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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Wed Nov 20, 2013 2:07 pm Post subject: Contactors

We have discussed contactors for years and I have always recommended the Kilovac EV200 and the Gigavac GX11, but there is a new contactor available from Gigavac to compete directly with the Kilovac EV200 and offers some additional benefits, such as no noise, terminal shields, and improved performance characteristics. I was considering selling these, but there isn't any meat on the bone left after getting them from Gigavac.



I have one and I like these more than the Kilovacs.



Part Number	Description			

GX200BB	350A, 12Vdc coil, 24" leads                                                                          	1-4  $116

5-9  $104

10-24 $99 



See: http://www.gigavac.com/pdf/ds/pp/gx200.pdf  



(ignore their weird warning to see their other contactors (remember Gigavac is refering to 200A continuous). Gigavac is known for having strange marketing, but great products. Also ignore their manual switches...they are made for really, really, high-voltage applications and are much too big.



But I recommend the GX200 as the best contactor for the task, if you are planning to use a contactor at all.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

jan(at)CLAVER.DEMON.CO.UK
Guest

Posted: Wed Nov 20, 2013 2:38 pm Post subject: Contactors

Hi Eric,



I hope they have improved. We changed from EV200 to Gigavac and had nothing

but problems .. This was in high voltage EV applications - must have used

more than 1000 units .. all had to go back .... it was a few years ago ...

so things may have changed ...



Strange thing was that application was fine ..all the Gigavac tech info

etc..was great .. but we keep getting welded contactor ... it was a very

expensive exercise, we will never use them again.  Never had problem with

the EV200.



Yes the circuit saver on the EV200 can be noisy. But have not been a great

problem. Also can use the EV200 with no circuit saver and use a external

circuit saver ...



--

jluckey(at)pacbell.net
Guest

Posted: Wed Nov 20, 2013 3:34 pm Post subject: Contactors

Eric,



As you know, the typical small experimental aircraft may typically have 2 contactors:

1. the "master" - continuous duty, usually rated for ~80 amps, typically handles < 40 amps

2. the starter solenoid - intermittent duty, rated for cranking 200-300 amps



For which of these missions are you suggesting the GX200?

Looks like a great device but seems to be overkill for these applications w/ a price to match.

-Jeff



        From: Eric M. Jones <emjones(at)charter.net>

 To: aeroelectric-list(at)matronics.com 

 Sent: Wednesday, November 20, 2013 2:07 PM

 Subject: Contactors

  

 

 --> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net (emjones(at)charter.net)>



We have discussed contactors for years and I have always recommended the Kilovac EV200 and the Gigavac GX11, but there is a new contactor available from Gigavac to compete directly with the Kilovac EV200 and offers some additional benefits, such as no noise, terminal shields, and improved performance characteristics. I was considering selling these, but there isn't any meat on the bone left after getting them from Gigavac.



I have one and I like these more than the Kilovacs.



Part Number    Description            

GX200BB    350A, 12Vdc coil, 24" leads                                                                               1-4  $116

5-9  $104

10-24 $99 



See: http://www.gigavac.com/pdf/ds/pp/gx200.pdf  



(ignore their weird warning to see their other contactors (remember Gigavac is refering to 200A continuous). Gigavac is known for having strange marketing, but great products. Also ignore their manual switches...they are made for really, really, high-voltage applications and are much too big.



But I recommend the GX200 as the best contactor for the task, if you are planning to use a contactor at all.



--------

Eric M. Jones

www.PerihelionDesign.com

113 Brentwood Drive

Southbridge, MA 01550

(508) 764-2072

emjones(at)charter.net





Read this topic online  here:



http://forums.matronics.com/viewtopic.php?p=413611#413611www.aeroelectric.com<    * HomebuiltHELP www.mypilotstore.cbsp;               -Matt Dralle, List Ad=================

 

 

  

 [quote][b]

jluckey(at)pacbell.net
Guest

Posted: Wed Nov 20, 2013 3:37 pm Post subject: Contactors

Eric,



As you know, the typical small experimental aircraft may typically have 2 contactors:

1. the "master" - continuous duty, usually rated for ~80 amps, typically handles < 40 amps

2. the starter solenoid - intermittent duty, rated for cranking 200-300 amps



For which of these missions are you suggesting the GX200?

Looks like a great device but seems to be overkill for these applications w/ a price to match.

-Jeff



        From: Eric M. Jones <emjones(at)charter.net>

 To: aeroelectric-list(at)matronics.com 

 Sent: Wednesday, November 20, 2013 2:07 PM

 Subject: Contactors

  

 

 --> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net (emjones(at)charter.net)>



We have discussed contactors for years and I have always recommended the Kilovac EV200 and the Gigavac GX11, but there is a new contactor available from Gigavac to compete directly with the Kilovac EV200 and offers some additional benefits, such as no noise, terminal shields, and improved performance characteristics. I was considering selling these, but there isn't any meat on the bone left after getting them from Gigavac.



I have one and I like these more than the Kilovacs.



Part Number    Description            

GX200BB    350A, 12Vdc coil, 24" leads                                                                               1-4  $116

5-9  $104

10-24 $99 



See: http://www.gigavac.com/pdf/ds/pp/gx200.pdf  



(ignore their weird warning to see their other contactors (remember Gigavac is refering to 200A continuous). Gigavac is known for having strange marketing, but great products. Also ignore their manual switches...they are made for really, really, high-voltage applications and are much too big.



But I recommend the GX200 as the best contactor for the task, if you are planning to use a contactor at all.



--------

Eric M. Jones

www.PerihelionDesign.com

113 Brentwood Drive

Southbridge, MA 01550

(508) 764-2072

emjones(at)charter.net





Read this topic online  here:



http://forums.matronics.com/viewtopic.php?p=413611#413611www.aeroelectric.com<    * HomebuiltHELP www.mypilotstore.cbsp;               -Matt Dralle, List Ad=================

 

 

  

 [quote][b]

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Wed Nov 20, 2013 4:53 pm Post subject: Re: Contactors

Jan,

 	  Quote: 	
		  

 I hope they have improved. We changed from EV200 to Gigavac and had nothing but problems .. This was in high voltage EV applications - must have used more than 1000 units .. all had to go back .... it was a few years ago ... 

so things may have changed ... 	




I have heard of problems with big contactors in EVs charging supercaps. Inless the caps are "pre-charged" or there is a line resistor, the current is ~infinite. These lessons were learned painfully in EVs. But Gigavac makes good stuff and they deserve a look. Gigavac makes scores of different contactors.



Jeff,



There are main battery contactors. Maybe more. They would be overkill for 40A.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

deej(at)deej.net
Guest

Posted: Wed Nov 20, 2013 5:26 pm Post subject: Contactors

On Nov 20, 2013, at 5:07 PM, "Eric M. Jones" <emjones(at)charter.net> wrote:



 	  Quote: 	
		   

 GX200BB    350A, 12Vdc coil, 24" leads                                                                              1-4  $116

 


	


This is not intended as a flame, and I am not trying to join the contactor war.  



I literally just received a starter contactor from Aircraft Spruce that cost $9.95, and I bought a pair of IN5402 diodes from Radio Shack for $1.99.  The contactor on my Glastar is identical as far as I can tell, and has been working for the last 14 years even though it has no diode installed on it.  Once this summer I pushed the button and did not get the "click" from the contactor and the starter did not turn. A few seconds later I pushed the button and it worked fine, and has worked fine for a few dozen starts since then. I'm replacing it "just because" and also because it is dirt cheap to do so.



Serious question, what benefit do I really get for that extra $104?



-Dj

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Wed Nov 20, 2013 5:55 pm Post subject: Re: Contactors

Dj-



I don't want to crank out another bushel of words on this either (and I'm certain Bob N is tired of it), but:



The type 70 you used is position-sensitive, operates up to only 122 degF (!), is not airtight, water-tight not fuel-proof, and sucks current. Yes, it has been used for years, and it is cheap. Time to change.



ps, if you'd used bidirectional Zeners instead of p/n diodes, the contactor would probably still be working.



pps, I am a proponent of using NO contactors if you can arrange it. So that's where I stand. Check the PDF and if it suits your plans, try one.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

deej(at)deej.net
Guest

Posted: Wed Nov 20, 2013 6:49 pm Post subject: Contactors

On 11/20/2013 8:55 PM, Eric M. Jones wrote:

 	  Quote: 	
		   

 The type 70 you used is position-sensitive, operates up to only 122 degF (!), is not airtight, water-tight not fuel-proof, and sucks current. Yes, it has been used for years, and it is cheap. Time to change.


	


Hi Eric,

     Thank you for responding.  I don't really feel that answers my 

question though, at least I don't think it answers it from my 

perspective as a typical experimental guy on a budget.  This email (and 

the previous one) really isn't directed at you specifically, although I 

suppose it might look that way.



     Literally, what benefit do I really get for that extra $104? All I 

want is to push the button and have the starter turn.  At $9.95, the 14 

year old contactor provided that for 71 cents per year.  I do not 

understand how the more expensive contactor is going to do the job any 

better.  Budget is a concern for me, so if I am looking at a $12 

solution compared to a $116 solution, I really need to see some clear 

benefits before I am willing to spend the extra money when they both 

seem to do the same thing.



     Having said all that, understand that I'm not an electronics 

expert, and am unlikely to appreciate the finer nuances of the method of 

how each of these types of contactors work.  That is probably fairly 

typical of most of the people on this list.  The $116 contactor may save 

a few amps of current, for example, but that really doesn't mean a lot 

to me.  I have a 20 ah battery, and I use the contactor for a few 

seconds to start the engine, then the battery gets charged back up 

during the flight.  Whether it uses 1 amp versus 5 amps (made up numbers 

for illustration), it doesn't really have an impact on how I use it, at 

least in this case.



     I live in New England, so 122F as a limit isn't a concern (-20F 

might be!   ), and even a 10 minute turnaround for a fuel stop in the 

summer so the cowling is still hot hasn't seemed to create any issues.  

Airtight and watertight doesn't seem to matter since it is inside the 

cowling and protected from the elements.



     The one item that you mentioned, not being fuel proof, could be a 

potential safety issue if somehow fuel were to be sprayed onto the 

contactor and an internal spark when I push the button caused it to 

ignite.  It is pretty far away from my fuel system though, and I have a 

gravity feed fuel setup, so very low pressure.  The chances of fuel 

getting to the contactor seems very slight even in the event of a fuel leak.



     This email went on longer than I intended, but I thought it useful 

to offer a perspective from someone that I think is a typical 

representation of people on this list.



 	  Quote: 	
		   ps, if you'd used bidirectional Zeners instead of p/n diodes, the contactor would probably still be working.


	


     For clarity, the 14 year old contactor has never had diodes (or 

zeners) installed on it, and it is still working.  I don't really have 

any reason to replace it except for that one blip a few months back, and 

that I am completely re-doing a bunch of electrical items on the plane 

and it is convenient to do it while I have everything apart.  The new 

one that I will be installing will get a diode across it.  Maybe it will 

last 28 years instead of only 14...  



     I hope this email is taken in the positive spirit in which it is 

intended.  I mean no offense, and hope none is taken.



-Dj



-- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Thu Nov 21, 2013 6:58 am Post subject: Re: Contactors

Dj--

 	  Quote: 	
		  Hi Eric, 

Thank you for responding. I don't really feel that answers my 

question though, at least I don't think it answers it from my 

perspective as a typical experimental guy on a budget. 	




Flying is a pretty expensive sport no matter how you do it. But I don't encourage everyone to immediately change to the latest and greatest. If you are happy with what you have, then by reading this list and doing some investigation, you at least know what's available. If you want to build an aircraft to be a stellar example of wonderfulness, and aren't so concerned about budget, then different choices might apply.



Even Bob N's book and writings show "simple, more complicated, sophisticated" approaches and Z-diagrams. Over the years my aspirations have slipped from whiz-bang to much-simpler. For example I don't want a dual battery system, an inverted fuel system, and probably won't have an AOA either. I'll probably put  off the autopilot for later. 



As for the 122F spec limit, If your contactor is under-cowl, then it is a real limitation. Evidence seems to indicate that the modern type-70 is not the same device it was some years prior.



So what do you get for an additional $104? A lot better, safer, lower hold-current, higher-temp device. It makes sense in my checkbook, but might not in everyone's. But I am still aiming at a contactor-free simple design.



ps, I'm building a Glastar.

pps, The Gigavac and Kilovac designs use bidirectional Zeners as coil suppressors. Wonder why? Because the diodes recirculate the current and slow the opening of the armature, causing arcing; the bidirectional Zeners don't.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

jrevens(at)comcast.net
Guest

Posted: Thu Nov 21, 2013 8:59 am Post subject: Contactors

 	  Quote: 	
		  On 11/20/2013 Dj Merrill wrote: ”For clarity, the 14 year old contactor has never had diodes (or zeners) installed on it, and it is still working. I don't really have any reason to replace it except for that one blip a few months back, and that I am completely re-doing a bunch of electrical items on the plane and it is convenient to do it while I have everything apart. The new one that I will be installing will get a diode across it. Maybe it will last 28 years instead of only 14...  ” I just want to point out that the “blip” you experienced was very possibly caused by the switch controlling the contactor, not the contactor itself. A diode is usually installed to protect the switch contacts from excessive arcing, and not the contactor itself. I don’t believe that the diode will directly do anything to help the contactor have a longer life. John Evens   	
0  

   

   

   

      

   

       [quote][b]

jrevens(at)comcast.net
Guest

Posted: Thu Nov 21, 2013 9:11 am Post subject: Contactors

 	  Quote: 	
		  On 11/20/2013 Dj Merrill wrote: ”For clarity, the 14 year old contactor has never had diodes (or zeners) installed on it, and it is still working. I don't really have any reason to replace it except for that one blip a few months back,and that I am completely re-doing a bunch of electrical items on theplane and it is convenient to do it while I have everything apart.The new one that I will be installing will get a diode across it.Maybe it will last 28 years instead of only 14...  ”  	
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No virus found in this message.

 Checked by AVG - www.avg.com

 11/20/13    [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Nov 21, 2013 10:03 am Post subject: Contactors

As for the 122F spec limit, If your contactor is under-cowl, then it 

is a real limitation. Evidence seems to indicate that the modern 

type-70 is not the same device it was some years prior.



   And in what way are these 'differences' a step-down

   from what was done in the past?



   Please do not side-step this question Eric. In what

   way have you discovered that the modern incarnation

   of the 70-series contactor is inferior to that which

   first flew on the C140 in 1948 or any other era in

   between?



   Published temp limits are founded in the outcome of an

   MTBF study where operating temperature strongly influences

   service life of organics (insulation and molded

   bobbins). A 70-series contactor on a golf-cart

   or fork-lift is subject to 100x the service-stress of a

   battery contactor in a light airplane. The question

   to be asked and answered is assuming that a 70-series

   device at 122F is good for xx,xxx operations at

   full switching load and 122F, how badly does that

   xx,xxx number degrade at say . . . 160F?

So what do you get for an additional $104? A lot better, safer, lower 

hold-current, higher-temp device. It makes sense in my checkbook, but 

might not in everyone's.



   Quantify 'better' and 'safer' . . . cite any instances

   where failure-to-perform by a 70 series contactor has

   presented anything other than a maintenance event.



   Cite also the outcome of a failure mode effects analysis

   that should the demonstrably low probability contactor

   failure actually happen in flight. Have you deduced

   a heretofore unidentified risk to airframe/people in

   an airplane fitted with an e-bus?



  But I am still aiming at a contactor-free simple design.



   No problem. Lamar offers a line of all solid state

   contactors which they say are suited to both

   battery and starter control. Aircraft Spruce

   offers them right now.



   http://tinyurl.com/or73cxr



pps, The Gigavac and Kilovac designs use bidirectional Zeners as coil 

suppressors. Wonder why? Because the diodes recirculate the current 

and slow the opening of the armature, causing arcing; the 

bidirectional Zeners don't.



   I proved this assertion incorrect some years back on

   the bench. The plain vanilla diode does extend operating

   delay but has no measurable effect on transition velocity

   (arcing). The operating delay is on the order of milliseconds

   and transparent to the pilot and ship's systems.



   Consider Figures 5 thru 8 of this document.



   http://tinyurl.com/36783n7



   Particularly the arc signature of a spreading relay

   contact where (1) the coil is not suppressed in any

   way and (2) suppressed with a plain vanilla diode.



   If this document is in error, I need to know. Help

   me out . . .



   Consider this article published in the Cessna 120/140

   Forum.  http://tinyurl.com/oe2m52v



   Here the author claims to have measured the effects of

   coil spikes induced directly onto the bus of his

   C182. He cites some startling numbers . . .



   We have discovered through simple bench tests and rudimentary

   logic that 99.99% of the energy from a collapsing contactor/relay

   coil is expended across the contacts of the controlling

   switch . . . that in fact, the energy does not propagate out

   onto the system.  It would be nice if he had published

   a wiring diagram for his experiment so that it could

   be repeated.



   Eric, if your wish is to be a persuasive teacher,

   you're going to have to bring your science to

   the discussion. If you have evidence that argues with my

   deductions, nobody would be happier than I to know that

   what I've been teaching is in error.

   Bob . . .



                    ////

                   (o o)

    ===========o00o=(_)=o00o=========

    < Go ahead, make my day . . .   >

    < show me where I'm wrong.      >

    =================================

jan(at)CLAVER.DEMON.CO.UK
Guest

Posted: Thu Nov 21, 2013 10:43 am Post subject: Contactors

Hi Jeff,



I am well aware of the issue around pre-charging of capacitors. That is

bread and butter stuff to anyone involved in the EV industry or dealing with

any systems that have large capacitors ...



What was so frustrating in our experience was that what Gigavac was

proposing as an alternative to the EV200 ... all looked right on paper ..

but did not work in our application ... the EV200 did .. and still do.  More

frustrating was the Gigavac was not able to come up with a answer to the

problem. He we had to pull them all. And re-fit EV200 ...



Anyway ... as a starter or main contactor on a light aircraft ... Well .. I

have no further comment to add. 



Jan



--

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Thu Nov 21, 2013 1:31 pm Post subject: Re: Contactors

It would be nice to have gotten an answer from Gigavac. I'll contact them and try to dig up what happened.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Nov 21, 2013 1:45 pm Post subject: Contactors

I just want to point out that the "blip" you experienced was very possibly

caused by the switch controlling the contactor, not the contactor itself.

A diode is usually installed to protect the switch contacts from excessive

arcing, and not the contactor itself. I don't believe that the diode will

directly do anything to help the contactor have a longer life.



John Evens



      AGREED!



     Bob . . .

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Thu Nov 21, 2013 2:14 pm Post subject: Re: Contactors

EMJ said-As for the 122F spec limit, If your contactor is under-cowl, then it 

is a real limitation. Evidence seems to indicate that the modern 

type-70 is not the same device it was some years prior. 



 	  Quote: 	
		  And in what way are these 'differences' a step-down 

from what was done in the past? 



Please do not side-step this question Eric. In what way have you discovered that the modern incarnation of the 70-series contactor is inferior to that which first flew on the C140 in 1948 or any other era in between? 	




The photo you showed of the type-70 with the red RTV seal. I haven't opened many type-70s. In 1948 they probably had phenolic bobbins, now they have nylon bobbins. 



 	  Quote: 	
		  Published temp limits are founded in the outcome of an 

MTBF study where operating temperature strongly influences 

service life of organics (insulation and molded 

bobbins). A 70-series contactor on a golf-cart 

or fork-lift is subject to 100x the service-stress of a 

battery contactor in a light airplane. The question 

to be asked and answered is assuming that a 70-series 

device at 122F is good for xx,xxx operations at 

full switching load and 122F, how badly does that 

xx,xxx number degrade at say . . . 160F?

	




The historical engineering data is not available for the type 70. I have tried. All we can go by is the published specifications. Why does this bother you?

 

So what do you get for an additional $104? A lot better, safer, lower 

hold-current, higher-temp device. It makes sense in my checkbook, but 

might not in everyone's. 



 	  Quote: 	
		  Quantify 'better' and 'safer' . . . cite any instances where failure-to-perform by a 70 series contactor has presented anything other than a maintenance event. 	




Better and safer means higher temp and fuel proof....for a start. Previously I published a comparison of the type-70 with the EV200. Maybe I'll do it again. 



 	  Quote: 	
		  Cite also the outcome of a failure mode effects analysis that should the demonstrably low probability contactor failure actually happen in flight. Have you deduced a heretofore unidentified risk to airframe/people in 

an airplane fitted with an e-bus? 	




Sounds too much like a waste of time for anyone whose mind is made up. The 122F limit is enough to have it put on the Do Not Use List.



But I am still aiming at a contactor-free simple design. 



 	  Quote: 	
		  No problem. Lamar offers a line of all solid state contactors which they say are suited to both battery and starter control. Aircraft Spruce 

offers them right now. 	
 

pps, The Gigavac and Kilovac designs use bidirectional Zeners as coil 

suppressors. Wonder why? Because the diodes recirculate the current 

and slow the opening of the armature, causing arcing; the 

bidirectional Zeners don't. 



 	  Quote: 	
		  I proved this assertion incorrect some years back on the bench. The plain vanilla diode does extend operating delay but has no measurable effect on transition velocity (arcing). The operating delay is on the order of milliseconds 

and transparent to the pilot and ship's systems. 



Consider Figures 5 thru 8 of this document. 

Particularly the arc signature of a spreading relay contact where (1) the coil is not suppressed in anyway and (2) suppressed with a plain vanilla diode. 



If this document is in error, I need to know. Help me out . . . 	




At the time I didn't like your test. I won't dig it up now. Sometimes just doing the best engineering approach is the logical thing to do. Since you know using a p/n diode SLOWS the contactor opening and causes arcing...why would you do that?



 	  Quote: 	
		  Consider this article published in the Cessna 120/140 

Forum. http://tinyurl.com/oe2m52v 



Here the author claims to have measured the effects of 

coil spikes induced directly onto the bus of his 

C182. He cites some startling numbers . . . 



We have discovered through simple bench tests and rudimentary 

logic that 99.99% of the energy from a collapsing contactor/relay 

coil is expended across the contacts of the controlling 

switch . . . that in fact, the energy does not propagate out 

onto the system. It would be nice if he had published 

a wiring diagram for his experiment so that it could 

be repeated. 	




The article has some issues which I will answer later. The key problem is that neither he nor you seem to understand why a bidirectional zener is far better  to use in coil suppression service, and what it does that a diode does not do. NOBODY makes a commercial contactor that uses a p/n diode for coil suppression for good reasons. NOBODY. The sine qua non of coil suppression is to reduce the opening time. I don't think everyone ought to tear out the parts and replace them, but when buiding a system from scratch, why not do the right thing?



If you want to claim the wrong way is "good enough", okay.  



 	  Quote: 	
		  Eric, if your wish is to be a persuasive teacher, you're going to have to bring your science to the discussion. If you have evidence that argues with my 

deductions, nobody would be happier than I to know that what I've been teaching is in error. 

Bob . . . 	




No, you wouldn't. But I respect your work.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Nov 21, 2013 5:58 pm Post subject: Contactors

The photo you showed of the type-70 with the red RTV seal. I haven't 

opened many type-70s. In 1948 they probably had phenolic bobbins, now 

they have nylon bobbins.



  Yes. Ownership and marketing of the 70-series devices

  has changed several times over the years. Most certainly,

  they have benefited from a host of changes that were either

  (1) consistent with processes and materials of the new

  owners and/or (2) process and materials improvements

  that did not degrade original design goals.



  It's easy to fall into the 'trap' for taking notice

  of new, faster, cheaper or convenient changes and translate

  them into some nefarious or incompetent decision to reduce costs

  while sacrificing original design goals. The cars we all

  drive are much cheaper than machines we used to purchase

  50 years ago yet they come with more features and longer

  service lives. Your notice of historical variation in

  design as a driver for safety and reliability is without

  foundation.



  No doubt this DOES happen but I challenge any notion

  that the present incarnation of the 70-series contactor

  is in any way a poorer return on investment than it was

  in 1949.



The historical engineering data is not available for the type 70. I 

have tried. All we can go by is the published specifications. Why 

does this bother you?



  It doesn't bother me in the least. How did a lack of

  historical data offered by manufacturers become a solid

  foundation for declaring a product of poor value and an

  operational hazard? I don't know much about the internal

  decisions that produced the cars I drive either . . . but

  no way would I spend the same money in 2013 dollars for

  a 1960's automobile as a point A to point B transportation

  machine. Given the service life and features of the last

  5 cars I've owned I can confidently assert that cheaper

  is better.



Better and safer means higher temp and fuel proof....for a start. 

Previously I published a comparison of the type-70 with the EV200. 

Maybe I'll do it again.



   I didn't see that. Was it published here on the AeroElectric

   List? I'd like to read it. But if it's simply a tit-for-tat

   listing of features on the promotional literature, be sure

   to explain how the lack of some new feature posed

   a risk to cost of ownership or safety.



 >Cite also the outcome of a failure mode effects analysis that 

should the demonstrably

 >low probability contactor failure actually happen in flight. Have

 >you deduced a heretofore unidentified risk to airframe/people in an

 >airplane fitted with an e-bus?



Sounds too much like a waste of time for anyone whose mind is made 

up. The 122F limit is enough to have it put on the Do Not Use List.



   Waste of time? How so? If your assertion is that I preach

   the gospel of bad science, poor design goals and risky

   decisions based on bad science, then I must be a menace to

   children and other living things. What is the science upon

   which your opinion is based? My mind is not 'made up' . . .

   show me (or more important - the members of this List)

   where I'm wrong. I don't write for you and I don't ask you

   to write for me . . . do it for the membership of this List.



At the time I didn't like your test. I won't dig it up now. Sometimes 

just doing the best engineering approach is the logical thing to do. 

Since you know using a p/n diode SLOWS the contactor opening and 

causes arcing...why would you do that?



   How do I KNOW that? Can you do an experiment

   on the bench that demonstrates it? If you didn't

   like my test then, why did you let it slide?



The article has some issues which I will answer later. The key 

problem is that neither he nor you seem to understand why a 

bidirectional zener is far better  to use in coil suppression 

service, and what it does that a diode does not do. NOBODY makes a 

commercial contactor that uses a p/n diode for coil suppression for 

good reasons. NOBODY. The sine qua non of coil suppression is to 

reduce the opening time. I don't think everyone ought to tear out the 

parts and replace them, but when buiding a system from scratch, why 

not do the right thing?



   Really? How about the S701 series starter contactors

   I sold for years with a plain vanilla diode factory

   installed? How about the fact that plain vanilla

   diodes have been installed on the Cessna single

   engine products for decades  . . . with no overt

   demonstrations of bad engineering? I aware of no

   contactors with factory installed, zener based

   coil suppression . . . lots of devices are sold with

   plain vanilla diodes.



   Small relays are offered with bi-directional devices

   so that the system designer can use them in both

   simple power management -and- controls where drop

   out delay could become an issue.

If you want to claim the wrong way is "good enough", okay.



 > Eric, if your wish is to be a persuasive teacher, you're going to 

have to bring your science to the discussion. If you have evidence 

that argues with my

 > deductions, nobody would be happier than I to know that what I've 

been teaching is in error.

 > Bob . . .



No, you wouldn't. But I respect your work.



    You respect my work but I'm lying? Okay Eric. I think

    this conversation is over. Until such time that you

    conduct and publish the outcome of demonstrations that

    argue with what I have published and defended, you are

    asked to keep your opinions on contactors off this List.

   Bob . . .

Fred Klein

Joined: 26 Mar 2012
Posts: 503

Posted: Fri Nov 22, 2013 1:36 pm Post subject: Contactors

I confess to confusion about the need for a separate starter contactor...one which would substitute for a solenoid built into the starter.



  What I don't understand in particular is that w/ my Subaru starter (with solenoid)...which seems to be a durable and robust combination with a trouble-free history in the automotive industry...what is gained by a separate starter contactor? 



I will still have a hot wire from my rear battery to my firewall...(which is where I would mount such a separate contactor)...so all I gain is a 3 foot length of "not hot" wire from my (superfluous?) contactor connecting to the starter solenoid...and this same length of wire would become "not hot" immediately after I kill the master contactor.



What am I missing here?



Fred

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 22, 2013 2:23 pm Post subject: Contactors

 	  Quote: 	
		  What am I missing here?


	


   See:

http://tinyurl.com/op5cs2g



   Bob . . .

Fred Klein

Joined: 26 Mar 2012
Posts: 503

Posted: Fri Nov 22, 2013 4:01 pm Post subject: Contactors

Thank you...I'm on it...F.



On Nov 22, 2013, at 2:22 PM, Robert L. Nuckolls, III wrote:



 	  Quote: 	
		   

 

 

> What am I missing here?

 

  See:

 

 

 http://tinyurl.com/op5cs2g

 

 

 

  Bob . . .

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