Shadrach Posted March 6, 2019 Report Share Posted March 6, 2019 (edited) 19 hours ago, Marcopolo said: I've been told the same, and there's the rub. Stay with me here, I'm only theorizing. if the only oil that makes it past the crankshaft oil port into the "baby jar" is the first bit of oil it sees then where would all that lead come from. In order for oil to carry lead there in the quantity I see on a regular basis I would think (opinion) it would have to be replacing a small portion of oil in that baby jar somewhat regularly. Now I am saying this with absolutely no knowledge of how much oil would have to go through that area to leave how much residue, but to have any lead in the oil (careful here because engine oil could contain a zinc additive) you would think it had been through the engine and picked up lead via blow by from combustion or from the cylinder walls and then run through the governor to that area of the prop/crank and refreshed in small quantities to leave the amounts I see from annual to annual on many different airplanes. Again, I'm only trying to figure this out for my own education as I clean this sludge out of more than a few cranks and hubs on a regular basis. I cycle my prop once during the first run-up of the day just to make sure it works and doesn't spray oil on the windscreen (BTDT). I do not think cycling the prop three or four times replaces the prop control system with an entire fresh batch of warm oil. And again my apologies to the OP! Ron I will know what it is soon enough. I do not believe it is lead. I also have the rare privilege of shoe-horning a 77.5" Comanche prop into the back of my F model for a 245nm trip to my buddy's preferred prop shop. Edited March 7, 2019 by Shadrach 1 Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted March 6, 2019 Report Share Posted March 6, 2019 45 minutes ago, Marcopolo said: Really? Sticking with your human lung analogy, can you tell me what left the sludge in your throat? That's the question in the end of this, I was only trying to explain out loud how I thought the sludge/deposit was created in the "throat" of the crankshaft. Ross has given a suggestion to first determine where it came from and that will lend to the next event of determining how that vehicle left it. It's an annoying analogy, but if you think of oxygen from outside air as being "sludge" from outside engine oil, a person who is take shallow breaths will be mixing oxygen in the upper part of their airways. If their breaths are less than the volume of the airways (IIRC, this is called anatomic dead space), they will only mix oxygen in that volume of the upper airway. Everything lower than that in the airways and in the alveoli will simply recycle the same air over and over. If your breaths are exactly the same volume as the airway dead space, you'll get oxygen throughout your entire airway, but not into your alveoli. Only if your breaths are larger than the dead space volume do you start getting oxygen where it is useful. So consider the stroke volume of the piston hub as the size of the breath. If that volume is less than the volume in the prop control system (past the sump return), the volume in the prop control system up to the same volume as the piston stroke volume will be mixed with engine oil, but everything past that will simply be the original piston oil. So you will see engine oil make it in, and any sludge it is carrying to a certain point. If the piston stroke volume happens to be exactly equal to the volume in the prop control system, engine oil will be mixed throughout the entire line, but not into the piston itself. Quote Link to comment Share on other sites More sharing options...
Marcopolo Posted March 6, 2019 Report Share Posted March 6, 2019 14 minutes ago, jaylw314 said: So consider the stroke volume of the piston hub as the size of the breath. If that volume is less than the volume in the prop control system (past the sump return), the volume in the prop control system up to the same volume as the piston stroke volume will be mixed with engine oil, but everything past that will simply be the original piston oil. So you will see engine oil make it in, and any sludge it is carrying to a certain point. If the piston stroke volume happens to be exactly equal to the volume in the prop control system, engine oil will be mixed throughout the entire line, but not into the piston itself. So one big difference in the prop control system as opposed to the human lung is the prop control system can rest, so there is a time where whatever oil that has made to the crank/hub can possibly run back into the engine sump (I don't know if there's a check valve here) or I assume (trouble) it can also mix with the oil in the prop piston area at that point. My head hurts! I guess none of this really matters other than I'm wondering what it is I'm cleaning and why, sorry! Marcopolo out! Ron Quote Link to comment Share on other sites More sharing options...
carusoam Posted March 6, 2019 Report Share Posted March 6, 2019 +1 on Jay’s lung analogy... but worse.... the gov has a positive displacement pump.... it is constantly turning, and constantly delivering oil into the gov... The volume of oil is directly related to the rpm of the pump, and engine.... What The gov is using for prop control, is the pressure being delivered by the pump... The pressure is controlled by the flyweights... The flow of oil is mostly in and out of the gov, as depicted in Ross’ gov diagram... The oil in the prop is interesting... as the prop ‘breathes’, each time the blades cycle.... the highest volume of oil enters and leaves each time the prop is cycled... If you are familiar with flow in a dead leg.... the prop seams to be quite the dead leg.... Expect the dead leg to be open to oil exchange... some oil will be constantly entering and exiting... aided by the prop blades moving as the load on the prop isn’t always constant.... more change in attitude, more exchange of oil.... a few deep breaths, and a lot of small ones... combined with oil transport via eddy currents caused by oil flowing past the dead leg... Anything that is higher density than the oil is going to want to separate in the rotating parts... Higher density junk floating around in the oil, may get preferentially separated inside the prop... similar thing is going on in the oil pan... Separation requires a driving force... gravity.... Or g force of rotation... what allows it to collect... low levels of flow.... Now Compare That to the lungs.... dirt, smoke, and asbestos particles enter the lungs, but it is terribly hard to get it all to come back out by taking deep breaths... we have cilia and coughing to help with that.... but lungs are the ultimate dead leg, that changes volume.... Expect the oil analysis is going to look a lot like the sludge that builds up in the oil pan... Great analogy... PP thoughts only, not a biologist.... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted March 6, 2019 Report Share Posted March 6, 2019 I have to disagree on the oil volume in a typical constant speed propeller on a reciprocating engine. In my experience around a quart of oil drains as the prop is removed. And it typically takes a quart to top up the engine when the prop is reinstalled and run up, cycling the prop to purge out the air. That reminds me, if it’s a closed system how does the air get out? The oil transfer tube from a rear mounted governor is 3/8” ID and about 2.5” long and contains about 0.01 gallons of oil. Significantly less than the prop holds. Of course front mounted governors as used on many Continental engines have internal transfer passages holding even less oil. Clarence Quote Link to comment Share on other sites More sharing options...
Shadrach Posted March 6, 2019 Report Share Posted March 6, 2019 10 minutes ago, M20Doc said: I have to disagree on the oil volume in a typical constant speed propeller on a reciprocating engine. In my experience around a quart of oil drains as the prop is removed. And it typically takes a quart to top up the engine when the prop is reinstalled and run up, cycling the prop to purge out the air. That reminds me, if it’s a closed system how does the air get out? The oil transfer tube from a rear mounted governor is 3/8” ID and about 2.5” long and contains about 0.01 gallons of oil. Significantly less than the prop holds. Of course front mounted governors as used on many Continental engines have internal transfer passages holding even less oil. Clarence Agree the prop holds a fair amount of oil (I think it’s less than a quart though). The discussion relates to how much oil is used to actuate from fine pitch to course. That is significantly less than the hub’s capacity. Quote Link to comment Share on other sites More sharing options...
Cody Stallings Posted March 7, 2019 Report Share Posted March 7, 2019 15 hours ago, M20Doc said: First thing, what did your engine overhauled say about oil system cleaning? Many will have a clause about warranty denial if the oil system wasn’t decontaminated. Hate to lose a warranty claim over not doing the prop. Secondly, If there is no oil flow through the prop from the governor and the oil in the hub is the same oil from the original start, in this case clean mineral oil, can someone please explain to me how all the sludge appears in the crankshaft bore when I pull a propeller? Clarence The thick grey crap your talking about is the solids from the oil that has been centrifuged. Quote Link to comment Share on other sites More sharing options...
Guest Posted March 7, 2019 Report Share Posted March 7, 2019 7 hours ago, Cody Stallings said: The thick grey crap your talking about is the solids from the oil that has been centrifuged. I’m aware of what it is and how it gets there. The point of debate is some people believe that the propeller oil system is closed with no continuous oil flow. If there is no flow then how does the sludge accumulate in the crankshaft bore, and why does dirty oil pour out when the prop is removed? Clarence Quote Link to comment Share on other sites More sharing options...
mooniac15u Posted March 7, 2019 Report Share Posted March 7, 2019 Any amount of engine oil that enters the system will be subject to hundreds of hours physical and thermal cycling an engine vibration. It would be hard to imagine that oil wouldn't mix. 1 Quote Link to comment Share on other sites More sharing options...
Shadrach Posted March 7, 2019 Report Share Posted March 7, 2019 3 hours ago, M20Doc said: I’m aware of what it is and how it gets there. The point of debate is some people believe that the propeller oil system is closed with no continuous oil flow. If there is no flow then how does the sludge accumulate in the crankshaft bore, and why does dirty oil pour out when the prop is removed? Clarence I can’t say for sure but my best guess is that the particles that form the sludge are oil soluble. Over hundreds of hours, any thing in solution will continually be dispersed throughout the system. Imagine a chain of interconnected water filled, glass cylinders sitting on a vibrating table. No imagine a steady drip water soluble dye into one of the cylinders. Over hundreds or thousands of hours the dye would disperse itself throughout the system. Quote Link to comment Share on other sites More sharing options...
Buckeyechuck Posted March 7, 2019 Report Share Posted March 7, 2019 To @spike kavalench. Don't know if this was previously communicated. There is a spinner currently on eBay. $150. Might want to check it out. 1 Quote Link to comment Share on other sites More sharing options...
Guest Spike Kavalench Posted March 7, 2019 Report Share Posted March 7, 2019 Thanks. Quote Link to comment Share on other sites More sharing options...
bill98 Posted March 7, 2019 Report Share Posted March 7, 2019 If someone needs a prop lemme know. Can be in serviceable Relatively quick It had a prop strike. Can sell for decent price if desperate. Hartzell Scimtar. Came off 65 M20E. Only has 350ish hours on it (plus.... the prop,strike) it’s not curled or anything. @gsxrpilot has probably seen it next to his aircraft. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted March 8, 2019 Report Share Posted March 8, 2019 (edited) 16 hours ago, bill98 said: If someone needs a prop lemme know. Can be in serviceable Relatively quick It had a prop strike. Can sell for decent price if desperate. Hartzell Scimtar. Came off 65 M20E. Only has 350ish hours on it (plus.... the prop,strike) it’s not curled or anything. @gsxrpilot has probably seen it next to his aircraft. Can you elaborate on the strike or point to a thread that does? Edited March 8, 2019 by Shadrach Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.