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Time To Fix Some Stuff.

For a while now, the MGL RDAC XD engine monitor module has been a little weird, mostly in the form of erratic oil pressure and temperature readings. To wit: Whenever the oil temperature would get above a certain point, the reading would bounce around all over the place, and the oil pressure reading would do the same, resulting in a low pressure warning. It’s very important that neither of those two lie to me, so I installed a steam gauge for the pressure. Oil pressure is solid on the steam gauge, no matter what shenanigans the temp and pressure sensors are up to.

The story so far…

Oh, that’s just a bad ground, you’ll say. Check your connections. Yeah, been there, done that. A lot. And it’s no use. A couple of weeks ago, I went for a nice flight after all the rain, and on takeoff from OXR, I had a complete failure of the RDAC module. Every measurement flashed “rdac fail.”

This, as you may imagine, was almost a code brown, at least until the RDAC came back to life, upon which I promptly flew back to SMO. Popped the cowl, checked the connections to the EFIS, to the grounding block, to all the things. Went for another flight. This time, the RDAC packed up over Malibu and didn’t come back. I flew home old-school, with only the sound of the engine (which I know by heart) as my RPM indicator.

Eventually, I made the connection: When the RDAC gets heat-soaked, it fails. It’s mounted on the firewall, which is extremely convenient because only a couple of wires go through the firewall port back to the panel. Unfortunately, it’s a harsher environment than I anticipated, and after less than 200 hours, I suspect the RDAC has succumbed to the heat and vibration of the engine compartment.

So now I have a job to do: Replace the RDAC, with MGL’s shiny new RDAC XF unit, and this time, don’t mount it low on the firewall where the engine radiates all the heat into it. And maybe, figure out some sort of enclosure for it to keep the worst of the engine’s emissions off it.

When I first installed the RDAC, I had no engine, no accessories, and no clue. I had a vast, untouched expanse of stainless steel where just about anything could go. Over the course of the build, the left side of the firewall got really crowded, and I think the logic was to avoid running data wires along the main power cable coming off the battery on the right-hand side. What we have is a job broken into two lists, for starters: stuff to buy and things to do.

Oh, and by the way, it’s time to start thinking about plumbing the mandated ADSB equipment for 2020. But that’s a whole ‘nother post.

To Buy:

  • MGL RDAC XF
  • CHT probes and wire (2x probes, 4x wire, steel crimp connectors)
  • EGT probes and wire (2X probes, 2x wire, steel crimp connectors)
  • Heat-resistant shrink tube
  • 3-wire shielded cable (+, -, and ground, plus shield). See http://spectrum-instruments.com/resources/documents/splicing_STP.pdf
  • 4″ SCEET tube (See the oil cooler scoop post, the tube’s getting ratty).
  • 1″ Fire sleeve for firewall port
  • 3″ Fire sleeve for cable wrap in firewall port
  • Aluminum Z-channel to mount new RDAC (this is a maybe)
  • Blast tube (look for this in the garage)
  • EZ-Up (to keep the sun off while working. Yeah, I park outside at SMO)
  • Fire barrier goop
  • Tarp/cover (in case I have to leave the cowl off overnight. Or for a whole damn week)

To Do:

  • Dismount Oil Cooler Scoop, gain access to old RDAC
  • Dismount CHT probes from 1 and 4 (these are the ones that work intermittently)
  • Dismount old RDAC, fill firewall holes
  • Mount new RDAC. Somehow.
  • Extend fuel flow wires to new RDAC location
  • Extend fuel pressure and oil pressure probe wires to new RDAC location (Do this at home)
  • Run and wrap all wires to new RDAC location (The existing Adel clamps will work)
  • Wire up new RDAC.
  • Remount Oil Cooler Scoop
  • Devise a way to keep the hose clamps from cutting up the SCEET tube
  • Install SCEET connection from baffle to cooler scoop (Do it right this time)
  • Test all connections!
  • Fly.

Oil Cooler – Day 5. Progress.

Today sucked a lot less than yesterday.  I got the oil cooler attached to the engine mount, which is a significant milestone.  I also learned that you can attach anything at any angle using this One Weird Trick, which I’ll describe later.

The oil cooler itself doesn’t weigh all that much, and there are no significant loads placed on it.  The attachment method is Adel clamps, which serve to isolate it from some of the engine’s vibration.  Given that, it seems that the beef I put into the brackets is unnecessary and an example of overengineering.  That said, it’s really, really important to me that the oil cooler stays firmly attached and that it retains its structural integrity until the end of time.

Forward Bracket - Oil Cooler

Forward Bracket – Oil Cooler

The  Weird Trick I mentioned earlier is shown below.  On the right of frame, there is a large-ish piece of angle connected to another angle bolted to the cooler.  The way this works is that there’s enough span on the opposite side to cover the distance needed  by two Adel clamps when the angle is laid up alongside the tube and the adjacent side lines up with the angle connected to the cooler.  This made for a much easier test-fitting, and the same technique is in use on the bracket shown above.

So it’s come to this.  The oil cooler is suspended where it needs to be to get air to it from the big hole in the baffle. At this point, the whole setup will take nearly my full weight, so I’m not terribly concerned about the parts failing.  At this point, the weakest parts are the flanges of the oil cooler itself, and they can be reinforced with angle or bent sheet.

This is the best fit possible for access, airflow, clearance from other important things (fuel line, for example).  There should also be enough room to get a  fiberglass intake plenum between the cooler and the middle engine mount tube.  I measured.  But “best fit” means the least hideous compromise.   Now for shaping the  plenum.  Yay, fiberglass.

Happy New Year.

Oil Cooler, Day 4

This suuuuucks.   I usually feel a certain smugness when my predictions come true, but not this time.  I knew this was going to blow going in, that’s why I delayed it for so long.  I was on the money with this one.  Not one part of this has gone smoothly.  Most of it has to do with the fact that it’s impossible to suspend an oil cooler in mid-air in the place it will eventually go so measurements for bracketry can be taken.

I guess if it was easy, everyone would do it.  Today I took a different tack, and unfortunately I didn’t take any pictures, because there was nothing to shoot.  Just a lot of head scratching and pondering, followed by some fairly intense metal work.  Oh, and I managed to burn the f**k out of my left thumb and forefinger trying to grab a piece of hot angle off the bandsaw table.

At least I have a proper metal shop to do stuff in, even if it is at the opposite corner of the hangar from where my plane is.

Eventually, I was able to draw up some rudimentary plans plans based on some measurements.  That actually worked and I have a main bracket that should, in theory suspend the oil cooler in the correct position from the engine mount tubes in three places. There is also no chance in hell it’s going to break. It’s reinforced at the cooler mount point with .062 angle.

I also need a new oil hose, which is shaping up to be around $250.  Argh.

Oil Cooler, Day 3.

I thought this was going to be a fairly easy exercise.  After all, what’s the big deal, right?  Attach a flange to the baffle, mount the cooler, fab up some fiberglass ducting, slap on a length of SCEET, and presto, done.

Nah.  Slow your roll, dude.

First thing that needed to happen was removing the old cooler mounting flange.   Rather than take the baffles apart, which may have been a poor decision, I figured I’d just unzip all the rivets along the top and left of frame so the baffle can open up, swinging open from the bend right about where the spark plug wires go in.  That hypothesis was borne out.  After some less-than-stellar de-riveting, I have the baffle exposed, but even opening up, it was difficult to get any kind of squeezer or rivet set into the area by the engine mount tubes.  Before anyone freaks out, yes I did clean up the mangled rivet holes, and a couple of them went away entirely when I cut out some excess for the 4″ flange opening, seen in the next shot.

So now there’s a big plate of aluminum doubling up the baffle, to which is attached a beefy 4″ aluminum duct flange from an industrial dust collection system.  Fun fact about that:  Originally, this duct was two pieces, which included a sliding gate to control the amount of air going through the duct.  Cool setup, but it was not to be.  I either had edge-distance issues or conflicts with other parts of the structure, and it didn’t look like I would be able to set up the control cable and mount it.  Bummer, but that’s the way it goes.   I want to return to flight ASAP, I don’t want to be back to project status for any longer than necessary to make this a safe, effective modification.

The final configuration looks a little different from the above.  The flange is flipped over to provide material to rivet along the top where the baffle parts connect, and I cut one of the tabs off to allow for clearance of something else.   But it looks like I have enough room for a 90 bend of SCEET (or one of those boy-racer intercooler inlet elbows) and a diffuser.

This is where I plan to put the oil cooler.  I’ve checked for clearance to mount tubes, wires, and my fuel line (important, that), and it also clears the lower cowl.  I think I can connect to the engine mount with Adel clamps in at least 4 places, both from above and below.  It also looks like there are no immediate obstacles to exit air, but I’m not sure how airflow will be affected by the proximity of the engine mount tubes, but there is nothing directly up against the fins on the bottom.

So I guess my New Year’s resolution for 2018 is to solve all my cooling issues.  Among the things that keep me awake at night is the possibility that the 4″ duct will now steal too much cooling air from the cylinder heads.  Also on the list is to rework the baffle seals to be fewer, more continuous pieces, made of silicone instead of the black rubber baffle material.

Today is New Year’s Eve.  It’s unlikely I’ll be making more headway on this until after I go back to work, but if I keep it chill on tonight’s festivities, I might be able to put in some work tomorrow.

Happy New Year, everyone!

More oil cooler fun

Finding a spot for the new oil cooler was just part of the adventure.  I needed to make room by disconnecting the plug wires and temperature probes from the left side so I could work.  I also needed to find a new spot for the fuel pressure sensor.  Fortunately, that’s easy. I can clamp it to the top strut of the engine mount, pretty much where you see it resting now, top middle of the frame.

Ordinarily, I hate working with steel.  it’s sharp, unyielding, and awkward to work with.   This all changes when you have the proper tools. EAA 96 has a plump machine shop, with a shear, two sheet metal bending brakes, numerous drill presses, grinding wheels, table saws, a massive lathe, and two Bridgeport mills, one of which is working, but neither of which I know how to use.  There are also a number of projects in the hangar that utilize the tube-and-fabric method, so there’s a scrap can full of 4130 steel tubing and sheet cut-offs.  So that’s where I went to get the brackets I needed.   I’m sure there’s some fancy engineer-y math I could have used to bend a bracket so it works in one piece like papercraft, but I was able to get this together with two pieces.  This connects to an angle brace on the cooler and suspends it from the engine mount at the angle and distance I’ll need to get a fiberglass plenum on it, which will connect to the baffle via 4″ SCEET tube.

I chose steel because it was available, I have the tools to work it, and I can get away with less material.  I don’t have the right circumstances to do a solid aluminum webbing, so steel it is.

There will also be a support member on the bottom of the cooler, where I have to battle the mechanics of attaching to the engine mount without blocking the airflow from the cooler.  I paid for 10 rows of cooling, I want all 10 rows cooling.

New oil hoses will also be a necessity.  The top one barely made it to the cooler with an acceptable bend in the line.  There’s no way it makes it now.   I may be able to repurpose the from-cooler line as the to-cooler line, but that’s doubtful, given the fittings necessary.

Oil Cooling hell.

Yesterday, I went from having a flying airplane back to having a project.  For quite a while now, my oil temperatures on hot days and climbouts have been marginal to unacceptable, and since I have the break in the work schedule, I figured I’d do something about it.   So I joined the Compton EAA chapter and rented a space in the hangar for a month while I sort it out.  My oil cooler is the stock Van’s 7-row Niagara oil cooler that seems to work on most RV installs, but not mine.   There are a few reasons this might be: timing, blow-by (which would suck, the cyls are more or less new) bad baffling (worked when I first flew, so wtf) or carbon deposits in the cooler.  It’s actually fine as long as the OAT is 65f or below.  I can settle in to cruise at 190-195F no problem.  But on hot days, or long climbs, I will go above 220 real fast, and that’s no good.   Last year, I purchased a 10-row cooler with the intention of replacing the stock one, but I never put it on.  I first attempted to seal up any baffle leaks.  This improved things a bit, but not enough to matter.  Cylinder head temps are fine.   I’ll hit 400 on those if I mash it and rabbit up to 10,000ft, but they cool down pretty fast once leveled off, and usually settle in around 350-375.  I’m sure there’s more I can do, but for now I need to solve the big one.

The 10-row cooler will not fit on the back of the baffle like the stock one does.  It’s too wide.  There are a number of ways to mount the cooler on the firewall, but none of them work because my firewall is already full of stuff, namely the RDAC, fuel pump, and brake line fittings.

I supposed I could probably move the RDAC and fuel pump, but that’s less appealing to me than mounting on the engine mount and connecting it with a SCEET tube to a flange on the baffle where the original cooler was mounted.

So it’s off to Compton I go, first to do exploratory surgery, then some design work, and then hopefully some fabrication.  They have ALL the tools.

More little things.

4.5 hours.

I brought the newly painted cowl back to the airport and yes, it looks way more badass in olive drab than pink.  I also took care of some things that have been bothering me for a while but never got around to doing.   I re-did the cotter pin on the prop pitch control on the quadrant because I’d forgotten to put a washer between the pin and the lever.   This is now fixed.   The left control stick now has a cotter pin as well.

After that it was the endless tedium of safety-wiring a bunch of hose clamps and other fittings.   I hate safety wire, but I can’t argue the fact that it can keep you from having a really interesting day.      I think I got most everything on the right side.   I’ll do the left side next time.

I also need to make an appointment with Randy to get my avionics calibrated, but I’ll have to wait until Monday.

Idle fixed.

5.5 hours.

 

I don’t have time for a lot of jibber-jabber, so I’ll make this short and sweet:

I installed the new idle linkage bearing and spent a bit of time dialing in the idle.   I got it to idle smoothly at 750 RPM with a solid transition to power on throttle advance.   CHT’s sitting there uncowled don’t get past 245, which is good.   We had a really strong wind today, so it was a good day for engine testing, but a crap day for flying.  Nobody was out there, so I was left to my own devices.  The idle fix took about two hours, so then I went for a drive.   I taxied down to the west end of the runway, then came back.   20+ knot winds variable from 070 to 085 make for some fast footwork on the pedals.

After that was done, I set about making the fire extinguisher mount.   I ended up putting it on the fuel pump cover, in easy reach of both pilot and copilot.  Of course, if the fuel pump’s on fire, getting the the extinguisher is going to be interesting.   I had to reinforce the fuel pump cover with some .032 so the bracket could be safely bolted on, but it seems to work.

 

Red Goo.

5 hours.

A shortish day, after Thanksgiving weekend.  But decent.   I got the pax side restraint system involved in addition to the pilot side crotch strap or “anti-submarine” restraint, as it’s called.  That took longer than I thought because of the number of times I had to hop in and out of the plane to find washers and other hardware and tools.

But now they’re both in.  This unflattering photo is just to show that both seat belts are hooked up.

IMG_1687

So I went on to the red goo.   I’ve been putting this off, because of my usual aversion to non-solids, but it was finally time to RTV the baffles.   Squeezing a tube of red RTV into all the places it has to go is really hard on the hand muscles, especially when you have to get the nozzle into nooks and crannies now blocked by FWF equipment.

IMG_1685So I’m not the best RTV’er in the world, but I think the bases are more or less covered – a bead running along the baffle meterial, and anywhere light gets between the baffle and the engine.   OK, maybe not everywhere, but everywhere I could get the stuff in there.

IMG_1686Oops.  Didn’t get around the right magneto blast tube.  I’ll have to get that later.

But I was sure to get RTV into all the gaps between baffle and oil cooler, because that’s kind of important, and as for other leaks, we’ll have to see what happens to CHT’s in flight.

Odds, ends, and annoyances.

6 hours.

Last weekend I had to work to deliver a product launch, so no airplane.   This weekend, I had a list, and I knocked out a bunch of stuff on it.  To sum up:

  • Tensioned and safety-wired alternator bracket
  • Removed protective plastic from aft canopy and removed tape residue
  • Relabeled mag switches and made “OFF” labels for everything else
  • Reconfigured quadrant for extra travel on governor
  • Added a wider heat shield to protect the throttle cable
  • changed out a too-short bolt on the purge valve cable bracket.

Apparently the way you do alternator belt tension is by increasing belt tension until it takes 12 ft/lbs of torque on the alternator nut to slip the belt.   That’s it.   That also gives you the 1/4″ deflection (on a new belt) called out by the usual procedure.   This is important, because a slipping belt can cause over/under voltage problems.  I did that, and safety-wired the bracket tension bolts together, like so:

Alt bracket saftey wire

Alternator bracket Safety wiring

 

When I put the aft canopy in all those many moons ago, I left the protective plastic on it, because why not?  Why subject the vulnerable plexiglas to my fumbling ministrations while I’m climbing in and out of the tailcone to adjust one thing or another, swinging tools and wires about?   Because once the canopy is attached, it’s difficult if not impossible to get all the plastic out from between the roll bar support and the canopy.   I had to put a space heater in the cockpit and run it for a while, until it was a balmy 75 degrees and the plexi and surrounding aluminum were warm to the touch.  I took out all the fasteners and removed the aft canopy section, which I put on the bench, then removed the rest of the protective plastic and cleaned off all the tape residue I couldn’t get to before.  100% better.

Protective plastic and tape residue gone

Protective plastic and tape residue gone

 

The magneto switches on the panel were cryptically labeled “MAG 1” and “MAG 2.”   I don’t know why I thought this was a good idea, and it broke with common practices in aircraft UI/UX design.   I relabeled them “L MAG” and “R MAG” because that made the most sense, and that’s how everyone else does it.   While I was in a labeling mood, I made about a dozen or so “OFF” labels to describe the down position of most of my toggle switches.   The double-throw switches like flaps up/down already had good labels in both directions, but there wasn’t anything labeled “OFF” anywhere.  The switch pointing toward the function described seems obvious to me, but apparently it isn’t to whoever wrote that reg at the FAA, so now everything is labeled according to the AC’s.

IMG_1669

Like I said, there were odds, ends and annoyances.   Firewall forward, there was the matter of a heat shield, a too-short bolt, and the prop governor travel.

Heat shield on throttle cable

Heat shield on throttle cable

I did have a shield in place at this spot, but I remembered I had an extra double-wide one, so I put that one on in its place.  On the topside of the engine, I changed out the bolt holding the purge valve cable.   It was a temporary thing when I did it, and it didn’t have the required number of threads showing to meet spec, and since it’s pretty important that the purge valve remain closed in flight, it’s also important that everything connected to it is not half-assed.  This is what the proper bolt length looks like:

Purge valve cable bracket

Purge valve cable bracket

As to the prop governor, if you’ll recall from last time, the prop didn’t cycle at the low end of the throw.  The quadrant was only moving the lever arm about halfway through its arc of travel.   The simple fix to that was to drill a #12 hole about 5/8″ up the quadrant lever from the original one and voila, I get me 75-80% travel instead of 50%.   That story ended with a quick runup to 1800rpm and getting the prop to cycle, so that’s good enough for now.   Whether or not I have the rpm set right due to the arm position relative to the governor shaft is another story, and it will be resolved on either a full power run or first flight.  Even so, the engine is more responsive, now that it’s firing on all the plugs, which are now more or less synchronized in their ignition, so that’s a plus as well.

What was really awesome about this weekend was that for the most part, it was forward motion, not playing catch-up.  New things got done and good fixes were made, rather than unsuccessful stabs at a persistent and difficult problem.   There’s still a bunch of stuff to do to get ready for first flight, but I think if I can keep up the pace, I’ll be on track to fly it in early 2014.