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RV10 heater box servos

TS Flightlines

Well Known Member
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NOT my area of knowledge, but recently I had the pleasure of looking at a good friends RV10 for another reason. He has these little servo gizmos for the heater boxes and the oil cooler shutter. Really cool idea.
The discussion came around to a failure they had on one box where it failed in the open position allowing ALOT of heat in the cabin. Ok, easily fixed. He has this same servo gizmo on the oil cooler shutter to help regulate oil temp. I asked, "what if the gizmo failed in the closed position?" Oil temps probably would get excessive and you may not be able to get down before some sort of overheat issue occured. I asked if he had a manual overide, like a push/pull cable on it. Nope---

It got me thinking---might be a good idea to have some sort of override---just in case.

Tom
 
My thought exactly. I'm building a 10. I was planning on using the servos for the heater boxes and oil cooler but I have the exact same concerns.

What if the oil cooler servo fails closed?

What if heater boxes fail open?

What if there's an engine fire and the heater boxes fail open?

I've decided to go with push-pull cables across the board.
 
Chris-----look at the possibility of using BOTH systems, with a push cable as a backup. May never have to use it----BUT---

Tom
 
If the servos in question are TCW, let me chime in and say my cabin heat servo failed after a few hours of phase 1 and the good fellow replaced it for me under warranty. He was amazed this happened; my installation was identical as far as we could tell with what he is using on his own RV-10. I installed the new servo and controller only to have it fail again, followed by the failure of my oil cooler air servo of the same make and design. I have removed them and replaced with Bowden cables which, while heavier, are reliable and would have been far cheaper at the outset. I was beguiled by the sex appeal of an all-electric panel I guess.

If anyone would like my original servos and controllers (minus the wiring harnesses which are pro sealed into my firewall penetrations and are not coming out in one piece) they are yours for shipping. I consider them junk at this point.

I cannot imagine any benefit to keeping these servos in place but bootstrapping a backup push cable in case they failed - worst of both worlds for weight, cost, looks...
 
What benefit (over just push-pull) does the servo drive bring to justify the added complexity of installing the push-pull backup?

Overall the servo drive for heater boxes and oil damper seems like a novelty to me.
 
You, sir, are correct. A better-looking novelty than Bowden knobs, and several ounces apiece lighter. The benefits certainly end there, IMO.
 
I have ordered my avionics and am planning my panel layout. I have been considering using servos for my heater because I like the look and am unsure where to put the pull style knobs for the bowded cable where they won’t interfere with the control sticks. I’m trying to keep things clean like everyone else so I’m curious if anyone can show me pictures of a Aerosport 310 panel with heater controls using bowden cable style pull knobs.
TIA
Lester
 
Good discussion and worth some thought. I did the same set-up but used a Actuonix linear servo and controller. This set-up lets you mount the controller external to the servo in an area that has less heat exposure. For sure closing the door in flight within 30 secs get the oil over 225 F and climbing. If the servo would fail you would not have long to find a place to park it. Normally I would open and close the servo on the ground during run-up. Less than a year the servo failed partially closed. Went back and wired it full open so I could continue to fly. The servo failed in what looked like an overheat issue as the thermoplastic material in the servo came unglued. Replaced the servo and added a blast tube. To date I occasionally test it (On the ground) or else in the pattern but don't have confidence to use it for what it was intended. Maybe for ambient air use where all I would get is hot (Or cold) is ok but if their was a failure an issue so for the oil damper I'm using a cable. It might be the location for the 14 is an issue and I'll need to see where servos for the 10 heat system would need to be located. My servo was installed very close to the stock oil cooler location and have a thermocouple in the area for the battery (To monitor temp of the Earth X) and it never went over 120 F on the hottest of days.
 
I have ordered my avionics and am planning my panel layout. I have been considering using servos for my heater because I like the look and am unsure where to put the pull style knobs for the bowded cable where they won’t interfere with the control sticks. I’m trying to keep things clean like everyone else so I’m curious if anyone can show me pictures of a Aerosport 310 panel with heater controls using bowden cable style pull knobs.
TIA
Lester
A quote from Aerosport "On each side of the lower console is an area in which a parking brake or environmental controls could be placed." I believe there is space on each side for 2 push pull cables, for a total of 4. This could be 2 for heat, alternate air and parking brake. Or whatever works for you. If you look closely at the photo of the lower section on the aerosport page you will see the bumped out area where the cable knobs would be.
 
A quote from Aerosport "On each side of the lower console is an area in which a parking brake or environmental controls could be placed." I believe there is space on each side for 2 push pull cables, for a total of 4. This could be 2 for heat, alternate air and parking brake. Or whatever works for you. If you look closely at the photo of the lower section on the aerosport page you will see the bumped out area where the cable knobs would be.

I have considered that area. I do have a parking brake so I was thinking parking brake and fwd heat on the left and rear heat on the right.
 
I don't have any pics handy, but there are two places on each side of the tunnel with the Aerosport 310 panel where you can mount push pull cables.

On the 10 I'm building, I have the parking brake and the oil butterfly valve on the pilot side, and the two heater box controls on the co-pilot side.
 
I have ordered my avionics and am planning my panel layout. I have been considering using servos for my heater because I like the look and am unsure where to put the pull style knobs for the bowded cable where they won’t interfere with the control sticks. I’m trying to keep things clean like everyone else so I’m curious if anyone can show me pictures of a Aerosport 310 panel with heater controls using bowden cable style pull knobs.
TIA
Lester

Pic taken when the servos were still installed. Bowden cables went in same holes after enlarging. Cutout below is mounting hole for Dynon D3.
 

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Pic taken when the servos were still installed. Bowden cables went in same holes after enlarging. Cutout below is mounting hole for Dynon D3.

Thanks Bill for the reply on the thread I hijacked. Sorry Tom if I sent it a direction you didn’t intend it to go.
 
Servos and controllers

Pic taken when the servos were still installed. Bowden cables went in same holes after enlarging. Cutout below is mounting hole for Dynon D3.

Bill,

Did you get my pm on the servos and controllers? If still available, I would like them…thanks!
 
Thanks Bill for the reply on the thread I hijacked. Sorry Tom if I sent it a direction you didn’t intend it to go.

Putting the heat and oil air controls on the sides of the tunnel is a workable idea. I didn't because my controls started out electronic/servo and then were replaced with the Bowdens. My alternate air and parking brake Bowden controls started out and still are on the sides of the tunnel, in the AeroSport center console panels in the designated spots. If I had gone with all Bowdens to begin with, I could have put two controls on each side of the tunnel, although those on the right side are VERY hard to reach from the pilot seat - you'll be taking your harness off to do so.
 
Bill,

Did you get my pm on the servos and controllers? If still available, I would like them…thanks!

Bob, I did get your message. I will message you about shipping. PM me your address, please.

I had several people send private messages after yours. Sorry I can't make but one person happy today :)
 
Sounds like another primer wars discussion. I run full electronic ignition, so maybe I’m just OK at taking risks?

I personally dont think this is a big risk. First I think chance of failure is small - although I do see that someone has had multiple failures which seems strange to me - not saying things like that dont happen. I have had good luck with a number of TCW products that I have, and if something didnt work right or I had difficulty installing, I had zero trouble getting support.

When I adjust my oil cooler using their controller and servo, I see a change to the oil temp within 10 seconds… so you would notice this right away. And it would not be an emergency. You dont go from really cold air to warm air instantly. Redline for the oil temp I believe is 250. I like to keep mine around 190. As soon as I see my oil temp off by 5 or 10 degrees, I make changes.

My $0.02, your mileage may vary.

NOT my area of knowledge, but recently I had the pleasure of looking at a good friends RV10 for another reason. He has these little servo gizmos for the heater boxes and the oil cooler shutter. Really cool idea.
The discussion came around to a failure they had on one box where it failed in the open position allowing ALOT of heat in the cabin. Ok, easily fixed. He has this same servo gizmo on the oil cooler shutter to help regulate oil temp. I asked, "what if the gizmo failed in the closed position?" Oil temps probably would get excessive and you may not be able to get down before some sort of overheat issue occured. I asked if he had a manual overide, like a push/pull cable on it. Nope---

It got me thinking---might be a good idea to have some sort of override---just in case.

Tom
 
Certainly didnt mean to start a flame war here----it was just something I noticed on my friends 10 and we talked about it. My/our thought was oil temp on climb out and "what if" the servo gizmo didnt open? When are you the busiest? Takeoff/climbout and decent/landing.

I liked the idea of the servo thingys. But the "what if" part of my brain that drives all of you crazy said, "hum, what if the thing stuck or failed in the closed, or barely open position?" It would be a bad thing if the oil temp got way up, before you could get the plane down and bearing damage occured.

Just food for thought---

Tom
 
Certainly didnt mean to start a flame war here----it was just something I noticed on my friends 10 and we talked about it. My/our thought was oil temp on climb out and "what if" the servo gizmo didnt open? When are you the busiest? Takeoff/climbout and decent/landing.

I liked the idea of the servo thingys. But the "what if" part of my brain that drives all of you crazy said, "hum, what if the thing stuck or failed in the closed, or barely open position?" It would be a bad thing if the oil temp got way up, before you could get the plane down and bearing damage occured.

Just food for thought---

Tom

That is part of my Pre Takeoff/run up checklist...Oil Cooler --- Full Open
 
What if... yeah

What if I paid a small ransom for those things and they stopped working and they replaced them and the replacements stopped working - at what point is having no heat in flight and having to pull the cowl over and over and having stretches of AOG downtime simply not worth it anymore? That should have been my thought process during the build but it wasn't.
 
Gosh Bob and Bill----didnt mean to open up a can of worms here---it had just occured to my friend and I that on climb out the oil temps could get excessive and yes the alarm would go off, but if youre at 6000-8000, by the time you could get it on the ground there might be an issue.

I dont know about the oils used today, or the temps when they start to breakdown----but excessive temps even for a short time are still not good. Maybe not as bad for the main bearings, but the cam lobes and tappets would surely suffer.

Maybe one of our engine gurus can chime in here.

I know this is thread drift----but at altitude, you cant pull over and pull the cowling to physically move the shutter.
Just saying--

Tom
 
That is part of my Pre Takeoff/run up checklist...Oil Cooler --- Full Open

I do the same thing… in fact, during my preflight, i exercise the shutter full open and closed prior to starting the engine. In my hangar, i can hear the servo move open/close. When I’m outside, its a little more difficult to hear.
 
I have been thinking about the probably of a servo failure in this application for sometime now. This is partially the reason I havnt ordered the actuators for my heater vents yet. I do currently have one for the oil cooler. If these failures happen due to excessive heat FWF I could always fabricate a bracket behind my panel that the actuator mounts to and the actuator could drive a Bowden cable through the firewall. I’m probably way over thinking this but I like the linear actuator idea but would not like a actuator failure during flight.
 
After my second heater box servo failure but before the oil cooler servo failed, I could hear it cycling/fluttering regardless of setting, when powered up. TCW warned me it would eventually fail if it acted like that. It didn't take long. I'm just tired of the labor involved in constant removal and replacement of devices that fail in their intended application, even if covered under warranty.

I'm glad for those who find that these things work for them as intended - like my ASA cowl flap servo does in the same FWF environment and temperatures.

Rocketman, I'll get my cast-offs in the mail to you this weekend, I hope.
 
Certainly didnt mean to start a flame war here----it was just something I noticed on my friends 10 and we talked about it. My/our thought was oil temp on climb out and "what if" the servo gizmo didnt open? When are you the busiest? Takeoff/climbout and decent/landing.

I liked the idea of the servo thingys. But the "what if" part of my brain that drives all of you crazy said, "hum, what if the thing stuck or failed in the closed, or barely open position?" It would be a bad thing if the oil temp got way up, before you could get the plane down and bearing damage occured.

Just food for thought---

Tom

This is why I didn't use them for the oil cooler. Though I did use RC aircraft servos (In the cabin attached to bowden cables) for the heat. I really like the precision they offer and the risk of failure is low, as they don't get hot. I don't feel there is a safety risk if they fail in the open position.

Larry
 
Gosh Bob and Bill----didnt mean to open up a can of worms here---it had just occured to my friend and I that on climb out the oil temps could get excessive and yes the alarm would go off, but if youre at 6000-8000, by the time you could get it on the ground there might be an issue.

I dont know about the oils used today, or the temps when they start to breakdown----but excessive temps even for a short time are still not good. Maybe not as bad for the main bearings, but the cam lobes and tappets would surely suffer.

Maybe one of our engine gurus can chime in here.

I know this is thread drift----but at altitude, you cant pull over and pull the cowling to physically move the shutter.
Just saying--

Tom

Most modern oils will not begin to oxidize and break down until about 260* At those temps, it will take some time before the oil fails to lubricate properly. The larger issues is the viscosity reduction. pressure can reduce in some cases. This is a larger issue for multi-viscosity oils that use synthetic additives for viscosity control.
 
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After my second heater box servo failure but before the oil cooler servo failed, I could hear it cycling/fluttering regardless of setting, when powered up. TCW warned me it would eventually fail if it acted like that. It didn't take long. I'm just tired of the labor involved in constant removal and replacement of devices that fail in their intended application, even if covered under warranty.

I'm glad for those who find that these things work for them as intended - like my ASA cowl flap servo does in the same FWF environment and temperatures.

Rocketman, I'll get my cast-offs in the mail to you this weekend, I hope.

Ah…. That’s good information Bill. That’s really an installation issue. I had the same thing and it’s my own fault. The way these things work is you command it to a certain position. The controller gets feedback as to where it is. Your scenario happens when you’re at the fully open or full closed position you tell it to go to zero for example and it tries but because it’s at the end of travel, it might get to zero, then it stops moving and it moves one tick to one, then the controller tries to get it back to zero and it moves back to one… that’s what causes the jittering.

The goal during install is to NOT mount it in a location where you need all the travel from end to end. You want to mount it where there is 1/16-1/8” of buffer on each end.
 
I was careful to do that, following the instructions.

The chattering/hunting behavior was going on in all positions. the controller got too hot to hold in my hand and in one spot the soldered IC pins on the underside of the circuit board melted 8 tiny holes in the heat shrink covering. I wasn't going to tolerate any electronics at that temperature inside the cockpit with me.

One thing I do know: these servos beat out the Bowden cable in sexy looks and lighter weight. In all other categories (like cost, ease of installation and reliability), the push-pull metal cables sweep the awards categories. I wish I had used them from the beginning.
 
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I was careful to do that, following the instructions.

The chattering/hunting behavior was going on in all positions. the controller got too hot to hold in my hand and in one spot the soldered IC pins on the underside of the circuit board melted 8 tiny holes in the heat shrink covering. I wasn't going to tolerate any electronics at that temperature inside the cockpit with me.

One thing I do know: these servos beat out the Bowden cable in sexy looks and lighter weight. In all other categories (like cost, ease of installation and reliability), the push-pull metal cables sweep the awards categories. I wish I had used them from the beginning.

Bill, sounds like you've had a bad experience here. And I certainly appreciate your perspective on the dirt-simple approach of a push-pull cable.

However, I've been using linear actuators in the power industry on scales from micro actuators to ones that provide several tons force - for many years with great success. They generally outlive the valve or component they're operating; and I'm talking literally thousands of them. The MTBF on the lower end ones is >10,000 hours, and the higher end ones are well over 200,000 hours. I have units that have been in operation 24/7 for over 10 years and still working great - in nasty industrial environments of high ambient heat, moisture, and vibration.

I have the TCW actuator, which is a high quality component, for my oil cooler and like it. Components do fail, but in this case it is super rare - and almost always an installation issue or infantile failure (if it's going to fail, it will happen early on).

My plan if the thing every did fail, which in my opinion is highly unlikely, I'd pull the power back and land. In my experience, I just don't see that happening within the life of the aircraft with a properly setup actuator.
 
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My plan

Timely thread, I’m just tackling this now.

I want both the cabin heat valves and oil cooler shutter to be ran by servos. My concerns:
1. Want to minimize electronics foreword of the firewall
2. There should be automatic built in testing for latent servo failures
3. I want the heater valves shut in a fire situation

My plan of attack is an arduino with 2 small motor controllers. I should be able to 3d print a nice package to mount behind the panel. The actuators have a built in potentiometer which the arduino can read. No smart servos FWF.
When the unit powers up it will sweep the actuators through their range. A discrete output to the efis will report any issues.

The fire case might be a bit overboard. But I don’t like worrying about a wire burning and loosing control. I thought about Bowden cables to inside mounted actuators but instead landed on mounting a thermocouple at the cowl exit. Arduino also monitors that and shuts the vents if things go awry. Maybe another discrete to the efis for fire warning also.

I know there’s more what-ifs in the fire case but this design gets me comfortable with the setup.
 
Temperature range ?

I am fairly sure temperature was the issue when my first servo went bad. I believe the linear servo TCW uses is produced by Actuonix. If that's not correct feel free to chime in. TCW in their specifications has an operating range up to 70 C but Actuonix states that the operating range is up to 50 C. I have added a blast tube for the servo and to date that seems to have helped but I don't trust it after the failure so leave it open in flight closing it sometimes in the pattern to land. I monitor (Via thermocouples tied to the G3X) the battery temperature's (Earth X) for both locations on the firewall and never see this area over 120 F (Stock RV-14 location) before the blast tube was positioned and of course after.
 
How About Climate Control?

There are good arguments on both sides. I was thinking about using servos to control heat and vent air. My feeling is a servo for the Aerosport overhead would definitely be a nice add. However, adding servos so you can twist a potentiometer vs push and pull a cable seems like your adding possible failure points for little additional benefit. It's just a different kind of manual input.

But... and a big but... what if the servos are tied to some logic that makes them more useful? I have an idea to build a logic board that would open and close the vent and heat servos so the climate control is more like a modern automobile.

Thinking it works like this for a -10.

1 servo front heat
1 servo rear heat
1 servo to feed vent air to front pass via overhead
1 servo to feed vent air to rear pass via overhead
Vents on panel remain manual
Side vents to rear pass remain manual

Auto Mode
Temp sensors in the front and rear cabin
Logic board opens and closes heat and cool butterflys depending on the desired set temp. Passengers can still open manual panel vents or rear side vents and system will try to compensate by adding heat.

Vent Mode (AKA anti puke mode)
Front and back passengers can set a desired temp and the flow of vent air and the logic board adds heat to try and maintain a set temp. This lets you open the panel vents and side vents as well as fully opening the overhead vents and the system will add heat to try and reach a target. This is a max airflow mode. Sorta reminds me of driving a Jeep with the top off in the winter. You have all of that airflow and the heater turned on high.

Manual Mode
Front and back passengers can open and close heat and cold servos manually. This is what we have now without the added benefit of seeing the temp for front and rear displayed on the panel.

Off
Closes all servo controlled butterflys.

Am thinking oil cooler is a cable as I view the oil cooler more as a safety of flight item vs controlling cabin temp. Also thinking of mounting the heat control servos inside the cabin attached to cables. Separate the heat and electronics and in the unlikely event of a fire you could potentially reach down and pull the cables closed if for some remote reason the servos get toasted.

This can all be controlled with a touch screen. Which lets you do unlimited things like control interior lighting etc. I have a mock-up built and running using a single temp sensor and servo. Pics attached.

Would welcome input and collaboration if anyone else is interested in doing something like this.
 

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There are good arguments on both sides. I was thinking about using servos to control heat and vent air. My feeling is a servo for the Aerosport overhead would definitely be a nice add. However, adding servos so you can twist a potentiometer vs push and pull a cable seems like your adding possible failure points for little additional benefit. It's just a different kind of manual input.

But... and a big but... what if the servos are tied to some logic that makes them more useful? I have an idea to build a logic board that would open and close the vent and heat servos so the climate control is more like a modern automobile.

Thinking it works like this for a -10.

1 servo front heat
1 servo rear heat
1 servo to feed vent air to front pass via overhead
1 servo to feed vent air to rear pass via overhead
Vents on panel remain manual
Side vents to rear pass remain manual

Auto Mode
Temp sensors in the front and rear cabin
Logic board opens and closes heat and cool butterflys depending on the desired set temp. Passengers can still open manual panel vents or rear side vents and system will try to compensate by adding heat.

Vent Mode (AKA anti puke mode)
Front and back passengers can set a desired temp and the flow of vent air and the logic board adds heat to try and maintain a set temp. This lets you open the panel vents and side vents as well as fully opening the overhead vents and the system will add heat to try and reach a target. This is a max airflow mode. Sorta reminds me of driving a Jeep with the top off in the winter. You have all of that airflow and the heater turned on high.

Manual Mode
Front and back passengers can open and close heat and cold servos manually. This is what we have now without the added benefit of seeing the temp for front and rear displayed on the panel.

Off
Closes all servo controlled butterflys.

Am thinking oil cooler is a cable as I view the oil cooler more as a safety of flight item vs controlling cabin temp. Also thinking of mounting the heat control servos inside the cabin attached to cables. Separate the heat and electronics and in the unlikely event of a fire you could potentially reach down and pull the cables closed if for some remote reason the servos get toasted.

This can all be controlled with a touch screen. Which lets you do unlimited things like control interior lighting etc. I have a mock-up built and running using a single temp sensor and servo. Pics attached.

Would welcome input and collaboration if anyone else is interested in doing something like this.

Just an fyi. If you are using the aerosport overhead for vent air, it is typically pressurized from the aft naca vents. Splitting the fore and aft would require additional mods. I actually saw a servo operated naca ramp that someone did that would be really cool.

Unfortunately, though I wanted the automotive style control and logic, I wanted to fly it more…so I went with the aerosport vent valve for the overhead, and linear actuators for the heat valves and oil cooler. I used Actuonix actuators and their LAC board for control. Over 200 hours on the airplane and no issues so far…

Oh, and I started out using the RC version of the actuator; it required a 6v regulator and servo PWM control. Has issues with the actuators constantly hunting so I replaced them with the standard 12v models. No regulator and the LAC board takes care of control…
 
Oh, and I started out using the RC version of the actuator; it required a 6v regulator and servo PWM control. Has issues with the actuators constantly hunting so I replaced them with the standard 12v models. No regulator and the LAC board takes care of control…

Thanks Bob. Yeah, I'm getting the logic programmed with cheap hobby servos for now and will look at the 12v servos. I'll have to step down the voltage for the controller but like the idea of just running 12v from ships power. I'm also thinking about using a VPX and need to look to see if I can configure circuits with different voltage outputs. Might eliminate the need to run a separate circuit.

I'm wrapping up my tailcone and should have wings to start in the next month. Figured I could get this figured out well ahead of getting started on the fuse.
 
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