Overhead vent upgrade project

[Utah20Gflyer]

On 1/25/2022 at 10:06 AM, AH-1 Cobra Pilot said:

That looks great!  Depending on the material you use, the screw threads may not last as long as you would like.  That is why most similar applications use an insert such as this:

Print it with the hole no more than 0.001" larger than the insert, and with a hole for the set screw.  Then use heat, such as a soldering iron, to push/melt the insert into place.

I did previously have that old style vent.  The link is to the vent I used.  The angle on the vents is right about 30 degrees.  I don't know the exact height but it's about 2 inches.

The metal insert is a good idea.  I was considering it but didn't have any on hand so I went with an undersized hole on the back side of the part so the #4 screw would cut threads into it.  Long term after repeated install/removal I expect they will fail.  I think I'll order some inserts and integrate them into the design.  

I appreciate the input. 

[AH-1 Cobra Pilot]

I had already 3-D printed replacement vent covers, but I have not installed them.  If you have enough of a lip on the outsides to keep them in place, you will have to remove the panel, which I am loathe to do.  So, I chose another path...

This prototype is PLA, but the final version will probably be nylon or ABS.  (It is two-colored because I ran out of the orange filament before the print was finished.)  Nylon can be dyed, but ABS can be painted.  Nylon is more heat resistant and can be made with long fibers for better stiffening, especially around the attachment point.

I will also install the eyeball vents into these, but the beauty is that they can be installed without removing the overhead panel; just a bolt through the center to attach it to the old place.  Still a bit of a PITA, but better than the alternative.  (There is a metal pin in the overhead plastic I will have to account for by putting a hole in the bottom of this, but that will also keep these from turning on the bolt.)  Note that this particular part will fit on the copilot seat and the left-rear seat.  A mirror image part is required for the pilot and right-rear seats.

My eyeball vents are due on Friday, so I will have more to show then.

Edited January 26, 2022 by AH-1 Cobra Pilot

[Utah20Gflyer]

2 hours ago, AH-1 Cobra Pilot said:

I had already 3-D printed replacement vent covers, but I have not installed them.  If you have enough of a lip on the outsides to keep them in place, you will have to remove the panel, which I am loathe to do.  So, I chose another path...

This prototype is PLA, but the final version will probably be nylon or ABS.  (It is two-colored because I ran out of the orange filament before the print was finished.)  Nylon can be dyed, but ABS can be painted.  Nylon is more heat resistant and can be made with long fibers for better stiffening, especially around the attachment point.

I will also install the eyeball vents into these, but the beauty is that they can be installed without removing the overhead panel; just a bolt through the center to attach it to the old place.  Still a bit of a PITA, but better than the alternative.  (There is a metal pin in the overhead plastic I will have to account for by putting a hole in the bottom of this, but that will also keep these from turning on the bolt.)  Note that this particular part will fit on the copilot seat and the left-rear seat.  A mirror image part is required for the pilot and right-rear seats.

My eyeball vents are due on Friday, so I will have more to show then.

Interesting, yes mine requires removal of headliner but I had to take mine off to address an issue with a rheostat anyway.    I'd like to see how your install goes.  

[Oscar Avalle]

Based on your suggestions, I moved ahead and did the modifications... Here are some pictures of how it looks now... Thanks for all the ideas...

[Browncbr1]

On 1/26/2022 at 3:39 PM, AH-1 Cobra Pilot said:

I had already 3-D printed replacement vent covers, but I have not installed them.  If you have enough of a lip on the outsides to keep them in place, you will have to remove the panel, which I am loathe to do.  So, I chose another path...

This prototype is PLA, but the final version will probably be nylon or ABS.  (It is two-colored because I ran out of the orange filament before the print was finished.)  Nylon can be dyed, but ABS can be painted.  Nylon is more heat resistant and can be made with long fibers for better stiffening, especially around the attachment point.

I will also install the eyeball vents into these, but the beauty is that they can be installed without removing the overhead panel; just a bolt through the center to attach it to the old place.  Still a bit of a PITA, but better than the alternative.  (There is a metal pin in the overhead plastic I will have to account for by putting a hole in the bottom of this, but that will also keep these from turning on the bolt.)  Note that this particular part will fit on the copilot seat and the left-rear seat.  A mirror image part is required for the pilot and right-rear seats.

My eyeball vents are due on Friday, so I will have more to show then.

I like the idea of incorporating the slats on the inside to replace the metal ones and just bolt right in place.  I was going to attempt to model a print-in-place wemac and dome, but haven’t found the time.   Holy crap wemac vents are expensive.  I’d like to get a hold of one to reverse engineer though.   Perhaps an eyeball that articulates, but the whole dome swivels on the center pin to modulate flow like the OEM would be easiest to model.  

Edited January 29, 2022 by Browncbr1

[Utah20Gflyer]

Here is the latest version of a vent lever, this model is made from PETG which should have a UL94 rating of V2.  I incorporated a brass threaded insert and increased infill to 50 percent.  I think this should last longer than the plane.  

[carusoam]

U20G,

You are getting really good at this prototyping thing!

Nice work.

-a-

[AH-1 Cobra Pilot]

On 2/2/2022 at 11:20 PM, Utah20Gflyer said:

Here is the latest version of a vent lever, this model is made from PETG which should have a UL94 rating of V2.  I incorporated a brass threaded insert and increased infill to 50 percent.  I think this should last longer than the plane. 

Did you melt the insert into the plastic?  Or press it into place?

[hmasing]

On 1/29/2022 at 1:49 PM, Oscar Avalle said:

Based on your suggestions, I moved ahead and did the modifications... Here are some pictures of how it looks now... Thanks for all the ideas...

I haven't read the whole thread, but is there an option to share your STL's, molds, etc?  My plastic vents suck, and my next major project is interior plastics and ventilation.

[Utah20Gflyer]

On 2/4/2022 at 8:34 AM, AH-1 Cobra Pilot said:

Did you melt the insert into the plastic?  Or press it into place?

Combination, pushed it in with a soldering iron.   Pretty quick process, I changed the design to provide a correct size hole for the metal insert. 

[Utah20Gflyer]

Here is what the finished product looks like.  Now the only thing left is to test for function in the air. 

[Utah20Gflyer]

On 2/4/2022 at 9:40 AM, hmasing said:

I haven't read the whole thread, but is there an option to share your STL's, molds, etc?  My plastic vents suck, and my next major project is interior plastics and ventilation.

I'm considering different paths forward at the moment, including uploading files to thingaverse and also potentially fabricating parts and selling them.  Unfortunately work is really busy so progress is slow.  Hopefully this week I'll get my plane out of annual which will give me some additional free time.  I've been doing owner assist and been spending a lot of time at the hanger wrenching on stuff.   I spent the whole weekend refurbishing my headliner. It's going to be nice having a flying plane again rather than a part time job fixing a plane.  

[AH-1 Cobra Pilot]

I was having a lot of residual stress cracking with the ABS.  I thought it might be a bad lot of filament, but that is unlikely.

It would otherwise work pretty well and can be painted.

So I made one with nylon.  I also put a little carbon fiber in the base to make sure it is rigid and will never sag.

It looks great, but painting is problematic, and they are expensive.

Next to see how it looks and works in the Mooney.

[Utah20Gflyer]

52 minutes ago, AH-1 Cobra Pilot said:

I was having a lot of residual stress cracking with the ABS.  I thought it might be a bad lot of filament, but that is unlikely.

It would otherwise work pretty well and can be painted.

So I made one with nylon.  I also put a little carbon fiber in the base to make sure it is rigid and will never sag.

It looks great, but painting is problematic, and they are expensive. 146.56 kB · 0 downloads

Next to see how it looks and works in the Mooney. 109.12 kB · 0 downloads

Those look good,  

Could the issue with the ABS be moisture related?  I haven't tried printing with it yet but understand it can have issues if not dried adequately.  

Are you going to install a gasket around the perimeter of the base?  Maybe double sided tape would be a good way to seal it against the plenum and also provide some support?  

[carusoam]

Some polymers are sensitive to moisture… the molecular weight gets destroyed when melted… PET is one that is sensitive…

some absorb water easily in small amounts… and the releases it as bubbles when the plastic is melted…

If you have difficulty with moisture during printing…

Try drying the material before using it… a typical oven for an hour will probably work… time and temperature go with the thread’s diameter…  it is a great mass transport challenge.  Get the moisture to travel from the center of the thread to the outside….

it may be faster to just try a few variables… 

 

PP thoughts only, not a plastic guy…

-a-

 

 

[AH-1 Cobra Pilot]

11 hours ago, Utah20Gflyer said:

Those look good,  

Could the issue with the ABS be moisture related?  I haven't tried printing with it yet but understand it can have issues if not dried adequately.  

Are you going to install a gasket around the perimeter of the base?  Maybe double sided tape would be a good way to seal it against the plenum and also provide some support?  

Nylon is probably the worst of the commonly printed materials.  Even storing nylon filament in air-tight containers with desiccant does not work for long, you still have to dry it.  You can usually hear the water vapor bubbles pop as you print. 

ABS is not too bad for moisture absorption; I think this has more to do with the shape.  As each layer cools and shrinks, it puts lots of stress on the lower layers.  Being a round shape means it pulls equally around the circle rather than having one stress point.  That probably increases the tendency to delaminate the layers.  You can sometimes help relax the stress by boiling the parts right after printing, and with ABS you can paint the part with acetone, which also smooths the surface and makes it stronger by bonding tiny voids. 

That is what I did with this part.

It is a little thicker in places than the original design, but it is far stronger.  It can also still be painted with an acetone-based pant, (common in spray paints).  I found two suppliers of vent covers made from vacuum-formed sheet, just like the originals; one was out of stock and charged $115, the other wanted $55/each.  These are much less.

The ball-vent apparatus may need some kind of gasket.  The double-sided tape sounds like a good idea.

Edited February 8, 2022 by AH-1 Cobra Pilot

[Utah20Gflyer]

9 hours ago, AH-1 Cobra Pilot said:

Nylon is probably the worst of the commonly printed materials.  Even storing nylon filament in air-tight containers with desiccant does not work for long, you still have to dry it.  You can usually hear the water vapor bubbles pop as you print. 

ABS is not too bad for moisture absorption; I think this has more to do with the shape.  As each layer cools and shrinks, it puts lots of stress on the lower layers.  Being a round shape means it pulls equally around the circle rather than having one stress point.  That probably increases the tendency to delaminate the layers.  You can sometimes help relax the stress by boiling the parts right after printing, and with ABS you can paint the part with acetone, which also smooths the surface and makes it stronger by bonding tiny voids. 

That is what I did with this part.

It is a little thicker in places than the original design, but it is far stronger.  It can also still be painted with an acetone-based pant, (common in spray paints).  I found two suppliers of vent covers made from vacuum-formed sheet, just like the originals; one was out of stock and charged $115, the other wanted $55/each.  These are much less.

The ball-vent apparatus may need some kind of gasket.  The double-sided tape sounds like a good idea.

I was thinking you could add some vertical fins that go from the base to the dome, it would make the base much stronger and could possibly assist with the warping issue. 

[carusoam]

Interesting challenges…

Internal stress comes from the long polymer chains being stretched in their molten state….

Melting and flowing in the nozzle has a tendency to elongate the molecules…

After they solidify in place… the stress gets locked up as well….

Heat works well for allowing the polymer chains to relax… unfortunately heat does some evil to their molecular weight too….

 

The surprise happens later… when the part gets warmed on a hot day….

As the part nears it glass transition temperature, or melt temperature…. The stress starts to get relieved by motion of the molecules….

The molecules want to be in tight random balls…. And abhor being pulled out straight….

The stronger the polymer is… the stronger its intermolecular forces are…. Stronger entanglements …

The hotter the melt is… the better chance it has time to relieve stress before solidifying…. Until it becomes a challenge to the printing process…

The lower the molecular weight is… the less entanglements will be there to cause problems… of course you start missing out on impact strength as well…

 

Thermoformed products have these challenges as well… making the sheet implies a ton of stress… then forming the sheet implies a whole new level of stress…. 

Injection molded products have a similar process challenge… mold time.  Cooling the part before removing from the mold takes time and energy… if it isn’t cooled enough, it warps before the shape is fully frozen… some polymers recrystallize over time… building stress even more… 

PET has such a low melting point it will want to turn back into the pellet shape it was in before it got extruded, at temperatures found in hot cars…. (A bit of playful exaggeration)

PP thoughts only, Back in the day, I did a lot of work with PolyPropylene…. 

Best regards,

-a-

[Utah20Gflyer]

Pirep time.  So I finally got my plane back from it's 3.5 month annual and had an opportunity to fly it.  The vents work as I expected with the air flow hitting me directly in the face in the centered position.  Airflow is low on the ground but once in the air is more than adequate.   The vents are attractive and should be much more durable than the ABS plastic deflectors the plane came with.  Overall I am very pleased with how the project turned out.  

I just wanted to thank everyone who contributed to this process.  It was helpful to have input from lots of people with much more experience in many different areas.  

To those interested in aquiring something like this I am still planning on producing something in the future that people could purchase but it's going to take a little while to make that happen.  I'm thinking along with vent adapters I may try to produce a lot of the levers, etc that can be difficult to find for our older birds.   To keep the costs down they will be owner produced parts.  I need to think that through though. I understand that inspecting a part for quality fit and function can qualify a part as owner produced even if someone else made it.  

Anyway,  I'll post more projects in the future.  I have two in the beginning stages now.

Thanks again!

 

[carusoam]

Great follow-up U20GF!

There is an interesting thread around here recently regarding owner produced parts…

Kind of a how to manual and things to be aware of…

More detail than you probably want…

 

Go for it!

Best regards,

-a-
 

 

[Oscar Avalle]

Here is my end product.



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[Utah20Gflyer]

3 hours ago, Oscar Avalle said:

Here is my end product.



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Nice work, looks good!

[Oscar Avalle]

Nice work, looks good!

And it works much better than than the old one


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[AH-1 Cobra Pilot]

41 minutes ago, bluehighwayflyer said:

Would any of you guys with those talents be willing to sell me four of those molded parts?  I love it!

Jim

I would be comfortable selling you nylon ones.  I can do white, black, red, blue, and maybe even a few other colors.  The one I pictured earlier in a clear nylon would be more expensive, but it is also the best material.  Any of these could also have carbon-fiber reinforcement in the base, and again, that adds to the cost.

I am experimenting with glass and CF-filled ABS, which can be easily painted, but is not ready for 'prime-time' just yet.  They will also be much less expensive than the nylon ones.

[Utah20Gflyer]

On 3/12/2022 at 12:16 PM, Oscar Avalle said:

And it works much better than than the old one


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Mine work much better as well. I'm really enjoying the upgrade.