Oil Breather & Plug Wires

I'm bouncing around to all sorts of FWF tasks these days.  Something I purchased a while ago and need to install is the crankcase vacuum modification.  As a standard approach, Van's has you route a rubber tube from the oil breather port back to the firewall, connect it to a large aluminum tube, then terminate that tube just above the exhaust.  The idea is that oil that is blown out the breather will drip onto the exhaust and be burned up.  In reality, people find that while it may mostly burn up, it still creates a huge mess on the belly of the plane.  One option to fixing that is to put an air/oil separator in the loop to remove the oil from the air and send it back to the crankcase.  I chose to go with kind of a hybrid between the two approaches.  Antisplat Aero has what they call a crankcase vacuum kit.  It's supposed to be used in conjunction with an oil separator, but is commonly used on its own.  It takes that rubber tube from the oil breather port on the engine and connects it to a one way valve that is piped directly into the exhaust pipe.  This essentially serves the same function as the Van's approach, but because it goes into the actual exhaust stream, the oil is truly burnt up.  Pilots say that this alone keeps the belly clean, even without an oil separator in the mix.  The other advantage to this is the slight vacuum that it creates in the crankcase (hence the name).  It keeps a slight negative pressure in the crankcase, and people say that it essentially stops oil leaks from happening.  Many people have commented that they had leaks around the crankcase that went away completely after installing the vacuum kit.  So that's what I'm going with.

This does come with a maintenance gotcha though.  You need to pull the valve off of the exhaust during oil changes to make sure that burnt oil is not clogging up the tube.  You don't want the passage to get blocked, which would then cause pressure to build up in the crankcase and potentially blow out seals.  As a safety measure, Antisplat provides a second .25 psi pop off valve that gets T'd off of the main rubber hose.  If the exhaust port were to get blocked, the safety valve would open to keep pressure from building up.

I couldn't fit the saddle mount fitting and valve right by the firewall exhaust exit, so I moved it upstream a bit.  Antisplat said the valve can sit anywhere on the pipe as long as it's at least 45 degrees or less from vertical.  I drilled the hole to accept the tube that sets down into the exhaust.

The saddle mount fits fairly closely, but not close enough.  For now I used a piece of fiberfrax heat barrier material as a gasket to keep any exhaust gasses from leaking out (although so close to the cowl exit, I'm guessing they would be sucked right out anyway).  I may switch this over to some gasket material at some point, but the thickness of the fiberfrax made filling the gap easier than a thin piece of gasket material would.  I thought about silicone gaskets, but silicone can't withstand the extreme heat of the exhaust pipe.  Once I'm done sorting some of the other wires in the area I'll connect the oil breather tubes.

Next up, I routed and connected the oil cooler lines.

There is a bolt that goes through the engine block, through a 7/8" aluminum spacer and into the rear baffle.  You can barely see it to the right of the pushrod down by the cylinder fins.  The fit of the baffle was bugging me because it was being distorted in a weird way here.  I pulled out the bolt and made a slightly longer spacer.  Just getting the bolt back in took me a solid hour of course.  Real estate for hands is getting hard to come by behind the engine!  But the longer spacer made a huge difference and made the baffle fit much more evenly across the cylinder.

The mechanical fuel pump has a drip line that comes off of it and has to be dumped somewhere.  This is essentially a plastic tube that gets connected to the fitting on the pump, then also connected to a small aluminum tube that exits under the engine mount.  I bent the aluminum tube to fit around the mount.  I don't have a final picture, but it then got safety wired to the plastic tube.  There is no space on the engine mount to put an adel clamp, so a zip tie is the only way to hold all of this (although it's pretty solid anyway since I also put RTV around the aluminum tube where it exits the firewall).  I don't want to have a bare zip tie attached to the engine mount since they have been known to be able to saw into the steel over time though.  I've ordered a few grip lock zip ties to replace this one.  The grip locks are ridiculously expensive for a zip tie, but they have a rubber pad on the back side.

On to wiring routing!  Since the spark plug wires are the bulkiest, I started there.  The wires for Pmags have to be kept separate.  I use high temp zip ties with a chunk of rubber hose as a separator.  I did both left and right side the same way.  After I took this picture, I also added an adel clamp to the engine mount to keep the wires from bouncing around.  I haven't figured out how to handle the top wires yet.  The are longer than they need to be (these cross over to the opposite side Pmag for redundancy) so have more slop to deal with.  I could cut them down, but I'm hoping I can make them work without having to do that.

Spark Plugs

Just a few random things today in between house chores.  I sorted out which spark plug wires go where based on the lengths and started figuring out the routing to the PMags.  I'm going to leave the top plugs out of the cylinders until it's time to run the engine.  That will let me keep the dessicant plugs in place as long as possible.

I drilled the plug wire holes in the left side back baffle (I had drilled the right side a while ago).  Something so simple turned out to be rather difficult just due to access.  I definitely should have drilled the holes before I put the baffle in place.

The cylinder 3 and 4 baffles have holes for spark plug access in them for other engine configurations. Since I don't need the holes, they have to be plugged up.  Van's supplies a few screws and tinnerman washers.  This closes up the holes, but I'll still put some sealant on them I think.

The right side uses much thinner angle on the outside (I modified the left side to beef up the oil cooler corner), so the nut bottoms out on the shank of the screw.  I grabbed some 1/8" aluminum scrap and made a disc for the inside washer to nest in.  That was enough to allow everything to snug up nicely.  A little goofy to do, but it's faster than ordering new hardware.

A major benefit of using PMags is the fact that they can use standard automotive spark plugs - much, much cheaper than aviation plugs.  They are a different diameter than aviation plugs, so use an adapter.  The adapter is threaded onto the spark plug first (finger tight only), then the combo is threaded into the engine.  The spark plug is then torqued down to 18 ft/lbs.

Next I need to sort out the routing of the plug wires.

Oil Cooler Mounting

Rose helped me get the corner gussets of the front baffles dimpled today, so I was then able to rivet them in.  I couldn't easily get the aft couple of rivets done, so I left those out for the time being.  The side baffle will eventually be trimmed quite a bit to leave room for fiberglass ramps that get glassed into the top cowl.  When I trim them, I should be able to get those last few rivets using the squeezer.

Back at the oil cooler doubler - I got all of the holes laid out and match drilled to the baffle.

I had to take some creative license to get the support box in front of the cooler to fit.  I chopped off pieces and added pieces until it did the job it's supposed to do.

I needed more real estate on the aft portion of the support box in order to be able to capture the rivets going into the oil cooler doubler, so I added a large piece of angle to it.

The support box not only stiffens the area for the oil cooler, but it also creates a front face for the baffle material to be riveted to.  I trimmed the front edge of the box so that it would match the cowl contour.  Riveting these back baffles and parts together was quite the chore.  I ended up having to pull it all out to rivet it on the bench.  Even doing that was easier said than done.

Here you can see the oil cooler and the shutter temporarily in place.  I really wanted to have the shutter lever activate in the opposite direction than it is in this configuration (so pulling the control knob out would close the shutter), but there just wasn't a great way to make it work.  So as it is now, pulling the control knob out at the panel opens the shutter, which will be the most frequent position.  That means I'm going to have to redo my label on the panel (it currently says pull is closed), but it's easier to redo the label than figure out some convoluted method to reversing the lever direction.

I need to order some longer bolts to mount the cooler.  With the thickness of the shutter and my large angle corner modification, the provided bolts are too short.  The bolts go through both fore and aft flanges on the cooler with a spacer in between.  The small bolts in the picture are just temporarily holding it on.

Here's what the shutter looks like when closed.  I'll also be making a support arm that will go from one of the inside bolts to the top rocker cover screw.  The baffles are known to crack over time with the weight of the cooler.  The solution is to beef up the corner, which I've done, then also create some sort of a bracket that essentially makes a triangle and keeps the cooler from vibrating.

And the shutter open.  I did waffle a little on putting the shutter in because the design of it means that even in the open position it's still blocking a decent amount of air.  Most people say it's a non-issue though.  Some people report a 5 degree rise in temps after putting the shutter in, but still within limits.

This area had a ton of modifications, including making a number of the parts from scratch.  Straying from the plans definitely turned an hour job into 8, but I'm happy with the outcome.  The last pieces for the cooler will be mounting it permanently once I get the bolts, and  then connecting the oil lines.

My next step on the FWF is to connect my new oil breather line to the exhaust (yet another modification based on feedback), as well as route the fuel pump drip line.

Baffle and Oil Cooler Fit

I've continued to chip away at the baffles this week.  I didn't get any pictures, mostly because the work involves hours of fiddling just to get something trimmed 1/8".  Not much to show with that kind of progress.  I got the front center baffles riveted to the intake ramps and the conical gussets for the corners finished and match drilled to the ramps and side baffles.  I couldn't get the gussets riveted in place yet though - I have to wait for Rose to get back home so she can help me dimple a few of the holes that my squeezer won't reach (they're 1/8" rivets, so my pop rivet dimpler won't work either).  I need her to hold a block with one of the dimple dies in it so I can hold the other one and hit it with a hammer to set the dimple.

In the meantime, the next task is to trim down the baffles so they fit underneath the cowl.  The plans say the top of the baffles should be between 3/8-1/2" from the cowl.

You have to put the top cowl in place to scribe the contours, but just setting it in place doesn't do any good since then it's propped up by the baffles and not setting on the bottom cowl.  So the top cowl has to be held in place but higher up.  I made some blocks to hold the top cowl 4" up from the bottom, then used a block of wood and sharpie to scribe.  The first cut line just needed to be enough to let the cowl set down all of the way without surpassing the 1/2" gap allowance.  It took me a couple of rounds of trimming to finally get it.

Once the initial trimming was done, then the stressful part began - slowly cutting away at the baffles to get the right gap.  One of the tricks I saw online was to use paper clips to help find the cowl contour.  I put paper clips all around the baffles then set the cowl in place, pulled it off, then measured 1/2" down from the top of the paper clips.  It didn't work perfectly, but it was good enough to get me 90% there.  Then it was just a lot of back and forth to creep up on the right gap.  Time will tell if I got it good enough.  I realized after the fact that I had neglected to screw down the cylinder 3 and 4 baffles again before I did the trimming.  Doing that ended up pulling the baffles down a bit, so the gaps for those might be a little bigger than ideal, but I had tried to get about 7/16" for most areas, so I have a little wiggle room.

With the baffle height done, I can finally start working on the oil cooler.  The plans say to set it as high as possible for the best cooling, but you can't do that until you know where the top of the baffles are.  There are a number of pieces to the oil cooler mount.  There's sort of a shelf that goes in front of the rear baffle to act as a stiffener for hanging the cooler.  It's super hard to see in the picture - it's the mirror looking piece.  In order to get this put in place, first I have to figure out where the cooler is going to fit.

I spent way too much time going back and forth trying to figure out where the cooler should be.  I finally landed on a spot, but unfortunately it means I'll have to make a few changes to the normal setup.  The reason it's going to be slightly different than the plans is because I changed the corner of the baffle design a long time ago.  The stock setup is well known for causing cracks in the baffles over time.  The weight of the cooler shaking on the engine is just too much for the baffles, usually causing cracks on the corner flanges.  One fix for this is to beef up the corner with some 1/8" aluminum angle, which is what I did.  The problem is that the stock rivet and bolt locations for the cooler bracket just won't quite work with the angle there.  Most people just slide the cooler over just enough to barely let the rivets clear the inside corner of the angle, but in doing so you end up blocking almost a full row of the cooler.  I don't love that, hence my decision to tweak a few things by making my own parts.

I ground down a portion of the inside cooler flange to fit around the engine mount.  Van's shows a number of different options for how to orient the cooler, but all of them require grinding away the flange somewhere.

The stock method for mounting the cooler is to first rivet a bracket onto the baffle, then bolt the cooler on top of it.  I'm also adding in an oil cooler shutter, which will have to be sandwhiched in between the bracket and the cooler.

Here you can see the baffle stiffener a little better.  This is going to take some thought to make it work.  I will definitely have to cut off the flange on the lower portion because it won't line up well with the cooler bracket.  I'll probably just rivet a new piece of angle to the top side of the shelf and use that to rivet it through the baffle to the bracket (the standard flange drops below the shelf).

I tried and tried, but nothing I did allowed the stock bracket to be in a position where the cooler would bolt through the outside baffle corner in the right places.  So I just decided to make a new bracket instead.  It's essentially the same as the stock one, but with a wider outside portion.  That gives me a lot more room to slide the rivets further to the outside so they are in the right place on the corner, but still allowing the cooler to be further inboard where it can catch the most air.

That's where I ended the day.  Tomorrow I'm going to do my best to get the cooler and shutter mounted before I have to leave for the week for work.

Front Baffles

I don't have a lot to show for the last few days of work on the baffles.  The conical gussets that each inlet gets seemed like they should have been straight forward to make, but that didn't end up being the case.  If they were made out of thinner material, it probably would have been pretty easy, but the thicker material called for was a lot more difficult to work with than I anticipated.  After 3 or 4 iterations on each side, I finally got a fit that I was happy (enough) with.

I won't rivet the gussets in place until I'm done with the rest of the baffle fit.  Next up were the two pieces behind the flywheel.  I trimmed the bottom of each side to match the bottom baffle.

The left side requires two clips to attach it to the bottom baffle.  The back clip has a couple of rivets that just go through the bottom baffle, and then the center rivet that goes through to the bottom bracket I attached a while ago.  It seems simple enough to do, but locating everything and drilling into pieces that you can't see can be quite the puzzle to figure out.  I ended up making one of the holes oblong in the clip because of the odd angles (hard to tell in the picture, but you can't actually get a drill bit perpendicular to the part), so I cut another piece of scrap and will rivet it on top to make up for the bad hole.

All of this required putting the bottom cowl on and off a half dozen times. The side clip was next - much easier access and quicker to do.

Tomorrow I'll finish the clips for the right side. With that done, I will probably start the process of trimming the top line of the baffles to fit the top cowl.  That needs to be done before I can finally mount the oil cooler, which needs to be done before I can finalize my oil and fuel lines and finally finish the FWF wiring.