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Engine Dehydrator Home made?

Engine dehydrator

About 2 years ago, EAA Sport Aviation magazine had an article on how to build an engine dehydrator. They used an air pump for an aquarium, pumped air into the bottom of a bottle with desiccant and fed the output from the top of the bottle to the engine. My guess is that this article can be retrieved from the EAA web site.
 
There was a writeup maybe 6 or 8 months ago--Sport Aviation? Kitplanes? Probably Sport Aviation because a guy in our EAA chapter built one and I doubt he takes Kitplanes because he flies a Cherokee. I have seen ads for these things factory built for a few hundred bucks. You can build one for less than $50.

Anyway, it's pretty simple. He used a large size pop bottle, filled it with silica gel. Get that at craft stores, maybe $15. It comes in white and it comes with maybe 2% blue indicator granules. You want the indicator granules so you can tell if the stuff needs to be dried. He filled a large size pop bottle with the silica gel, put some kind of filter over the end of a plastic tube and stuck it almost all the way into the bottle. The other end of the tube hooked up to an aquarium aerator pump. Another tube went from the pump to his oil filler spout thru a plastic cap he found that fit perfectly over the oil filler tube.

He runs the pump whenever the plane is parked. The pump draws very little current and it pumps a very small amount of dry air into the crankcase all the time.

He ran it for 3 months this summer and fall and the silica gel still showed blue. In western Oregon we don't see the humidity you folks east of the rockies see, so you might have to dry the silica gel more often.

I got silica gel for free from our shipping and receiving department where I used to work. Now I just need to build the thing. Thanks for the reminder, I'll get right on it.
 
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Here It Is

The article came out in the April 07 issue of Sport Aviation. This link has a picture, kit for sale and also lists the parts needed for assembly.

http://www.barkeraircraft.com/Engine-dryer-kit.html

The article recommends that you get a silent aquarium pump as opposed to a vibrating reed pump due to the noise that the reed pump makes.

Assembly:

Use a two-liter bottle with screw on bottle cap. Drill 2 3/16" hole in bottle cap. Cut 2" piece from rigid tubing and hot glue 2" piece in one hole and the 10" remainder in the other. Place Air Stone filter on end of long rigid tubing. Filter should be about 2" from bottom of bottle. Fill bottle with silica gel and attach cap. Use the tygon 1/8" flex tubing to connect pump to 2" piece. Rest of tubing goes from the long rigid piece to you engine oil filler cap or the engine vent.

When the silica turns blue, place silica in oven and heat at 350*F until it turns pink again.

Thanks for bringing this up as I wanted to build on of these and had forgotten about it.

JF
 
There was a correction in a later issue about the color of the silica gel. Blue is good, pink is wet & needs to be dried.
 
I built this from the article in Sport Aviation and it was easy to do. Here in Florida you have to bake the pellets pretty often to dry them out. Get enough silica pellets to fill the 2 quart bottle a couple times so you can bake one while the other one is doing it's job. You can get one of these from ACS for $200.00+ but you can build it for less than $30.00.
Danny
 
Engine Dehydrator

Just built one of these this weekend. I'll be interested how it does in the cold damp Illinois winter.

If you buy the silica crystals at Michael's, they are in the flower drying department. They are in a canister labelled "Flower Drying Art". The staff didn't know what i was talking about and it took a while to find them. Cabella's also has them available on their web site--for keeping guns dry while stored in gun cases.
 
I've considered building a desicator for my airplane and thought that one would need to couple the exhaust pipe as well and the carb air intake to make it fool proof. Seems to me that a couple of the valves will be open which allows moisture into the cylinders to cause corrosion. I would think that if you interconnected the exhaust, intake and the crankcase vent to a gallon of silicagel the natural change of temperature would cause the engine to breathe through the silicagel and keep it dry...
 
The system dries for the crankcase, not the cylinders, keeping a positive pressure there and most of the air probably goes out thru the vent. Use dessicant plugs to protect the cylinders if you aren't going to fly for awhile.

Here's another approach for the crankcase, or one you can use in addition to the dryer. Every time you put the plane away after flight, open the oil filler cap, then put a wet/dry vacuum on the crankcase vent while the engine is still hot. The vacuum will suck out vapors before the crud condenses on the metal. The air you suck in thru the oil filler cap contains less moisture and none of the corrosive byproducts of combustion. Only takes a couple minutes. Does it work or is it a crackpot idea? A guy who ran his Bonanza engine for 2,600 hours, about 800 beyond TBO publicized the idea. You can smell the crud while you run the vacuum, so you know it's sucking stuff out. I think it works; it can't hurt.
 
Richard, a few weeks ago I opened the oil filler cap just after a flight and there was vapor of some sort coming out. Sounds like a plan if I can just remember it. Still need to finish that engine dehydrator.
 
Sounds like a fine idea as long as the vapors you're sucking through the shop vac are non-combustible. Those motors are not without sparks.
 
venting the crankcase

I open my oil filler cap and let it vent every time I land for the day. A fair amount of visible water vapor escapes. I have no data on whether it really helps, but I feel better getting all that water vapor out of the crankcase. Never tried the vacuum, preferring to just let nature and heat do its thing. Interesting idea.

Every time you put the plane away after flight, open the oil filler cap, then put a wet/dry vacuum on the crankcase vent while the engine is still hot.
 
Every time you put the plane away after flight, open the oil filler cap, then put a wet/dry vacuum on the crankcase vent while the engine is still hot. The vacuum will suck out vapors before the crud condenses on the metal. The air you suck in thru the oil filler cap contains less moisture and none of the corrosive byproducts of combustion. Only takes a couple minutes.
Or modify an old hairdryer to disable the heating elements, put a reducing cone on the output end, and run it on a low setting for a few minutes through the oil fill/dipstick tube to blow the worst of the vapors out the 'case vent.....
 
This is very timely for me. Since moving my project out to my hanger it has become a little more exposed to the relative weather. I have been looking for some sort of fan or air pump to use for a closed circuit air dryer. Good post, it gives me a little more hope of actually being able to come up with something.
 
Time for my follow up. Engine dehydrator units have become a fairly large and recurring topic of discussion at the Eugene Oregon EAA chapter meetings during the last couple of months. Our Ex president and chapter founder “Wally Anderson”, known best in our circle as the creator and driving force of Synergy Air, had visited Northern Europe where the use of home made engine dehydrators apparently is common. At our last meeting Wally brought a unit he had constructed from parts easily found or purchased. His project was inspiration to me and I set off to construct a simple unit to use on my own engine while my engine basically sits on the nose of my unfinished 7A. With slight modification to the engines inbound air connection I'll be able to continue the use of the air desiccator unit (pictured below) after the completion of my 7A project. My cost of parts (less Silica gel) came to just a touch over $30.00 and assembly of the parts assortment took about one hour and fifteen minutes. Among the parts are, Storage containers from K Mart which were to my surprise of very good quality and very air tight, three short threaded tubes (the type used to construct lamps with), One fairly high volume aquarium air pump, One medium dab of red RTV used to seal the wire excursion through the main canister wall, Three feet of vinyl hook up tubing for the air pump and Twelve feet of larger diameter vinyl tubing for the unit to engine run, One short piece of porous tubing (also found at the pet supply store) for use as an air diffuser inside the desiccant canister. I ended up with a few varieties of Silica gel. I found some fairly course gel at the local industrial compressor shop which given the size of the bag I was able to purchase didn't fill my second stage canister quite enough to please me. I found a One and a half pound bag of Silica gel at Michael's craft store. Craft store gel is similar to course beach sand and at first the grain size was a bit of a concern to me as to what it's overall compaction and resistance to air flow would be, However, it turns out that it works just fine. Water bottle tests of the finished unit show the assembly to have a very adequate stream of air being returned to the engine. So with that here is how it works. Air enters the main canister through the top. The air pump sitting on the bottom of the main first stage canister and to one side vacates the air from the large first stage canister to the small nested second stage canister via small diameter vinyl tubing which penetrates the smaller canister through a slightly under size hole. Connected to the tubing from the air pump and secured to the bottom of the second stage canister is the optional porous bubbler tubing to encourage the diffusion of air. Both canister lids are connected permanently via one of the short threaded lamp tubes. As you can see from the pictures the small canister is where the desiccant lives.

des1.jpg


des2.jpg


des3.jpg


des4.jpg


des5.jpg


des6.jpg
 
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I got mine going about two weeks ago. The clay-like desiccant had no moisture indicator so I bought the Michaels desiccant with color changing crystals. I want to find some desiccant that is coarser than Michaels.

I got a 30-60 gallon pump from Walmart but want more air flow. At least I am pumping some really dry air in the engine even if not optimal.
 
I've noticed a common misstatement throughout this thread. Although in the long run it's not important it may be good information for others that collect this sort of useless info. Silica gel doesn't turn turn pink when it's saturated, it's the indicator pellets or grains that turn pink. Indictor pellets or grains are Cobalt Chloride and are readily dried in a 250* hot oven. Apparently Silica gel takes a hotter, longer oven to dry out thoroughly, in other words your indicator will have dried out long before your Silica gel has had much of a chance to dry. To make matters worse there is a coated Silica gel (coated with Cobalt Chloride) that does turn pink when saturated but that gel becomes "worn out" after several cycles of saturation because the Cobalt Chloride migrates into the individual grains of Silica gel and loses the obvious effect of color change. From what I've been able to gather once you have your batch of Silca gel or Cobalt Chloride you pretty much have all you'll ever need so long as the quantity you need doesn't change.
 
Rivethead

Last week I pulled my left magneto to replace the carbon brush and cam to comply with SB2-08 and SB3-08. I was appauled at the rust on the parts from inside the accessory case of my 100 hrs TT Aerosport O-320 Lycoming. Needless to say I?m building a dehydrator this weekend. I like your style better then the 2 liter bottle method due to the fact your system is a closed system in regards to air circulation. Leaving the pump in open air would seem to simply suck ambient moisture from the surroundings and dumps it into the dessicant. Your system should be a lot longer between drying periods of the dessicant.

As I round up parts my main question is on the pump. What is considered ?high volume?? I went to the pet store and they are classified as per 10gallon, 20gallon, etc. What size in gallons is considered adequate? The 10 gallon was $20.00, the 20 gallon=$25.00. I went with the 20 gallon, but if it is not enough I can exchange it for larger.

Also, You have any extra old oil dipstick caps laying around that can be drilled out? I liked that idea also.

Thanks
doug
 
Rivethead,
Nice writeup and setup.
One tube is connected to an old oil fill cap. Where's the other tube connected to the engine?
Thanks
Tom H.
 
Design consideration

I looked into building my own dessicator before finally purchasing a Tanis dehydrator. While expensive, it does have a built in heater for renewing the silica crystals.

The unit also has a digital thermo / hygrometer that records hi and lo readings. I use this in concert with the blue colored crystals to determine when to renew the silica.

I've been using the unit for over two years now, and I'm glad that I purchased the unit, as I find myself using the heating unit far more often that just every couple of months. During dry periods, I've gone 2+ months, but there have been a couple of periods where I had to dry out the crystals after only 4 weeks.

After seeing the unit first hand, I've often thought about how to go about duplicating the unit. It is essentially a toolbox with a gasketed / hinged lid, and a small plastic centrifugal blower over the top of a tub of silica inside of the box. Also buried in the tub with the silica is an insulated heating wire (similar to a water pipe heater to keep them freezing in the winter). It takes between 4 and 6 hours to dry out fully saturated crystals, but I normally put the system in the renew mode while I'm out flying, and rarely do I have to do a full heating cycle.

The draw side of the blower fits to the oil dipstick tube (works great for pulling out water vapor just after flying), while the pressure side goes into the crankcase breather. When I know I'll be away for more than a few days, I stuff a red rag into both exhaust stacks -- be sure to leave some hanging out so you remove them before start.

Don
 
I finished mine last month for under $40 which included a new plastic Stanley 16" tool box from WalMart. Mine is a closed loop system drawing through the breather vent tube, into the tool box holding the silica bottle at one end and sucked out through the other end via the aquarium pump with a stone filter buried in the silica. The dry air then is pumped into the oil filler tube sealed with a rubber stopper. I like Rivetheads use of an old filler cap to screw on and will modify mine to do the same. My stopper worked loose one time. Its a nice portable system with everthing self contained in the tool box.
 
Todays flight to Pueblo was uneventful. Upon return home and after putting the plane in the hangar I removed the oil filler cap and some vapor came out. This was five minutes or so after engine shutdown.

I left the cap unscrewed to allow vapor to escape and came back about 30 minutes later. No obvious vapor. I put the dehydrator output into the crankcase breather hose bottom and plugged the system in as I was looking at the oil filler tube. After less than a minute I believe that I saw more vapor coming out. No flashlight so this observation has some uncertainty.

If correct, it appears that my lowly 30-60 gallon Tetra whisper pump is doing some good.

This is not a closed system at this point.
 
In answer to a couple of questions. There was a choice between a 10, 20, 40, 60, or 100 air pump. I have no idea what the numbers actually stand for so I assume (I hate asking store help anything) they are suggested aquarium size. I chose the 60 as a guess and found that the air moves quite enough. I have access to an anesthetic machine and at some point may measure the actual air flow using the meter on that unit. A conservative guess from anecdotal evidence shows me that the unit moves about **.5 cfm. I consider this way more than enough since the entire internal volume of an assembled engine can't be more than a couple of cubic feet and is probably far less. Pumping air 24/7 .5 cfm becomes a lot of air exchange. Return air is sent back into the engine via the breather. Pictures of that area were so poor I didn't bother resizing them to post. I have a question of my own now for dtw_rv6. In the system you bought you say it dries your silica gel using a fan to move air over the crystals. Q: Where does the water vapor go after it leaves the gel? Is it somehow vented back to the general atmosphere? I'm assuming it's not being returned to the engine that's been dried out but I'd like to know how it's done with a, closed?, system. Also another point bothered me. I spend to much time dwelling on minutia and every new project I enter into begins with more research than it probably deserves, but. From what I've discovered, and I've mentioned this before, Silica gel takes several hours in a hot oven to thoroughly dry on the other hand Cobalt Chloride, the blue stuff, readily dries in a fairly short time at a significantly lower temp, 250* hot. All of the suggested temperatures I've found are hotter than most plastic tool boxes that I've ever seen can stand. With that said "Thoroughly" becomes a key word. There is a technique used in preserving art using Silica gel to hold air in an enclosed space at desired humidity level. The process used is a type of "tempering" of the gel to work only in a very small range. I'm wondering here (I'm not trying to disparage your unit) if your not actually training your dehumidifier to keep the air at a higher than optimal level for your engine.

(edit)

I'm noticing people liking the use of my dip stick cap as a modified tube inlet. I used the old cap rather than using a rubber stopper or cork because occasionally it rains in my hanger and I really didn't want to find a puddle of water settling into my oil filler tube around a stopper. So far the old hanger only gets damp with a few local areas of leaking water from the roof in bad rain storms. I've never had any part of the engine actually get wet other than a little dew so in this case it's precaution. That old cap was available and turned out to be very easy to drill out.

(another edit)

** Curiosity got the better of me so I measured the air flow. Turns out to be 7 liters per minute @ the return end of the system.
 
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I followed the Barker instructions for the 2 liter soda bottle type and it came out great. Also, it is a closed system and cost about $30.
 
I finished mine last month for under $40 which included a new plastic Stanley 16" tool box from WalMart. Mine is a closed loop system drawing through the breather vent tube, into the tool box holding the silica bottle at one end and sucked out through the other end via the aquarium pump with a stone filter buried in the silica. The dry air then is pumped into the oil filler tube sealed with a rubber stopper. I like Rivetheads use of an old filler cap to screw on and will modify mine to do the same. My stopper worked loose one time. Its a nice portable system with everthing self contained in the tool box.

is your stone filter the bubbler that comes with the aquarium tank? if so, i'd take it off, it is just a restriction on the system you don't need.
 
Danny, the stone filter/bubbler appears to be a way to keep desiccant dust out of the engine. Why do you suggest that it is not needed?
 
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I have avoided the return system cus I didn't want to get oil vapour into the dessicant. Notsure if it will or not. So I use a once thru using ambient air. I did find that using a 5 foot tall column made the dessicat last longer....trouble is this added to the pressure drop so I had tochange to a bigger pump. Petco have those own brand now and for $12 I bought one that is a monster compared to my tetris thing. Pumps way more air.

Oh ifound cheapest place for dessicant was good old harbor freight at $5 for 2.2lbs and this is the indicating type
 
Looking for extra oil filler cap

I'm looking to build one of these... does anyone have an extra Lycoming bayonet style (not screw in) oil filler cap that they would like to part with? I don't need the dipstick, just the filler cap, hopefully with O-ring.

This is for an O-235, but I think it might be the same part for the O-320

PM me if you have one!
 
Update...went for my post annual check out flight...plugged in the dryer and saw a visible plume of steam from the filler cap...of course it was minus 5degC...very satisfying knowing that was coming out of the crankcase
 
worked for me

I built one of these this winter for the Skipper - I get the satisfying plume of moisture everytime I turn it on. The first 1/2 inch or so of the HF pellets have turned pink. I'm glad that moisture isn't in my engine any more!
 
Oil filler Cap alternative

For those wanting to create a closed system, I recently discovered that an AN14 o-ring boss plug fits perfectly on the O-360. Drill and tap for a brass nipple available at hobby stores (I used one made by Dubro), and you're set for less than $10.

Paige
 
Holy thread resurrection Batman!

I'm sitting here looking at a military sealed ammo box getting ideas it looks like a dehydrator. :rolleyes:
 
to put a little different twist on this.........i have a 25 watt stick on heater on my oilpan and one on my crankcase. my oil temp stays 50 degrees above oat and the heads stay 12-15 deg. above. i take out my oil filler cap and i am thinking my oil will quickly evaporate any moisture as it is so much warmer than surrounding air and any steel on the engine is less likely to rust because i am above dewpoint by 10 degrees. 50 watts isn't a big deal to run 24/7
 
I built one of these this winter for the Skipper - I get the satisfying plume of moisture everytime I turn it on. The first 1/2 inch or so of the HF pellets have turned pink. I'm glad that moisture isn't in my engine any more!

I built and used one last winter and did not get any or at least much moisture out. I am in the West and it is a much dryer climate though.

I will be using it again as the moister weather is arriving.
 
ok, i have read all the posts on this and unless i am missing something i can't see how this can be reducing moisture in the air it pumps by more than a miniscule amount. the pump is pulling air from the hangar and into the engine? if the pump was pumping a closed circuit from engine back to engine maybe but this pump is probably taking at least a couple cubic foot of air a minute. i don't in a million years believe that a quart of silica can be pulling the moisture out of a volume of air like that for very long. i imagine the calculations could be done to figure the water in a cubic foot of air at stp and a given humidity and i am not going there but i bet the air humidity change in and out with the air pump can't be measured. also, the air is being sent all around the parts that are constantly splashed with oil. no way for the air to get the upper cylinders etc.
my thoughts on keeping rust away are always shut down the engine after getting it hot, remove dipstick cap and keep all the engine metal warmer than the surrounding air.

and i could be all wrong.
 
Dehydrator

Reviving this thread just for grins.
I assembled a closed loop dehydrator on the cheap.
Aquarium air pump and dessicant beads were the only real cost.
Old clear plastic gallon jar.
Scrap plastic bottle
Hoses & fittings
Bucket
The gallon jar has a fitting on the bottom. My wife's food strainer fit in the bottom. Dessicant beads poured right over the strainer.
Hose from the engine crankcase vent goes into the liquid capture plastic jar.
Hose from liquid jar goes to the bottom of the dessicant jar.
Hose off the top of the dessicant jar goes to the vacuum side of the pump.
Hose from the pressure side of the pump goes to the oil filler.
Everything fits in an old bucket with the pump on top.
My shop is pretty dry. 25%. Engine hasn't been run so this may not work at all, but so far it seems to at least a little. Photo is a temporary capture bag from the crankcase vent.
20221221_150152.jpg
 
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ok, i have read all the posts on this and unless i am missing something i can't see how this can be reducing moisture in the air it pumps by more than a miniscule amount. the pump is pulling air from the hangar and into the engine? if the pump was pumping a closed circuit from engine back to engine maybe but this pump is probably taking at least a couple cubic foot of air a minute. i don't in a million years believe that a quart of silica can be pulling the moisture out of a volume of air like that for very long. i imagine the calculations could be done to figure the water in a cubic foot of air at stp and a given humidity and i am not going there but i bet the air humidity change in and out with the air pump can't be measured. also, the air is being sent all around the parts that are constantly splashed with oil. no way for the air to get the upper cylinders etc.
my thoughts on keeping rust away are always shut down the engine after getting it hot, remove dipstick cap and keep all the engine metal warmer than the surrounding air.

and i could be all wrong.

I have three humidity meters that I threw into the dessicant chamber. The ambient humidity at my hangar today was 74%. The humidity in the chamber containing the air that is being pumped into my engine is 12%. I conclude that the air is being pumped into my engine is substantially drier than the air that would be there if there was no dehydrator. I could be wrong.

edit: I don't do a closed circuit like Wirejock. I did, but it was too much of a pain to get down there and plug it into my oil separator after each fligh, so I just go open circuit. Probably have to cook the dessicant more than he does, but I think the humidity of the air going in is what matters.
 
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Just to revive an old discussion, the humidity in ANY IC engine, even the Rotax 912, 915 is the by-product of combustion of gasoline (and likely diesel, too). Yes, the ambient humidity matters as well but it's not the same in all places.

As an aside, there is also sulphur in the blow-by gasses. If you combine water vapor, heat and certain sulphur compounds you will get H2SO4 (AKA sulphuric acid). Of course, pure water plus most iron alloys will rust, too. Is this why used oil becomes more acidic? Hmmm.

With the Rotax, the pump needs to push dry air up the exhaust pipe. With the Lyco type engine, you can pump it in through the oil vent. Either way, there will be very high levels of RH inside the engine immediately after running it. Quickly getting rid of that moisture is a good thing. Leaving the RH to condense inside the engine is a bad thing. The degree to which the residual RH matters is arguable but it's not arguable that it exists. Since it does exist, if you want to ignore it that's your personal decision.

Many otherwise reasonable people think that running an engine gets rid of the moisture that finds its way inside the engine from outside. That is simply a river in Egypt. Running the engine will create water vapor and the hot conditions inside the engine will retain high amounts of water vapor. The RH will increase as the temperature decreases. When the dew point is reached, condensation happens. None of this can be denied. It can be ignored as not harmful or not very harmful or some other excuse. But the physics don't care.

I use a dehydrator. There are various solutions but any one of them is probably better than not doing anything.

-30-
 
Open loop vs closed loop

I have three humidity meters that I threw into the dessicant chamber. The ambient humidity at my hangar today was 74%. The humidity in the chamber containing the air that is being pumped into my engine is 12%. I conclude that the air is being pumped into my engine is substantially drier than the air that would be there if there was no dehydrator. I could be wrong.

edit: I don't do a closed circuit like Wirejock. I did, but it was too much of a pain to get down there and plug it into my oil separator after each fligh, so I just go open circuit. Probably have to cook the dessicant more than he does, but I think the humidity of the air going in is what matters.

I removed the return side last night and ran the dehydrator as an open loop. No difference in the humidity coming out the crankcase vent. 10%. Our climate is so dry, I'm switching to open loop. It eliminates a bunch of tubing and fighting to plug the hose into the crankcase vent pipe. Much simpler. The assembly fits in a bucket. Just one connection. No wet air getting sucked into the dessicant. We shall see.
 
Some numerical examples based on the absolute humidity of the air/water mix.

If you shut down your engine with a oil temp of 180F each cubic foot of air in the crankcase might have about .32 ounces of water mixed in. A saturated 180F air/water mix.

If you pumped in 70F 100%RH air until the engine cooled it would lower it to .016 ounces per cubic foot. Doing that alone is a factor of 20 reduction of water in the crankcase.

If you used a desiccant to lower the RH of the 70F air to 10%RH it will lower it to .0016 ounces per cubic foot. A factor of 200.
 
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One strategy is to use a pool toy inflator or similar to blow a higher volume of ambient air through the crankcase for several minutes after returning to the hangar, evacuating any post-shutdown moisture-laden air, thereby less crankcase moisture to condense as the engine cools back toward the dew point. I don't do that routinely, but I do have a 12v-inflator in the hangar somewhere. I mostly just plug in the dehydrator as soon as I get it in the hangar.
 
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One strategy is to use a pool toy inflator or similar to blow a higher volume of ambient air through the crankcase for several minutes after returning to the hangar, evacuating any post-shutdown moisture-laden air, thereby less crankcase moisture to condense as the engine cools back toward the dew point. I don't do that routinely, but I do have a 12-inflator in the hangar somewhere. I mostly just plug in the dehydrator as soon as I get it in the hangar.

4 minute purge of ambient air followed by a 4 hour flow of dry air into the engine oil filler tube.
I have been using the open loop method for over a year now and recently stopped recording data because I have not seen the internal engine humidity level over 40%
Data shown in this link https://vansairforce.net/community/showthread.php?t=200758
 
Has anyone built an engine dehydrator? Are there plans available?

Jeff...this is what I did...

https://vansairforce.net/community/showthread.php?t=188376

The original design had a fish tank pump...which worked ok. I now have a vacuum pump for composite bagging, and this moves more volume.

This is a closed circuit design so the beads don't saturate very quick. I've been using this for over 2 years and only dried the beads once.
 
This is a closed circuit design so the beads don't saturate very quick. I've been using this for over 2 years and only dried the beads once.

I use a container that contains 15 lbs of silica gel beads. With my “open-loop” technique, I find that the beads have to be “re-charged” two-three times per year and I do that when I see the humidity in the container gets to about 15%, at which point they are more orange than blue. I have a second container of 15 lbs so I just do an exchange and bring the used ones home for baking. My wife has taken over the concept of baking them dry, based on the fact that I’m unable to do that and get them into the containers without a number of the beads getting loose in the kitchen :D . She works hard at getting them nice and blue again, which I sincerely appreciate. I will neither confirm nor deny that spilling beads all over the kitchen in the cooking process has been less than “accidental”.
 
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Here is my design. Humidity meter shows 10% (minimum the meter will measure) when the pump is running. Changed the beads after a year but hardly any had changed colour.

Fin 9A
 
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