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Thread: Rotec R2800 oil drain problem.

  1. #11

    Join Date
    Nov 2011
    Location
    Galesburg, Illinois
    Posts
    6

    Default Re: Rotec R2800 oil drain problem.

    I've owned a couple of Rotec R2800's for several years. There are several causes for the oil "leak" issue.
    First, gravity is the main culprit, of course. Second, fluid will seek its own level. If the oil tank is located above the centerline of the engine, oil will drain into the crankcase. From there it will spill over into the cylinder bases. Some engines have cylinder bases that extend into the crankcase forming a dam of sorts. However, the Rotec has notches in clyinders 4 and 5 to allow for clearance of the connecting rods. This allows the oil to run into the "jugs".
    There being no such thing as a perfect seal, eventually oil will seep past the rings and into the combustion chamber. One of the lower cylinders will either have an intake or an exhaust valve open. Oil will drip out of the intake drains or the exhaust.
    In addition, the engine has a scavenging issue. The sump tank needs to be larger capacity to allow for crankcase drainage after shutdown. It's normal to find 2 -3 quarts of oil in the tank even after a scavenging procedure. The addition of the microfilter in the line from the sump to the scavenge pump lowered the overall scavenging of the engine. It seems to be adequate, but a larger capacity would aid in all around lubrication system performance. Oil temp. would run lower, better scavenging at low rpms--less oil in the sump.
    If you look closely at the location of the sump fittings, you'll see that the cylinder drain interconnects T into the sump at the very bottom of the tank. Now remembering that fluid seeks it's own level and that there is most likely 2 - 3 quarts of oil in the tank, where do you suppose the oil in the tank will try to to go? Yep, back to the cylinder. It would surprise you how much hydraulic pressure is created and how little pressure is requires to backflow. The tank should be a little longer which would let us lower the crossover drain input to the tank. Jacobs had the same problem on some of their engines. They addressed it by adding an additional in series tank.
    Most radial engine manufactures addressed the problem of "seepage" by incorporating check valves (known as seepage valves) in the oil pump assembly. That removed the need for a tank shut off valve and the risks involved with it's use. A hi (stainless) quality inline check valve installed at the oil filter block inlet would accomplish this. A 10 psi unseating pressure should be adequate. The oil pressure in that line is very high and will pose no problem in oil circulation.
    Sans such system, a shut off valve is necessary. I'd recommend installing the valve at the tank outlet with a Bowden cable to the cockpit. A microswitch in the starter solenoid line is another good idea.(I do not introduce the ignition during start until I see oil pressure. More than once it's saved my bacon.)

  2. #12

    Join Date
    Oct 2008
    Location
    paul
    Posts
    62

    Default Re: Rotec R2800 oil drain problem.

    The Rotec indeed does have notches cut into the lower cylinders this was a compromise during the design stage, this allowed the engine diameter to be reduced considerably which is a very important feature. The absence of the notches would only marginally improve the oil filling the lower cylinders. It will always drain down the wet rods and spill over the small cylinder spigots anyhow. If protruding cylinder spigots was all it took then no other radial would ever see oil in the lower jugs. Fact is they all do.

    The mini catch sump between the lower cylinders does have a T that intersects the rocker boxes and the mini sump itself. But being that the Rotec has modern valve stem seals then this oil can NOT re enter the cylinders.

    In fact the only oil that can enter the combustion chambers of the lower cylinders is via the piston rings. Period.

    With all radials you can expect to experience some oil pass the rings after shut down. I don’t think the Rotec is any worse than other radials, in this regard.

    On shut down the lower cylinders will have a lot of oil welling up on the underside of the pistons as the cylinders act as oil catch buckets. One trick is to hand prop after shut down so as the pistons move towards bottom dead center the oil is then displaced and falls down the ample case drain ports, this will remove most of the oil welled up in the cylinders. If an after run pump is fitted then this oil will be whisked away to the main oil tank.

    For some time now Rotec have supplied a new oil filter that has an anti drain valve built in that simply stops the oil from slowly filling the engine after shut down. Others have fitted an inline oil shut off tap. But the new filter alleviates the need for this.

    Bottom line is its a good little radial, 12 years in production with over a1000 units sold word wide with very few failures and no major design changes, so other than dropping some oil after shut down it does not use or leak any oil during operation if assemble correctly.

    Some engines are now flying well past 1000hrs. To date only one replacement cylinder head and barrel has been sold as a spare part.

    You will enjoy the R2800 engine powerful generally reliable, but it will always be a radial and with that comes radial tendencies, they are more than manageable and they are part of the joy of owning an engine such as this. If you want to just get in a turn the key then the Rotax 912 is for you. The Rotax 912 is nice little engine BUT like AH's every one has one.

  3. #13

    Join Date
    Nov 2011
    Location
    Galesburg, Illinois
    Posts
    6

    Default Re: Rotec R2800 oil drain problem.

    Perfect seal finally invented?

  4. #14

    Join Date
    Dec 2009
    Location
    Summerville, SC
    Posts
    5

    Smile Re: Rotec R2800 oil drain problem.

    There have been several comments about the Rotec R2800 engine leaking oil "PROBLEM". PaulC is correct. What some pervceive as a "PROBLEM", IS NOT A PROBLEM! It is just an annoyance, which is inherent with all RADIAL engines. The R2800 is a RADIAL engine, and it will drain oil from the exhaust stacks after shut-down. THIS IS PERFECTLY NORMAL. You can either deal with this normality, or switch to a pancake engine. I have found a way to deal with the oil dranining from the engine after shut-down. The electric scavange pump, is not worth the money, and will not sufficiently provide a remedy. Some are affraid of installing a valve to shut off the oil supply after shut-down, due to the fear of leaving the valve shut during the next engine start. My solution came about after much study. It involves removing the electrical ground from the starter solenoid, simultaneous with closing an oil shut-off valve, AFTER engine shut-down. This is accomplished with a locking control in the cockpit. Once that control is pulled, the electrical ground to the starter solenoid, is removed. Now, no oil flows through the shut-off valve (located between the oil tank and the engine) to the engine. On the next engine start, you cannot engage the starter until the locking control cable is pushed in, thereby providing an electrical ground to the starter. It works on my engine, and provides a fail safe valve positioning. When pre-flightiing an engine, you will notice just a few ounces of oil drip out of the exhaust stack when checking for a hydraulic lock. Collect it and save until there is a sufficient amout to put back in lthe oil tank. Forget the oil scavenge pump! I hope this helps.

  5. #15

    Join Date
    Nov 2011
    Location
    Galesburg, Illinois
    Posts
    6

    Default Re: Rotec R2800 oil drain problem.

    Does the scavenge pump system incorporate a filter? Normally a micron filter is installed in line from the sump to the scavenge pump. It does catch some contaminants. I'd hate to see that stuff sent to the oil tank, etc.

  6. #16

    Join Date
    Oct 2008
    Location
    paul
    Posts
    62

    Default Re: Rotec R2800 oil drain problem.

    Buckshot is on the right track.
    The R2800 is a radial and as such has typical radial tendencies. If your used to flying a flat engine these "radialisms" may become a slight inconvenience, as you need to hand prop before each start. Takes a hole 3 mins. What the rush? But once started a well built Rotec wont leak and burns next to no oil in flight at all. It runs modern valve stem seals also. So this helps a lot.

    Its like my Honda and Harley. I use the Honda to wiz down the shops for Milk and bread but I take the Harley out when I want some fun!

    One installation I did I fitted a shut off valve, that cuts off oil supply from the remote oil tank to the inlet of the engine oil pump. I installed a simple 30amp mini relay that engages the main starter solenoid when the starter button in pressed. All you need to do is mount a contactor or micro switch that disables the mini relay when the oil tap in the closed position.

    But the oil filter Rotec supply now how a light valve built in that does this automatically. Seems to work fine.

  7. #17

    Join Date
    Oct 2008
    Location
    paul
    Posts
    62

    Default Re: Rotec R2800 oil drain problem.

    The VDO scavenge pump has a small filter built into the pump itself, this can be flipped out and cleaned periodicaly.

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