Remote oil thermostat

[Av8r3400]

Yes, actually, I am an engineer. I work in a different area now, but my background is mechanical engineering.

This isn't a heavy diesel or automotive application where when you blow a pressure oil line you can stop, shut down the machine and fix it. It's an airplane. When you blow an oil line you will quickly loose the engine. This means you land. Hopefully safely, without injury or loss of life.

As an experimental, you can do as you please and I wish you luck. I choose to follow the Rotax engineers' advise as to cooler location and operations. They know more than I do.

[Slyfox]

I just looked at my plane and yes it is put together just like rotax says. will I change it. don't know. I run on the premise of, "if it ain't broke don't fix it." I know when I put my lines on I used silicon on the hose to fittings and then the clamp. I've been doing this forever on auto applications. if the clamp happens to loosen a bit it is still sealed. now I don't use cheap silicon I get mine from ford. it really dries solid. Now another thing I did is put that thermostat on the top of the gear box. my theory is it has the line coming out of the tank going up high. makes the oil stay in the tank. I checked my oil level today and it's been since sunday that I last flew it. the oil was all the way up. I also have it plugged in, yup I do that also, I know that is another thread going. but I plug my plane in and forget it. it has the reise system with the thermistor to control temp and a ring around the tank and the element on the engine. engine was warm and the oil at the top of the stick. it's always like that. even after sitting for about a month here recently cus it was real cold and windy, flew the rv instead. the oil was still showing on the stick when I checked it. I think having my thermostat on the gear box does this.

will I change my line routing, more than likely not. but I do now understand any leak in the lines before the pump can be BAD.

[jiott]

A leak on the suction side can be bad alright, but I agree with Av8r3400 that a leak on the pressure side is much worse. I also think that a cooler on the pressure side is more likely to fail because it is seeing relatively high pressure (way higher than a coolant radiator) cycles all its life. Most oil cooler failures I have seen are from pressure fatigue rather than contaminant blockage.

[jiott]

One thing I have learned after 40 years as a hydraulics engineer is that there is always more than one way to do something, as we see here in this thread, so choosing the best way is usually a compromise between many factors such as:

• Proper function
• Longevity
• Ease of installation
• Ease of maintenance
• Failure modes & probability
• Results of failures
• Likelihood of errors in installation & maintenance
• First cost & life cycle costs
• Overall reliability
• Environmental factors
• Cosmetic appearance

I have probably missed several areas, but you get the idea. The engineer has to weigh all these things, and I tend to trust the factory engineers who focus their whole effort and have many years of product experience to call upon. That is compared to those of us on this forum having fun trying to second guess them in a few minutes of our spare time. Hey I know this is experimental aircraft and there have been many new and better ideas come out of it, but be carefull, you are dealing with your life and a $20,000 engine. My 2 cents.

[Slyfox]

but in my line of work, these type of coolers have not been a problem. now the ones in the radiator, oh my. but those generally will fail with pressures over let say 80psi. and have seen it. aka the Nissan radiator failures which is a direct result of cooler line pressure up tward the 120psi area. which can be controlled with a different spring. the stacked cooler like we use can even withstand that pressure. but those radiators not a chance. not trying to muddle anything just saying. mine will probably stay the same for it is WORKING the way it is and I like the fact that my system keeps the tank level up. but knowing that there is like 8 connections between the tank and my oil pump inlet has got me to say the least, interested in keeping things sound.

[Kurt.A]

Did not mean to get under anybody's skin with my previous post. Yes we are all allowed our own opinion, we have many to thank for our freedom of speech. I fully understand the potential for an external leak being disastrous but no more disastrous than any other eng failure which could easily be caused by a variety of reasons. The plate coolers are very tough units as compared to the coolant radiators. They live right in prop wash and can be subjected to stones and pebbles even on a paved strip. something as simple as a pebble strike could cause a cooler to leak. With the cooler on the pressure side the leak would be obvious and draw immediate attention. With a leak on the suction side through the same pebble strike would still cause the eng to go down after many hours of aerating the eng oil and creating huge dollars in repairs. With the environment that I will be flying in I can definitely see that eng life would be increased with plumbing the cooler in after the filter. Just honestly makes more sense to my brain.

[jiott]

Kurt, just curious if you plan to plumb your cooler after the filter there is nowhere on the 912 to put it except in the scavenge line from the bottom of the crankcase to the oil tank. Or are you planning some modification to the engine case to get an oil in & out port on the pressure side?

[jrevens]

Kurt, just curious if you plan to plumb your cooler after the filter there is nowhere on the 912 to put it except in the scavenge line from the bottom of the crankcase to the oil tank. Or are you planning some modification to the engine case to get an oil in & out port on the pressure side?

I had the same question in mind with one of my previous posts. There's a lot to consider here, and I tend to agree with Jim and some others who like the cooler where Rotax says to put it. I'll say again that I believe the engine will see higher oil temps if the cooler is piped between the engine & the oil tank. Is it enough to be a factor worth thinking about? I don't know. But how do you propose to install the cooler "downstream of the oil pump & filter"? The only access I know of is downstream of the whole engine. The only pressure on that line is crankcase pressure. It seems to me there might be more chance of potential clogging of the cooler on that line than after that big "engine moisture, sludge & any other crap that may come out of the crankcase" trap called the oil tank.