New Main Circuit Breaker Panel Installed and Working
With all the electrics torn down to basics, getting the main circuit panel installed and working was a big milestone.
Here is the old panel. Note the breakers and rocker switches which were common on all the Cessna models until they came out with the new single engine line in 1997.
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture152.aspx
An interesting thing about the way Cessna (and many others) did their electric back then. That really big breaker (in this case 60amp) means that there is a hot side of the breaker unprotected inside the panel. This 8 awg wire of course can be switched off with the master switch but while the master switch is on there is a 60 amp power source coming in unprotected.
The new aircraft have dual essential power busses with breakers in an electrical box on the firewall near the battery. The only battery / alternator related breaker inside is the alternator field breaker which just supplies power to the field side of the regulator.
Anyway I thought it too big of a jump to redesign the original electrics in the aircraft so I put the 60 amp breaker back on the panel. I also tied the 2 essential busses together (you can see the bus bar jumper) so there was one essential bus identical to the original design. The 2 areas that did get changed for the better were the loss of seperate switches and the dual avionics busses.
On the original design there was a relay that would cut off power to the avionics bus when the starter was energized. While this is good, there can still be voltage spikes on the line when the engine shuts down which is the main reason they all went to an avionics master switch. On this new panel I have 2 - 20 amp breakers that then go through the split rocker switch to power 2 avionics busses - way cool and the way it should be.
Also the new design uses switch breakers and I incorporated them to eliminate the need to have a breaker and switch like the original design.
Here are a couple of pictures of the power panel front and rear -
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture182.aspx
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture183.aspx
And here is what the panel looks like now with all the basic electrics operating -
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture184.aspx