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Heated pitot tube connections

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FLYaDIVE(at)aol.com
Guest

Posted: Mon Jul 24, 2006 2:31 pm Post subject: Heated pitot tube connections

In a message dated 7/24/06 5:55:36 PM Eastern Daylight Time, 

will(at)willcrook.com writes:



 	  Quote: 	
		    The terminals are sinply two straight rods extending from the pitot tube 

 chassis, and I think I could craft some female spade fittings to slip on, 

and 
	


 	  Quote: 	
		   securing it with some RTV.   Obviously, it would be a sad day if these two 

 leads were to short, but all of these $88.50's keep adding up.  Sometimes, 

 when the widget looks very straightfoward, I tend to try and get cheap  

   

  Thoughts?

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


Will:



I like the way you think.  You will have to do a little hunting but there are 

round slip on connectors just like the spade design but only one half and 

larger in size to handle the current.  The ceramic type is exactly that but with 

a ceramic case.  

As for them shorting or causing a problem ... Distance is always a great 

insulator and you could also make one from a small piece of Teflon ... If you go 

this way you will need something that can handle the heat.



Will, you said something that caught my eye ... Ground leads ... Do not use 

the planes ground as your return line.  Run a separate wire so that you have B+ 

and Neg wires going out there.  THEN if you wish ground the Negative out at 

the wing tip.  This will greatly help with other wiring such as your Strobe and 

Nav Lights.  Most problems over time are related to a poor ground.



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Mon Jul 24, 2006 5:04 pm Post subject: Heated pitot tube connections

Barry;

  

 I may be mistaken, but I believe this advice on  grounding is totally contrary to what has been taught on this list for the past  several years.  My understanding of Lectric Bob's advice and lessons on  grounding, are, that local grounds are OK for such things as pitot heat,  position lights etc. but that running a ground wire to a wingtip for an  accessory, as you suggest, and then grounding it there as well is a no-no as  this is likely to create a ground loop. Grounds should be local OR run to the  "forest of tabs" ground point on the firewall. They should not be both for any  single item. (and local grounds are only used for certain specific items as  described in "The Connection".)

  

 Bob McC

  

  

 [b]---

_________________
Bob McC
Falco #908
(just starting)

nuckollsr(at)cox.net
Guest

Posted: Mon Jul 24, 2006 6:20 pm Post subject: Heated pitot tube connections

At 08:57 PM 7/24/2006 -0400, you wrote:



 	  Quote: 	
		  Barry;



I may be mistaken, but I believe this advice on grounding is totally 

contrary to what has been taught on this list for the past several 

years.  My understanding of Lectric Bob's advice and lessons on grounding, 

are, that local grounds are OK for such things as pitot heat, position 

lights etc. but that running a ground wire to a wingtip for an accessory, 

as you suggest, and then grounding it there as well is a no-no as this is 

likely to create a ground loop. Grounds should be local OR run to the 

"forest of tabs" ground point on the firewall. They should not be both for 

any single item. (and local grounds are only used for certain specific 

items as described in "The Connection".)



Bob McC


	


    This needs some clarification. "Ground Loops" ALWAYS exist when

    multiple accessories ground to DIFFERENT parts of the airplane.

    Ground loops are not always evil. The problems arise when

    potential victims (radios, audio systems, instrumentation,

    etc) SHARE the airframe (or distributed ground system in a

    composite) with potential antagonists like alternators. Alternators

    do not become antagonists until they're asked to supply substantial

    currents for the purpose of running high power accessories like landing

    lights and pitot heaters. Discharged batteries are also "high power"

    loads while being replenished. I had a builder complain about alternator

    noise in a system that went away after a few minutes of flight . . .

    his battery was the major antagonistic contributor to ground loop

    noise that went away when the battery assumed recharge.



    Now, one may ground all the antagonists you wish to the

    airframe or distributed ground 'cause all they can do is

    yell at each other and as long as they a deaf . . .

    ist macht nicht.



    The things that are vulnerable are immune from any yelling

    going on elsewhere as long as their respective and collective

    grounds DO NOT participate in the noisy ground loop. Best yet,

    if all potential victims share a single point (or slightly

    distributed single point as shown in the audio systems

    chapter) then there will be order in the world.



    Hence the suggestion about local grounds. Notice that all the

    devices called out are not potential victims and they participate

    only in the generation of noise because they're high power

    loads for the noisiest device in the airplane, the alternator.

    So you may ground them at any convenient location for good

    bonding without regard to potential noise issues.



    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Mon Jul 24, 2006 6:30 pm Post subject: Heated pitot tube connections

At 02:44 PM 7/24/2006 -0700, you wrote:



 	  Quote: 	
		  I have a standard heated pitot tube.  The instructions call for an AN-3115 

connector to terminate the power and ground leads.  Alas (I love using 

that word...), I don't have this little gem.  Looking on the B&C site, I 

don't see anything resembling what I need.  AS&S has the phenolic 

connector, but it is really pricey at $88.50.  The terminals are sinply 

two straight rods extending from the pitot tube chassis, and I think I 

could craft some female spade fittings to slip on, and securing it with 

some RTV.   Obviously, it would be a sad day if these two leads were to 

short, but all of these $88.50's keep adding up.  Sometimes, when the 

widget looks very straightfoward, I tend to try and get cheap  



Thoughts?


	




   I have a client who asked me to look into alternative sources

   for the AN3115 connector. I've studied some of the connection

   science issues and looked at the processes available. Problem

   is that the connection at the pitot tube is subject to elevated

   operating temperatures + extended 3x inrush currents. Building

   a really GOOD AN3115 is not a trivial task.



   Problem is that this is such a low volume part that by the time

   we tool up to build a decent part, the non-recurring costs

   are breathtaking.



   If it were my airplane (and if I were supplying pitot tubes) I

   would silver solder 12", 14AWG Teflon pigtails onto the pitot

   tube pins. Cover the joint in Teflon heat shrink and then make

   connections to the airplane at the ends of the pigtails with

   some attractive, robust splice. PIDG knife splices covered with

   heat shrink tickle my fancy.



   Very straightforward, very cheap.



   Bob . . .



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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

fvalarm(at)rapidnet.net
Guest

Posted: Mon Jul 24, 2006 6:53 pm Post subject: Heated pitot tube connections

What about soldering wire female leads to the  terminals.  

  

 Bevan

 RV7A finish kit

  



   From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of  William Crook

Sent: Monday, July 24, 2006 2:44 PM

To:  aeroelectric-list-digest(at)matronics.com

Subject: AeroElectric-List:  Heated pitot tube connections

 

  I have a standard heated pitot tube.  The instructions call for an  AN-3115 connector to terminate the power and ground leads.  Alas (I love  using that word...), I don't have this little gem.  Looking on the B&C  site, I don't see anything resembling what I need.  AS&S has the  phenolic connector, but it is really pricey at $88.50.  The terminals are  sinply two straight rods extending from the pitot tube chassis, and I think I  could craft some female spade fittings to slip on, and securing it with some  RTV.   Obviously, it would be a sad day if these two leads were to  short, but all of these $88.50's keep adding up.  Sometimes, when the  widget looks very straightfoward, I tend to try and get cheap   

  

 Thoughts?

dsvs(at)comcast.net
Guest

Posted: Mon Jul 24, 2006 7:57 pm Post subject: Heated pitot tube connections

--

nuckollsr(at)cox.net
Guest

Posted: Mon Jul 24, 2006 8:29 pm Post subject: Heated pitot tube connections

At 08:53 PM 7/24/2006 -0700, you wrote:



[quote]



--

FLYaDIVE(at)aol.com
Guest

Posted: Tue Jul 25, 2006 1:21 am Post subject: Heated pitot tube connections

In a message dated 7/24/06 10:55:02 PM Eastern Daylight Time, 

fvalarm(at)rapidnet.net writes:



 	  Quote: 	
		   What about soldering wire female leads to the terminals.  

   

  Bevan

  RV7A finish kit

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


Brevan:



Soldering in 99% of the cases is a NO-NO.  Even though we are experimental we 

still have to follow good building procedures and AC 43-13 A&B.  Soldering 

creates HARD POINTS that are subject to vibration failure.  Do I solder?  In 

some cases YES   But not in this case.  Use crimp-ons.



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

FLYaDIVE(at)aol.com
Guest

Posted: Tue Jul 25, 2006 1:34 am Post subject: Heated pitot tube connections

In a message dated 7/25/06 12:03:08 AM Eastern Daylight Time, 

dsvs(at)comcast.net writes:



 	  Quote: 	
		   Bob,

  Is the silver solder just for heat resistance?  If I am not mistaken silver

  solder is not as good a conductor as tin/lead, or is that an old wives 

tale?
	


 	  Quote: 	
		    Don

  

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


Don:



There are many Old Wife's Tails out there and the Internet does a tremendous 

job at propagating them and producing even more.  But, SILVER is a Much, Much 

better conductor than tin or lead.  Just look at the Periodic Table of 

Elements. Silver has more free electrons than the other two.  Or just look up the 

conductivity of silver.  While you are at it check out GOLD, PLATINUM, COPPER and 

especially ALUMINUM.

And then consider how good your electrical system is.



Silver solder is around for other reasons other than conductivity.  STRENGTH 

is its major consideration.  It is quite a bit stronger than electrical 

solder.  Silver solder is broken down into two classifications:

Silver bearing (NO! Not like ball bearings) and Percentage Silver.  Unless 

you request a particular percentage you will get silver bearing and that is only 

3% Silver MAX.

 BTW ... If you have purchased solder in the past few years, especially if 

you purchased it through Radio Shack you did NOT get Tin/Lead solder ... The 

LEAD has been removed.  Too many environmentalist chewing on circuit boards.  



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

nuckollsr(at)cox.net
Guest

Posted: Tue Jul 25, 2006 7:31 am Post subject: Heated pitot tube connections

At 05:14 AM 7/25/2006 -0400, you wrote:



 	  Quote: 	
		  



In a message dated 7/24/06 10:55:02 PM Eastern Daylight Time,

fvalarm(at)rapidnet.net writes:



 > What about soldering wire female leads to the terminals.

 >

 >  Bevan

 >  RV7A finish kit

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

Brevan:



Soldering in 99% of the cases is a NO-NO.  Even though we are experimental we

still have to follow good building procedures and AC 43-13 A&B.  Soldering

creates HARD POINTS that are subject to vibration failure.  Do I solder?  In

some cases YES   But not in this case.  Use crimp-ons.


	


    No so.  See:



http://aeroelectric.com/articles/rules/review.html



http://aeroelectric.com/articles/Solder_Lap_Splicing/Solder_Lap_Splices.html



    Solder and crimp are of equal reliability and, for the

    most part, interchangeable wire joining technologies.

    Obviously they require different tools and skills but

    aside from matters of convenience or personal preference,

    there is no reason to pick one technology over the other.



    The prejudices against solder are largely fabricated of

    misunderstanding of the science and techniques.



           Bob . . .



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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

nuckollsr(at)cox.net
Guest

Posted: Tue Jul 25, 2006 8:02 pm Post subject: Heated pitot tube connections

At 05:29 AM 7/25/2006 -0400, you wrote:

 	  Quote: 	

In a message dated 7/25/06 12:03:08 AM Eastern Daylight Time,

dsvs(at)comcast.net writes:

 > Bob,

 >  Is the silver solder just for heat resistance?  If I am not mistaken 

 silver

 >  solder is not as good a conductor as tin/lead, or is that an old wives

tale?

 >  Don

 >

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

Don:

There are many Old Wife's Tails out there and the Internet does a tremendous

job at propagating them and producing even more.  But, SILVER is a Much, Much

better conductor than tin or lead.  Just look at the Periodic Table of

Elements. Silver has more free electrons than the other two.  Or just look 

up the

conductivity of silver.  While you are at it check out GOLD, PLATINUM, 

COPPER and

especially ALUMINUM.

And then consider how good your electrical system is.

   Let's consider simple ideas that do not ride on anyone's tales . . .

   The amount of solder in series with the electron flow through

   any joint is small compared to the total circuit resistance. Yes,

   lead has 13x the resistance of copper but consider that when you

   twist two wires together, the joint is as good as it will ever get

   right at that moment. Adding solder serves to immobilize and encapsulate

   the joint to prevent future degradation due to corrosion and loss of 

pressure.

   In low current, hi impedance circuits (like surface mounted integrated

   circuits) the higher resistance of solder compared to the conductors

   being joined does not add significant resistance to the system.

 	  Quote: 	
		  Silver solder is around for other reasons other than conductivity.  STRENGTH

is its major consideration.  It is quite a bit stronger than electrical

solder.  Silver solder is broken down into two classifications:

Silver bearing (NO! Not like ball bearings) and Percentage Silver.  Unless

you request a particular percentage you will get silver bearing and that 

is only

3% Silver MAX.

  BTW ... If you have purchased solder in the past few years, especially if

you purchased it through Radio Shack you did NOT get Tin/Lead solder ... The

LEAD has been removed.  Too many environmentalist chewing on circuit boards.

    To amplify on this, "silver solder" is a term that can apply to

    MANY alloys for different purposes. Silver bearing solder is low

    temp stuff used in specialized electronics where silver plated

    parts are being assembled and you don't want the solder to dissolve

    silver from the base metal. An example is seen here:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=093-584

    Note the very low melting point of this material. Ordinary soldering

    irons do fine.

    Hard solders melt at much higher temperatures. Here's an example:

http://www.jewelrysupply.com/index.php?main_page=product_info&cPath=16_25_260&products_id=8243

    This pretty cool product combines the flux and powdered silver solder

    in a dispensing syringe. Ideal for making the pitot tube pin-to-wire

    joints being considered in this thread. Note the higher melting point.

    This takes a gas flame.

    Bob . . .

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