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OLi

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Reply with quote  #1 
Old gbx only angular roller bearings as thrust bearings, vertical machine the rest is not anti friction. Thin oil used "100".
Likely 37 and 166 teeth, is that good? Input 167RPM.
Why would I get something that looks like gearmesh at 187Hz and in some positions 112 Hz and also 150Hz and in at least one place all 3? Gear look to have uneven wear some teeth worn, some nothing at all. Noisy like very noisy "but it always been like that". I can add some plots shortly. Lower bearing have a large play on generator like 0.55 mm.

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Walt Strong

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Reply with quote  #2 
Olov,

So the generator speed is only 749 rpm (167x166/37)? Is generator a synchronous or induction type? Line frequency 50-Hz? MW rating? "Noisy like very noise", but the silly numbers don't fit the scene of the crime!

Walt
John from PA

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Reply with quote  #3 
Something not right. 187 Hz mesh would be 11220 cpm or 303 RPM on 37T rotor; 67 on 166T rotor.
OLi

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Reply with quote  #4 
Generator is synch. 50Hz grid and yes something is wrong that's why I ask. I have seen dominating 0.5xGearmesh due to excentricity but not these numbers. I will be back with some data to look at.
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John from PA

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Quote:
I have seen dominating 0.5xGearmesh due to excentricity but not these numbers
I have never seen a 1/2X of mesh due to eccentricity nor could I explain how something like that could happen. Normally eccentricity causes mesh with sidebands at +/- of the rotating rotor speed. If you have two assembly phases you could get 1/2 of mesh even in a healthy gearset. In the event that severe wear had occurred due to a mismatched reassembly, you would still likely get a high 1/2X mesh, a low 1X mesh but little if any sidebands.
OLi

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Ok, I hade one case many years ago (25+) and it was 1/2 gearmesh dominating. It was a petrochem plant and gears were from some funny material for unknown reason. I could not figure it out and they did not look inside, just swapped it so I have no proof, it was not born that way it was something that occured, maybe a crack somewhere? It never so far happened again. Youtube have a scary description from Airbus on the GBX /bearing fail of a SuperPuma helicopter in Norway so they now inspect them 4 times as often and "technology do not yet allow us to detect such problems but we are working on it". Seems to be a outerring damage escalating to a crack and a gear tooth collision and explosion. Supposedly started by gearbox being involved in a truck crash in transport but that must be more like guessing than based on facts. I have worked on and seen those gbx's when we did fly those here. I was not impressed.
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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
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John from PA

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Reply with quote  #7 
Oli, anything new on this GB?
OLi

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Reply with quote  #8 

Thank you for asking, here are some squigglies to look at.

There are a smaller aux gear that used to drive the exciter, that is all electronic now, it only drives the lube pump. It would be impressive if that would create 20mm/s and increasing but that is the cheapest thing to attack in short term, disengage that gear and add a electric lube pump so that is considered. It is actually close to that little gear where vibration are highest and that is also a indication. Not so much is known of that gear it may have one set of teeth around 33 teeth and is angular. Swapping the lower generator bearing that have the large clearance require stripping the complete set due to stupid design so it will not happen until it runs out of water in the summer. Data is approx from generator NDE to turbine NDE and the last are starting over but at different load, I believe higher. In some cases I have seen weird frequencies that came from something like a damage exciting the gear wheel resonance. There is a flywheel hanging beneath the gen brg with hi clearance so it may be acting like a pendulum hitting the gear radially but the flywheel inertia should be damping that some but maybe it made a nice striking action.

 
Attached Files
doc HydroGBX.doc (163.00 KB, 8 views)


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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
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John from PA

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Reply with quote  #9 
Anything with respect to tooth counts and shaft speeds?
OLi

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Reply with quote  #10 
Sorry about that, being distracted, this should be included it is about all I know part from load bearing being similar to 29456E but of a unknown brand. A photo from previous lift maybe will be good for you? Are the colours funny?lyft kugghjul.jpg 

 
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pdf 0371_100.pdf (34.41 KB, 8 views)


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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se

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