Started on the making of the mold for the throttle console. I’ll do the gel coat and fiber glass backing tomorrow. Hopefully all goes well and I can get the mold down to the carbon fiber guy next week and have the parts by the end of the year.
Plug ready to go, just need some waxing and mold release.
Let me start with this. I’m not an electrical engineer so if anyone can bring some clarity to this I’m glad to hear it. As I get closer to actually having to wiring the charge system using both the external and internal alternators I’m trying to pin down exactly what I need to implement as far as the charge circuit and interconnection of the internal and external alternators. As I look around for ideas and wiring examples I’m facing some conflicting information. My original drawings (available in the Resources menu) were based on what TAF provided in their electrical system manual and what Rotax shows in their 914 installation manual. I’ve found conflicting (well different) wiring diagrams from Rotax regarding the wiring of the internal alternator. I also was thinking that passing the field trigger through the VPX for the internal alternator might be a bad idea. If the VPX dies then the engine should keep running, but restarts would not be possible since the VPX would be controlling the relay that ties the Engine Circuit to the battery. I’m also unclear why some Rotax manuals and TAF manual show a relay being used to connect the “B” terminal of the integrated alternator to the battery and also a relay to control the field terminal of the external alternator to the battery (to active the alternator). I believe the field connect of the external alternator can just be done with a normal switch between the IG (field terminal) and aircraft power since it’s fairly low current. The “B” terminal of the integrated alternator could just be connected directly to the battery (or via a diode) and then the “C” (field terminal) could be switched to enable or disable the alternator/generator. So why use a relay? If I don’t need to install a relay then I’d rather not since that’s one less part to break.
Also all the diagrams I’ve seen show no concern that the external and internal alternators all tie to the main aircraft power bus. From some research I found this is a big No No. You want to keep the alternators completely independent if both are on at the same time. This is different then a primary and backup alternator situation. The internal alternator should only be used to drive the main fuel pump, the turbo servo and other engine components. While the external alternator is used to drive all the avionics and the aux fuel pump. Of course the catch is that the battery needs to connect to both the Aircraft Power Bus and the Engine Bus so I would think you’d need to use a diode to connect the battery and internal alternator so the alternator doesn’t feed into the main aircraft power bus, but no diagrams show this.
NOTE (12/10/2017): Found this little nugget in the Rotax 914 Installation Manual which explains a bit about the reason to use a relay to switch the connection between the internal alternator and the battery. From the Rotax 914 Installation Manual:
“Never sever connection between terminal C and +B of regulator (e.g. by removal of a fuse) while the engine is running. Overvoltage and regulator damage can occur. During engine stop break circuit between battery and terminal C to avoid discharge of battery!”
This diagram (from Rotax) makes sense to me. When the master solenoid (19) is closed then the internal alternator (5,6) is enabled via terminal “C” connecting to the battery. Plus the engine components have battery power for starting. The external alternator (10,11,12) is enabled by the double pole master switch (16) which directly connects the battery to the IG (field) terminal. The only thing missing is isolation of the integrated alternator form the main aircraft power bus.
And here’s a similar digram from Rotax. The difference is the use of a relay (58) that is closed when the master solenoid (38,39) is closed and connects the B and Field terminals of the internal alternator to the battery. I also just notice that the main fuel pump was added to that part of the circuit as well. But still that doesn’t explain why you use a relay instead of just allowing the master solenoid to supply battery power to these devices directly. I always thought that the reason to use a relay is to switch a high current load with a load current load. In this case you’re not really doing that and it’s not adding any isolation between the integrated alternator and the rest of the aircraft power.
Time: 0.5 hr
It’s not what was accomplished today it’s the tool that helped get it done that counted. Today I only installed 2 M3 rivnuts for the cabin heater box in the firewall. There are a total of 6 rivnuts 4 or which were straight forward to install. There were 2 that were close enough to the nose wheel bracket that my rivnut puller couldn’t fit to install them. The thought of removing the whole engine mount wasn’t something I really wanted to consider, but it seemed like the only solution until I found this simple compact rivnut installer. For a grand total of $7.58 plus shipping the problem was solved without having to tear apart the front of the airplane. The tool is considerable harder to use then the puller. You need to keep pressure against the rivnut as you use the allen wrench to compress the rivnut. Also it’s a bit difficult to sense if you’ve tightened it enough. I suppose you probably would get to a point where you couldn’t tighten it anymore and at that point the rivnut would be fully compressed, though I guess you could over tighten it. Fortunately I was able to see the back of the rivet enough to see if it had compressed enough. But for these few times where space is an issue I think it was well worth the money spent 🙂
With this done I’m hoping the the correct EarthX battery box will get here by tomorrow so I can get that installed along with the 2 mounts for the GPS antennas. I’m also checking with Torrance TAF if I can get the brackets needed for the coolant overflow bottle and oil tank so I can get those riveted on. The only remaining parts will be the fuel pumps which I’m told come with the engine and Vertical Power PPS which isn’t available yet. The PPS is nice because I was looking at trying to use a solid state master solenoid and their solution is just that. It also takes the place of the starter solenoid and main fuses. It supposedly will be shipping this January for around $1500.
The simple tool that saved the day. I probably could have made one from an M3 screw and a drilled out nut. The operation of it is simple: hold the body with a crescent wrench while turning the allen wrench which compresses the rivnut.
Here’s the problem. Now why didn’t the manual say to install these before installing the engine mount 🙂
Here goes nothing.
Easy Peasy. They’re installed. Happy Me.
Did a few things on the firewall today:
- Installed M3 rivnuts for the heater box
- Installed M6 rivnuts and rubber mounts for the generator regulator
- Looked at how to install the EarthX battery box
So it turns out there are two types of EarthX battery boxes. One is called custom fit and the other is multi-use. I ordered the custom fit box from Aircraft Spruce and it was back ordered. It eventually showed up a few days ago and it looked a bit different then I remembered, but I thought maybe they just changed the design. After looking at the EarthX site for battery dimensions I notice din fact that there were two different boxes and Aircraft Spruce sent me the wrong one. I ended up getting the other box directly from EarthX since it was a bit cheaper. The custom fit box is a little smaller and mounts with two M6 screws rather then 3 so it will make the mount a bit easier and the large holes for the M6 rivnuts don’t need to be drilled in the channel brace that runs cross the firewall.
I also installed some M3 for the heater box. Most went fine, but the last two in the center by the nose wheel can’t be installed with the rivnut puller I have unless I take the hole engine mount and hose wheel off so I can get to them with the tool. I found an M3 puller that looks to be very low profile so hopefully that will fit in there so that the rivnut can be installed otherwise I’ll have to remove the engine mount to install the two rivnuts…ahhhhh!
Installed 2 M6 rivnuts and rubber mounts for the generator regulator.
The mount screws stick through a bit on the front of the firewall. I can cut them back later.
Here’s the M6 rubber mount I found on Amazon. The screws are M6 x1mm so they screw into the M6 rivnuts fine.
Installed the 45º fittings on the parking brake and -4AN fittings on the lines. I wanted to finish this up because I will be making a mold of the throttle console piece for the carbon fiber part. BTW I have toe brakes so my parking brake is a little more involved then the simpler leveler brake type.
Left side of the center console. I have 90º fittings in the back and 45º fitting in the front. The lines are run kind of weird so that the bends in the lines aren’t too tight. The left and right lines run from the pedals and attach to the parking break with left on the left and right on the right, but then they leave switched. This is because it was just cleaner to leave the caliber lines on the sides on the channel that they came up on. The bend into the channel is pretty tight so from say the left brake caliper the line runs into the center channel and stays on the right side of the channel up to the parking brake rather then cross them back over.
Here’s the right side of the center console.
The 90º fitting will hit each other so I had to angle them a little oddly. I was thinking of putting an extension on the top one, but I think this angle works fine.
Here’s a side view of the parking brake. This is a little older photo when I had the straight fittings on the front. Those were changed out with 45º fittings to make the angle better on the brake lines.
Time: 0.5 hrs
Trying to just keep doing some things on the plane while I wait for parts. I installed a few rivnuts in the firewall. Now that I know I’m going to use the 914 I think these ones are safe to install. They’re for the TCU mount (M4), static pressure sensor (M4) and the starter solenoid (M5). The manual calls for M3 for the heater box, but then it says something about riveting it on the heater box construction page. I’m thinking I can drill out the 6 holes and put in rivnuts so the heater box is removal. The only odd thing is that the rivnut will also hold in the channel piece on the cockpit side so not sure how that will work out. I would imagine the end of the rivnut will fold over and hold it ok… just kind of weird maybe. I guess I’ll wait until I get the heat box just in case.
Since I’ll be using the LifoPo EarthX battery I bought a battery box for that from Aircraft Spruce. It should be here soon. Hopefully the install will go easy and I can reuse some of the existing holes. I just need a few more mounts from TAF and I should be able to wrap up most of the firewall stuff.
Put some screws in the rivnuts… boy that was hard 😁
Just finished up the work from yesterday on the channel cut into the main gear for the brake lines. I filled a few spots where the router bit hit the edge of the channel with some fiberglass epoxy and primed it. Not perfect but looks good. When the brake line goes in it will look even better. I also found these polyester UV resistant clamps that would be good to use on the top and bottom of the gear to hold the brake line. The RTV will hold the line in fine along the back of the gear, but it may not be enough to hold it where it makes the bend into the brake caliber and at the top where it bends into the fuselage. I guess I’ll have to see when the time comes for that.
Now to cook some turkey.