Sunday, February 15, 2009

Sparking some interest

I managed four or five hours on the boat this weekend and managed to get something done in regards to the engine electrical system.

But first, over the past month, this beautiful creature has been growing right next to me at the boatyard. Today, I saw it turning for the first time. Silent and beautiful and clean. I love it.

I continued glueing up the engine instrument panel frame. Doing the frame one joint at a time is introducing some uneven-ness that will have to be rectified later. I should have bought four clamps and done it all at once so I could control the layup better. I can fix it but I could have done better.

I started making up the wiring harness for the engine. First, I had to clean up the old wires. I really wished I had something to clean the engine with. It is looking dirty with lots of fiberglass and primer dust on it but the water at the boatyard is turned off for the winter so a good scrubbing will have to wait.

I forgot to bring anything to clean up the connections so I just left them loose for now. I thought I had more electrical terminal strips but a couple of them looked old and dirty so I ordered a few more. I installed the two decent ones that I had over the engine to get me started. The upper one is connected to the battery. The lower one is downstream of the 'ignition' switch. I will add a third one soon that the nav lights will connect to. Nearby, I will install a fourth for the ground connections.

I thought I had ordered an externally shunted ammeter but I guess I didn't. I have an internally shunted ammeter*. That means I have to run the full charging load through the meter which will be located at the aft end of the cockpit. For a run that long I need some larger wire that I didn't have on hand so I had to skip that bit. The battery connects to the hot terminal on the starter. A second wire off the starter hot terminal will run to the ammeter and back to the 'battery' terminal strip. On the other end of the terminal strip is the alternator connection. That puts the ammeter between the battery and alternator and the rest of the load where it belongs. The ammeter doesn't really measure total system draw, it measures the charging / discharging current to the engine start battery. When the house system goes in it will have a separate ammeter for keeping track of total power consumption.

Not too exciting. I ran the wires from the 'ignition' terminal block to the oil pressure safety switch / electric fuel pump. Also, on the same terminal, the power to the coil and electronic distributor.

When I get the rest of the terminal blocks installed I can run the rest of the wires and bundle them up in a nice neat harness. Pictures now would look boring and slightly hideous. After I finish writing this blog I am going to spend a bit more time with the electrical panel and get that ready to wire into the terminal blocks. There really isn't much to an A4 electrical system.

On a side note, I took my electrical temperature guage to the boat and was reading 71 degrees near the cabin roof and about 60 degrees down by my knees. The temperature outside was just below freezing so I think the cabin insulation is definately working.

That's it for now. I took some more pictures of the engine so I can update the 'engine' page on the website - dirty engine and all but I need something to do weeknights.

Roughly 15 weekends before launch. I am starting to feel the pressure.

*For those of you that want to know what shunting and ammeters have in common:

A typical ammeter is a sensitive electrical device requiring only a few milliamps to operate. Running the whole load through the a meter would require a huge and heavy device to handle the big electrical currents. The shunt is a bypass. Most of the current goes through the shunt and only a little goes through the meter. Now for the meter to operate properly, it needs to be calibrated to the shunt. The meter has to know that, say for example, 99% of the load is going through the shunt and 1% is going through the meter. That way the meter can read 100 times more than what is actually going through it so that it can accurately show the full system current. An internal shunted ammeter has terminal connections for the full load. The whole load is taken to the meter case. Inside of the case the shunting occurs. On an externally shunter ammeter (which is what I wanted but didn't get) the shunt is located somewhere convenient, say off of the starter terminal, and two tiny wires carry 1% of the system current back to the meter. That would have been better in my system with the meter 6 feet away from the rest of the system. Its okay. It will work. But I will need to buy 12 feet of 4 guage wire or something like it to carry that much current over that distance.


Tim said...

It might take you a while to get your woodwork done clamping only one joint at a time! ;<)

Interim pictures are never boring, as least not to the sad sort of person (like me) who's probably reading this blog anyway.

Nice windmill. I really want one of those. (Actually, I want about a dozen to just drop from the sky into my field and start spinning.)

brushfiremedia said...

Yeah, those windmills are great.

At least, until something like this happens...