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Flamer- Thank you for the kind words. Yes we are still here despite the fact that RUclips no longer pays us for the advertising. We don't plan on removing these videos because of people like you. Thank you for your interest. John Piotrowski.

The explanation for why the vibration decreases is explained in slide 16 in the tutorial. Here is the text for the narration of that slide ... If you remember, a short while ago, when we were talking about things that put static loads on bearings, it was mentioned that three very common sources of static forces on bearings were gravity, or the weight of the rotor, belt tension, and shaft misalignment. So, let’s examine the static forces that are present in these two shafts and for this discussion we are viewing the shafts in the side view. The shaft on the left has some weight so there is a downward force on it due to gravity. Each bearing produces an upward force opposing the gravitational load. Similarly, the shaft on the right sees the gravitational force and its bearing produce an upward force to oppose the gravitational load on them. If we begin to misalign these two shafts, the flexible coupling accommodates a certain amount of the misalignment but once that is exceeded the shafts will start elastically bending. The gravitation forces are still there but now, through the coupling, the shaft on the right induces a downward force on the shaft on the left. This force now produces an additional force on the inboard bearing in the downward direction but it will produce an upward force at the outboard bearing. The shaft on the left produces forces on the shaft on the right also. Through the coupling, the shaft on the left induces an upward force on the shaft on the right. This force now produces an additional force on the inboard bearing in the upward direction but it will produce an downward force at the outboard bearing. If we continue to misalign these two shafts, the shaft begin elastically bending even more. The gravitational loads are still present, across the coupling, the downward force on the end of the left shaft has increased as well as the reactionary forces on its bearings and the upward force on the shaft on the right has increased as well as the reactionary forces on its bearings. Shaft misalignment induces static forces on the shafts that will diminish the amount of motion / vibration that is occurring.

Great suggestion Tom. Thank you for your input. John Piotrowski

You are most welcome!

Great suggestion Dennis. Thank you for your input. John Piotrowski

Thank you so very much for the kind words. I hope that this information has helped you. We are hoping that the remaining tutorials will be available in the next few weeks. Thank you for your interest. John Piotrowski

@@shaftalignment6105 Alright Sir, could you please make an announcement when they avaliable.

Thank you for watching.

Pravindra: Thank you for watching the video and the kinds words. John Piotrowski

Stephen: Thanks you for the kind words. Hope the information helped you in some way. John Piotrowski

Amir: The Validity Rule applies to either radial / rim OR face / axial measurements.

Thanks very much Engineer/ Sir John 👍

Hi

Darkland Curious: Thank you for the kinds words. I hope that this information will help with your rotating machinery. John Piotrowski

Mario: Thank you for the kind words. I hope that the tutorials will help with your rotating machinery. John Piotrowski

@@shaftalignment6105 they are very helpful in combination with recommended books.

Muhammed: Great question. Shafts that are supported in journal bearings (a.k.a. sleeve, babbitt, plain, hydrodynamic, bushing), require a certain amount of clearance for the lubricant to get between the shaft and the bearing when the shaft is rotating. This clearance is typically 1 mil per inch (1 micrometer/mm) of clearance. For example, a 6 inch diameter shaft would have about 6 mils (0.006") of clearance. Assuming that the shaft is horizontally mounted, once the shaft gets up to speed, the shaft does indeed lift up on a thin film of lubricant but the film thickness only ranges between 0.5 - 1 mil (0.0005" - 0.0010"). The shaft is not going to automatically center itself inside the bore of the bearing because it needs a film of lubricant to run on. If both shafts on a two element drive system have journal bearings, the they both would lift up about the same amount making the oil film thickness a non-issue. If one machine is supported in journal bearings and the other shaft is supported in rolling element bearings, then you could set the shaft supported in journal bearings about 0.5 - 1 mil lower to compensate for it but that's almost not worth worrying about. Thanks for your interest! John Piotrowski 3/30/2020

Tahseen, I hope these tutorials are helpful. Thank you for the kind comment! John Piotrowski

Carlos: For horizontally mounted shafts, typically the side (horizontal) readings are the same so they cancel each other out. Sag only affects the top and bottom (vertical) readings. For example, if you were using a bracket that had 10 mils of sag, when you check the sag, there would be 5 mils of sag on both side readings.

@@shaftalignment6105 I have another question, why divide they SAG value by two when using the reverse dial method, and when using rim and face method the SAG value is the complete value?

@@carlosaguilar4505 Carlos: For horizontally mounted shafts, when using mechanical brackets and dial indicators, the amount of "sag" that occurs from the 12 o'clock to 6 o'clock reading is being affected by gravity which needs to be compensated for when aligning your machinery. For example, if you had a bracket and indicator arrangement where you had 10 mils (-10) of bracket sag from the 12 o'clock to 6 o'clock measurements and you saw -40 mils for your bottom reading, 10 mils of that -40 is due to the "sag" in the bracket. If you would have had a "perfect" bracket that had no sag at all , you would have only measured -30 for your bottom reading, not -40. Why? Because 10 mils of the -40 reading is due to the sag in the bracket. To compensate the bottom reading for sag, regardless of whether it is a rim or a face reading, you subtract the amount of sag to the bottom rim or face reading. Sag also has an effect on the "side" readings and it is typically symmetric where the effect of the sag for the side readings is HALF of the amount you observed from the 12 o'clock to 6 o'clock position. This is true for any rim or face measurement and it's true regardless of whether you are using the Reverse Indicator, Face-Rim, Double Radial, Shaft to Coupling Spool, or Face-Face methods. Thanks for your interest! I hope I answered your question.

@@shaftalignment6105 thank you Mr. John, i have one more question, why in your book, specifically in the reverse dial method, You take it the readings in both dials at six o'clock? Thanks for your attention

Bikramjit: Thank you for your kind words. They are appreciated. Here is hoping this information will help you. John Piotrowski