Doing some catch up documentation from the last few days of 10 minute here and there build sessions.
I can't remember if I mentioned before, but my 3D printed fan guards turned out very nice, but when I screwed them down onto the glare shield, they curled up around the screws because I had made them so thin. 3D printed guards are probably not a great solution since I want them to be low profile. I think I'll probably end up getting them cut out of aluminum instead. I'm just waiting to see if I have anything else I need cut before sending the design to sendcutsend.com. I went ahead and spliced the fan wiring together so I could just run one pair of wires to the panel. Once the panel is in place and the canopy back on, I'll figure out how to deal with the slack needed in the wires for the canopy opening/closing arc.
I hooked the fans up to my bench power to ensure they worked. I'm glad I got the thicker fans. They actually move a lot of air!
I had already finished up most of the switches in the panel, but there were still a couple of oddballs left to do - the Pmag and Master switches. Neither of those go through the ACM. The Pmag setup took a bit of head scratching. The use of a three way switch for their OFF-ON-TEST functions is a little confusing to wire (mostly because unlike standard mags, the Pmags have a self powering function, which means they have to be able to be grounded in different ways to allow testing of both internal power and ship power scenarios). One of the requirements of the Pmag is having either a 3A circuit breaker or fuse in the mix. Usually a circuit breaker is used when a key switch is used for all of the runup testing, because then the interrupted power test can be done by pulling the breaker for each Pmag. Since I'm using toggle switches, the circuit breakers ($$$) are not really all that necessary. Pmag specifies that fuses can be used as long as they are the slow blow type, which allows for the potential initial startup surge. I don't need access to the fuses in normal operations, so I put them on the subpanel above the ACM.
For my future self - these are the fuses I'm using:
I believe all of my panel wiring is in place at this point (but not routed nicely - that's for after I finally install the panel). That means I can start creating a new rat's nest of wiring for all of the firewall forward connections. I started pulling wires to/from the EMS module, as well as continuing with the main wiring of the alternator, starter, etc. Still more to do there because part of cutting those big wires means figuring out their routing around the engine. I'm getting there, just mulling it over before committing.
One thing I've procrastinated on is installing the tailpipes on the exhaust. I was waiting on that because I needed to have an idea of where the lower cowl exhaust exit opening would set to ensure I had good clearance around the pipes. The pipes have an angle in them, so spinning them in place means there's a huge range of where the ends can exit the engine compartment and what the clearance to the fuselage and cowl is.
After a lot of iterations, I got both tail pipes exiting in a fairly symmetrical way. Perfect symmetry isn't possible because they both have a slightly different angle where they mate up to the rest of the exhaust. The tail pipes get connected to their feeder exhaust pipes using a clamp that has a 1/4" pin welded on the inside of it that keeps the pipes from moving out of position. I drilled a 1/4" hole through the pipes to accept that pin and clamped the pipes down.
The right tail pipe will be where the cabin heat muff is. I need to get this in place next because the bulky scat tubing to and from it will dictate where I can route some of my wires. The heat muff is just a thin cylinder that goes around the tail pipe, with fresh air feeding in one side and then going out the other end to the firewall cabin heat box.
One of the complaints about this design is that in cold regions it doesn't provide quite enough cabin heat. Some people put a second muff on the other tail pipe, but I've seen those installs and it adds a ton of scat tubing to an already cramped area. Instead I'm going with the increased surface area approach. A common solution to increasing surface area is to stuff steel wool into the muff around the the pipe, but the complaint with that is that it decreases the volume of air that can get through to begin with. I saw a builder who instead added stainless rings with fingers to the pipe. He said it has worked really well, once he found the right number of rings to add on (he had too many at first and was cooked out of the cockpit).
The right tail pipe will be where the cabin heat muff is. I need to get this in place next because the bulky scat tubing to and from it will dictate where I can route some of my wires. The heat muff is just a thin cylinder that goes around the tail pipe, with fresh air feeding in one side and then going out the other end to the firewall cabin heat box.
One of the complaints about this design is that in cold regions it doesn't provide quite enough cabin heat. Some people put a second muff on the other tail pipe, but I've seen those installs and it adds a ton of scat tubing to an already cramped area. Instead I'm going with the increased surface area approach. A common solution to increasing surface area is to stuff steel wool into the muff around the the pipe, but the complaint with that is that it decreases the volume of air that can get through to begin with. I saw a builder who instead added stainless rings with fingers to the pipe. He said it has worked really well, once he found the right number of rings to add on (he had too many at first and was cooked out of the cockpit).
A while back I drew up a design and sent them to sendcutsend to cut out. The muff sets off center around the pipe, so my rings have to account for that. One thing I didn't account for is a change in design of the muff from when I first saw it - it now connects the two end caps using steel rods that go inside the muff. Those would get in the way of my rings, so I'll have to chop of some of the fingers to allow the rods to pass through.
My next step is to do some tweaking of my ring material (I didn't get my measurements perfect when designing them), bend them around the exhaust and bend the fingers up. I think I'll start with 6 of the rings. Those fingers should pull a lot of heat off of the tail pipe and still let the air pass through pretty easily...I think.
