The Cessna 120-140 Association Forum

Hey does anyone use engine dryers? I seen a big discussion on em on another forum... Some claim results inconclusive, others swear they help prevent corrosion even during short amounts of storage. Honestly the concept makes a lot of sense to me, though it seems like the only the bottom side of the engine is going to get the benefit not the cylinders but that seems better than nothing by all means. Just wondering the thoughts on here about them...

Years back I built one out of a fish tank pump that one of the EAA chapters was selling. I made the mistake of building up an engine before the project was done. After years, probably over 15, the 120 project is nearing completion and I was getting a little nervous about the engine. I disassembled the engine and found no rust at all. I kept descant plugs in the cylinders.

Bill

I think im going to build one, makes intuitive sense to me... i like idea of closed loop but leave it open for a while to push the worst out before hooking the loop... like while packing other stuff up and such and hook the second side up before going? i haven't looked at plans in detail but if its not in the design would an outbound to engine air filter not be a good idea to stop any silica dust?

how do those plugs work? are those more just for long term storage than in between flights?

Ray

The descent plugs are for long term storage. Eventually the media will turn color as it collects the moisture and at some point will go in the oven to be recycled. I can't remember how long the system can go without recycling but I am guessing it was a few months.


Bill

There really is no way to run dry air through cylinders when not in use is there? I read one person doing the fish pump n hooking to exhaust or intake but tgat would only get one cyldiner at best unless im thinking wrong, the one w that valve open... am i thinking right or wrong on this?

Obviously a Tanis heating system is more expensive than a do it yourself system, but if you really want to keep your engine dry I am convinced it works. According to a Tanis rep who presented at the Faribault convention in 2016, keeping an engine moisture free is all about maintaining the engine temperature above dew point temperature regardless of ambient temperature.This theory makes lots of sense to me. My engine is outfitted with an old Tanis heating system which I have used extensively as have previous owners and had not been opened up till I did a bottom end overhaul in 2015. The engine was virtually rust and corrosion free.

6863 wrote: ↑Mon Oct 29, 2018 9:06 pm Obviously a Tanis heating system is more expensive than a do it yourself system, but if you really want to keep your engine dry I am convinced it works. According to a Tanis rep who presented at the Faribault convention in 2016, keeping an engine moisture free is all about maintaining the engine temperature above dew point temperature regardless of ambient temperature.This theory makes lots of sense to me. My engine is outfitted with an old Tanis heating system which I have used extensively as have previous owners and had not been opened up till I did a bottom end overhaul in 2015. The engine was virtually rust and corrosion free.

I will look into that... i am one of those guys that will work as hard as i can to be one of the ones that makes tbo or better, at least as a concous goal... and willing to put extra effort into it. im same with my cars i try to see how long i can keep em running tip top as they age... they may be messy but i keep on the maintenance... all you say makes total sense!

I tried four methods to preserve my engine long term. The dessicant dryer method by Ron Barker, storing the engine in a plastic bag that was evacuated with a vacuum pump, putting a nitrogen blanket over the engine, and buying the Protective Packaging solution. Protective Packaging worked the best with no maintenance, and it keeps humidity levels less than 40%. See attached photos. Details at protectivepackaging.net

More Photos. The key is to keep the RH < 40%. I learned of this solution by viewing the video at https://www.youtube.com/watch?v=ecCAklmipcU on how to preserve a 731 Honeywell jet engine. Although my engine is off aircraft, Protective Packaging offers many solutions for sealing odd shaped parts. I can imagine a barrier bag around the entire column of a Cessna 140. The barrier bag lets in air, but it prohibits water vapor. Key to preventing corrosion is eliminating water vapor, eliminating oxygen, or both. The barrier bag eliminates water vapor. The bag kit cost me $335, and the tech rep told me it is good for 5 years indoor storage--2 years outdoor storage. The MIL-PRF-131 bag is the key to the solution. My humidity plug has stayed at 30% or less for 6 months now.

Although the vacuum bagging method seemed to work, long term the heavy polyethylene bag developed small punctures that had to be resealed. Similarly, the same for the N2 blanket method, albeit at times, I could keep the RH at 30%. The key is to keep RH < 40%. The ProtectivePackaging.net solution is the most troublefree, and the MIL-PRF-131 bag is heavy duty.

The David Barker aquarium pump method by sucking air from the crankcase then drying it and sending it back into the crankcase is clever and complicated, but I never knew if it was working or not. The automatic humidity sensor that would turn on the light bulb to automatically dry the dessicant in the pickle jar never turned on. I augmented the David Barker solution by pulling air from the cylinders by fitting the spark plug holes with rubber stoppers then drying the air in dessicant placed inside of a 12-in long acrylic tube (about 1.5 in diameter). Only a 1/2 in of the dessicant turned pink, so I suspected that the air in the clearance space above the cylinders was dried.

If I had a better plastic bag, I think the the method to keep the engine stored under vacuum or nitrogen blanket would have worked too, but these are more complicated than the barrier bag method by Protective Packaging. The barrier bag method is essentially maintenance free, and the bag is very strong. The N2 blanket method requires a nitrogen bottle and regulator, and the vacuum bagging method the pump and a timer to turn the pump on/off periodically to contend with leaks. I purchased all of this equipment, but my success was never to my satisfaction.