CRANKSHAFT runout, out of round, taper. How to measure it all.

[Music] hello and welcome back to plain simple today we're going to be looking at how to measure uh runout on a crankshaft uh we can measure run out let's start from the beginning what is run out run out is a defect or a deviation from an intended shape of a rotating assembly i'll give you an example this crankshaft is this particular crankshaft is from an aircraft from horizontally opposed reciprocating piston engine up here this is the propeller mounting flange this is will flange where the propeller this is the front of the aircraft in front of the engine this is where you would mount the propeller in this particular case this flange you would want it to run perfectly perpendicular in a plane perpendicular to the center line of the crankshaft if that flange that plane of rotation wobbled any at all it would cause vibrations on your propeller which you don't want that's that's an indication of a bent crankshaft we're also going to look at run out on the journal bearings which all those points of support of the crankshaft are all in a line so that as a crankshaft rotates [Music] it rotates about the points of support which are the bearing journals the bearing supports these are the bearings that support the crankshaft the rotating assembly so all of these are supposed to be concentric or in a line and not have any deviation from there if you had run out here it would be it would mean the wobble in the rotating plane if you had run out or a deviation from its intended shape of the rotating assembly if you had run out in one of the crankshaft bearing journals that means that that's another indication that the crankshaft is bent in this particular example here if there was any run out in this bearing journal that means that the crankshaft as it rotated it would be doing this that would destroy your bearings at that location and every other location and i'm going to show you how to measure runout and the bearing journals and the propeller flange as well as another consideration how to measure out of round in the crank pins or the bearing journals we're going to start since we're set up over here we're going to start with measuring out of round in the bearing journal let me bring you in closer right now we're looking at the number three bearing journal this is a throw or a crank pen crank pin this is a bearing journal the way you would measure for out of round is to measure the diameter of this crank pin 90 degrees offset you measure in one direction and then you rotate 90 degrees and you take a second measurement and compare the two basically you can go take a measurement and say in this direction write down whatever your reading is and you take a measurement 90 degrees from your original measurement whatever that difference is is an indication of being out of round pretend this is a side view of that crank pin journal you would measuring for that a difference between this direction and that direction there's a limit to that and the overhaul manual to whatever engine you're working on will specify that limit but that is what is meant by out of round if you're looking at a perfectly round uh bearing journal both measurements in both directions would be identical same same diameter if it was out of round i'm exaggerating this of course but if it was out around one direction will be shorter than the other indicating out of round to measure taper something else that you can check here or that you do check for is taper taper meaning how far away from parallel the wear patterns are on that crankshaft bearing journal the way you would do that is you would measure and compare the diameter from one side let's say the forward end the forward side of that journal and compare that to the aft end of that journal whatever that difference is from one side to the other will give you an indication of taper or how far away from parallel that journal is again that has its wear limits okay now we've moved on to uh measuring run out at the crankshaft bearing journal using a dial indicator the dial indicator will give you give us a reading of any wobble in the crankshaft in this direction meaning that the crankshaft is either bent or is within specs within limits you would start out with your dial indicator zero it out which i zeroed out before but now then i turn the crankshaft but once you zero it out you slowly spin the crankshaft and take note of the lowest and highest readings you get out of that pointer in this case the lowest reading that i get is zero and it goes up to four thousands four thousands of an inch and it's going right back to zero again that means that this crankshaft has a run out or out of line with the rest of the crankshaft or four thousandths of an inch whether that's within spec or where this crankshaft is trash the overhaul manual would tell you that every crankshaft every engine is different and the specs for that would come from the overhaul manual but this is how you would measure run out of a crankshaft at the bearing journals using a dial indicator now we are back to the propeller flange or the front end of this crankshaft and we're going to use the same dial indicator using the same technique to measure run out of this flange in this direction we're measuring for run out or out of plane not in this direction but in direct the direction that the dial indicator is set now you want to measure that as far out the overhaul manual will give you specifics of where on this face of the flange to take your readings from this particular case it is taken as far out in the diameter of this flange as possible the reason for that is that's we're going to give you the most exact reading the further in you go closer to the center the smaller the readings will become but not any less important to give you the most detailed reading you want to go as far out as possible that's the worst case scenario that's where you would get the most amount of deflection if there's any and you would set up your dial indicator the same way reading where you want to go zero out of your pointer or zero the dial face to where the pointer is so you you start from a good point of reference and again you slowly rotate the crankshaft and you take note of your highest which now we're looking at one two three four five six seven thousands of an inch it starts to take note of your highest reading and your lowest reading so that went up to nine down to four up to nine again down to four i'll call that i guess i wasn't exactly zeroed out it hadn't settled in when uh when i started turning this but highest rating was nine thousands lowest rating was four thousand so we have a five thousandths of an inch run out in this propeller flange that's a wobble away from its intended plane of rotation to wobble away from that of five thousands of an inch and that's how you would use a dial indicator to measure propeller flange run out on this aircraft crankshaft i hope that uh helps you guys i always find all this interesting if you have any questions feel free to ask in the comments and uh thank you for coming along for this journey see you next time

Channel: Plane Simple

Views: 10,454

Rating: 4.9679999 out of 5

Keywords: crank shaft, crankshaft, dial indicator, run out, taper, bent, out of round, concentric, concentricity, eccentric, micrometer, run-out, runout

Id: vZ0lYmdNqJo

Length: 10min 30sec (630 seconds)

Published: Fri Aug 21 2020