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.

Gascolator and Starter Solenoid

Time: .75 hrs

Installed the gascolator and starter solenoid today. I used the newer version of the ACS gascolator (10585HP). It has a little different way the cup mounts onto it and also is a little lighter then the classic 10580. I also put I the 74 micron screen instead of the 120 micron screen that comes with it. Rotax calls for at least a 100 micron filter that can be part of a water removal device (gascolator) so this satisfies that requirement. I also have the 2 40 micron filters in the cabin from each tank. I ended up using a stainless steel bracket that is used to mount a sign to a pole. It seemed to be the perfect size. Its a tad on the heavy side, but not too bad. I also had to modify the bracket a little since the bolt hole was too large. I drilled it out and installed an M5 rivet which seems to be a good size to use with the adel clamps.

The starter solenoid was quite a bit easier. I was originally just going to bolt it directly to the firewall then I saw that the firewall forward manual calls for rubber mounts. That seemed like a reasonable idea and also raise the starter solenoid a little off the firewall so not so much of the heat shield needs to be removed.

Sign holder bracket modified with an M5 rivnut. It’s a little heavy but should do fine. I’ll see if I can find something better.

Gascolator ready to be installed. This is the newer ACS 10585HP with 1/4″ NPT to -6AN 90 degree fittings. There is also a center 1/8″ how that I just put a stainless steel plug into.

I’m using adel clamps with fluorosilicone inserts. The fluorosilicone is good for high temperature environments and also stands up to petroleum based liquids well. Plus it’s blue so that’s kind of cool. I just used the insert from a larger adel clamp on the hose clamp. I may need to turn the other adel clamp around because the gascolator may be mounted a little high, but eyeballing it looks like it’s OK.

And lastly the starter solenoid installed on 2 M5 rubber mounts with M5 locking nuts.

I really need to figure out what I’m going with the fuel pumps. It’s going to hold up the engine mounting if I don’t get that going. Also I need to install the master solenoid which should be here next week. After that I think I should be good to mount the engine.

Firewall Work

Time: 1.25 hours

Just did some tinkering on the firewall over the past few days. I mounted the oil canister and working on figuring out where the TCU and servo will get mounted. The cable for the servo is quite a bit shorter then I expected so I don’t know if it will reach through the existing hole in the firewall. Possibly if it’s mounted on the right side and a new hole is made for the cable then that could work, but trying to use the large hole where the wiring passes through the firewall may not be an option.

I need to figure out what I want to do with the fuel pumps. Right now I’m thinking maybe I get the mounting box for the 912 and figure out how to mount the 2 pump inside that and also a bunch of fittings to connect the pumps and check valves. TAF supplies all of this in their firewall forward kit, but I want to use -6AN fittings for all the fuel lies so that I can use stainless steel hoses. The TAF plumbing uses hose barbs, which are fine, but they don’t work well with stainless steel hoses. I’ll also have to swap out the banjo bolts on the engine itself in a few places.

I purchased a master relay that I’ll need to mount to the engine side of the firewall. The electrics manual doesn’t show a master relay, they seem to put the full load on the master switch. I guess that works, but I’d rather go with an actual master relay, especial because I’m using the external alternator.

A couple of more things added… still lots to do before the engine goes on.


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)┬áDavid 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 ­čÖé

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 ┬ácable 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.

Engine Ordered

Not much to report on the plane except I finally plunked down the cash and got the engine order. So I guess no new car for me, mine will just have to hold out for a few more years. I ended up ordering the 914UL2 from TAF and it should be here in a few weeks. Now of course Rotax will cut the prices… just my luck. Anyways it’s good to know I’ll be able to start making some progress on the plane soon.

Oh yeah. While I was there Jean and I tested out their new ordering system. I think it’s going to be pretty cool. Basically you just sign into the website and order whatever parts you want by part number. You can also choose whether it’s to replace a missing part or a new part, etc and then they ship it to you. It looks like shipments go out once a month towards the end of the month so it will still take some time to get them, but should be much easier to get the parts.