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RRS_Dave

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Reply with quote  #1 
can you tell me the most likely number of teeth on a double reduction Lufkin gearset, with the HS ratio being 2.453:1 and the low speed being 3.75:1. Overall ratio is 9.1981

I've got some pics they sent me, but they are such low quality and skewed that I can't with any degree of certainty count a quarter of the teeth and multiply.

I think I see the gear mesh in the spectra, and I know input and output speeds, but the division doesn't come up with what I think is feasible for this size box.

Dave
John from PA

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Reply with quote  #2 
Dave,

Attached is the the potential tooth combinations for the ratio you've provided.  I've sorted the combination for each gear set by ratio to help you find the best possibility.  

Some precautions: Gear box nameplate ratio for run of the mill gearboxes can vary by as much as ±5% (depending on drive type).  Some background information...in 1959, AGMA published information sheet #271.02, "Ratios for Helical and Herringbone Gear Speed Reducers" which listed "standard" ratios based on a (1.5)^0.5 progression. It included a table of "Gear Ratio Tolerances": ± 3, 4, 4 and 4% for single reduction, double, triple and quadruple reduction, respectively.  AGMA 420.04 (enclosed drive standard) in 1975 repeated the ratios, but modified the tolerances to 3, 4, 4, and 5%.  Current enclosed drive standards (e.g., 6010 or 6009) have a clause on preferred ratios, but any mention of tolerances has been deleted. The standards only say that ratio is to be indicated on the nameplate, but does not stipulate nominal or exact.  Checking Falk, Flender and Hansen websites it is interesting to see what they do in their catalogs. Falk's standard products state the 3-4-4-5% tolerances apply. The other manufacturers indicate they give exact ratios, but only to three or four significant figures.

More on picking and choosing.  I input 20 as the minimum teeth and although that is likely to be the very minimum in a helical set, bevel sets can and frequently go below that minimum.  So if you have a bevel reduction let me know.  A pinion between about 25 to 28 and about 50 is also more likely to occur than something around 50 to 60 or higher.  This is because the higher the number of teeth, the finer the pitch and this drives the horsepower rating down.  It also makes for a quieter gear set so it isn't impossible, just not likely.  Another design situation; the higher the service factor (driven by shock loading) the coarser the teeth pitch, i. e. less teeth on the pinion.  A gear tooth is essentially a beam in bending so to get increased rating, I have to have a fatter tooth, which means coarse pitch, which leads to lower number of teeth.

No promises but if you give me the nameplate order number and serial number and other details, I may be able to find out the exact combinations through some contacts at Lufkin (Texas).  I again can;t make promises as Lufkin Texas was pretty much closed down and moved to Lufkin France.  I haven't had contact with many of the people for many years so I'm not sure of their status.  



 
Attached Files
pdf 3.75 ratio possibilities.pdf (4.06 KB, 10 views)
pdf 2.453 ratio possibilities.pdf (4.72 KB, 10 views)

RRS_Dave

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Reply with quote  #3 
John,

Thank you for the quick response. I am working on the report now, and am some what guessing at what I believe to gear mesh to be. If what I think it is is correct, one of the gears should have 28 teeth, with the int shaft speed modulating.

Here is a pic of the name plate and a couple of the inside of the box. I couldn't be there the day the customer had a man from Cleveland at a rebuild shop come in and they opened it up. The pics were less than I desired, but customer took them on a phone with poor lighting. I was glad to get them. He found a print in the archives (this box has seen some hard times, but gear set looks surprisingly good. Pressure oil system for mesh and bearing lube) that gave me bearing numbers and these for part numbers of gears. 

19426200 HS Pinion.
19426300 assembly HS Gear/LSP Pinion. 
BM145927 assembly LSP Gear/LSP Shaft

I appreciate your help. I'll look at the info you gave me and see if either of is close. [smile]
Thanks again,

EDIT: I just looked at your data, and the 28-105 set fits in. It is the intermediate pinion

Dave

Attached Images
jpeg IMG_1029.jpg (315.32 KB, 16 views)
jpeg Line 9 Mixer Lufkin Gear Train2 9-5-19.jpg (368.55 KB, 15 views)
jpeg Line 9 Mixer Lufkin Gear Train3 9-5-19.jpeg (50.13 KB, 13 views)

John from PA

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Reply with quote  #4 
Dave, in checking for something near 28 teeth, I noticed that the 2.453 ratio possibilities did not print all the pages up to the desired upper limit of 2.500.  Use the attached in place of the first set of sheets I sent you for the 2.453 ratio.

 
Attached Files
pdf 2.453 ratio possibilities_mod.pdf (5.89 KB, 6 views)

RRS_Dave

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Reply with quote  #5 
I found an output mesh with output speed sidebands, and it works out to the output gear having 105 teeth.
The 105-28 ratio works.
Now trying to find something that will match up on the HS side.
RustyCas

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Reply with quote  #6 
Dave, I don’t do a lot of gearboxes anymore, but intermediate pinion mesh was 2nd most common problem I saw (after H.S. Pinion) and it was almost always a bearing issue causing misalignment.
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RRS_Dave

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Reply with quote  #7 
And that is what I believe is the problem. This thing ran with no oil pump for an undetermined amount of time 6 or 8 years ago (someone smelled something hot for a week or so before they got interested enough to start looking. They found this box too hot to touch. It sits 8 foot off the floor with no access). I believe the bearings in the int position are smack worn out. High spike energy but no discernable bearing fault freqs. The int gear mesh is high with 6 or 8 sets of sidebands at int shaft speed. They couldn’t find any gear damage, but when I asked what the pattern looked like I was met with a blank stare. The “gearbox man” was there to do the inspection.

Oh well, it’s getting rebuilt on the 29th of this month. I’ll see what they find.



D
John from PA

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Reply with quote  #8 
Quote:
Originally Posted by RRS_Dave
And that is what I believe is the problem. This thing ran with no oil pump for an undetermined amount of time 6 or 8 years ago (someone smelled something hot for a week or so before they got interested enough to start looking. They found this box too hot to touch. It sits 8 foot off the floor with no access). I believe the bearings in the int position are smack worn out. High spike energy but no discernable bearing fault freqs. The int gear mesh is high with 6 or 8 sets of sidebands at int shaft speed. They couldn’t find any gear damage, but when I asked what the pattern looked like I was met with a blank stare. The “gearbox man” was there to do the inspection.

Oh well, it’s getting rebuilt on the 29th of this month. I’ll see what they find.



D


Dave, exactly what does this thing drive?  It is a bit unusual to see the use of a double helical through the gear train unless someone made a conscious effort to cancel thrust by the use of double helical.

By the way my contacts at Lufkin have been (so far) unresponsive.


John from PA

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Reply with quote  #9 
Quote:
Originally Posted by John from PA


Dave, exactly what does this thing drive?  It is a bit unusual to see the use of a double helical through the gear train unless someone made a conscious effort to cancel thrust by the use of double helical.

By the way my contacts at Lufkin have been (so far) unresponsive.


Dave, I got confirmation of the tooth counts a few minutes ago.  They are as follows:

The high speed gear set us carburized and ground  53 x 130 teeth

The low speed gear set is through hardened and  hobbed  28 x 105 teeth

PM me with an email address and I'll send you the parts list drawing.




RRS_Dave

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Reply with quote  #10 
I drives a plastics mixer John that drops hot plastic into an extruder where it is then chopped, spun dried and the pellets drop into a shipping container to be sent out. The mixer is actually two screws also, just no pressure at end where material drops out bottom

I'll send a PM
Thanks for your help

D
John from PA

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Reply with quote  #11 
Quote:
Originally Posted by RRS_Dave
I drives a plastics mixer John that drops hot plastic into an extruder where it is then chopped, spun dried and the pellets drop into a shipping container to be sent out. The mixer is actually two screws also, just no pressure at end where material drops out bottom

I'll send a PM
Thanks for your help

D


Drawing on its way.
Danny Harvey

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Reply with quote  #12 
Dave,

Lufkin is very forthcoming with info about their gearboxes.

If you need, give me a call and I'll give you the contact info.
RRS_Dave

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Reply with quote  #13 
Thanks Danny.
Right now we're covered. John provided what I needed to get me by this one.
When I run across another I'll holler at you.
D
John from PA

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Reply with quote  #14 
Quote:
Originally Posted by Danny Harvey
Dave,

Lufkin is very forthcoming with info about their gearboxes.

If you need, give me a call and I'll give you the contact info.


Danny, when did you last have contact with your contacts?  Not sure if you are aware but GE in May 2016 announced a restructuring of Lufkin which included moving most of their gear manufacturing to France.  It supposedly resulted in a loss of 300 to 500 personnel in Texas although I didn't follow what happened in any detail.  I do know that several contacts I had in the group that makes high speed gearing left or retired and I went from a list of about 5 to 6 people down to 2.
Danny Harvey

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Reply with quote  #15 
John,

It's been years, mostly due to the fact that none of their drives I cover ever has any issues which is in turn due to the fact that Lufkin is one of the best around.

I didn't know that GE was involved but a GE purchase has never worked out well for anyone in our line of work, imo.

Sad to hear.
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