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Jabiru Starter contactor and solenoid

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p.mulwitz(at)worldnet.att
Guest

Posted: Wed Dec 06, 2006 8:11 pm Post subject: Jabiru Starter contactor and solenoid

Hi Matt,



 I'm no expert on Jabiru or engines in general, but I was an electrical engineer for many years.  So, take my suggestion as a starting point rather than a final word . . .



 I think the point of the battery contactor on an airplane is to shut down all electrical power for fire prevention (well, almost prevention) in case of a forced landing.  It is also nice for stopping an electrical fire.  



 The starter solenoid (technically, it is a relay since its purpose is to switch electricity rather than perform a mechanical function) is in place to allow switching of the huge current needed to start the engine.  You will not find a panel mounted switch that will switch more than 20 or 30 amps, and I think starters can use more like 100 amps.  So the way to think of the starter solenoid is to consider it a switch extension for the starter current.



 These are two completely different functions that cannot be combined in one switch.  I would suggest the "Battery Master" contactor be installed near the battery (wherever it winds up being installed.  The starter solenoid should be installed with either a separate cable to the battery or to the master contactor output.  It shouldn't matter if it is directly connected to the battery since it won't get any power unless the starter swtich on the instrument panel is activated.  Similarly, it can work through the master contactor just as well as with a direct battery connection.  The difference will only be really noticeable if you have to run an additional heavy cable from the engine compartment to the battery if it is installed in the rear portion of the plane.



 If you study the specifications for both of these components you will probably find the starter solenoid is only meant to be turned on for short periods while the master contactor is meant to be turned on for many hours at a time.  These are not interchangeable parts.



 If my guess is correct, the diode is meant to clamp the coil on the solenoid.  This prevents the natural tendency of any coil to increase its voltage in attempt to continue current flow when the circuit is opened.  The diode will prevent high voltage (perhaps very high voltage) from appearing on the battery circuit when the starter is turned off.  Some planes are equipped with an "Avionics Master" switch which also deals with this kind of problem, but the diode is a lot smaller and less expensive to install.  I would recommend putting power diodes on both solenoid/contactors.  They are installed to be inactive when power is applied for normal function between the two sides of the coil.



 Good luck,



 Paul

 Still working on airframe - engine to follow soon . . .



 

 At 06:54 PM 12/6/2006, you wrote:

  	  Quote: 	
		   

 I have a Jabiru 3300 and have a 702-1 starter contactor from B&C.  I have a question about the solenoid supplied with the Jabiru.  I am considering just hooking up the 702-1 contactor directly to the starter.  It looks like the "solenoid" supplied by Jabiru is really just another contactor.  It is wired and works the same as the 702-1 but with out the diode.  I am planning on hooking up the contactor similar to what is depicted in aeroelectric Z-20. There it has the lead off of the 702-1 contactor hooked to the Jabiru solenoid.   It sure looks to me that all I will be doing is putting two contactors in series.  I am not sure of the value in this.  I am considering just leaving off the Jabiru solenoid and connecting the 702-1 directly to the starter.  

  

 Is this smart or is there something I am missing?

  

 Thanks 

 Matt 

 www.zodiacxl.com

 	
 

 ---------------------------------------------

 Paul Mulwitz

 32013 NE Dial Road

 Camas, WA 98607

 ---------------------------------------------

     [quote][b]

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zcrj90(at)yahoo.co.uk
Guest

Posted: Thu Dec 07, 2006 12:08 am Post subject: Jabiru Starter contactor and solenoid

Hi Matt and Paul, 

  

 Paul's summed up the issues and I've already wired my latest Jabiru as he has recommended. 

  

 The only issue he didn't mention is starter solenoid sticking.

  

 What do you do in the unlikely event that the starter solenoid (contactor/relay) sticks closed? 

  

 With the master contactor powering everything you merely open the master and all goes quiet. If the starter solenoid is wired direct you can't do this. A 'starter engaged warning light' powered from the starter feed is also a good idea to warn you off this problem.

  

 Regards, Clive

  

 P.S. I've sent my latest wiring diagram to you direct for information. If you see anything wrong with it let me know!



Send instant messages to your online friends http://uk.messenger.yahoo.com  [quote][b]

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N1BZRich(at)aol.com
Guest

Posted: Thu Dec 07, 2006 6:07 am Post subject: Jabiru Starter contactor and solenoid

In a message dated 12/7/2006 3:09:53 A.M. Eastern Standard Time,  zcrj90(at)yahoo.co.uk writes:

  	  Quote: 	
		     P.S. I've sent my latest wiring diagram to you direct for information. If    you see anything wrong with it let me know!

	


 

 Clive,

     Would you mind sharing your wiring diagram with our  EAA Chapter.  We are building a 601XL and are about ready to hang the  engine for the final time.  It is in my hangar and I hope to make the  initial flight sometime relatively soon.

 Blue Skies,

 Buz

  [quote][b]

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archermj(at)swbell.net
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Posted: Thu Dec 07, 2006 9:52 am Post subject: Jabiru Starter contactor and solenoid

Thanks for the reply.  I probably didn't  explain my question correctly.  I have been using the Aeroelectric  semantics for my basic set up.  Follow this link to my schematic  

 http://www.zodiacxl.com/Electrical.html

  

 I have a continuous duty contact (701-1 from  B&C http://www.bandcspecialty.com ) as my  battery contactor and the 702-1 intermittent contactor as my starter  contactor.  The Aeroelectric (http://www.aeroelectric.com/ )  figure for  the Jabiru (Figure Z-20)  shows the starter  contactor energizing the Jabiru "Solenoid".  But the Jabiru solenoid is set  up the same and looks functionally similar to the 702-1 contactor.   I  have the specs on the 702-1 but nothing on the Jabiru solenoid.  I am  planning on just using the 702-1 and hooking it up to the starter.  What I  think happened with the Jabiru hook up from Aeroelectric is that they didn't  have the current Jabiru solenoid in mind when they came up with their layout for  the Jabiru (Figure Z-20).  It looks like they just have the two contactors  in series which does not make sense to me for the starter part of the  circuit.

  

 Thanks for the help

  

 Matt

 www.zodiacxl.com

  

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Gilles.Thesee(at)ac-greno
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Posted: Thu Dec 07, 2006 12:15 pm Post subject: Jabiru Starter contactor and solenoid

Matt & Jo a écrit :

 	  Quote: 	
		   Thanks for the reply.  I probably didn't explain my question 

 correctly.  I have been using the Aeroelectric semantics for my basic 

 set up.  Follow this link to my schematic

 http://www.zodiacxl.com/Electrical.html

  




	


Matt and all,



Had a quick glance at the diagram. Very close to the Aeroelectric Z 16. 

A very good basis indeed.

As already mentioned, it is important to have the battery contactor 

power everything in the ship, including the starter contactor. Thus you 

have some control in case of starter contactor sticking. Besides, you 

comply with the FARs which require that no big wire be "hot" when the 

master switch is off. It is a safety issue.

I do not concur with the "starter direct from the battery" opinion. Very 

large aviation engines, with lots more cranking amps than the little 

Jabiru are using the battery contactor architecture.



I would like to point out that the "avionics and lights" bus switch is a 

single point of failure. Should the switch fail, you lose all radios, 

lights, low-voltage warning, fan (?) and all ...

Have you considered feeding the radio and transponder from the E-bus ?



Apart from this point, your architecture seems very sound to me.



 As for the rest of your message, I'm not sure what the point is with 

the Jabiru starter solenoid.



Regards,

Gilles Thesee

Grenoble, France

http://contrails.free.fr

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archermj(at)swbell.net
Guest

Posted: Thu Dec 07, 2006 8:10 pm Post subject: Jabiru Starter contactor and solenoid

Thanks for your review.  I struggled with the radio and transponder on the E 

bus at first.  My logic for taking it off is that if I do have a problem I 

want the minimum to get it down.  Really don't need the radio and 

transponder for that.  Plus they present a significant load.  So I moved 

them over to the avionics buss.  I uploaded my final diagram to my website. 

This one removed the Jab solenoid and I made some other changes.



http://www.zodiacxl.com/Electrical.html



I would like to say this is the final. But I will probably change it a 

couple of more times.  I also have a copy of the Delta CAD file if anyone is 

interested.



Thanks for all the comments.



Cheers



Matt

www.zodiacxl.com

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vozzen

Joined: 25 Aug 2006
Posts: 12

Posted: Fri Dec 08, 2006 7:18 am Post subject: Re: Jabiru Starter contactor and solenoid

Matt--

On taking redio and transponder off the E-bus:



I think you'll find that the radio, on receive, takes minimal current.  The transponder could be left in standby (ident/on when needed), also using little juice.   And do you have ON/OFF switch on each?

Dont forget,  the master relay (unless you're using the Z-20 (IIRC) version without it) pulls about 1 amp, probably as much as both radio and xponder on "idle".

In other words, why not leave radios on Ebus, so they are available, if needed, without the master being on.



I agree on your orginal question that the starter relay and "solenoid" are redundant.



[is it ever really "final"??]

--Rico, XL/3300, modified Z-16

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p.mulwitz(at)worldnet.att
Guest

Posted: Fri Dec 08, 2006 5:17 pm Post subject: Jabiru Starter contactor and solenoid

Hi Doug,



 Rather than flame you, I want to thank you for extending the conversation on electrical design.  I am new to this issue and am happy to consider different ways to go.



 I am building a Zodiac XL for (primarily) day VFR use.  I definitely appreciate the starter motor over hand propping, and would like to have enough radios to penetrate busy airspace.  Still, I opted for navigation and strobe lights.  On the other hand, I don't really need fault tolerance to insure safe flight completion.



 I guess I would like to understand the simplest approach to electrical system design.  From that point it makes sense to consider things like master contactors to deal with possible electrical fires and things like that.



 For general consideration about adding parts to an airplane I will attempt to quote the designer of a plane I built many years ago.  He suggested:  "Throw it up in the air.  If it comes down it is too heavy."



 Best regards,



 Paul



 

 At 03:27 PM 12/8/2006, you wrote:

  	  Quote: 	
		  I suppose I should keep my mouth shut, but in case there are other folks who are daunted by the diagram Modified Z-16, I want to affirm your desire for simplicity.  I am impressed by the efforts of Vozzen and Rico. I dont mind the efforts of electical engineers to plan for every possible failure mode.   I understand that some experimental aircraft builders want to build an electrical system to rival any of the General Aviation fleet.

  

 But there is another strategy. If you are careful about the avionics you purchase,   use some common sense and dont install a comprehensive lighting system ( how badly do you want to crash at night? ... if you dont have lights you wont be tempted..) and are willing to just read your own voltmeter, you can have a simple system that can be installed in a few hours instead of a few months.   

  

 It is ok to use a couple toggle switches for your ignition kills.  It is ok to just run breaker switches or switch and fuse to a couple radios.  If you keep your electical loads down, then you dont need much of an alternator.  As you may know, if you have too big a load on the Jabiru alternator, you can crispy the stator.  You can add another seperate alternator, but why would you want to?  

  

 The notion of a solonoid operated by a master switch sounds good, but if the wire or coil in it goes south, so does your electrical power.   That may balance the possiblity of shorting the big wire to the starter solonoid.

  

 If you are building a small, high performance bird like a Sonex and want to make it IFR, by all means design and build as complicated an electrical system as possible.  May I suggest autopilot,  a Garmin radio stack,  electrical gyros and a seat warmer?   The extra time it takes to build all that will prolong your life just that much longer.

  

 I am just saying that IN MY OPINION, it is perfectly OK to only have a couple circuits.  One for the start,  one for the radios and one for a couple other small things.  If you are a bit paranoid, then include a switch in the charging circuit so you can shut off the alternator power to the battery if your volt meter gets too high.   Hook the power circuits  to the post on the starter solonoid that the big battery cable goes to...just so it is easier to disconnect the battery.  It is true that if the solonoid sticks, you will have some drama while the starter twirls the engine until the battery dies...but when is the last time your car did that to you?  It is wired the same way.   Just buy a new start solonoid every 500 hours or so.  That should preclude the arcing from dirt.

  

 Ok, so let the reactions begin.   I'm sure I deserve  to be flamed.

  

 Doug Koenigsberg

 	
 

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