140 Electrical Sytem Upgrade & Weight Loss

[phil123]

Another thing to check before you go through some major work is to make sure the screw on the back of the housing holding the compass in place is "brass or stainless" not the standard steel which is magnetic and will screw up the compass big time.

[a64pilot]

Many times stainless is magnetic, it has a lot to do with how it’s worked, many think magnetic stainless is lower quality, and they would be incorrect.
Go with brass instrument screws, for all instruments, they are cheap.

https://www.greenwoodmagnetics.com/reso ... ess-steel/

Probably 95% of stainless hardware is 304, 18-8 is another way of saying 304

Most all threads are rolled, and that’s cold working the metal, and certainly can make SS magnetic. High quality threads are rolled, not cut, besides rolling is much faster to accomplish

However having a motor mount that needs to de-gaussed or having magnetic items close to the compass is easy to distinguish, the error will be constant where if it’s from the magnetic field created from producing electricity, it will of course come and go with the electrical production, and increase and decrease with how many amps the alternator is making.

I messed up and commented to Engineering that the aircraft we manufactured had compass errors when the airconditioning was on (close to a 100 amp draw at 28VDC)
Anyway Engineering wrote up a report and I was having to fill out two cards, one with the AC on and one for when it was off.

I know this isn’t supposed to be said, but does anybody actually reference the mag compass?

[8474]

I know this isn’t supposed to be said, but does anybody actually reference the mag compass?

Not since the invention of GPS

[meloosifah]

So I weighed the airplane this week. I am at exactly 1100 lbs with full fuel. That puts me at 950 lbs empty weight. That included my ram mount, Dynon D3, headset and full oil as well, so minus the Lightspeed and Dynon it’s probably 948 or so. It did not include carpet in the baggage, hat shelf or child seat, but otherwise a full interior. I still have a heavy transponder and com radio, original speaker and an intercom. There might be a pound or two to lose when I do the avionics upgrade but I will gain that back with the child seat and seatbelt.

For reference, I have a full VFR panel but no AI or DG, Dynon D3, com, transponder, intercom, full interior, 3200 tw, Cleveland brakes, original Grimes landing light, original seats, Whelen beacon, 150 exhaust, no extenders.

Pretty happy with it overall.

[8342]

I am installing the Plane Power alternator along with the new regulator in my 140 and I cannot figure out where to put one of the original wires.
It is #7 in Figure 42 which went from the Master switch to the Generator.
The new alternator has two wires that go to the new regulator but I cannot find anything in any of instructions as to where the #7 wire now goes.
Any advise would be greatly appreciated.

Rick

[6298]

The field on the generator was grounded by the master switch. The field on the alternator is positive, and I believe it comes from the regulator.

[6643]

The master switch has two original functions. First, it energizes the solenoid that connects the battery by grounding the solenoid winding. Second, it connects the generator field terminal to the regulator field terminal. The second function is obsolete when you install an alternator and is handled by the alternator switch, which is separate and operates differently. The alternator modification should specify a separate alternator exciter switch.

[8342]

Thanks Randy and John but I still would like to know what to do with the #7 Wire.

I was hoping someone that has done this specific operation could let me know what they did with theirs.

None of the instructions give any advice on it.

Rick

[6298]

You can discard the #7 wire and save some weight. Its purpose was to ground the field on the generator that you are no longer using. I have a Plane Power alternator on one of mine, and it has a wire that comes with it to enable the voltage regulator. It goes to a positive source.

[8342]

Copy Randy, thanks.

Rick