Once again, I’m absurdly behind on writing these blog posts. Not that I’ve been hilariously productive, but I have been doing stuff. The fun part will be remembering half of this.
Basically, with the oil door done, it seemed like a good time to switch gears to the engine baffles. Some of this stuff I’d fitted before, but that was a while ago. The first order of business was starting back with the baffle pieces along the back of the engine. These were a royal pain when I was fitting them, mainly due to maneuvering the pieces that wrap around the cylinders into place. But here’s the thing – since I have a Titan engine with tapered cylinder barrels, I need to modify some of this stuff anyway. The factory baffles are design for non-tapered cylinders, and won’t sit pull tightly in place, which in turn will compromise cooling, After all, the entire objective here is to force as much air as possible through the fins on the cylinders.
The fit for this is to cut off these parts, and fabricate some new custom bits designed for the tapered cylinders. Fortunately, that last part won’t be so bad; other builders have gone before, and one person was nice enough to upload templates for making the new pieces. That portion of the program is still in the future. though; for the time being I just had to do the cutting:
Once I’d gotten all that done, I reinstalled the rear and side baffles onto the engine. This, again, was stuff I’d done before, so at least a lot of the head-scratching was behind me. The one thing I hadn’t yet figured out was how to brace the center of the rear baffle. Normally this is supported by a brace that attaches to a pair of the case through bolts, but those are the bolts that are not being used to mount the upper coil pack.
I did a ton of thinking about this, and even spent some time with cardboard trying to mock up a complex bent piece that would tie into the coil pack mount, but none of it really seemed right to me. It’s hard to design a piece that provides decent bracing, but still stays clear of the actual plug wires. Plus it’d probably have to attach via the bolts between the coil pack and the mount, which would mean modifying the spacers, and probably some other annoyances.
Bottom line, I still haven’t solved this. The idea I landed on after that night of experimentation was to just get a big block of aluminum and sandwich it between the back of the coil pack and the baffle. The would let the coil pack do the bracing work, while also spreading the load over a fairly large area. I order a big chunk of aluminum, and…it’s heavy. Maybe heavier than I want for this task.
It’s kind of tough to see in the photo below, but it’s a split between the left and right sides of the rear baffle, right behind the coil pack:
Eventually I kind of left that issue alone for a while, and instead got to looking at the baffle pieces that attach to the front of the cylinders. These are long flat pieces that lead up to the cowl inlets, and do the first part of directing the air to the cylinders. Fitting these things was quite a bit of fun – they interfered with the complex curved part of the case just behind the crank snout, and there was nothing to do except endless rounds of trial-and-error – fitting, marking interference points, filing off some more material, fitting again, and so on.
The real fun came with the right-side ramp; over in this spot is the crank sensor mount for the SDS electronic ignition, which I mounted in place ages ago. That mount, along with the guard I fabricated for the wiring harness (to protect against damage in the case of an alternator belt failure) interfered heavily with the baffle. But before I could even deal with that, I had the same fitment issues with the crankcase itself mentioned above, so I started by just removing the mount.
After handling the initial fitment issues, I came to the realization that having the prop on the plane was a real annoyance. Not just working around the blades, but having the flywheel in place would make it a royal pain to work with the sensor mount while handling those fitment issues. So I decided it was time to pull the prop off. I always knew I’d have to do this, since I neglected to install the alternator belt before hanging the prop.
The main difference is that instead of briefly pulling it off to install the belt, now it’s going to stay off for a while, probably until I’m feeling somewhat close to first engine start. That means I need to figure out storage, since I (perhaps unwisely) disposed of the crate it came in a while back. For now it’s just sitting on top of a big trash can – which actually works pretty well as a place to lay the prop down, but definitely is not OK for long-term storage. I think I’ll probably end up modifying my rolling engine cart for this purpose – I’ve got some ideas there.
In the meantime, I get to look at a prop-free airplane for the first time in quite a while:
Removing the prop was today’s first task, and after that I was freed up to get to work on that pesky sensor mount. At first I’d been intending to trim the baffle around the mount, but I was worried about air leakage, and that thought had been bothering me for a while. At some point today, it occurred to me that it’d be way smarter to modify the baffle as little as possible, and instead modify the cable guard (which was the most egregious source of interference).
So I only had to take a small notch out of the baffle for the mount, and that finally let me sort-of hold the mount in place and get an idea about how to start trimming the cable guard. Basically, I needed to shorten it from the rear, and then cut off some of the lower material on an angle to follow the inlet ramp:
That, too, was another long run of trial-and-error fitting, but eventually I had it where it fit nicely. This photo is a little more cluttered, as I have another baffle piece in place – the vertical portion behind the mount:
That vertical portion is the last major part of the baffling, which basically encapsulates the area behind the prop and none of that inlet air goes tumbling around that area instead of actually cooling the cylinders. Those pieces are temporarily held in place for the the being:
The last bit of work I did for the day was to make a first attempt at putting the lower cowl in place to see how the ramps fit to the cowl inlets. This, too, became another gradual trim party – both the ramps and the side baffles are too long as-is to allow the cowl in place. I took a couple iterations at trimming them, and got pretty close, but I never did actually get the cowl in place before it was time to quit for the day.
Maybe I can get that done tomorrow. I’m off work until January 2, so hypothetically I should be able to get some good work done. Today was a very productive day, and I feel like I’m back in that productive mindset – let’s see if I can keep that momentum going.