the calculator. So the 108 (carrier) divided by 360 (sun) gave me the .3.