Could anyone help me out here. I dont have a update program that will show tooth engagement but I know I have 2 different scenarios here.

1 ) board machine A - 47 tooth pinion / 68 tooth gear( LCF is 1 ) which should show 47 tooth pinion gear #1 tooth meshes with every tooth on 68 tooth gear before coming back in contact with #1 tooth on gear. Creating a 1 wear pattern.

2 ) board machine B - 44 tooth pinion / 76 tooth gear ( LCF is 2 ) but from the program I have shows this setup creates 4 wear patterns, but each pattern is the same. with #1 tooth on pinion meshing with the same order of teeth on the gear, it shows this tooth rotation order 4 times, calling it wear pattern 1 thru wear pattern 4 and then ends.



Thanks

Mike

This message has been edited. Last edited by: MikeH,

Mike,

44 and 76 have a common factor of 4.

Danny

Thanks Danny
I am still looking at the prime numbers common to each, instead of the largest common factor.

So every each tooth will contact every 4th tooth on the other gear.. this is why we have 1/4x gearmesh as gears wear?

What do you think would happen, if the gears were taking out, reinstalled in same location but not timed the same. Would you expect to see higher gearmesh vibration levels as new wear patterns are being produced?

Would you suggest to your customer, if a gear train in a dryer section has a LCF of 2 or greater, to always time gears before removing so you could install in same manner not disturbing wear patterns?

Thanks Danny

Mike

Mike,

1. Yes.
2. Yes.
3. Yes.

If you would like I can post some example spectra. I only have the after spectra because I was called in after a rebuild because of noisy gears.

Danny

Thanks ! and Yes I would appreciate seeing your example spectra.

Same scenario we are dealing with.. rebuild, new hood and new dryer cans in 1st section. Old Gears and Bearings taken out, laid on floor in holding area, reinstalled 10 days later.!!!

After rebuild noisey gears.

Did customer want a date for how long it would take to wear in?

Thanks again
Mike

The following is a method to compute these assembly phases without factoring the number of teeth into primes.


One does not need to know the primes to find the greatest common denominator, gcd. This comes from Euclid’s Elements with a modern take.

Take the smaller number and divide into the larger, keep the remainder, R.

44 into 76 = 1 with R = 32

Then

32 into 44 = 1 with R = 12

Repeat,

12 into 32 = 2 with R = 8

8 into 12 = 1 with R = 4

4 into 8 = 2 with R = 0 when one gets 0 remainder means you have found the GCD

4 is the gcd of 44 and 76.

This is very easy to program using a modulo function. It’s not too difficult to do by hand. As a note, the Euclidean Algorithm as this is called works for polynomials as well to find the gcd of two polynomials over the ring of integers, etc.

Thanks to Danny and Bill for the valued info.

I wonder why vibration software/hardware companies do not include a gear tooth engagement program in the bundled software they provide.
I would think this would be a good extra to throw in where one could easily show teeth engagement and how gears with LCF higher than 1 will wear more rapid.

Thanks again

Mike

Mike,

I looked back and the one I had in mind had several other factors that make it not such a good example after all. In that case there were two sets of gearing and they both had a high common denominator. One was matched and the other was not. The one that was not matched was the helical high-speed gear set. I'll review the data some more before I post, but as I remember it, the gcd on the high speed gear set made it so that assembly phase matched motor speed. This was complicated by a bent agitator shaft with a rub at output speed that modulated what was either motor speed or assembly phase. To make it even more fun, I think that also matched bpfo of one of the bearings.

I'll try to clear things up when I can post detailed info.

CSI does include gmf calculations and automatically inserts them when you use the wizard to build the database and input all the data there. (There are tricks to doing this that I will share if you need.)

I'll post the data anyway (have to do it from another computer).

Here's your frequencies with a input speed of 1785 RPM.

44x76.doc (28 Kb, 57 downloads)

A good primer for gear frequencies is in
http://www.foxlang.com/PDF%20files/May99_Geometry101.pdf
Gerard

VCI has or had a good gear calculator that was free for 30 uses.

http://www.vibcons.com/gears.shtml