Firewall Forward

Fitting the engine mount

Well, I’m still paused on the canopy front until I get in the replacement slide block from last week’s shenanigans, but in then meantime I get to kick off a whole new category with the first bit of firewall forward work. Most of the weekend has been spent working on other stuff around the house, but I wanted to keep making progress on something and so I decided to see about fitting the engine mount to the airplane.

The firewall and the structural bits behind it came with an existing pilot hole at each corner, and I drilled those holes out to 3/16” quite some time ago to allow for the fuselage rotisserie mount. The final bolt holes are 3/8”, but final-drilling those requires some attention, since individual engine mounts can vary even though they’re welded up in a jig.

So the first step is to do a rough evaluation of fit out of the box. To do this, I installed a couple of long AN3 bolts in the upper two holes and used those to loosely hang the mount in place. Doing this allowed me to establish a good starting point, as I could verify that the width of the two upper mount points were at (or very nearly) the same width as the two pilot holes. That meant I didn’t need to do anything dramatic to get those first two holes drilled…well, almost. The construction manual calls for drilling the holes using the engine mount as a guide, which I imagine helps ensure that the holes through the fuselage structure are in line with the actual mount sleeves. So the most interesting part of all of this was figuring out how to “clamp” the mount against the firewall. I probably should have gotten a photo of the final setup, which involved some ratchet straps going from a piece of lumber across the mount to the setback support in the cabin…

In any case, the upper two holes are now drilled and bolted in place. This gives me a nice base to work off of for the other two holes at the bottom: 

However, things down here are a bit less simple; the engine mount holes are a good 3/8” or so above the pilot holes in the firewall. I figured this out by putting flashlights inside the fuselage, pointed at the pilot holes; with that light sources inside, I can easily spot the pilot holes from outside, even if I’m looking through the engine mount itself. Note the pilot hole at the bottom of the engine mount hole, mostly occluded by the mount itself:

So in order to get these drilled, I’m going to need to rig something up to precisely stretch the engine mount. I made a first rough attempt at this tonight, which didn’t work so well. I figured since both lower holes are high, I’d see about trying to push both down, so I flipped one of my large hand clamps to make it into a spreader, and put it between the upper and lower center of the mount. I was able to move the lower holes by maybe 1/4” or so, but still nowhere near into alignment.

I’m not entirely sure yet how I’m going to work this problem, but so far I’ve had some vague ideas involving threaded rods, nut, and bearing blocks, but the hard part would be getting any of that stuff braced in the right place on the mount. Normally I’d prefer pulling for something like this, but I don’t really have anything to pull against…unless I were to put concrete anchors in the floor just for this one operation, and I don’t really want to do that.

So anyway, something to mull over. I’m sure it’s a solvable problem, I’ve just got to work it out.

Posted in Firewall Forward | Hours Logged: 1.5

Finishing with the engine mount, doing some wire routing

As I headed out into the hangar to get to work this evening, it occurred to me that I hadn’t had a single super bright idea about how to stretch out this engine mount to get the second pair of holes drilled. All that random thinking about making a jig with threaded rod and so forth hadn’t gone anywhere concrete. So I ended up just trying to stare at things and work out a solution, and eventually I got to something.

Basically, there are two ways to approach this: either I need something inside the mount exerting outward force to spread things, or I need something pulling down on the bottom of the mount. The latter seemed impossible since I had nothing to pull against, but finally I realized that if I stopped thinking in terms of using something like a ratchet strap, there were other ways to approach this. What if I could just hang weights off the bottom of the mount and try to work with the positioning that way?

And that’s how I ended up with this amusing Rube Goldberg setup:

We’ve got a 30-pound kettlebell hanging on the center of the mount, using an S-hook normally reserved for hanging up a caliper while working on the car brakes, plus another 30 pounds of dumbbells lashed together with some spare paracord and hung from the corner with more spare paracord. The only real issue with the hanging-weight idea is that you don’t have a lot of fine control over how much the mount stretches, and that’s where the big clamp comes in. Hanging the weights as shown here got the hole just a tiny bit above where it needed to go, so with the clamp in place, I could carefully apply that last bit of force to get it all lined up nicely.

The only remaining issue was how to pull the mount snug against the firewall while doing this; as it sat, the mount face wanted to sit about 1/4” off the firewall. I initially tried using a ratchet strap secured to a long piece of lumber going through the center section, but the strap would have been bearing on the edges of the forward side skins and the firewall flange, and surely would have bent something if I’d started cranking down. Then I had another epiphany – the other lower hole could be used for this. I just had to run a 3/16” bolt through the hole and the mount, add a large washer so it’d bear against the mount hole, and tighten the whole thing down.

That pulled both lower holes up nice and snug, and once I had the lower right hole drilled and bolted, the other was already lined up nicely and didn’t even need any drama to get it set up. The only concern here is how annoying it’ll be to attach this mount unless I permanently stretch it, so I’ll probably have a go at that at some point, but not tonight.

Instead I decided to continue thinking about FWF type stuff. One item I’ve been putting off for a while is drilling the 3/4” hole down the right side of the aircraft for all the engine sensor wires and such to pass through. That seemed like a nice digestible project for tonight, so I got to it. I’d been thinking that laying the hole out properly would be a challenge, but once I got down to it it wasn’t tough at all. The only hiccup I had was that the unibit drifted a bit as I was opening the hole, and got into the edge of one of the firewall angles, so I had to then go in with the dremel and sanding drum to smooth things out.

Once that was done, I installed the snap bushing and had the fun of feeding the wire bundle through from inside, and now I’ve reached the milestone of having random wires sticking out through the firewall:

Assuming I don’t get that replacement canopy block in sometime soon, I think I might start marking up the firewall for component locations, just to sort of spitball ideas. The FWF plans include some suggested layouts that I’ll likely start with, but I’ll have to consider some other items not shown there that I’m adding – like the battery-bus fuse block and E-bus relay. Those are pretty small but they still need homes, and routing of wiring is also a concern.

The other item I could work on now would be feeding the CPI2 FWF harnesses back through the firewall and finishing up the lacing of the relevant harnesses in the cabin. Those had to wait until now, as they’re already terminated no the engine side and so can’t be fed through in the other direction. It’d be kinda nice to finish up those harnesses inside, I suppose. We’ll see.

Posted in Electrical, Firewall Forward | Hours Logged: 2

Firewall planning

So not a ton to talk about tonight really. Initially I’d figured on threading those CPI2 harnesses back through the firewall and getting the pertinent harness bundles laced for hopefully the final time…but then I got to thinking about whether that was a good idea. The whole reason I had to wait until I pulled the rest of the harness through the firewall is that the engine side of the CPI2 harnesses are already terminated, meaning they have to be threaded through bulkheads from the engine compartment. Thing is, that firewall passthrough may not be the only place I need to thread them. For example, one of the ignition coils will be mounted on top of the engine case, which means that harness will presumably have to pass through the baffles.

Now, that might not be a huge deal down the line – the coil connector plugs can probably be depinned if necessary, I’d just have to identify the connectors and get the right tool. But the crank sensor is a different matter – the wire connections aren’t detachable there. I’m not 100% sure whether or not those wires will need to pass through baffles, but in the end it seemed that the better choice here was to wait on these bundles. I might well end up with a chicken/egg type setup here, though…if I wait until I’m doing the engine baffles, that’ll mean I’ve fitted the cowl, which almost surely would require that the forward upper skin be riveted in…and once that’s done, finishing up the harness bundles will be a lot less fun. But still, I have little to lose by waiting; there’s nothing at stake right now other than me wanting this task done.

So instead I turned to the firewall layout. Some low-hanging fruit here was to go ahead and mount the brake fluid reservoir and cabin heat control box, both of which already have prepunched holes in the firewall. Getting the brake reservoir in place also required riveting a couple nutplates, which I guess were skipped way back when I first did the firewall. The heater box I just clecoed in place for now; it’ll need to be sealed when I final-mount it, and even though that’s still just using a couple bolts, I figure I’ll wait on that.

From that point forward, I was kind of on my own. The one thing that I figured I’d definitely lay out was the manifold block that’ll be used for the fuel and oil pressure sensors. The FWF drawings provided specify a location for that block, and while I don’t necessarily have to abide by that, I see no reason not to. Rather than actually mount it – I’m definitely not ready to commit to anything like that – I just drew an outline of the block and marked the two hose attach locations.

It’s not much, but it’s a start:

The next thing I tried to tinker with was the location of the battery box; since this is a relatively large item and accessibility is a concern, it seems like something to work out early. The FWF plans call for putting it on the right side of the firewall, about halfway up; I’m sure I’ll end up on that side of the firewall, but I’m less enthusiastic about the vertical location. The big question is how to tie the box into the firewall angles; they’re not exactly conveniently located for this. I suspect I’ll probably end up needing to add another angle on the back of the firewall to accommodate this, but the main takeaway is that this requires some thought. Something else to mull over a bit, I suppose.

Of course, somewhere near the end of the night I remember that I could also have been working on stretching the engine mount to better fit the firewall mount holes. Maybe I’ll work on that next; I’m sure I’ll want to install and remove it a few times while working out some of this firewall layout stuff.

Posted in Firewall Forward | Hours Logged: 1.5

Motor mount massaging

So here I am, back after another little break. I have yet to figure out my headset noise issue from last time, but fro some asking around I did dine one other person who’d had a similar problem with a Lightspeed headset. I’ve been meaning to shoot them an email asking about potential issues, but things have been kind of bananas with work and other stuff.

Continuing on the electrical front, I looked a bit at handling my control stick disconnects a few days ago, and was pleasantly surprised to find that I already have all the connector hardware I need on hand. Still need to actually do those disconnects, though…and even better, my engine has been assembled at Titan and should be shipping pretty soon…well, once I send them a check for the remaining balance.

The engine news has me thinking about FWF stuff again, which got me to revisit the engine mount fit. I’d been wanting to see about stretching the mount vertically a bit so that inserting the bolts was less of an ordeal, so I decided to look into that. The good news here is that I only need to stretch things by about 1/8”, but the bad news is that this structure is far beefier than the canopy frame I bent before.

To make a long story short, I tried a couple different setups before settling on the one that finally worked, as seen in the following photo:

Here I have the bottom portion of the mount secured to my work table with a 2×4 and a few clamps. This gives me a good angle to attach a ratchet strap from the mount ring to a large eye bolt under the table. Once again considering the forces at play here, instead of a small ratchet strap I grabbed one of the big ones I have for securing a car on a trailer. I’ve also placed some hard plastic tubing, split down the middle, on the table corner to avoid a potential stress concentration.

I’ll just say up front that exerting this kind of force was more than a little scary, especially since with me standing by the table cranking on the strap, I’d be directly in the line of fire if my clamping setup were to fail. With that in mind, I added a backup safety strap between the mount and the clamp side of the table, hoping that if a clamp did fail, that’d keep the mount from becoming a deadly projectile.

In the end it took about three iterations – each one just going one tooth further on the ratchet – to get the stretch I wanted. The end result still isn’t perfect, but the force needed to align the mount while inserting the bolts is easy to exert with one hand, a huge improvement. Overall I’m very pleased; going into this I figured there was at least a 50/50 chance that I’d chicken out on cranking the ratchet strap before anything moved at all.

So at this point I’m working on a punch list of inside work I want to get done before the gear legs go on. I kind of want to go ahead and build the cover plate for the rear stick base, but I can’t be sure the full range of motion of that stick until the wings are installed and rigged, so I may end up waiting on that…or maybe I’ll fab up the plate but skip cutting the actual hole for the stick, I dunno.

Other things on the punch list are rigging most of the brake lines (but probably not leaving the pedals in place afterwards) and securing a few more electrical components under the seat floors, but…I think that’s about it.

Posted in Firewall Forward | Hours Logged: 1.5

Engine is hung!

So technically, the most reasonable next thing for me to work on after adding the gear legs would have been the brake lines, but…well, I couldn’t resist the allure of getting the engine off its pallet and attached to the engine mount. This was never intended to be a permanent arrangement, but with the engine and mount married, I can install/remove the assembly with relative ease.

Yesterday, while out, I picked up some lumber and other supplies and built out an engine stand. This stand has four bolts that match with the firewall side of the engine mount, and I’ll be able to store the engine on that while I work on mounting accessories to it as well as building out the firewall. Once that was done, I got to work on actually mounting the engine.

I first attempted to put the engine on the mount with the mount on the firewall, but it was clear that wouldn’t work without removing several parts. There was no way to slide the engine straight into the mount ring without the oil filter, fuel pump, and prop governor line interfering. Some more trial showed that with the engine hanging on the hoist, I could maneuver the mount over it if I detached the output line from the fuel pump.

I was able to get the two upper mounts installed with the engine on the hoist, and at that point I remounted the assembly to the fuselage. The construction manual suggests pulling upwards on the engine to help align the lower mounts, and after a good bit of tinkering, I was able to get one of the lower mounts installed, but I called it a night on Saturday after being unable to get the fourth one installed.

This afternoon, with some help from a neighbor and my father, who was visiting, we were able to maneuver things such that that fourth mount got installed, which was a real moment of victory. In barely over a week this project has gone from a canoe on sawhorses to really starting to look like an airplane.

That was the end of useful work for the day, but I was unable to resist the opportunity to temporarily mount the prop as well, just to make for an even shiner picture:

Unfortunately, that will probably be the end of productivity for a bit. We’re heading out on vacation this Friday, so I think this week will be taken by preparation, and once we get back I’ll only be home for about a week and a half before I head up to Oshkosh. I have a few odds and ends I’d like to get done in that time – most notably, some more testing of my intercom setup. A friend lent me his Lightspeed Zulu headset to test with, in order to see if the feedback problem happens with two different Lightspeed sets. If that band out, then I’ll feel pretty confident going to Lightspeed with my concerns.

Posted in Firewall Forward | Hours Logged: 4.5

Shop wheels, engine accessories

So, here we are, back at it. Vacation is over (well, vacation #1, at least), plus some other personal stuff, and I’m also having to deal with this super-hot Houston summer. This is actually work I did yesterday, too, I just forgot to write it up before going to bed.

Item #1 was to replace the actual main wheels with some smaller (and disposable) wheels to use for moving around the shop. This lets the fuselage sit a little lower, while still retaining the ability to go over the sliding hangar door tracks if I want to roll the fuselage outside. The wheels were removed from some heavy-duty casters I got at Home Depot, and the lumber is just scrap I had lying around.  Pretty straightforward setup, just took a bit of time to drill the mount holes and get everything assembled:

Next up was removing the engine and mount from the fuselage to give me some room to start working on accessories, as well as getting into firewall planning. Sliding this whole assembly off the fuselage and onto the fixture I made is really easy; all told I think it took maybe 20 minutes. The fixture is super stable, though a bit cumbersome to move around with all the weight on the casters. Gets the job done, though:

I decided from there to try the easy accessory first, namely the main alternator. The boss mount went on easily, as did the alternator itself and the belt tension adjustment bracket. Then I tried adding the V-belt I’d bought with it, and…it’s too short. B&S specifically mentioned using the shortest belt possible to pull the alternator tight against the engine, since RV cowls tend to be tight. I intentionally bought the shortest one they recommended, knowing this might happen, so it wasn’t a huge surprise. I’ve already ordered the next-longest one from Amazon, and it should be here tomorrow.

I also did a bit of working on where I wanted to mount the battery box. I already know I want to mounted low on the right side of the firewall, but I hadn’t really got into the exact location and orientation. I’ve seen several folks suggest mounting the box sideways, so the battery is removed by sliding out the side, as opposed to from the top. I’m not really sure I can make this work, though – if I orient the top of the box outboard, the the firewall flange interferes with sliding the battery out. This will only get worse later on when I add the hinge for cowl attachment. So maybe upright is the right way to go; I’ll just have to think through where to put the contactors and battery bus so they don’t block battery removal. I didn’t get very far with this before the midday heat drove me inside, though.

One interesting thing I found from some battery-box research was someone with the box sideways, but the top facing inboard – an interesting idea. I’m not sure this is great for me, though, as I suspect the prop governor on the back of the engine will interfere with removal. I might just have to rehang the engine once I get the governor installed to see how that works in practice, though. I’m a little intrigued by the idea, but also skeptical…

Posted in Firewall Forward, Fuselage | Hours Logged: 3

Prop governor install

Nothing too exciting tonight. I wanted to start adding more accessories to the back of the engine, and the prop governor seemed like a reasonable place to start. I just had to remove the blanking plate left by the folk at Titan, and get the mounting pad nice and clean:

Then paint up the new gasket with sealant and get the governor in place. It only mounts one way so there’s no concern of whether I should clock it a certain way or anything. Sorry for the dark photo; the high bay lights in the hangar are out of commission, so this was taken as we crept towards dusk:

I also attempted to install the standby alternator on the vacuum pump pad, only to find that it interferes with the oil filter adapter. Unlike the governor, the alternator can be clocked one of four ways, but all four had interference issues. I guess I’ll be needing some other kind of oil filter mount; this will require some research on my part.

One final point – I got in the longer belt I ordered for the primary alternator. When I installed it, I was a little surprised that the alternator ended up at about the middle of the adjustment rang provided by the bracket; I’d figured it’d be much tighter against the engine. It got me wondering whether I’d been careless with the shorter belt, so I tried using the original one and…yup, it fits after all. I’m guessing when I tried before I didn’t have it fully seated in the flywheel groove. Long story short, the second belt I ordered wasn’t necessary at all.

Now I guess I need to start figuring out the oil filter issue.

Posted in Firewall Forward | Hours Logged: .5

Assorted FWF research

OK, so this is mostly an I’m-still-here type of post. I spent a week at Oshkosh, plus all the pre- and post-vacation stuff that tends to happen, and while I don’t have a lot to physically show on the build, I have been making small progress. The thing is, there are lots of knowledge cliffs I have to climb for the FWF stuff.

First, let’s revisit the topic of my last post – the oil filter adapter conundrum. After some research, I decided that my best bet was to get some parts from B&C, the same folks who made my alternators. They specify a particular oil filter adapter, as well as a drive extension for the alternator, that will work together. The combination wasn’t cheap, but knowing that they’d work is worth some money to me. Unfortunately, the drive extension is backordered for some indeterminate period of time. I’ve got the new filter adapter, so I guess I can at least install that, but I should probably just move past the standby alternator installation for now. Maybe I can figure a way to mock up the alternator just to make sure I don’t cause problems while working on other stuff.

Outside of that, I’ve been thinking through some of the other concerns I have. A big one is the routing of the fuel line from the mechanical pump to the throttle body. As provided from Titan, this line just passes down under the sump, which puts its uncomfortably close to the exhaust. I got a look inside the cowl of a couple planes at Oshkosh, and saw where some folks had routed this line above the intake runners. I think this is a reasonable course, but I’ll probably need a new fuel line. And before I could even think about that, I wanted to verify that the orientation of the throttle body was correct for my expected mixture/throttle cable routing. Cue some more digging into plans drawings…but hey, good news, the current orientation is correct.

Then there were other menial tasks. For example, the CHT thermocouples – I know they get installed into the cylinders, but where? More documentation diving. Oh, it’s that little hole by the lower spark plug. Also, where do I tap to get manifold pressure? Oh, apparently these little primer ports. Also I need to think about getting MAP to both the EMS sensor as well as the SDS CPI ignition unit. I spent some time mocking up where the vacuum block and sensor might get mounted.

So that’s where I’m at. Not a lot of “shop hours” logged, but plenty of time diving into documentation and doing research. It doesn’t feel especially productive, but it’s stuff that has to get done.

Posted in Firewall Forward | Hours Logged: 1

New oil filter adapter

As the title indicates, tonight I worked on swapping in the new shorter oil filter adapter from B&C. This is half of the work needed to allow the standby alternator to be mounted, but it’s all I can do for now. The drive adapter is backordered with no estimated ship date, so I have no idea when I can expect it. I guess maybe I’ll see about mocking up the alternator for the purposes of firewall planning…

Anyway, not a lot to be said about the adapter swap – the hardest part was breaking the oil filter loose. I’m not sure who installed that thing but I’m pretty sure they exceeded the torque spec by quite a bit. I also had to move over the vernatherm (which regulates flow to the oil cooler) from the old unit, and I went ahead and installed the oil temperature sensor as well. These can be seen in this photo; the vernatherm is the large piece below the smaller sensor:

The one thing left to do here is to get this stuff safety wired. That might be interesting, as the temp sensor isn’t drilled for safety wire. I’ll either need to drill it myself, or take the common alternate approach of adding a stainless clamp around the hex portion to wire to. I’m not too sure how I feel about the clamp approach, but I also don’t have a jig for the drilling, so…still gotta think about that one.

Posted in Firewall Forward | Hours Logged: 1.5

Ignition stuff

Today was mostly one of those sort of head-scratching days. I did some research last night about mounting the SDS coil packs, mainly wondering if there was a way around using the case top mount even with the fuel injection lines. Oddly enough, I never had the obvious thought of just fabricating my own mount, but I ran across someone who’d done just that. Pretty simple too, just need some angle of the right size to make the mounts and raise the coil pack a bit for the lines to pass underneath. I just don’t have the right size angle on hand, so that’s something I’ll need to order.

Having decided to stick with the case top mount simplifies some stuff for me, though. I never got around to ordering another mag mount from SDS, and now I don’t need it. It does add a new decision, though – which mag mount should I use for the one coil pack I am using? I did some test fitting of the coil and eventually decided that the left side of the engine was better – the right offers lots more obstacles thanks to the prop governor below and the standby alternator above the mag mount.

It would have been nice to go ahead and mount that coil pack, as well as the blanking plate on the other side, but…I don’t have the right nuts on hand. More stuff for the to-order list. I ended up just pausing and focusing on fleshing out a Spruce order. I know I’ll want some more adel clamps to use for FWF routing of stuff, plus I’ll just want a general stock of the metal lock nuts for FWF mounting. I suppose I’ll wait and see if I come up with anything else tomorrow before maybe placing the order on Monday.

So finally I moved to something I could actually do and not just plan – mounting the Hall sensor up on the nose of the engine. This requires loosening the two front case bolts and replacing the nuts with standoff nuts that the sensor can then bolt to. The sensor mount itself requires a bit of trial and error to get the proper air gap between the sensor and the inside of the flywheel – there are a few washers to move around to tune the spacing. Once I’d worked that out I torqued the bolts and…it was time for some safety wiring.

To make a long story short, it took me about four tries before I was satisfied with my work here. I haven’t done a ton of this, so I’m still kind of learning the ropes. And probably the second and third tries would have been serviceable, but…I guess I get a little perfectionist with this stuff. Here’s the final product on the sensor mount:

At this point, since I already had the wire stuff out and was in the mood, I went ahead and final torqued the alternator mount boss bolts and safety wired those as well:

I’ve still got a little work to do with the hall sensor mount – most folks fabricate a cable guard out of small angle to protect the sensor cable in case the alternator belt breaks. Seems like a good, cheap insurance idea, so I’ll be doing that tomorrow. Once that’s done I should be able to mount the sensor, and then I get the fun of drilling the flywheel for the trigger magnets.

Posted in Firewall Forward | Hours Logged: 3