I put in a new set of desiccant plugs in the engine this weekend… after two years of service, the old ones were starting to lose their magic ability to dry out when I put them in the oven every few months.
Archive for the ‘Firewall Forward’ Category
Desiccant plugs
Saturday, May 9th, 2009Engine ground straps
Tuesday, September 16th, 2008I installed a braided ground strap between the back of the engine and the firewall ground block. This is the heavy-duty conductor that carries the hundreds of amps of starting current back to the negative terminal of the battery. It's fastened at both ends by adel clamps, so there's no strain on the actual terminal ends.
Closeup of the attachment to the engine… it's secured to one of the auxiliary alternator mounting studs with a nut and lockwasher, and is clamped to a neighboring stud.
Then, because I have equal love for both belt and suspenders, I installed a second one. If the first one were to somehow come off, the full current of the starter would flow back to the negative battery terminal through all the various sensor wires, control cables, etc… quickly turning them into smoke. Thus, a backup ground strap. This one goes between a sump bolt on the left side of the engine, over to a nutplate on the lower firewall. I couldn't find a way to provide strain relief for the ends, but it's only a backup.
There's so much stuff back there that it's hard to get a good picture, but you can sort of see where I put some heatshrink tubing over the second strap. There's no danger of a ground wire shorting to ground, obviously, but I wanted to guard against it accidentally rubbing against the engine mount. It doesn't touch it currently, but it's possible that it might flop around and tear up the powder coat.
Propeller arrived
Sunday, September 14th, 2008Eight and a half weeks after placing the order, the propeller arrived. It is a thing of beauty. Heavy, expensive beauty.
The box is like eight feet long and weighs ninety pounds. With it sitting like this, there's barely any room to walk. Or store empty beer bottles.
I dragged it over by the wings, and raised it up on some boards so the cardboard doesn't soak up moisture from the concrete garage floor.
For reference, here's the current status of the fuselage:
And the rest of the garage… what a mess.
Ordered propeller
Thursday, July 10th, 2008Last night I sent Van's a big chunk of change for a propeller – specifically, a Hartzell C2YR-1BFP/F7497-2. That's an aluminum constant-speed prop with a pair of 72" blended-airfoil blades specifically designed for the two-place RV's, and will look something like this.
I kind of wish I'd ordered the prop sooner, since it has a 12-16 week lead time and I find myself with the following chicken-and-egg scenario: In order to finish the FWF plumbing and wiring I kind of need to have the baffles in place, for which I need to have the cowl fitted first, which means I need the prop to fit the cowl. Actually I guess that's a whole series of chickens/eggs. Theoretically you can fit the cowl without the prop if you make some kind of spacer, but even Van's suggests you wait for the real thing to arrive if you have a constant-speed prop like I will. Apparently there's something different about how the spinner is mounted…? We'll see.
Meanwhile, I suppose I will continue to work on interior fuselage systems, when I have time.
Sniffle valve
Sunday, June 29th, 2008Fuel-injected Lycoming engines can sometimes experience a phenomenon wherein excess fuel drips down the induction tubes and pools in the intake manifold after shutdown. This can be a problem, since it could cause a troublesome fire during the next start. To alleviate this, you install a simple little one-way check valve in the bottom of the intake, which lets the fuel drip out of the engine onto the ground. For whatever reason, this item is colloquially referred to as a sniffle valve.
Here's a bad picture of the one I bought from Airflow Performance for a few bucks – it's basically just a normal AN fitting that's been drilled out and had a ball bearing and retainer clip inserted. Reduced pressure inside the manifold causes the ball to be sucked up to close the valve when the engine is running, but it drops down and lets the fuel drip out when the engine is shut down.
I knew from previous reading that the sniffle valve is too close to the exhaust pipes on an IO-360 with horizontal induction, so I installed it in a 45-degree brass street elbow to clear the pipes. The exact orientation of the valve is said not to matter much, as long as the ball is free to drop when the airplane is at rest. I also attached a 1/4" hose barb to 1/4" AN flare adapter, similar to the one I used for the fuel pump drain line.
I ran another 1/4" aluminum line from the firewall up to the sniffle valve, using a length of 1/4" rubber fuel hose as a flexible coupling. The forward (engine) end of the aluminum tube is ever so slightly flared to give the clamps something to work with – using a real beading tool would have been best, but I can't afford one and this is not a critical application. The aft end of the drain tube is attached to the firewall flange with an adel clamp, just like its twin the fuel drain line.
One more of the million firewall forward tasks is complete… and with that, I'm off to try and make a dent in the beer and ice cream still left over from Saturday's party.