What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Engine dehumidifier

Michael Henning

Well Known Member
I assembled a dehumidifier today. It is a fish tank air pump that feeds into the bottom of a 12?long (vertically oriented)x 3? diameter pvc pipe. I screwed one end cap to a board, then glued the pipe to that, with a threaded end cap for the top. On the base, I tapped in a brass fitting for the air from the pump, and filled tube with blue desiccant that turns orange when saturated. Off of the top cap, I tapped in a air tool filter/dehumidifier as a final filter, and tell tale for the desiccant inside the tube (the filter from harbor freight also has the blue desiccant visible). From that filter I put a barbed adapter to connect the plastic airline to my engine oil breather tube. It continuously pumps dry air through engine.
Comments??? Concerns??? And, no, I don?t have my breather tube notched.
 
Bob is right. You really want to make a closed loop system pumping moist hot air out of one opening, such as the oil filler, running it through the desiccant, , filter the dry air, and push it back through the engine using the breather tube. Once the oil is cool and stops emitting moisture, turn it off or put it on a timer to run a few minutes every day. I set mine to turn off after 2 hours when I was done flying, and then used my daily timer.
 
Drier

I have been doing this for about 10 years after seeing the idea in an EAA magazine.

I use an old dipstick with the rod punched out and put the dry air in through the dipstick tube. Mine is just one time...in the dipstick and out the breather. I also put pill bottles over the exhaust outlets and keep the carb heat on to minimize air infiltration through the open valves. I tried recircing by putting a return line from the breather back to the pump. My only issue with this was when drying the desiccant in the oven at home it released an oil fume smell into the house so I stopped. No fumes with the once through method. Some of the guys on the field have built them and added a box with a hygrometer in it which turns the unit on off to the set point. I don't personally agree with this as you aren't really sensing the air in the engine...only in the box in the line but each to his own. Recircing did extend the time between dryings by more than double (2-4 weeks depending on the season). Some guys have microwaves in the hangar they use for drying but I found the oven works best...just stir it up occasionally when drying.

Does it work? Who can say for sure. The first winter I used it the oil looked much more like oil, instead of the brown sludge look it had before. And yes I change the oil regularly, between 35 and 50 hrs. I figure $30,000 is a ton of money for an engine so between this, CamGuard and flying as often as I can I feel I am doing all I can to protect the cam.

Good luck with yours!
Al
 
Dehumidfier

How about purging the crankcase of moisture with a few cubic feet of nitrogen?


Keith Rhea
RV7
donated 2018
 
I built a closed loop version to use on the -10 while it is down for upgrades this winter ... it has been running 24/7 since early Nov, connected to the oil filler neck and the breather. I have a gallon of dessicant beads.

It has been very humid (lots of condensation with all the propane we've been burning) and none of the dessicant has even changed color yet. My guess is that this is because it is circulating a pretty small volume of air, and once dried it stays that way.

Makes me feel better about the engine downtime.
 
Bob is right. You really want to make a closed loop system pumping moist hot air out of one opening, such as the oil filler, running it through the desiccant, , filter the dry air, and push it back through the engine using the breather tube. Once the oil is cool and stops emitting moisture, turn it off or put it on a timer to run a few minutes every day. I set mine to turn off after 2 hours when I was done flying, and then used my daily timer.

Definitely recirculate, the post indicator is a good idea and is the final test of dry air going into the engine. One thing, when using the system after each engine run, oil aerosols and very moist air will be drawn into the unit. A catch bottle filled with something with a lot of surface area (like cotton balls) will collect both the condensate from the suction line and oil aerosols that will contaminate your silica bed.

Update:4-29-20 -**** After using a recirculation system for a couple of years, I have done some new experiments and conclude that a dry air supply for an hour is enough to completely displace the crankcase 3x over. Then shut it off. It is easier to push out the water rich air than clean it with a recirculating system - voice of experience. I am concerned about the steam in the engine will condense before it is expelled so now developing an initial 3 min purge to replace the crankcase with ambient then start up the desiccant stream. ****

If you are not flying yet neither is an issue. . . yet.

One more thing - silica is very abrasive stuff and we use a small lawnmower fuel filter as a final filter to prevent any dust from entering the engine. Those aquarium pumps leak badly so make sure all the dry side is pressurized.

How about purging the crankcase of moisture with a few cubic feet of nitrogen?
Keith Rhea
RV7
donated 2018

It would work after a flight to do this. But kind of a pain, as you would still likely want the dryer for outgassing from the remaining oil. Virtually no moisture will travel up the breather tube. Test results prove that. Some remove the dip stick immediately after flight and let thermal siphon work, some use a vacuum cleaner after flight to pull the high moisture content blow-by out, some just attach the dryer. One can only do so many things before they become a pain.

Using cam guard will protect for 30 days anyway, but personally I don't like the moisture in there. 2-4 tablespoons will condense each flight, and some additional captured as vapor.

[Edit/Update:12.23.23 Implemented a 20l/min purge with ambient air then a 60 min run with 2.5 LPM desiccant air. N2 for the purge should eliminate oxygen, water and that should to it for a while - how long unknown. I would do that if nitrogen was available. Currently investigating molecular sieve to replace silica gel - initial results (20F ambient) show -20F dew point, much better than silica gel. ]

A PCV system could all but eliminate this phenomenon but it creates more serious issues than it solves.
 
Last edited:
Engine dryer

I have two recirculating dryers for my IO-360. One for drying the crankcase, and one for the cylinders. The one for the crankcase recirculates air between the oil filler tube and crankcase breather tube after passing through a canister filled with silica gel, and the one for the cylinders recirculates air from the exhaust into the air intake. The crankcase dryer has a fan connected to a timer which operates for about an hour per day. The crankcase one, of course, requires you to rotate the prop a few turns to move the air. Not a problem as I am at the hangar almost daily. The photo shows both dryers hooked up.

20180126_173032.jpg
[/URL][/IMG]
Warren
RV-7
Minneapolis Crystal
 
Last edited:
Dehumifiers

Given the cam - lifter spalling problems caused by corrosion, this sounds like it should be very effective. From reading the thread, it seems like closed loop is the way to go.

It would be nice if some hard data could be found to measure the effectiveness of closed loop desiccant de-humidifiers. Are there any poll taking facilities on this site? (I?m a newbie, and this is my first post)
Anyone who has used such a device might be polled with questions like:

Do you use a closed loop desiccant system?
How long has it been in place?
Has a overhaul been done since its installation?
How long had system been used up to OH time?
Was there spalling upon tear down?
If no tear down yet, what are compressions, after system in place for xxx time?
 
Hi All,

I've had some questions lately on my dehumidifier system that I installed when I first hung my engine and based on my experience with it over the last year, so I thought I'd post a few photos etc. to explain things.
Mine is a closed loop system. This is pretty critical, otherwise you will saturate your desiccant very quickly. It generally keeps the air at 10% or less humidity inside the crankcase. You won't see corrosion occurring at this level, even on unprotected steel. I've got 2.5kg of methyl violet (orange) desiccant in a 6 liter container as my drying medium. The cobalt chloride blue desiccant kills you, so I don't use it. The container has a silicone seal around the top and clip-lock lid to keep it air tight.
At the top of the box is a respirator filter mounted to filter any dust out of the dry air before it is drawn into the engine. I used a respirator filter for this because it was something I had laying around unused that didn't fit my mask. I just found a cap that approximately fitted one end, then used some sikaflex polyurethane sealant to keep it air tight. There are some barbed brass fittings screwed into a hole I drilled in the cap so I can attach the air transfer hose. I cut an approximate hole in the lid of the box for the filter to draw air through, then sealed around the perimeter with sikaflex. The air is pulled out of the filter into the fish tank pump. A fish tank pump contains an oscillating diaphragm that normally pulls air from the body of the pump. You need to find this input port to the diaphragm body, then drill it out enough that you can stick the hose into and seal it in place. The other holes in the pump body are just to ensure that the motor stayed cool as you have re directed the air that would normally circulate over the internal parts everytime the pump oscillated. Probably not necessary given that the pump is only 2W, but I didn't want to find out that it was the hard way. The pump size is not really critical. Once the engine humidity is down to the baseline level, it only takes a small amount of air circulating to keep things at a low humidity level. The pump I use pushes 50 liters per hour and costs less than $5 per year to run. The only upside to a bigger pump/hoses are that they will reduce the moisture level faster after a shutdown, however it is totally unnecessary to have a large volume of air recirculating through the engine. After shutdown, my system can reduce the humidity in the engine at a rate of 2% per hour.
The air is pushed into the engine via a plug where the dipstick goes. When the engine is supplied from lycoming it will have a plastic threaded bung where the dipstick tube will go. I removed this bung, drilled a hole in it with my uni-bit, then screwed a brass threaded barbed fitting into the center for the silicone tube to attach to. The exit air from the engine comes out the crankcase breather hole, so you do a similar thing here allowing you to attach a tube. Once you've finished your engine installation and you have your breather tube and dipstick tube in place, you'll need to make respective fittings for these ports. I may put another jar here to act as an air/oil separator to stop my system being contaminated by oil draining out the breather, but thus far I have had no issues.
The exit air from the engine returns via a glass jar. This contains one of those AAA battery operated room temperature and humidity monitors that you can find at your local electronics store dirt cheap (jaycar in my case). It's handy for keeping an eye on things and will give you more of a precise understanding of the humidity level than the coloured beads. From the jar, the air then feeds back into the box, via an "air stone" that sits along the bottom of the box. This allows the air to be distributed along the length of the box before getting drawn up through the beads. This leads me to my last point. If I was to do this over again I would go with a much taller vestle, rather than the wide, flat one I have at present. Currently the beads in the center of the box reach saturation point rather quickly, whereas the beads around the perimeter stay in their dry state. A taller container would mean that the air is being pulled up through a greater number of beads for the same mass of beads, which would ultimately mean that you will be able to go for more starts before you need dehydrate the beads. I have currently only dehydrated the beads once in a year of operation and 6 starts since I first commissioned my engine, but looking at the actual number of beads that had changed color, it was only a small proportion of the total, and only those pretty much directly above the air stone. Based on the number that had changed color, I suspect in the future that I should be able to run the engine for 20 or more starts between dehydration session. My humidity meter would normally sit at 10% (the lowest it will read anyway) but when I found it holding steady at 20% after my sixth start, I decided to dehydrate the beads. The dehydration is performed by placing the beads on a couple of large baking trays in the oven at approximately 105degC for a couple of hours or until they have returned to their orange state. You want the layer in the tray to be as shallow as possible (an inch or less) to allow the moisture to crack off quickly.
In addition to the dehydrator, don't forget to tape off the intake and exhaust ports (or pipe if you have it installed) and insert a desiccant spark plug in the top plug hole of each cylinder. These are available from Aircraft Spruce amongst other places.
A breakdown of the dehydrator cost is as follow (remembering this is AUD which is about twice what it would cost in the US). Some of the smaller fitting (barbs/caps etc) I had on hand.
Aquarium pump and tube $30
6l box $8
2.5kg Orange desiccant: $70
Room temp/humidity monitor $20

Anyway, I hope this answers everyone's queries.
Cheers,
Tom.




 
Last edited:
I built a closed-loop fish pump system while my used engine sat before first flight (a total of about 10 months). I also used dessicant plugs. I actually nerded out and built an arduino system that monitored the internal humidity compared with the external. Unfortunately I don't have that data still, but I do know it was significantly drier than the ambient air. About 300 flight hours later and my engine, which now has about 1000 SMOH and 300 STOH has consistently perfect oil analysis. I do fly frequently now, and use camguard.

Chris
 
Considering the merits of open-loop vs. closed loop driers.

First of all, I wonder how the folks with closed loop systems connect to their breather pipe.

My breather pipe is 1/2" O.D., bent in a gentle arc pointed aft, cut off at 45 degree scarf angle, and positioned about 1/8" away from the top of my exhaust pipe. This puts any blow-by oil onto the exhaust pipe where it burns, rather than coating my belly with oil. It would be near impossible to slip a piece of tubing over the end of it.

So I am pretty much committed to an open-loop drier.

For continuous operation, obviously closed-loop is better, since you eventually get all the moisture out of the engine, and the circulating air doesn't add additional moisture beyond what was in the engine shortly after shut-down. Which is quite a lot.

An open-loop system will quickly blow all the moist blow-by air out of the engine without loading up the desiccant with all that moisture. You are only removing ambient moisture first to fill the engine with dry air.
At some point in time, you would reach a cross-over point where the accumulation of ambient moisture into the desiccant would be more than the dose of moisture from the engine.

I am thinking that a few hours of open-loop operation would remove all the blow-by moisture, leave the engine full of dry air, and then turn it off. Over time, ambient air moisture would diffuse back into the engine through the breather. So, the value of the open-loop system really depends on how humid an environment you live in. Certainly in the South, Southeast, and Midwestern states, the humidity in the summer is high enough to warrant a closed-loop system. Here in the west, our humidity is so low that it is not worth the bother. I'm wondering if during winter, the humidity in the west might be high enough to benefit from closed-loop? Similarly, with our lower humidity, even continuous operation of an open-loop system may give fairly long desiccant life (the goal would be a full winter season).

Certainly an open-loop system is much better than doing nothing, and better than just leaving the dipstick tube open after a flight. And given my challenge of attaching to the breather line, I think that is at least a good starting point.
 
Steve,

I have been using dessicant driers for the last 15 years on 3 different planes. I found the closed loop would last about 3 times longer in all seasons here in southern Ontario. In winter my 2L bottle will last about 3 weeks and in summer about 1 week between dryings, with my open loop system. I remove the dipstick for at least 30 minutes after a flight before connecting the drier. I also use plastic supplement pill bottles to close off the exhaust pipes.

I used 1/2" ID rubber hose for my breather tube and could flex it away from the exhaust pipe to install the rubber plug when I used the closed loop. I didn't do the closed loop for long since the dessicant absorbs the engine vapours and I was drying the silica in my oven at home. The vapours would be released as the silica dried. Not cool in the house!

You could probably make a manifold of sorts by connecting the exhaust plugs together with tygon tubing and returning it back to the pump. I imagine there would be enough leakage past the rings to give you a semi-closed loop system with the breather open.

I don't think any system is completely closed due to air infiltration through the exhaust and intake systems.
 
oil filler plug

... If you have a 3D printer, you can make this plug that a friend designed for the oil filler:
https://www.prusaprinters.org/print...NIhYjMy7cGr0DBemezqKXDX9dToSilOCXkm-tOtpId5Kg
Hej Magnus, I ordered this one to be printed by Shapeways, and they tell me it's on it's way. I'll know in a few days I guess if it works.

BTW, I'm using the Black Max (http://www.flyingsafer.com/p-n-2065.html) . I got them to make a 220v version. It's expensive, but if I can get extra time out of my engine, I guess it's worth it.

It seems to work fine, but check back with me in 20 years to see if I have any corrosion in my engine. :)
 
?If you have a 3D printer, you can make this plug that a friend designed for the oil filler:
https://www.prusaprinters.org/prints...CXkm-tOtpId5Kg?

I have an Ender 5 3D printer and just printed this. It threads on maybe 1 to 1/2 turns then stops. That?s ok for plumbing up a drier system, just be aware it won?t thread all the way down. I haven?t looked in to what the problem is yet.
 
Fittings

?If you have a 3D printer, you can make this plug that a friend designed for the oil filler:
https://www.prusaprinters.org/prints...CXkm-tOtpId5Kg?

I have an Ender 5 3D printer and just printed this. It threads on maybe 1 to 1/2 turns then stops. That?s ok for plumbing up a drier system, just be aware it won?t thread all the way down. I haven?t looked in to what the problem is yet.

If you figure it out, I would be interested in buying one. I'm building a dryer.
 
I have a smaller line for the dehumidifier. I put electrical tape over this line so that it fits snug into the breather tube. For extra safety, I have taped some locking wire to the line, close to the end, I wrap this around where by breather is attached to keep it secure.

If you have a 3D printer, you can make this plug that a friend designed for the oil filler:
https://www.prusaprinters.org/print...NIhYjMy7cGr0DBemezqKXDX9dToSilOCXkm-tOtpId5Kg

None of that helps if the end of the breather pipe is almost completely obstructed by the proximity of the exhaust pipe.
 
Steve

I connect to my breather tube with a piece of PVC tubing.

Of course, the breather tube needs to be clear of the exhaust.

Warren
RV-7
KMIC
 
If you figure it out, I would be interested in buying one. I'm building a dryer.

Well so far it looks like the OD of the printed threads is larger than the the stock dipstick.
Printed threads OD: 1.120?
Dipstick threads: 1.091?
My thread gauge only goes to 13 tpi so I can?t verify it?s printed at 12 tpi.
Next I?ll sand down the OD a bit and see if that does the trick.
Wirejock, You should talk to Steve/Amanda Melton about printing you one. I?m a rank beginner. I can?t draw/ fix threads yet (haven?t worked my way to the thread drawing chapter of the beginners solidworks book).
 
If you figure it out, I would be interested in buying one. I'm building a dryer.
I would be interested in buying one as well. Currently I am using a brass garden hose fitting from the local Home improvement store, with an o ring to seal it completely but I know it is not the exact thread size.
 
that's the one I've been using for about 10 years on different aircraft... total cost ~ CHF/EUR/USD 80 (of which 30 for the cap).
Pump, hose, bucket, and silica gel (needs about 2 hours oven time at 125°C to rejuvenate). Used to connect it to the breather, but the bypass hole is difficult to reach on my -6, so now hooked on spare filler cap with the dipstick removed. Works as advertised in the relevant EAA Sport Aviation articles :)


dessicator-1-480.jpg


dessicator-2-480.jpg
 
Last edited:
oil filler plug

I got my plug from Shapeways, looks ok. Have not yet tried it or measured it as my airplane and tools are in the hangar.

UNADJUSTEDNONRAW_thumb_5fda-1024x1024.jpg


UNADJUSTEDNONRAW_thumb_5fd9-1024x1024.jpg
 
I just sent an email to Steve Melton (rvplasticparts.com) to see if he would like to add the cap to his product line. I sent him the STL file link.
 
oil filler 3d printed

This worked perfectly, screwed right on all the way. Here's the dipstick and the plug side by side.

UNADJUSTEDNONRAW_thumb_5fe2-1024x1024.jpg




I got my plug from Shapeways, looks ok. Have not yet tried it or measured it as my airplane and tools are in the hangar.

UNADJUSTEDNONRAW_thumb_5fda-1024x1024.jpg


UNADJUSTEDNONRAW_thumb_5fd9-1024x1024.jpg
 
dissapointed

Well, I put together an engine dryer along the lines of the suggestions here.

1 gallon jug of silica gel, with a air tool filter on the outlet side.
Aquarium air pump - the 60-gallon size, with two outlets. I tee'ed the outlets together to a single line, blowing into the bottom of the jug of silica gel.

The pump can not develop enough pressure to overcome the pressure loss going thru the bed of silica gel. Essentially no flow through it, especially after adding 8 ft of 1/4 vinyl tubing to run up to the dip stick tube.

Anyone have any better ideas for a low cost, simple air pump?
 
Well, I put together an engine dryer along the lines of the suggestions here.

1 gallon jug of silica gel, with a air tool filter on the outlet side.
Aquarium air pump - the 60-gallon size, with two outlets. I tee'ed the outlets together to a single line, blowing into the bottom of the jug of silica gel.

The pump can not develop enough pressure to overcome the pressure loss going thru the bed of silica gel. Essentially no flow through it, especially after adding 8 ft of 1/4 vinyl tubing to run up to the dip stick tube.

Anyone have any better ideas for a low cost, simple air pump?
I am not sure what you mean by "low cost" but I am using this pump and it is working really nice. It takes about 5-10 minutes max to bring the humidity to 6% from 55-60% that I typically see after the engine shut down.

https://www.amazon.com/gp/product/B078H5MH75/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1
 
automatic crankcase dryer kit

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

I built one of these dryer kits and have used it on my Bellanca Cruisair for the past 6 years, it has worked great. Had to replace the desiccant dryer light bulb one time. It is 'automatic' in that when the desiccant gets to around 30% saturated, the air circulation pump shuts off, a silica gel container vent port opens and an immersed light bulb turns on to dry out the gel, then the valve closes and the pump starts again. During high humidity days I guess that it cycles maybe twice a day.

The kit was relatively easy to build. Recommend that you lay everything out and get a clear picture of the kit build and where you see possible gotcha's and figure out how to avoid do-overs.

I did phone Barker and he was helpful with some direction based on my questions.
 
Well, I put together an engine dryer along the lines of the suggestions here.

1 gallon jug of silica gel, with a air tool filter on the outlet side.
Aquarium air pump - the 60-gallon size, with two outlets. I tee'ed the outlets together to a single line, blowing into the bottom of the jug of silica gel.

The pump can not develop enough pressure to overcome the pressure loss going thru the bed of silica gel. Essentially no flow through it, especially after adding 8 ft of 1/4 vinyl tubing to run up to the dip stick tube.

Anyone have any better ideas for a low cost, simple air pump?

I have made a few of these, what bead size and flow area do you have for the silca gel? These pumps do have to pump air to the bottom of an aquarium so have some pressure capability. You only really need about 2 l/min. After some discussion we can talk pumps, but the better pumps are much higher price.

Oh - -just to add, it would be better to use 3/8" tubing, but my 10 friend uses 1/4" ID and it works fine too.
 
Last edited:
Mehrdad, that looks like a great pump. A bit pricey, but no doubt it will work well.

BillL, I just put ports into a 1-gallon jug of gel beads. One port in the cap, and one in the side of the jug about 2" up from the bottom. The beads are about 1/10" diameter on average, some bigger. One difference between what I tried and what is shown in pictures by TShort on a different thread is that he sucked through the silica jug, while I am trying to blow through it. I can not feel any suction at all on the inlet port on the Tetra Whisper 60. Again, I sealed the case inlet with calk and tapped a 1/8NPT port into the case.
 
Engine Dehumidifier

I just built a prototype of my own design. Unlike most, I am not doing it closed loop. I?ll explain why. First, it?s difficult to connect to the breather tube, which rests on an exhaust pipe. And I dont want to alter that. But it is almost inaccessible, practically speaking it?s a big hassle. OK, what about losing the advantage of closed loop ? The advantage of closed loop is touted as getting a lower final humidity, and not needing to rejuvenate the silica as often. I addressed this by using a 10 ft long 3/4? ID clear tubing as the Silica container.
I coil it up for compactness. The idea is that the very long length amounts to a series of successive reductions in humidity. Suppose the first ft lowers humidity by 10%. And the next ft lowers THAT another 10%, and so on. What this amounts to is that the humidity at each stage is .90 times the previous stage. So the final humidity would be (0.9)^10=.35. This is an example, not necessarily the actual numbers. And there are other subtle complications to this, but we will not get into that. In running this, it worked where the upstream blue changed to pink, progressively as time accumulated. I ran 24 hrs continuously to see how fast the silica would change color. About 1.5 ft of upstream silica had changed after that time. However in actual use, I am using a timer to turn this on and off automatically. I have a timer that has 24 selections, each allowing a 1/2 hr on period. Supposing that I set 4 periods of 1/2 hr duration per day, that?s 2 hrs a day. Based on the 24 hr experiment, it would be many days before rejuvenation would be required. Probably weeks. So I think this accomplishes a simplification over closed loop, while retaining its advantages.
 
I just built a prototype of my own design. Unlike most, I am not doing it closed loop. I’ll explain why. First, it’s difficult to connect to the breather tube, which rests on an exhaust pipe. And I dont want to alter that. But it is almost inaccessible, practically speaking it’s a big hassle. OK, what about losing the advantage of closed loop ? The advantage of closed loop is touted as getting a lower final humidity, and not needing to rejuvenate the silica as often. I addressed this by using a 10 ft long 3/4” ID clear tubing as the Silica container.
I coil it up for compactness. The idea is that the very long length amounts to a series of successive reductions in humidity. Suppose the first ft lowers humidity by 10%. And the next ft lowers THAT another 10%, and so on. What this amounts to is that the humidity at each stage is .90 times the previous stage. So the final humidity would be (0.9)^10=.35. This is an example, not necessarily the actual numbers. And there are other subtle complications to this, but we will not get into that. In running this, it worked where the upstream blue changed to pink, progressively as time accumulated. I ran 24 hrs continuously to see how fast the silica would change color. About 1.5 ft of upstream silica had changed after that time. However in actual use, I am using a timer to turn this on and off automatically. I have a timer that has 24 selections, each allowing a 1/2 hr on period. Supposing that I set 4 periods of 1/2 hr duration per day, that’s 2 hrs a day. Based on the 24 hr experiment, it would be many days before rejuvenation would be required. Probably weeks. So I think this accomplishes a simplification over closed loop, while retaining its advantages.

I like your setup, simple to make and not many moving parts or sensors and even if anyone says it's not efficient it's still better than not doing anything for those times I can't go out and fly for a while ! Do you have pictures to complete my mental image of what you did? If you can't post a picture could you PM or email it to me? Thank you !!
 
engine dehydrator

I decided to set one up like this. Minimal cost. Well, less than $100. In the Spring I get condensation on the floor more than any other season. Debating with myself over closed loop, or not?

https://youtu.be/AQRZBwzU54Q
 
Last edited:
I decided to set one up like this. Minimal cost. Well, less than $100. In the Spring I get condensation on the floor more than any other season. Debating with myself over closed loop, or not?

https://youtu.be/AQRZBwzU54Q

So where I settled on the open loop vs closed loop question is that if I am going to be around at the hangar for a little while, I will run it open loop for a half hour, then put it on closed loop and it runs on a jacuzi timer for an hour and shuts off.

The idea is that initially, the gases inside the engine are way more humid than the ambient air, so open loop makes more sense. After a half hour or so, hopefully most of that moisture has been purged out, and then finishing up with an hour of closed-loop should leave it pretty darn dry. Then leaving the system all connected minimizes the diffusion of new moisture in as it sits awaiting its next opportunity to go fly.
 
that makes sense. I purchased a whisper 10 gal fish tank pump, plan to cycle on and off each hour.
 
I built 2 of them for my planes late last year. The canisters are Ocean Spray juice containers, and it's a sizeable amount, and it has a pump with 2 outputs.
I also bought vinyl caps for the exhaust (added "remove before flight" ribbons) to seal the exhaust. I bought stoppers and a stopper boring tool. Each plane used different stopper sizes for the dipstick hole and the crankcase vent. I did a closed loop system so I wouldn't have to change desiccant as often. I doubt it matters but I blow air in the dipstick and out the crankcase vent.
The first week or so I had it, it was an open loop system. My desiccant started to change color real soon. (I run my 24x7) After I switched to closed loop, I haven't even had it change color much at all. It looks nearly new. I feel much better about my engine with this thing on it, and although the moisture in the hangar is worst in the spring/winter, I think I'll just keep using this thing year round. It's working so well and if the Desiccant hasn't changed color now in over 2 months, it won't be much of a maintenance hassle.

There's more info on my site, but here are some pics.

Engine_Dryer_02.jpg


RV20191127-130715-001.jpg
 
AN4062 spark plug dehydrators have been around forever and they do work. Why not just make a larger version that fits down in the dipstick tube? Cap off breather and exhausts, screw this contraption in instead of the dipstick, done.
 
AN4062 spark plug dehydrators have been around forever and they do work. Why not just make a larger version that fits down in the dipstick tube? Cap off breather and exhausts, screw this contraption in instead of the dipstick, done.
I have been using a barbed brass garden hose with an O ring on it. It does fit well and the price is around $4-5 bucks.
 
I have been using a barbed brass garden hose with an O ring on it. It does fit well and the price is around $4-5 bucks.

I'm talking about making a dehydrator that fits in its entirety inside the dipstick tube.

In Continentals its common to see rust in the dipstick tube as water vapor tends to condensate there as the engine cools down.
 
I just built a prototype of my own design. Unlike most, I am not doing it closed loop....

I made my entire confirmed working system for about $35.00 ! Below are all the parts and where to buy them. I also bought a dehumidifier for inside of the cabin for another $25 so for a grand total of $60 and I have dry air running through my entire plane & engine :

Thanks to John here and his emails I used his idea and changed it up slightly then to make sure it's working I added a twist. You can see how the blue beads are turning pink as they absorb the humidity out of the air so I know the engine is getting dry air right?



Well actually the only way would be to monitor where the air is coming out of the engine so I took some pink beads (saturated beads that used to be blue) and put them in another short tube and inserted that into the breather tube. Now you can see how those pink beads are turning blue as the dry air blowing out of the engine goes through them.



Ok so now some things I have learned with this experiment and I hope it'll save you some time if you decide to try it out. I'm not a mechanic so if you decide to do this it's because you believe it'll help your engine, not because I'm doing it to mine :

1- I started with a low volume pump and I thought the engine wasn't getting enough air because I couldn't feel it coming out of the tube. I thought I might as well buy a bigger pump and test it. You DON'T have to buy an expensive pump, I bought this $13 pump at Walmart that has 2 air supplies. I had the aquarium tubing but if you don't then pick some up at Walmart too, it's the cheapest place to buy it anyway.

https://www.walmart.com/ip/Aqua-Culture-20-60-Gallon-Double-Outlet-Aquarium-Air-Pump/10532634

Boy what a difference when I used a T connector and was blowing both of the pump exits into my silica bead tube, but I also found out that I was blowing so much air that the beads were turning pink in 2 days (running continuously) ! So I now use only one output and that gives me more time between drying the beads. I run it continuously because apparently East Texas is more humid than I thought. You might want to try running it less often if you want. I live with my plane so removing and replacing the beads after microwaving them dry once a week (more on that below) is not a problem for me.

2- To connect the 1/2" hose to the aquarium hose just take the one way check valves that come with the pump and cut them in half, remove what's inside, and stick them into the hose. They fit perfectly !! See the picture above.

3- Regarding the top oil filler tube where I blow in the dry air, I just went and bought a $1.40 rubber plug at Lowe's and drilled a hole in it until I could fit the aquarium hose through it.

https://www.lowes.com/pd/Hillman-0-5625-in-Black-Neoprene-Hole-Plug/3013259

4- I also bought the 1/2" hose for $5.18 at Lowe's:

https://www.lowes.com/pd/EASTMAN-1-2-in-x-10-ft-PVC-Clear-Vinyl-Tubing/1000364771

5- I bought a quart of the blue silica beads on eBay for $13 (the price goes up and down weekly so just search for the best price. You can actually get it half that price if you want to wait a couple of weeks until it gets here from China. BTW a quart is an overkill because I can fill three 10' hoses with it but I just mention it so if you have a bigger tube or want to use a bottle you get an idea of how much to buy. You might be able to buy it locally too :

https://www.ebay.com/itm/1-Quart-Pr...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

6- For a filter I cut the hose and used a little Tupperware container I had in the kitchen with a spin off top. I hot glued the 2 pieces of hose to the 2 holes I cut in the sides. I then rolled up a cotton sock around some paper towels and inserted that into the container. This will stop any silica dust from getting to your engine.

7- When it comes time to dry the pink beads I could spend a couple of hours letting them dry in the oven but I researched and have confirmed that I can get them just as dry and blue (and it's just as safe to do it) by placing them in a shallow dish in the microwave for 6 minutes, and it's a lot cheaper due to less electricity to dry them in 6 minutes versus 2 or 3 hours. I recommend doing it in 2 minute phases so after the first 2 minutes you can move them around in the plate with a fork or spoon then nuke them again 2 minutes and move them around again then 2 more microwave minutes and you're done. *** Make sure you use a microwave safe plate. I used a plate that even though it didn't say it was microwave safe I always used in the microwave to heat up my food for 30 seconds with no issues, but when I heated it for 6 minutes, plus the heat off the beads, it cracked.

8- So I just came out of a condition inspection so I had my cowlings off. once they're back on I'll just plug in the oil filler part (oil filler is plastic and cools down in a few minutes after I shut down) so it starts blowing dry air immediately into the engine. Later when it cools down enough for me to touch the exhausts then I'll plug in the bottom part. After I play around with it like this for a while I might convert it to a closed system, but for now it works great and it was very cheap to build.

9- Not part of this system but 100% related, I also bought a small dehumidifier I leave running inside of my RV-8 and I can get at least 1/2 a cup of water out of it every few days !! When I bought it I only paid $25 so search for a lower price, at least you know what model actually works. You can also adjust it so it removes moisture up to a certain percentage and shuts down. I like it because I can also run it on 12 volts DC so I removed the transformer and now I'm running it off of my solar system:

https://www.ebay.com/itm/174036923824


... If I missed anything feel free to ask.
 
I'm talking about making a dehydrator that fits in its entirety inside the dipstick tube.

In Continentals its common to see rust in the dipstick tube as water vapor tends to condensate there as the engine cools down.

I'm afraid if I stick anything in that oil tube and it falls off I'll mess up my engine so I used a rubber plug. That blows air all the way through the filler tub so it should take care of that issue if used on a Continental engine.
 
Mine is very similar to Tim's but nowhere near as neat and organized ... now I have engine dryer envy!!

I have a gallon of dessicant, and run it 24/7 from right after shut down until next flight. It is closed loop, and I have had to "reset" the beads once since setup 2 years ago (this was last fall). I flew yesterday, and all the visible beads are still blue.

I think if you have a good volume of beads, running 24/7 on a closed loop is fine and eliminates cost / complexity...
 
I would agree. I have a pretty good amount of media in each one. The 2 bottles are simply because the pump I got was a 2 outlet pump. Each one though is a 1/2 gallon bottle. I pump air IN at the cap end and the pump came with 2 sintered filters so the bottom of the bottle has a tube that runs through the cap all the way to the bottom with a filter on the end. That's to keep dust from being pumped into the engine. That's the outlet tube. So in effect, it's pushing air into the bottle and through it, not sucking it through. The pump I used has no inlet hose, but just breathes in through it's base. So, the sealed case I put it in helps for that. The inlet to the case is just a hose running from the engine breather into the side of the case. Once there, it's just free air until it pumps it through the bottles for another cycle.
The case maintains a light negative pressure, so the single inlet flows slower than the 2 outputs that Y together inside the box.

At any rate, it's been since late 2019 and my beads are still blue, so maintenance on this system is going to be very long between media changes. I bought my desiccant in 1 gallon jugs, on Amazon, and bought 3 gallons worth (2 planes, 2 systems). So my plan is to just dump all the used media into one of the empty jugs to bring home for regeneration, and I have a spare 1 gallon jug in the hangar to fill it with. The case was the most expensive part and I think I paid maybe $35-40 or whatever Harbor Freight is selling them for these days. So it's about $50-60 plus media to build the whole thing. Of course, I had to drink 2 gallons of ocean spray grape cranberry juice to get the jugs. :)

Again, I also capped my exhaust with vinyl caps and "remove before flight" tags, so that keeps it fairly sealed other than the air filter intake for the engine. I didn't bother with that.

Cheap and simple.
 
another one

I don't like the connection at the upper cowl because the oil door is held open so I'll have to change that but otherwise it is operating. 3/8 tubing primarily with 1/4 tubing at crankcase breather connection then to 3/8.

IMG_20200327_124645_zps5re3eshl.jpg


IMG_20200327_124631_zpsdzu6p4fg.jpg


IMG_20200327_124608_zpsihtwbxer.jpg


IMG_20200327_124848_zpsk5vjjr4t.jpg
 
Last edited:
A couple of comments after testing & 2 yrs of use . .

A seemingly good reason to recirculate is to extend the regeneration time.

The reason NOT to recirculate is 1. the oil ladened air will contaminate the beads

And . . . if 2 liters/min is used to supply the engine simply removing moisture from ambient air actually yields less mass of water than from the water rich engine crankcase.

In theory, with 2 L/min flow, the 360 engine crankcase air is completely replaced with dry air in 20 min, but 60 min is best for all ambient conditions. A test validated the time.

A final filter should be used to ensure silica dust does not enter the engine.
 
I am running continuously with a 10 gal fish tank pump. Very low flow rate. I may put it on a timer.
 
A few more findings . . .

I am running continuously with a 10 gal fish tank pump. Very low flow rate. I may put it on a timer.

A 10 gal might only be 1 L/min. I used one like this for several years. It does get the job done.

Unfortunately, several factors mean unknown flow rates from these little vibrator pumps. 1. quite sensitive to back pressure, 2. leaks, 3. there is poor correlation between advertised tank size recommendations and flow rates.

I have about 5 of these pumps and am beginning to conclude the 2-4 L/min is better for the process. Space velocity (SV) for the media is a consideration. SV is basically air changes per min for the media volume. Air residence time for the adsorption process is the parameter, but SV is the typical industry term. 2-5 L/min is about right for 2+ qts of silica gel.

To understand what was happening, I got this little flow meter and was surprised at units sensitivity to back pressures.

The precise design parameters are yet unknown to me, but it seems a higher flow rate will clear the crankcase before the combustion gasses have a chance to condense as the engine cools down after a flight. [experimented with an initial high flow "purge" for 3 min to address this] The engine stays pretty warm during the first 20-30 min and really hot in the first 5 min. A low flow recirculation system left on for 24 hrs will absolutely dry the engine. Likely even 5 hours.

The blue/indicating gel works nicely, but will degrade with temperature during regenerations. The blue color returns well before the media has purged it's collected moisture. I switched to the white beads that tolerate a higher regeneration temperature (shorter time) and use a small amount of blue beads in a HF inline filter as an absolute indicator that the air going to the engine is dry. Opening the container to check bead condition got to be an added pain to flight ops. and . . . my regeneration oven has a time limitation to when the wife is not home (smell), so faster is better, YMMV. Smell is less during regen if the system does not collect crankcase oils. i.e. a single pass dryer design.
 
Back
Top