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Engine Dehydrator Questions (2)

tom_AZ

Well Known Member
I'm thinking about building a simple engine dehydrator. Ambient air in AZ is very low in humidity, so I don't plan to use dessicant. My goal is simply to provide air exchanges within the case for a couple of hours after flying to get rid of water formed by combustion. I've seen a thread on these, designs, etc..., but have a couple of (hopefully) simple questions.

1) The designs that I've looked at all seem to have the air entering via the case vent, and exiting via the oil filler. I have an air-oil separator (yeah, I probably wouldn't do that if I were starting over), that eventually sends air overboard via a piece of scat hose. Connecting input air to that would not be quick and convenient. To the question, is there some reason not to pump the air in via the filler tube and let is exhaust through the scat hose?

2) Assuming the answer to (1) is no, I'm also interested in thoughts on how to secure the input line. My dipstick is not threaded, but rather held in place by an o-ring. A drilled rubber stopper would be easy, but I don't know whether it would reliably stay in place. Perhaps less of an issue if I extended the PE tubing several inches into the filler neck. Purchasing and modifying a second dipstick, e.g. tapping it to secure a barbed connector, would also be an obvious choice, but last I looked dipsticks were running between $100 and $300 on the used market, which seems a little excessive for what I'm trying to accomplish.

Thanks in advance.
 
I do the something with an aquarium pump. The air goes in the oil filler and out the crankcase vent. A stopper with a hole works well in this application. There is not much pressure
Mike
 

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2) Assuming the answer to (1) is no, I'm also interested in thoughts on how to secure the input line. My dipstick is not threaded, but rather held in place by an o-ring. A drilled rubber stopper would be easy, but I don't know whether it would reliably stay in place. Perhaps less of an issue if I extended the PE tubing several inches into the filler neck. Purchasing and modifying a second dipstick, e.g. tapping it to secure a barbed connector, would also be an obvious choice, but last I looked dipsticks were running between $100 and $300 on the used market, which seems a little excessive for what I'm trying to accomplish.

Thanks in advance.

You can make it as simple or complex as you like - you can just put the hose in, and stuff a rag into the hole to hold it and "seal" it to the dipstick.

A rubber stopper sounds like a good idea as well.

Or, you can get a 3-d printed stopper created for about $20, if you can find a design. There is one out there for the threaded dipsticks.

Any cheap aquarium pump will do what you need - they are about $10-$20.
 
Dehydrator

I built a dehydrator. Drilled rubber stopper with a section of aluminum tubing. Fits the oil filler plenty snug. Clear tubing fits over the aluminum tube. It's open loop because there's no way to connect to the crankcase vent. Waste air just comes out the vent.

Clear gallon container
Wife's food strainer (bought her a new one)
Aquarium air pump
Various fittings and pieces of hose
Home Depot bucket to hold it all.

The strainer fits in the jug. Fitting in the bottom of the jug but any opening will work for an open loop system. Pour dessicant beads in and the strainer stays put. Fitting in the lid. Aquarium pump pulls from the top fitting and blows into the crankcase vent. Toughest part was sealing the pump so it had to pull from the intake hole. I may buy a different pump that moves more air.
 
I built a dehydrator. Drilled rubber stopper with a section of aluminum tubing. Fits the oil filler plenty snug. Clear tubing fits over the aluminum tube. It's open loop because there's no way to connect to the crankcase vent. Waste air just comes out the vent.

Clear gallon container
Wife's food strainer (bought her a new one)
Aquarium air pump
Various fittings and pieces of hose
Home Depot bucket to hold it all.

The strainer fits in the jug. Fitting in the bottom of the jug but any opening will work for an open loop system. Pour dessicant beads in and the strainer stays put. Fitting in the lid. Aquarium pump pulls from the top fitting and blows into the crankcase vent. Toughest part was sealing the pump so it had to pull from the intake hole. I may buy a different pump that moves more air.
Sounds like a good design. I've seen that there is a lot of kitty litter that's made of the same silica beads, and it's cheaper than dirt. No need to stink up your house drying it when the blue indicators turn pink, just toss it. It's essentially sand, so no worries about disposal.
 
Clear the crankcase fast to prevent condensation.

Having gone down the engineering rabbit hole on this subject,

I think your use of ambient dew point purge is just fine, and will address 90% of situations. An air mattress inflator (with some filter) is suggested. Why? Because the DP of crankcase is around 180-200F when you shut down. And the condensation will begin when you stop. The inflator has much higher flow and will completely replace crankcase air in about 3 min, but I use 5 min to be sure.

I made a cap for a 540 (10Friend) that only has the o-ring and it is quite snug. My YIO-360 M1B is threaded, but also made an o-ring plug and it won't fall out or blow out.

I use a 120vac unit but my friend and I also have a 12vdc powered unit powered by a small sealed lead acid battery for traveling situations. It will run 5 min easily and not significantly affect life. The amperage draw is small. I don't remember the numbers.
 
I used a rubber 38 mm chair leg end - fits perfectly.

Fin 9A
 

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Engine Dehydrator--what I decided on

Thanks to all for thoughts and suggestions. Two pics attached to show what I ended up doing—one that shows components, a second showing the assembled apparatus.

  • Aquarium pump
  • 2 x ¼” barb pass-through connectors (supplied as a pkg of 5, with washers and hose clamps)
  • Air filter (for the intake side, supplied as a pkg of 2)
  • 1 ½” (i.d.) table leg protector (rubber, supplied as a pkg of 2)
  • PE tubing


Per my initial post, I didn’t think I needed a closed system with dessicant. Dewpoints here are almost always WAY below ambient temps here—typically 40-ish degrees F, so all I’m trying to do is get rid of residual water from combustion. The plan is to plug it into a timer, and run it for an hour or so after each flight.

The pump specs at 317 gph, or just over 5 gpm. Actual output may be lower given tubing resistance, etc…, but even if it’s half of spec I would think it should be more than adequate. The intake port is a bit too large for ¼” i.d. tubing, so I just a short piece of larger tubing to neck it down. An adapter would be a more elegant approach, but this seems to work well. The air filter (it’s dusty in the desert and I didn’t want to add a bunch of silicon grit to the oil, creating a new issue in the process...) looks to be for a snowmobile. Nothing magic about the model, I just picked a shape that looked like it would work. One end is solid and used for the pass through, the other is “open”, and needs to be sealed with duck tape or other means. Both the air filter and the output end will be stored in a Ziploc bag when not in use. Special thanks to Finley Atherton—I would not have thought of using a table leg protector, but a rubber one fits perfectly!
 

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I just used a drilled #60 rubber stopper I bought at the hardware store...works fine. I did look for 3D printed threaded connectors for my Lycoming IO-320 but the only one I found on Thingaverse was the wrong size. My buddy with the printer offered to scan and duplicate, but the rubber stopper work fine so I haven't done that.

If this thing sits on your plane 24/7, you don't need a very high-volume aquarium pump. The one in the photo above works fine, but it runs hot, is noisy, and doesn't appear to be particularly durable in my experience. It was attractive to me because it had a port for a return line allowing for a closed system (not sure if there's any benefit to that other than less desiccant saturation). Since you don't need desiccant, you don't need a return line. Up here, have to recharge the desiccant in the oven about 3 times per year. First time I did that, I spilled a lot of beads around the kitchen, so now my wife insists on cooking the beads. Structured incompetence for the win!
 
Sounds like a good design. I've seen that there is a lot of kitty litter that's made of the same silica beads, and it's cheaper than dirt. No need to stink up your house drying it when the blue indicators turn pink, just toss it. It's essentially sand, so no worries about disposal.

Clay-based Kitty litter is dirt cheap, but the "crystal" kitty litter, which is the silica gel, is more expensive. Also, if you've ever poured kitty litter into a littler box, you were likely impressed by the cloud of dust that accompanied. NOT something I'd want pumped through my engine. OP apparently doesn't need or want dehydration anyway, just moving air to "flush" the crankcase. The whole idea of a dehydrator is to keep the crankcase environment below the dew point, which apparently is pretty easy to do where he lives without using silica gel.
 
Air pump

I just used a drilled #60 rubber stopper I bought at the hardware store...works fine. I did look for 3D printed threaded connectors for my Lycoming IO-320 but the only one I found on Thingaverse was the wrong size. My buddy with the printer offered to scan and duplicate, but the rubber stopper work fine so I haven't done that.

If this thing sits on your plane 24/7, you don't need a very high-volume aquarium pump. The one in the photo above works fine, but it runs hot, is noisy, and doesn't appear to be particularly durable in my experience. It was attractive to me because it had a port for a return line allowing for a closed system (not sure if there's any benefit to that other than less desiccant saturation). Since you don't need desiccant, you don't need a return line. Up here, have to recharge the desiccant in the oven about 3 times per year. First time I did that, I spilled a lot of beads around the kitchen, so now my wife insists on cooking the beads. Structured incompetence for the win!

I found the pump you used. Plan is to replace mine.
I had to perform surgery on mine to seal it. It had an intake but basically sucked air all around the housing.
 
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I found the pump you used. Plan is to replace mine.
I had to perform surgery on mine to seal it. It had an intake but basically sucked air all around the housing.

After my closed pump died, I just went back to the previous open version...that pump just keeps on ticking. The only penalty I found with open vs closed is that the silica gel turns pink more often. I keep a humidity meter inside the gel canister...it keeps the pumped humidity at about 15%. When the gel beads start turning pink and I see the humidity begin to rise, I pour out the pink beads and replace with recharged blue ones, go home and cook the pink ones. I only have to do that about 3 times per year, so not too intrusive. My "dehydrator" is airtight food container that takes 15 lbs of silica at a time (silica gel beads) so I have 30 lbs of silica. It's been a few years since I bought the things...I see the price is now almost double what I paid.
 

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Pump

After my closed pump died, I just went back to the previous open version...that pump just keeps on ticking. The only penalty I found with open vs closed is that the silica gel turns pink more often. I keep a humidity meter inside the gel canister...it keeps the pumped humidity at about 15%. When the gel beads start turning pink and I see the humidity begin to rise, I pour out the pink beads and replace with recharged blue ones, go home and cook the pink ones. I only have to do that about 3 times per year, so not too intrusive. My "dehydrator" is airtight food container that takes 15 lbs of silica at a time (silica gel beads) so I have 30 lbs of silica. It's been a few years since I bought the things...I see the price is now almost double what I paid.

I purchased this one
https://a.co/d/iVLZc6Y
58 Watt. This thing moves a lot of air. So much I have a timer instead of running it 24/7. It has 5/16" inlet and outlet barbs. Makes it easy to plumb.
 
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I purchased this one
https://a.co/d/iVLZc6Y
58 Watt. This thing moves a lot of air. So much I have a timer instead of running it 24/7. It has 5/16" inlet and outlet barbs. Makes it easy to plumb.

I think you could service many aircraft with that beast! I'm still on the lookout for a pump with an intake hose barb. I think that would simplify a lot plumbing for homebrew engine dryers.

MacCool said:
Clay-based Kitty litter is dirt cheap, but the "crystal" kitty litter, which is the silica gel, is more expensive. Also, if you've ever poured kitty litter into a littler box, you were likely impressed by the cloud of dust that accompanied. NOT something I'd want pumped through my engine. OP apparently doesn't need or want dehydration anyway, just moving air to "flush" the crankcase. The whole idea of a dehydrator is to keep the crankcase environment below the dew point, which apparently is pretty easy to do where he lives without using silica gel.
That's a very good point. Most of these air pumps have a tiny intake filter, but they are probably not going to be able to handle a lot of silica dust.
 
I think you could service many aircraft with that beast! I'm still on the lookout for a pump with an intake hose barb. I think that would simplify a lot plumbing for homebrew engine dryers.

I looked for a while for that as well, then settled on putting a simple fish tank air pump in a Tupperware box with rubber grommets in three holes to seal the in air (just the box air), out air (from pump), and electrical cord. That way pretty much ANY fish pump will do when it comes time for a new one.

Air that first comes from engine goes through a jar stuffed with cotton balls from the wife's make up kit. That catches a noticeable amount of airborne oil over time.

Air going back to engine goes through this: https://www.amazon.com/FERRODAY-San...1678200596&sprefix=inline+air+,aps,164&sr=8-6 Over a few hundred hours I see what looks like a tiny amount of oil caught by that filter. But it could be rubber dust from the pump and of course there is probably some silica dust I can't see.
 
I just use aquarium pump filters on the inlet and outlet tubes in my silica gel bottle. Keeps any dust from entering the hoses and the pumps are designed to use them, so no issues.
 
Modifications

The "Beast" has an inlet and outlet. I plan to fill the void at the top of the container with cotton balls as a filter. Cheap and easy. It's open loop so no need for an inlet filter on the container. The inlet is on the bottom of the container.
I turned it on and held a hydrometer near the crankcase vent just to check. To be fair, it's very dry up here. Humidity went from 25 to 15 in about a minute.
 
Bit of advice...

.... when drying out the beads in the microwave, put them in a glass bowl and don't use the zip loc bag you brought them home in. Even on defrost it gets hot enough to melt the bag. I discovered this when I opened the microwave door and 47,000 beads rolled out on the kitchen counter and cooktop, then onto the floor.
 
Drying beads

.... when drying out the beads in the microwave, put them in a glass bowl and don't use the zip loc bag you brought them home in. Even on defrost it gets hot enough to melt the bag. I discovered this when I opened the microwave door and 47,000 beads rolled out on the kitchen counter and cooktop, then onto the floor.

I pour them into a cheap thrift store 9x13 cake pan and set them on top of the water heater. Next morning they are bright blue again. No need to upset the Boss! :D
 
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