Gear mesh frequencies

[8ptbuck]

This is my first question and I apologize if I'm going about this the wrong way. My problem is identifying gear mesh frequencies in a planatary drive. Nothing lines up in my spectrum. Sun Pinion 18t mating with 3 planatary gears with 28t mating with a 75 tooth ring gear. What are the frequencies assumming the sun pinion is rotating at 98 rpm. I am not able to open the drive up to get an actual count. All counts were given by the manufacturer.
please break this down as simple as possible so I may understand what I'm doing wrong or is the count wrong.

Thanks,
8ptbuck

 

[Hullmodaltest]

I believe you should have the following frequencies.

Sun rotational 1.633Hz
Output shaft speed 0.316Hz
Gear tooth contact 29.399Hz
Planet Gear rotational 1.0499Hz

 

[ronfrend]

I realise I have come late to this topic but what is the arrangement of the planetary gearing? It is possible to have the annulus locked or to have the planets locked. I have even worked on one box where the annulus actually gave the output.

If you give the arrangment I will send you the formulas for doing the calcs.

Regards -
Ron Frend
tel: 011 44 1253 400541
ron.frend@predicon.net

http://www.predicon.net

 

[jta2571]

Can anyone tell me what are the possible source of 3XRPM? We have this, belt driven over-hang dust collector fan running at 3200 RPM (pulleys are modified to run at high speed)driven by 1800 RPM motor. The torsion shaft bearings are newly replaced. But before replacement, the fan is running smoothly, vibration level are below the limits. And after bearing replacement, there the problem pop up. Radial velocity vibration reading reveals on spectrum that the source of high vibration is dominated by 3XRPM. Also, the vertical vibration is greater than horizontal vibration. Tried to balance it, to see if will do. But, it only lowers the 1XRPM which is usually the imbalance problem and still the 3XRPM is the dominant.
HELP!!!

 

[electricpete]

jta - intersting problem. Why don't you post it as a new thread?

 

[FredGarvin]

I don't suppose it'd be this easy...

The fan wouldn't happen to have 3 blades, would it?

 

[Buhrmann]

Your question on the mesh frequencies are very interesting. I calculate the same frequencies as hullmodaltest. Do your calculations correlate with this?

Your gearbox seem to be planet factoring, where the ringear 75t, and the sungear 18t are divisible with the number of planets 3. In theory this should give a cyclic beat, and slightly higher noise levels, as the same type of mesh occurs on the 3 planets mesh simultaneously with the ring and sungears. (Assuming some slight errors in the teeth)

The beat on the ringear should be 0.948Hz (the smaller one)
And a beat on the sungear of about 4.9Hz which should be bigger since it is coherent with the ringear beat

You have also used an even number of teeth in the planet gears, which has about the same effect.

The most important question to as is whether your gears are floated to move radially. This is extremely important to cancel out manufacting errors, and provide much better load sharing between the planets.

Regards....

 

[VibEngr]

I have tested several planetary gear systems and have found the following book to be very helpful.

The Gear Analysis Handbook
By James I. Taylor

 

[8ptbuck]

Thanks for the help.