Servo-Actuated Firewall Heat Box Selector

[aeropunk]

Just curious if anyone else has messed around with an idea like this? I thought it might be a neat way to avoid those push/pull cables, and also maybe to have some sort of automated cabin temperature control.



I'm concerned about issues of heat near the nylon servo, and also failure modes and some sort of fail-closed mechanism. Haven't decided to go this way yet, but I thought I'd see if I could get it to work.

Here's a video of the servo in action: http://youtu.be/vV5_2b3UdB0

Any thoughts?

[Jerry Fischer]

I think if you were to shield the servo from heat, i.e. a small aluminum enclosure acting as a heat sink/barrier or with ram air from a 1 inch scat tube should do the trick passively. a spring small enough for the actuator to overcome to open the box should work. Let us know what works out. I agree that the cables can be a pain in effective routing to allow smooth operation.

[868RM]

Brian, Can the servo be slowed down a bit ? It is sorta of an on/off switch at that speed. I use one on my oil shutter control. Two years, 220 hrs. and works fine. Had one on same heat control but was not as nice of servo and wires kept coming out of the servo. Your servo choice looks more robust. Ron

[aerhed]

Cool, but if you get an engine fire will you still be able to close them?

[spark68]

Brian,
I haven't purchased a heat box yet. Could you tell me - did you get this one from Van's? Part number?

Thanks,
Mark

[enielsen]

Originally Posted by aeropunk

Just curious if anyone else has messed around with an idea like this?
Any thoughts?

Oh sheesh... stuff like this may call for a new Forum category. Something like "Open Source Gizmos". That looks like an Arduino pro-mini running that servo which anyone here, that has programmed their EFIS, could do in a weekend.

Sensors, servos, robotics, camera gimbals on wingtips... is all quite prevalent in the R/C world. Surprised to not see it more in full scale EA.

I have tons of ideas with this kind of stuff but, frankly, don't want the liability or the 100% support that comes with trying to make money from it. That's the beauty of what defines "open source".

So let's go with some ideas:

1. APRS - This could be made cheaper than the $200+ options out there. Plus you could choose to encrypt your track for "your/family eyes only".

2. Accelerometer ICs and break-out boards are way cheap now. Why not have one in every flying surface wing-tip to measure trends on vibration, flexing, et al. A little more involved if you want to fuse the data from each sensor, real time, but post flight processing could fuse data with a simple spreadsheet.

3. Temperature and airflow maps under the cowling. Again, the sensors for all these things are so cheap now.

That's just a few and obviously the ideas need to remain non-flight critical. Bring on the ideas...

Disclaimer: This is coming a 30+ year,in the industry, microcontroller/data acquisition geek. I'm expecting mostly sigh's and eye-ball rolling.

[rleffler]

Originally Posted by aeropunk

Just curious if anyone else has messed around with an idea like this?

You mean like this:

http://www.tcwtech.com/control_valve_servo_kit.html

[DanH]

What heat issue? The servo would be on the cabin side of the firewall.

[PaigeHoffart]

Originally Posted by enielsen

1. APRS - ... Plus you could choose to encrypt your track for "your/family eyes only".

That would be a violation of FCC rules (97.113-a-4)

?messages encoded for the purpose of obscuring their meaning? are prohibited (with exceptions for space control, radio control of model aircraft, and emergencies)

Paige

[aeropunk]

Thanks for the feedback, everyone. This is great stuff.

@868RM: Ron, the servo can be slowed down (it actually is, a little), and also stopped at intermediate positions between open and closed. I haven't worked out the logic of how an automated controller might work -- would it make sense to have a half-open position, or just modulate the door open and closed as the cabin temp fluctuates?

@aerhed: My concern exactly. The "best" option might be a manual emer-close pull cable, which sort of makes this whole concept moot.

@spark68: That is the Van's VENT TG-10 Firewall Mounted "Warm" Air Selector/Bypass Box. Came with the FWF Kit.

@rleffler: That's a fine-looking linear actuator, and not really overly-expensive when you consider the price of a high-end, metal gear hobby servo these days. I'd just want to control it with something other than their controller board.

@enielsen: Couldn't agree more regarding the need for a "gizmos" category. Frankly, with all the geeks I suspect are out there building RVs, I'm surprised we don't see more of this stuff. I love the ideas of the accelerometers mounted around the aircraft structure and the cowling heat/airflow mapping sensors. I attended Sonja Englert's "Engine Cooling" talk at OSH, and so many of the "cooling mods" you see out on the flightline just don't make sense from either a drag-reduction or engine-cooling standpoint. If I took anything away from that talk, it's that you can't just eyeball it -- you need the data.

By the way, that is an Arduino Pro Mini doing the heavy lifting, with custom code on the board and a Python script on my laptop talking to the Arduino; it's all on GitHub if anyone wants it.