Misc Firewall Work

Time: 1.5 hrs

Did some miscellaneous stuff on the firewall today. I finished installing the TCU, Redid the install of the gascolator with the new bracket that finally showed up, and finally installed the Rotax fuel pump cover.

Jean from Torrance TAF and Jim G (a pilot friend who has built a Sling 2 and a Lancair) came by a few days ago to check out the progress. Jean and I spoke a lot abut the engine and various stuff I needed to do. They both were very happy with the work that I’ve been doing and were extremely encouraging. At times it’s been a struggle to keep the project moving forward from both a time standpoint and financially. So it was nice to be able to talk to seasoned builders to gain some prospective. Thanks for coming out and the spending time.

I had ordered an aluminum fuel pump bracket off Amazon a while ago and it finally showed up. I liked it better then the other bracket I had, so I decided to use it. The bracket was for a 2″ fuel pump, but with the rubber I added (from an Adel clamp) it fits very well. I like that it mounts to the end mount in 2 places so the gascolator doesn’t want to spin.

It was pretty quick mounting the TCU. I was going to use nylon type locking nuts to secure it to the mount brackets, but because of the rubber stand offs on the TCU being somewhat fragile, I ended up using standard nuts and washers and used Loctite (blue) on them.

Cut out done and M6 rivnuts installed for the Rotax fuel pump box. I’m going to use the case from the 912, Jean was able to find an extra one at the office. I was hoping that I could have just used the holes that were there for the original TAF fuel pump mounting bracket, but the holes were just a little off from lining up and I didn’t want to mess around with trying to elongate the holes and them enlarging them. I put the new holes in line with the original ones, just up about an inch. I also found that Goo Gone works well on removing the glue after the insulation material is cut away.

Now just waiting on the Master Relay from Aircraft Spruce which shipped out on Friday… Oh and the engine mounting hardware from TAF which should be here this coming week as well.

I still need to work on the mounting of the fuel pumps and the plumbing. I’m thinking maybe I can use the TAF plumbing and just add on an AN fitting to the in and out. I think that all the various tees and elbows that I’d need will be both expensive and too large to all fit in the pump box. For mounting I’m going to make a small stainless steel plate that fits in the pump box and use maybe 1/4 bushings to stand it off from the back of the case. I can then use Adel clamps to mount the pumps to the plate and the plate will get mounted using the same screws as the pump cover.

 

TCU Mounting

Time: 2.5 hrs

The aluminum I ordered for the TCU bracket and to build the shelf for the avionics came a few days ago so I decided to make the mount for the TCU. This was pretty straight forward, just had to cut the channel to size and drill a few holes for some screws. I’ll be mounting the TCU on the cabin side of the firewall so I needed to find a suitable place close to where the cabling passes through the firewall. I wanted to keep the ambient pressure sensor mounted on the engine side since in my opinion that would be the best place to read the pressure that the engine is experiencing, not in the cabin. However the Rotax provided cabling between the TCU and ambient pressure sensor is very short, maybe a foot long and the Rotax manual says to mount it in the cabin so I guess I’ll mount it in the cabin near the TCU.

I’ve also been thinking a bit about how to connect the two alternators (well one alternator and one generator) into the system. TAF seems to connect them both to the main bus, but from all that I’ve seen this isn’t a good idea. You’re not really going to get increased capacity from the second alternator like you think. One alternator, the one with the higher voltage output will be the one that gets taxed the most. The second one won’t really kick in until the first one has pretty much maxed out. Typically you want to run them at 80% capacity so that you don’t damage them. So to see any real added capacity you’re having to run one of the alternators very hard. My idea was to maybe split the main bus into two buses. One with most of the equipment and the other with the main fuel pump and a few other high load items, like the pitot heat. The tricky part is how to keep them isolated, but also allow some fail over should one of the alternators fail. I did end up working out a pretty nice arrangement using 2 SPDT relays which I may end up implementing. But I’m wondering if all the equipment is really going to draw more then 40A. Once I get the panel built and the other avionics installed I can do a test using an ammeter to see what the current draw will be, then add maybe 10A for comm transmits. If it’s pushing 50A then I move some things around and implement the dual relays arrangement.

I was going to mount it a bit lower on the left side, but it looks like the rivets would hit the reinforcing channel on the engine side of the firewall so I had to scout around for another place. Amazingly it fits really well on either side o the firewall support channel.

Looks like it will all fit nicely. Note the ambient pressure sensor mounted on the right. I’m glad I didn’t put the front top skin on yet… this would have been a pain to mount with the skin on. So now I’ll disassemble this and spray it with some etch primer and then some grey paint.

Engine Arrived

Today I picked up my Rotax 914UL2 from Torrance TAF. The engine only weighs around 100lbs. so it wasn’t too bad getting it on and off the truck. It was good to have some help though, so thank you to those that helped: (The loading crew) Vince L, Matt L, and the guy wanting to buy a Sling 2, (the unloading crew) David K, my wife, and my daughter.

After figuring out what came with the engine I have some things I need to figure out. I didn’t buy the full firewall forward kit from TAF so I now need to make or buy a few parts. I thought that maybe I would get a some plumbing and a nicer mount for the fuel pumps, also I’ll need an exhaust pipe and a few brackets for mounting the ambient pressure sensor and TCU (which I knew I would need). Also I need to get the oil and water coolers which I knew didn’t come with the engine.

So at this point I’m feeling a bit overwhelmed. There is now a ton of stuff that needs to get done and figured out. But its good to have some things to work on again.

Here’s a few photos of the unpacking.

Well at least they threw in some oil 🙂

Contents of the “loose parts box” (Losteilekarton): round-neck nut set M8, regulator for internal generator, 2 pin connector w/ pins, wire with connector attached, starter solenoid, and a banjo bolt for the oil canister overflow

I need to figure out what the connector and the wire with connector is for.

Fuel pumps box: 2 Pierburg fuel pumps, 2 Edel clamps, 4 small hose clamps and some mounting screws.

I was hoping that there would be some plumbing tubes, etc and a nicer mounting option, but I guess that’s why TAF supplies those in their kit. I found that the 912 has a nice mounting box and plumbing w/ check valves, etc but I can’t seem to find where to buy just those items. I can buy the box from California Power Systems, but it seems like you have to purchase the whole pump assembly to get the mount and plumbing parts and that’s around $1300. I can always get the TAF one, but I wanted to try to use -6AN connections through out so I can use stainless steel braided hoses and nit have to replace them every 5 years (as per Rotax). So I will try to cobble together some fittings and see what I can come up with.

The oil tank and most importantly Rotes stickers…. YAY!!!!!!!!

I also purchased the external alternator. This thing is pretty tiny. The alternator came with all the parts to mount and attach it to the engine so once the engine is mounted I’ll get this on the engine.

The TCU and servo come in a box with some wire and cabling attached to the engine. The  cable to the servo is surprisingly short. I wanted to mount it on the cabin side of the firewall, but that might be difficult. I have to wait to get the engine installed anyways because I don’t want to disconnect the cable now. The wire fro the TCU to ambient pressure sensor is also very short… only around 1 foot long so it really needs to be mounted close to the TCU.