Cowl Air Scoop

[Mark Dickens]

Has anyone modeled an intake air scoop for the nose bowl? This is one of my goals for the Companion. I got two spools of PAHT-CF for Christmas and I'm imagining a nicely faired "ram" scoop interfaced with my horizontal intake manifold. Not that it would alter the speed of the plane, but it would look cool

[Mark Dickens]

I modeled an air filter holder and base plate that bolts directly to my fuel injector (RSA-5 mount). The filter canister is modeled to hold a K&N RU-2790 filter. A side inlet will be plumbed to the bottom of the left baffle inlet ramp. I've printed a prototype and it just fits. I may elect to put a small bump on the lower nose bowl for clearance, but overall, I'm pretty happy with how it came out. I've sent it out to be SLS printed using PA12. When I get it, I will post a photo of it installed.

canister 2.png canister.png

[huntaero]

For our 4A we used an IO-520 intake tube and modified to adapt our airbox to the forward baffles which are the same size as the RSA fuel servo inlet dia, used two for redundancy, similar to the Cessna U206. Made to fit a K&N air filter and installed an alternate air-door manually controlled (canadian requirement). We used an Air flow performance 110-degree intake elbow with K&N E-0995 air filter and installed a 4 in prop extension for clearance, makes for a nice clean cowling.









SKS_5893b.jpg

[Bcone1381]

I'd like to encourage our group to be aware and exercise caution with 3d printed parts in the engine area due to material ability to handle high heat.

Be cautiously curious, understand the environment, and the nature of the material under high heat and do some testing. Temperature Testing on material is very satisfying and not a lot of time or effort. Set some temperature thresholds limits that are rather conservative.

Within the last year or so there was an accident of an experimental aircraft...If I recall correctly.... at least part of the intake assembly was beautifully fabricated using a 3d printer. The part was under higher-ish heat conditions. The suction force in the engine intake collapsed after it was softened by the heat. The collapsing blocked airflow to the engine and resulted in engine failure.

I have a turkey roaster....If anyone want to send me some 3d printed material I can test it for you. I also have thermocouples and readers. I'll lend them out too. This allows a builder to collect real temperature data inside the engine cowl.

[U2fletch]

Mark is sending this part out for SLS printing with a high temp material, so is exercising good choice of material. You are correct about the crash caused by the intake part collapsing. Using a thermoplastic above its rated temperature is a bad idea.

[Mark Dickens]

Nylon 12 has two things going for it, a relatively high heat deformation temp of between 140-147C, and when it does deform, it does so VERY slowly...in addition, this is used for air intake and would be in a relatively cool temp environment. If I have a situation where that environment is at 284F or higher, I have much bigger issues at hand.

I am using the same material and process for the oil cooler shroud too, which will be in a hotter environment, but again, I surely hope that the air cooler is not getting 284 F from cylinder fins!

[Mark Dickens]

Here's a good write up about glass transition temps and heat deformation: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-print-tips-archive/glass-transition-temperatures-not-what-they-seem

And https://vansairforce.net/threads/3d-.../#post-1892783. Scroll to post #18,,,good stuff there as well.

[Mark Dickens]

I received my filter canister today. The filter fit perfectly in the canister and with the 3" inlet, I think the engine will breathe well.

IMG_2302.jpg

Not that this is some kind of brilliant design, but if anyone wants the files, let me know.

[DBeaulieu]

Mark, curious about your thoughts in making that a side inlet? I have horizontal induction with FM150 fuel servo (RSA5 I believe) and hadn't thought about that configuration...looks interesting. I am just getting to this part in my Patrol project and still doing the "figuring out" part.

[Mark Dickens]

My objective was to see if I could avoid having to make cowl mods, like a ram air inlet. I did one on my RV-8 and it took a lot of time. This configuration mimics the Vans inlet which is also tied to the left baffle inlet ramp. When you opt for fuel injection and a horizontal manifold, you aren't left with much space inside the cowl. This set up leaves about 1/2" of margin. Plus, I like to come up with my own "solutions" and it's been fun learning Shapr3D to make a usable part.

[podo]

Mark, how did you determine the wall thickness for your PA12 part?
Pete

[Mark Dickens]

Mark, how did you determine the wall thickness for your PA12 part?
Pete

It's 1/8" and I probably overdid it but wanted to make sure it was strong...and it is, I've dropped the canister on the garage floor 3 times so far with no damage. With SLS printing, those walls are solid through out. There is no infill with SLS. Bottom line is that I made what I thought was a conservative guess

[Have-Purple]

Mark, how are the two halves held together?

[Mark Dickens]

Mark, how are the two halves held together?

The canister fits inside the filter base and I will mount a few platenuts inside the canister and use #8-32 screws from outside the base to secure it. While the filter mates tightly at its nose inside the canister (to hold the filter in place and maximize clearance with the nose bowl), the canister expands to 5.5" at its widest diameter which allows about 1/2" around the filter in free space, and allows clearance for the platenuts. It's a tight fit, but the filter is supposed to be a high flow performance filter and I don't anticipate any issues in terms of air flow.

IMG_2303.jpg
IMG_2304.jpg

[Have-Purple]

Those filters flow a ridiculous amount of air. No problems there. How about a1/4 turn “cam lock” thread built into the plastic that exposes the holes to the plate nuts? That way, if one of the plate nuts lets go or you bust a shop head, your engine doesn’t suck down the FOD since the air filter is still captured if the two halves stay together.

As far as air scoops, I am partial to the A/C air-scoop found on the nose of the F4D. My father flew them and I have always thought they looked sharp. I’m considering making one to feed my oil cooler.

Matt
IMG_1652.jpg IMG_0017.jpg

[Mark Dickens]

I gave the "what if something came lose in the canister" question a lot of thought. We had a RV-8A on our field suck a bolt head into the engine on takeoff. Fortunately, it was early and he was able to stop on the runway. I worked with him to replace the FAB after he had his engine topped. In his case, the bolts were inside the filter so there was nothing to prevent the bolt head from entering the engine. In my case, the plate nut is mounted outside of the filter and two rivets holding the plate nut would have to let go. I think the odds are against that kind of a problem, but I'm definitely going to watch it because I'm riveting into the nylon. The plate nut provides adequate support for the shop head, so I'll have to watch for loosening of the manufactured head on the outside of the canister.

Great idea on using the cam lock as I have a bunch of them in my parts drawers. Thanks

[Bcone1381]

You may have already Considered a soft rivet for the attachment into Nylon. The Hard Rivet is AN426AD is a structural rivet we all are use to. The soft rivet is made of soft 1100 aluminum, are easy to install, and put less stress onto the nylon material when squeezed. They are available at Spruce and are AN470A (Remove the "D" from the hard rivet AN number)

[Mark Dickens]

Agree on the soft rivets...I just have to wait until I have something else to order so the freight doesn't kill me!