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Minimal Electrics.

M

Mark Bolton

Active Member
I am building a RV - 4 and going the "minimal" route.
The only electrics are going to be :

Generator - off a Kubota tractor .

Voltmeter.

Skytech Starter.

Fuel Pump.

Fuel quantity.

Radio.

I am familiar with the convention of using a master relay and circuit breakers to protect the wiring.

As I am roughing the layout in my mind it strikes me that there is more wiring battery side of the breakers than there would be if I left the breakers out and that the only thing down stream of the master relay is the starter solenoid.

It all seems a bit redundant.

How about using a toggle switch with a 30 amp breaker as the "Master" and putting a little ni - cad battery behind a diode to keep the radio working in the event that a fault occurred in the electrics ?

Am I making sense ?

Regards

Mark

http://rv-4builder.blogspot.com/
 
Mark Bolton said:
I am building a RV - 4 and going the "minimal" route.
The only electrics are going to be :

Generator - off a Kubota tractor .

Voltmeter.

Skytech Starter.

Fuel Pump.

Fuel quantity.

Radio.

I am familiar with the convention of using a master relay and circuit breakers to protect the wiring.

As I am roughing the layout in my mind it strikes me that there is more wiring battery side of the breakers than there would be if I left the breakers out and that the only thing down stream of the master relay is the starter solenoid.

It all seems a bit redundant.

How about using a toggle switch with a 30 amp breaker as the "Master" and putting a little ni - cad battery behind a diode to keep the radio working in the event that a fault occurred in the electrics ?

Am I making sense ?

Regards

Mark

http://rv-4builder.blogspot.com/
Click to expand...

Mark,

The primary purpose of the breakers is to protect the wiring running to your accessories, not the devices themselves. You will have some 20-22 awg wire that won't be protected by a 30a breaker--a wire shorted to ground will burn before the breaker pops.

If you want to go minimal, you might consider using automotive blade fuses in a fuse block that will give you maximum wiring protection for little weight, cost or maintenance. The fuse blocks in my RV-6 have been totally reliable for over ten years.

Good luck with your project! Light is good. :)
 
This is what I meant

wiring+diag.jpg


Note that all the low current wiring is protected by a fuse. It isn't cockpit resettable but were there a short you would lose the lot anyhow.

The radio / intercom have a separate backup battery.

On reflection it might be better to put the starter push switch on the other side of the Master since in this config the starter is always hot. Nasty.
 
You might consider dropping the backup radio battery. Instead, add a switch that will power the radio straight off the aircraft battery in cause the master had to be opened for some reason.

This would be very similar to the "E bus" system many of us use per the recommendations in Bob Nuckoll's "AeroElectric Connection" book.

I applaud you for keeping it simple and light!
 
If you do this, you will need to make sure that all the wiring behind the firewall (after that fuse) is rated for at least 30 amps.

Definately move the start switch to the other side of the master....
 
Starter

Marc,
You're showing the starter switch tied directly to the battery instead of off of the main bus (other side of master). This will make the starter always hot. Don't recommend that.
 
I believe the polarity of your bridge is reversed. Agree with the recommendation for fuses for each circuit.
 
Thank you all

In reading your pointers it seems that the best way to do it is the same way as it always has been done including the master Isolator relay.

Separate breakers for both circuits.

Even in such a simple setup there is still sound reasons for sticking with the time honored way of wiring it up.

I am thinking of putting a hidden safety switch inside the cowls to make the plane safe from / for inquisitive youngsters etc.

Thank you all for helping me out on this one.

Regards

Mark
 
Does anyone know of a detailed electrical system sample website? Pictures, LUV pictures. Like Dr. McCoy, "I'm a programmer, not an electrician!".
 
The only thing worse than too complicated is too simple. I do applaud your desire for simplicity. Still you need to improve the electrical a little bit. Even a simple electrical system has to be well designed. Your close but needs some tweaking.

You MUST have breakers or fuses for the the circuits. It will be a fire hazard without. Also, you will need a battery relay. It'll go dead without one. Are you using a "generator" or alternator. As you may know generator's suck. They have no low RPM output and the field get's reversed polarity easily.

Do something like this

ALTERNATOR/REGULATOR
CURRENT LIMITER
BATTERY
STARTER SWITCH
BATTERY RELAY
STARTER RELAY
MASTER SWITCH
FUSE BLOCK/RATED FUSES
RADIO MASTER
RADIOS, PUMPS, ETC.

Should be really simple to wire.
 
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Another good resource for "super simple" are the Bingelis books - written a bit before the explosion in kit planes and advanced experimental avionics, they show you how to wire and plumb simple homebuilts in a safe and efficient (cheap) manner!

Paul
 
Second Thoughts

http://rv-4builder.blogspot.com/2010/02/electrical-system.html

I thank you all for your contributions and have refined my aproach.

Out with the generator - I will be using a automotive alternator / reg combo like the Van's one.

All my switches will have built in breakers.

I have decided to use a mechanical Isolator to serve the purpose of the Master relay. As you can see it is mounted right next to the battery and can be disabled in the event of any smoke. I cant see any faiilure mode that could lead to an un isolatable short.

Kind Regards

Mark
 
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