Vivid memories of helping Dad maintain our car, usually on a Saturday morning, dwell long after he passed. Driving around the block to get the oil warm, while it drained he'd install a new oil filter.
A career in the Army had taught him the value of preventive maintenance, and while we weren't poor, we also weren't made of money. It's from him I learned the virtue of filters. Not just oil, but also fuel and air filters.
Penny wise, pound foolish
Example DIY-lessons (as part of avoiding the expense of using a car dealership), included how a drop of oil on the rubber gasket made the next disassembly easier. Plus how prefilling a filter with oil before spinning it on meant engine bearings weren't starved on start up. Basically, he wanted things done right, but as a child of the Great Depression, it was as natural as breathing his focus on thrift became a special part of my early education.
Like blowing out an air filter with compressed air would extend its service life. And looking back, maybe only because I was at an impressionable age, but the immense cloud of dust as he chuckled and advised standing upwind before blasting remain unforgettable. His purpose, and the object of the lesson being . . . ending up with a clean air filter, without the expense of a new replacement!
Anyway, these days, and largely because of God's many blessings, besides driving to model events we fly a Bonanza. And guess what? It has oil, air, and fuel filters, too (moreover, I service all three myself to save a few bucks).
Considering we fly at 8-10k feet, where one would presume the air is clean and dust free, I'm always surprised at just how much yuk the foam filter element contains. And since rebuilding this engine amounts to $40,000, then you can take it to the bank I stay on top of maintaining its filters!
Ultimately, my old man taught me filters exist for good reason. True regardless of whether an engine spends its time on the ground, or in the air. After all, money doesn't grow on trees!
History
Traditionally, model airplane engines haven't had an air filter because the carburetor (being ahead of the cylinder and just behind the prop) lives in tight quarters. Didn't stop enterprising businesses from offering air filters for accessorizing your engine.
Long a fan of the Bru Line air filters (even though pals thought me sightly nuts), because I knew the fine scratches that developed on pistons over time resulted in lost horsepower (due to reduced compression), it meant I used one regardless of their knowing smirks.
How a chicken dance inspired action
Meanwhile, like Porsche developing their 356 before introducing their 911, our P6 was preceded by our Tiger 50 helicopter. One day, following a crash that devolved into my first chicken dance, I watched in horror as a cloud of dirt was kicked up.
This, of course, because the engine (protected within the side frames) kept running. Means it thrashed about because the clutch remained engaged, and the broken blades retained enough of a stub to dig in and drive the flopping about. It's the moment I came to appreciate what a good air filter brings to the helicopter-game!
Note; regarding the term chicken dance, it's an apt description because the heli beating itself to death closely resembles a wounded chicken after it's been run over by a car (yes, slightly gross, but very accurate).
So beyond the initial crash damage to the model, ongoing damage ensues (usually resulting in lost links, too). But the real damage, as it turns out, is to the engine. This, due to the cloud of dirt kicked up (and which, obligingly, the screaming engine ingests).
Incredibly, this went on for a good five minutes before exhausting the fuel supply. And as if it couldn't get worse, following crash repairs, the engine subsequently ran like crap! Developing barely enough horsepower to hover, that one oops-moment had ruined my engine.
Adding insult to injury (e.g. the crash damage to the model), the engine repair alone entailed buying piston, ring, sleeve, gaskets, and bearings. The latter being two items I routinely replace any time I'm inside an engine – call it cheap insurance. Anyway, the cost amounted to more than half the price of a new engine – grrr!
Design and development
Determined to do something about it, first I installed a Bru Line air filter. Problem is, helis spend a lot of time hovering near the ground. This kicks up a lot of shit. Point being, the filter quickly clogged.
Knowing the solution involved both a larger filter element and getting it into calm air, I designed and developed an air filter assembly for the Pantera. Importantly, if clears the fan shroud (thus allowing filtered air to bypass the abrasive particles created by wear between clutch shoes and the liner).
Added to which, because it emerges beneath the canopy, it's operating within a cocoon of calm air. This is important because turbulence can disrupt proper air/fuel mixing.
And there's a bonus, which is this air is cooler than that surrounding the engine. This last detail being especially important because as high school physics taught us, cooler air is more dense. Thus, it allows more fuel to be burned efficiently. End result? Burning more fuel means the engine's making slightly more horsepower, too!
Proof of purpose
If you're curious just how much crap we're talking about, the accumulation is readily visible any time you have access to the cooling fan or the inside of the shroud. The latter, especially, because of the fine mist of fuel standing off the carb at part throttle, which coats the inside (thus, adhering the dust).
But even on the cooling fan, dust accumulates rather heavily. And we're talking about both airborne dust and even worse, the minute particles of highly abrasive clutch liner dust. It's this dust, because it acts like fine sandpaper on moving parts, which is especially bad juju for your engine!
What you get
The optional air filter assembly packing, part number AUD0063, includes the soft molded silicone snorkel. There's also the open cell foam filter element. Plus a molded plastic filter base, a couple zip ties, and a sticky ring.
This last is intended to secure the foam element to the plastic base. Unfortunately, and proving I have feet of clay, this method doesn't work all that well – more later.
Installation
The how-to is simplicity itself. All you need is a hobby knife or Dremel with a grinding tool. Marks on the wall of the cooling fan shroud show were to clearance the frame material, and assembly merely involves slipping the base of the silicone snorkel over the carb's inlet throat. Finish the job by installing the filter base, secure each end with a zip tie, and finally, attach the foam element.
Note; turns out the adhesive ring we supply is absolute rubbish. It just won't adhere the filter base and foam for long. Worse, you need to remove it to clean and once you do that, the remnants of adhesive become history.
What we end up doing is using a rubber band, instead. Merely twisted and secured to the edge of the base, this works quite nicely to retain the foam filter element.
Cost? Virtually free!
Preventive maintenance
So the question which comes up, is this; how often must you clean it? Well, you know that last bit of fuel in the jug you can't (or don't want to) suck out and use? Knowing I don't want to run it through my engine due to concern it may have particles of yuk, this bit of fuel is what I use it to wash the filter element.
Best part is the oil suspended in the fuel coats the element after the alcohol evaporates resulting in optimal capture-efficiency! So in these next two photos, first we see the before, the quite dirty foam element . . .
. . . and now the aftermath. The after action is this photo of what ended up in a coffee filter after two gallons. Honestly? This totally persuaded me to wash the filter element after every gallon. Takes but a moment and presto, we're ready to go again!
Important since scratched piston/cylinder walls reduce compression, and cost horsepower.
Fuel filter - protecting the carburetor
Besides the air going into the engine through the carburetor, protecting your carburetor from foreign material helps ensure its reliable operation. After all, if the engine stops you'd better be up to snuff with your autorotation practice! The simplest of filters are welded to prevent leaks and are a straight shot - in and out.
Note; I make it a habit of flying out the last bit of fuel by shooting autos. The excitement comes in because the last one is for real since the fuel becomes exhausted at an unknown altitude . . . saying you'd best be on your game! Anyway, an AUD0113 protects the fuel tank from crap introduced at the pressure line, while an AUD0117 Filter-T gets inserted between the fuel supply (usually a 2-oz header tank) and the carburetor.
Anyway, T-type fuel filter make it easy to refuel whilst cutting down on wear and tear on the fuel line at the carburetor's nipple – win-win! As for the orange frame-mount shut off? That's a convenient little bugger, which I use to stop the engine.
Note; in addition to the AUD0117 Filter-T, the above photo also shows installation of a 2oz-header tank (part number AUD0090), the orange frame-mounted shut off (part number AUD0029-SO), and a yellow fuel shutoff (part number AUD0114). Here's a better look at using these when refueling at a Filter-T.
Wrap up
So that's it. Protecting your investment is easy as pie. Using filters at the air intake side of the carb and on the inlet side of the fuel tank (muffler pressure line) and between header tank and carb nipple. Best part? These don't cost much. Plus your engine may make a touch more horsepower due to drawing in cooler less turbulent air from beneath the canopy!
