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08-23-2019, 07:50 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by maniago
This is pretty good Otis. Kinda wished youd crunched your photos first, but its good. Not sure I quite get where you plumbed the pressure oil back into the system such that it doesnt push the oil backwards thru the passages.
To alay some fears, any rotation speed that will cause the oil to be flicked off a surface will suffice for oiling the cams. Starting rpms are plenty for this. Consider that the crank weights are revolving thru the oil in sump AND oil is spurting out of all the bearing surfaces - cam and crank. Its going everywhere, and the crank whips it into a massive oil fog right quick. Theres no need to worry about this. As far as the oil barrier being retained on the cam, that also is not a function of rpm at the slow speeds we run. The barrier will remain for a few cam revolutions without replenishment from the splash and fog. After that the starting rpms are enough to create the necessary splashing and fogging.
Not sure you believe that? Consider that if this wasnt the case, Lycoming, Conny (and any engine mfg for that matter) would tell us that if the engine doesnt start in one or two blades, stop, pull the engine and rebuild it cause its self destructed. But alas, we know thats not the case. Witness your hangar mate flogging his motor with a flooded or painfully long hot start.
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No. Just no.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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08-23-2019, 07:55 PM
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Join Date: Aug 2014
Location: Bowie MD
Posts: 886
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What Charlie said^^^.
The cup on the lifter body is what moves and takes up the lash gap when the lifter is pumped up with oil pressure (usually needs some 25 or more psi to come up) - and there by pushes the lifter down (Newtons 3rd) to hold it against the cam lobe. Once you remove the pushrod, theres too much of a gap for the lifter to put any pressure on the cam lobe. Obviously, it would then fall out of its bore, 'cept for the circlip at the top of the bore as you mentioned.
If you get a chance some time, take a hydraulic lifter apart. Quite an ingenious but simple device (hint: dont use a magnet to get it apart - that'll magnetize the individual parts and it wont pump up properly anymore)
__________________
Mani
Busby MustangII (FoldingWing) Pending DAR.
Don't be a hater; I'm a cousin with thin wings! 
N251Y (res)
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08-23-2019, 07:56 PM
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Join Date: Aug 2014
Location: Bowie MD
Posts: 886
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Quote:
Originally Posted by Toobuilder
No. Just no.
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Ah yes. Build a few motors amigo.
__________________
Mani
Busby MustangII (FoldingWing) Pending DAR.
Don't be a hater; I'm a cousin with thin wings! 
N251Y (res)
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08-23-2019, 09:43 PM
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Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
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Quote:
Originally Posted by maniago
This is pretty good Otis. Kinda wished youd crunched your photos first, but its good. Not sure I quite get where you plumbed the pressure oil back into the system such that it doesnt push the oil backwards thru the passages.
To alay some fears, any rotation speed that will cause the oil to be flicked off a surface will suffice for oiling the cams. Starting rpms are plenty for this. Consider that the crank weights are revolving thru the oil in sump AND oil is spurting out of all the bearing surfaces - cam and crank. Its going everywhere, and the crank whips it into a massive oil fog right quick. Theres no need to worry about this. As far as the oil barrier being retained on the cam, that also is not a function of rpm at the slow speeds we run. The barrier will remain for a few cam revolutions without replenishment from the splash and fog. After that the starting rpms are enough to create the necessary splashing and fogging.
Not sure you believe that? Consider that if this wasnt the case, Lycoming, Conny (and any engine mfg for that matter) would tell us that if the engine doesnt start in one or two blades, stop, pull the engine and rebuild it cause its self destructed. But alas, we know thats not the case. Witness your hangar mate flogging his motor with a flooded or painfully long hot start.
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Does it really do that? Or is the oil sump bolted under the crankcase and mostly separated by casting.
__________________
VAF #897 Warren Moretti
2019 =VAF= Dues PAID
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08-24-2019, 03:03 AM
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Join Date: Aug 2014
Location: Bowie MD
Posts: 886
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Quote:
Originally Posted by gasman
Does it really do that? Or is the oil sump bolted under the crankcase and mostly separated by casting.
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Ah yup, youre right. Theyre separated - I was thinking of a transmission I'm working on and flipped my thought gears. My bad.
__________________
Mani
Busby MustangII (FoldingWing) Pending DAR.
Don't be a hater; I'm a cousin with thin wings! 
N251Y (res)
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08-24-2019, 08:41 AM
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Join Date: Aug 2017
Location: Sebastopol,CA
Posts: 358
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Quote:
Originally Posted by maniago
What Charlie said^^^.
The cup on the lifter body is what moves and takes up the lash gap when the lifter is pumped up with oil pressure (usually needs some 25 or more psi to come up) - and there by pushes the lifter down (Newtons 3rd) to hold it against the cam lobe. Once you remove the pushrod, theres too much of a gap for the lifter to put any pressure on the cam lobe. Obviously, it would then fall out of its bore, 'cept for the circlip at the top of the bore as you mentioned.
If you get a chance some time, take a hydraulic lifter apart. Quite an ingenious but simple device (hint: dont use a magnet to get it apart - that'll magnetize the individual parts and it wont pump up properly anymore)
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My external oil pump by itself maintains 40psi at the port where oil pressure is normally measured in the lower left side of the crankcase, so at least 1.5 gpm is circulating through all of the oil galleys, bearings, and pressurizing the lifters. I?ve worked on automotive hydraulic lifters that have retainers that prevent them from pushing apart beyond a maximum length(in fact there is a spring inside that has to be compressed to install the clip). This may be true for Lycomings as well, but there is also a plunger that acts upon the push rod that can be removed when the cylinders are backed out enough to remove the pushrod tubes, see:
https://youtu.be/sRtKiV6QYaE
My concern is that if I remove the push rods and operate my external pump, this plunger will be forced out into the empty tube, and I?m not sure it would be easy to reinstall them with the tubes in place. If I could be confident that this would not be a problem, I would remove the pushrods, bring the system up to pressure with the external pump, crank the engine vigorously with the spark plugs removed, bringing system pressure up near 50 PSI, and afterward remove the #2 jug to allow me to verify or refute that this procedure has indeed splashed oil on the cam lobes.
This would be valuable information to post on VAF one way or the other, and would validate the use of an external pump in this manner if the cam did get oiled. I?d be willing to go to the trouble if I could be convinced that pressurizing the system and spinning up the starter with the pushrods removed would not lead to some such problem. I did spin the engine for about 20 seconds this way with the pump operating but fully assembled except spark plugs, and I guess I could just repeat that and pull a jug, but some posts here have me worried that I may be spinning a bone-dry cam against the lifters.- Otis
__________________
Otis Holt-
RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2019 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"
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08-24-2019, 08:50 AM
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Join Date: Aug 2017
Location: Sebastopol,CA
Posts: 358
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Quote:
Originally Posted by maniago
This is pretty good Otis. Kinda wished youd crunched your photos first, but its good. Not sure I quite get where you plumbed the pressure oil back into the system such that it doesnt push the oil backwards thru the passages.
To alay some fears, any rotation speed that will cause the oil to be flicked off a surface will suffice for oiling the cams. Starting rpms are plenty for this. Consider that the crank weights are revolving thru the oil in sump AND oil is spurting out of all the bearing surfaces - cam and crank. Its going everywhere, and the crank whips it into a massive oil fog right quick. Theres no need to worry about this. As far as the oil barrier being retained on the cam, that also is not a function of rpm at the slow speeds we run. The barrier will remain for a few cam revolutions without replenishment from the splash and fog. After that the starting rpms are enough to create the necessary splashing and fogging.
Not sure you believe that? Consider that if this wasnt the case, Lycoming, Conny (and any engine mfg for that matter) would tell us that if the engine doesnt start in one or two blades, stop, pull the engine and rebuild it cause its self destructed. But alas, we know thats not the case. Witness your hangar mate flogging his motor with a flooded or painfully long hot start.
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The engine oil pump prevents any significant reverse flow when my external pump is operating. If you look at flow diagrams of the vernatherm circuit, you can see that injecting oil anywhere in the cooler loop will pressurize the entire system in the same manner as does the engine driven pump regardless of the state of the vernatherm valve(i.e. the oil cooler loop remains fully pressurized regardless of valve position- the other end of the loop is always open)- Otis
__________________
Otis Holt-
RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2019 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"
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08-24-2019, 10:02 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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Quote:
Originally Posted by maniago
Obviously, it would then fall out of its bore, 'cept for the circlip at the top of the bore as you mentioned.
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You just keep giving erroneous data on this thread. There is no circlip in the lifter body and the oil pressure will blow the plunger assembly and cup out of the pushrod tube. without a pushrod installed.
Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 08-24-2019 at 10:07 AM.
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08-24-2019, 10:04 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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Quote:
Originally Posted by gasman
Does it really do that? Or is the oil sump bolted under the crankcase and mostly separated by casting.
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No, it doesn't. That is a major design no no. That would cause extreme cavitation and the oil would become entrained with air bubbles, reducing the effectiveness of the oil system across the board.
Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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08-24-2019, 10:17 AM
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Join Date: Aug 2014
Location: Bowie MD
Posts: 886
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Quote:
Originally Posted by lr172
You just keep giving erroneous data on this thread. There is no circlip in the lifter body and the oil pressure will blow the plunger assembly and cup out of the pushrod tube. without a pushrod installed.
Larry
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Ok fair enough. I'll step back from the conversation and listen while you guys help the OP out with detailed explanations so we all can learn instead of just throwing stones at me for trying.
__________________
Mani
Busby MustangII (FoldingWing) Pending DAR.
Don't be a hater; I'm a cousin with thin wings! 
N251Y (res)
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