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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Tue Nov 17, 2020 11:56 am Post subject: heat probe

i am looking for a way to measure temp. of a gearbox from the outside [no threaded holes]. my eis already has a lead for a resistive type 1/8npt oil temp probe. there must be flat, glue on probes available but i drew a blank with mcmaster carr and have no idea where to look.

 thanks, bob noffs

rv8iator

Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR

Posted: Tue Nov 17, 2020 12:50 pm Post subject: heat probe

Snip...

Q: i am looking for a way to measure temp. of a gearbox from the outside [no threaded holes].  

A: Thermocouple or thermistor ?  Both are readily available.  Thermocouples are of different types for specific temp ranges.  They output a voltage proportional to the temperature at the junction. 

Thermistors are resistors with a linear temp/resistance coefficient within a given range of temperature 

From Wikipedia

Type E[edit]

Type E (chromel–constantan) has a high output (68 µV/°C), which makes it well suited to cryogenic use. Additionally, it is non-magnetic. Wide range is −50 °C to +740 °C and narrow range is −110 °C to +140 °C.Type J[edit]

Type J (iron–constantan) has a more restricted range (−40 °C to +750 °C) than type K but higher sensitivity of about 50 µV/°C.[2] The Curie point of the iron (770 °C)[9] causes a smooth change in the characteristic, which determines the upper temperature limit. Note, the European/German Type L is a variant of the type J, with a different specification for the EMF output (reference DIN 43712:1985-01[10]).Type K[edit]

Type K (chromel–alumel) is the most common general-purpose thermocouple with a sensitivity of approximately 41 µV/°C.[11] It is inexpensive, and a wide variety of probes are available in its −200 °C to +1350 °C (−330 °F to +2460 °F) range. 

https://en.wikipedia.org/wiki/Thermocouple



A thermistor is a resistance thermometer, or a resistor whose resistance is dependent on temperature. The term is a combination of “thermal” and “resistor”. It is made of metallic oxides, pressed into a bead, disk, or cylindrical shape and then encapsulated with an impermeable material such as epoxy or glass.  Much less mechanically robust than a thermocouple.



https://en.wikipedia.org/wiki/Thermistor



...chris

RV-8

On Tue, Nov 17, 2020 at 12:09 PM bobnoffs <icubob(at)gmail.com (icubob(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com (icubob(at)gmail.com)>

 

 i am looking for a way to measure temp. of a gearbox from the outside [no threaded holes]. my eis already has a lead for a resistive type 1/8npt oil temp probe. there must be flat, glue on probes available but i drew a blank with mcmaster carr and have no idea where to look.

  thanks, bob noffs

 

 

 

 

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Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Tue Nov 17, 2020 1:07 pm Post subject: heat probe

On Tue, Nov 17, 2020 at 2:09 PM bobnoffs <icubob(at)gmail.com (icubob(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com (icubob(at)gmail.com)>

 

 i am looking for a way to measure temp. of a gearbox from the outside [no threaded holes]. my eis already has a lead for a resistive type 1/8npt oil temp probe. there must be flat, glue on probes available but i drew a blank with mcmaster carr and have no idea where to look.

  thanks, bob noffs

	
 

 If I had the proper 1/8npt probe on hand, I'd seriously consider just threading a small block of aluminum with a 1/8npt tap, screwing the probe into the block, and securing it with a couple of hose clamps if the location lends itself to that, or clean the location & glue the block  to the gearbox  with hi-temp epoxy (or RTV)   if the hose clamps aren't feasible. You can 'insulate' the adapter block with some silicone hose scrap, or just cover it with RTV. The interior will always be a bit hotter than the probe indicates, but that's the penalty for not having direct contact with the lube in the box.

Charlie



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Charlie

john(at)tipton.me.uk
Guest

Posted: Wed Nov 18, 2020 1:18 am Post subject: heat probe

When my friend pre flights his R22 helicopter he has to check various little stuck on ‘heat spot indicators’, would these be of any help as I presume you only want to know if the temperature is hotter than it should be ~



John



Sent from my iPad



     ----x--O--x----

 	  Quote: 	
		  On 17 Nov 2020, at 9:22 pm, Charlie England <ceengland7(at)gmail.com> wrote:







On Tue, Nov 17, 2020 at 2:09 PM bobnoffs <icubob(at)gmail.com (icubob(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com (icubob(at)gmail.com)>

 

 i am looking for a way to measure temp. of a gearbox from the outside [no threaded holes]. my eis already has a lead for a resistive type 1/8npt oil temp probe. there must be flat, glue on probes available but i drew a blank with mcmaster carr and have no idea where to look.

  thanks, bob noffs

	
 

 If I had the proper 1/8npt probe on hand, I'd seriously consider just threading a small block of aluminum with a 1/8npt tap, screwing the probe into the block, and securing it with a couple of hose clamps if the location lends itself to that, or clean the location & glue the block  to the gearbox  with hi-temp epoxy (or RTV)   if the hose clamps aren't feasible. You can 'insulate' the adapter block with some silicone hose scrap, or just cover it with RTV. The interior will always be a bit hotter than the probe indicates, but that's the penalty for not having direct contact with the lube in the box.

Charlie



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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Wed Nov 18, 2020 4:30 am Post subject: Re: heat probe

i really need to know the temp as the gearbox is lubed by engine oil. temp will be relative to engine oil temp

 bob noffs

kjashton(at)vnet.net
Guest

Posted: Wed Nov 18, 2020 5:23 am Post subject: heat probe

I would think a cheap sparkplug CHT thermocouple tightly bolted to the gearbox and a CHT gauge would do it.  It is also pretty easy to make a bayonet probe that could be screwed into your NPT hole.  This will give you some links  https://www.canardzone.com/forums/topic/33499-edm-sparkplug-gaskets-high-temps/?do=findComment&comment=63661



If you only need 6-8 feet of CHT wire, send PM-me your address and I’ll send you some.  You just twist the ends together to get a CHT probe

-Kent



 	  Quote: 	
		   On Nov 18, 2020, at 7:31 AM, bobnoffs <icubob(at)gmail.com> wrote:

 

 

 

 i really need to know the temp as the gearbox is lubed by engine oil. temp will be relative to engine oil temp

 bob noffs

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=499421#499421

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Wed Nov 18, 2020 6:09 am Post subject: heat probe

On Wed, Nov 18, 2020 at 6:36 AM bobnoffs <icubob(at)gmail.com (icubob(at)gmail.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com (icubob(at)gmail.com)>

 

 i really need to know the temp as the gearbox is lubed by engine oil. temp will be relative to engine oil temp

  bob noffs

  	
Knowing that makes the solution a lot simpler; I was working on the assumption that you couldn't tap the lube reservoir. If it's pressure-lubed by engine oil, just use a return line fitting in the case that's tapped 1/8npt for the sensor. You can buy them already drilled & tapped, or drill & tap one yourself. Attached is an image of one I drilled/tapped, with the 1st 1/8npt fitting that was handy. If the return line is a -4, then use a T fitting with the sensor tapped into one leg of the T. (Complete info is helpful to help find solutions.)

That method will tell you the oil temp *after* the gearbox heats it up. Be sure of the mfgr's specs; if they spec oil *inlet* temp (most common for engine oil temp specs), then you'll scare yourself unnecessarily. Ideally, I'd want both inlet and outlet temps, so I could see temp delta through the box. If you only have one sensor input available on the monitor, you could achieve that with a simple double throw switch in the sensor lines.

If you don't like those ideas, you could always tap the drain plug itself for the sensor (if it has one).

Hope that's useful,

Charlie



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Charlie

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Wed Nov 18, 2020 6:21 pm Post subject: Re: heat probe

thanks for all the ideas.

 my gearbox has a drain line from the bottom of the box to the oil sump. engine oil is fed in the top of the box. my plan it to put a tee in the drainline and a temp. sender in the tee. i think with this setup i can watch for any changes in gearbox temps.

 bob noffs

yellowduckduo(at)gmail.co
Guest

Posted: Wed Nov 18, 2020 8:17 pm Post subject: heat probe

After many years of monitoring a couple of aftermarket psru's I found 

that temperature and real time vibration monitoring was of minimal use.  

Filter residue told the story but it might be many hours between oil and 

filter changes.  A magnet that can easily be checked definitely saved my 

bacon though.  One was In a brass T fitting such as you describe for a 

temperature sensor.  Even better is a magnetic chip detector with a 

cockpit warning light if there are significant concerns.

Ken



On 18/11/2020 9:21 PM, bobnoffs wrote:

 	  Quote: 	
		   



 thanks for all the ideas.

   my gearbox has a drain line from the bottom of the box to the oil sump. engine oil is fed in the top of the box. my plan it to put a tee in the drainline and a temp. sender in the tee. i think with this setup i can watch for any changes in gearbox temps.

   bob noffs





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=499427#499427

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Thu Nov 19, 2020 3:43 am Post subject: Re: heat probe

the chip detector sounds like a much more positive way to go than a magnetic plug.  i will look into that too. hopefully there are industrial ones that don't have the faa's million dollar stamp of approval. thanks.

 bob noffs

glastar(at)gmx.net
Guest

Posted: Thu Nov 19, 2020 4:41 am Post subject: heat probe

Hi Bob,



a friend of mine had very positive results with EATON,Part No: B3225C,

5/8" x 18 UNF



He did add this on a Rotax where he had a catastrophic engine failure

(and no metal in the oil filter).



Thttp://www.experimental.ch/wp-content/uploads/2013/05/Viktorwings_Chip-Detector-%C3%96l-Schnellablass.pdf

<http://www.experimental.ch/wp-content/uploads/2013/05/Viktorwings_Chip-Detector-%C3%96l-Schnellablass.pdf>



On 19.11.2020 12:43, bobnoffs wrote:

 	  Quote: 	
		   



 the chip detector sounds like a much more positive way to go than a magnetic plug.  i will look into that too. hopefully there are industrial ones that don't have the faa's million dollar stamp of approval. thanks.

   bob noffs





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=499431#499431

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Nov 19, 2020 5:38 am Post subject: heat probe

At 01:56 PM 11/17/2020, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com>



 i am looking for a way to measure temp. of a gearbox from the outside [no threaded holes]. my eis already has a lead for a resistive type 1/8npt oil temp probe. there must be flat, glue on probes available but i drew a blank with mcmaster carr and have no idea where to look.

  thanks, bob noffs 	


   That is a problem. Legacy pipe-thread temperatures

   sensors are of the thermistor type . . . which is

   CORE to the problem. Thermistors come in a constellation

   of characteristics for temperature vs. resistance and

   a host of non-linear curves.



   Does your eis installation manual call out a

   suggested part nu



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Thu Nov 19, 2020 11:36 am Post subject: Re: heat probe

i have looked into the temp sender and it appears to be a resistive single wire. i think these are very common. a cross reference # took me to one used in a cont. 0-200. sold by dynon so i think i have got that part. i was hoping for a flat, platelike sender compatable with my eis. i can make do with the 1/8'' npt type sender.

 bob noffs

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Thu Nov 19, 2020 11:45 am Post subject: Re: heat probe

i would be interested in reading about the chip detecter but the link didn't work. i can not find that part number.

 bob

johnbright

Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

Posted: Thu Nov 19, 2020 12:38 pm Post subject: Re: heat probe

 	  bobnoffs wrote: 	
		  i would be interested in reading about the chip detecter but the link didn't work. i can not find that part number.

 bob 	




It had an errant T in front of it. Here it is without the T.



http://www.experimental.ch/wp-content/uploads/2013/05/Viktorwings_Chip-Detector-%C3%96l-Schnellablass.pdf

_________________
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
N1921R links

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Fri Nov 20, 2020 3:31 am Post subject: Re: heat probe

the chip detecter looks like a good idea but i don't have a place to mount it. it is way over my head to drill and tap a hole in the gearbox case.

 maybe down the road it would be a job for someone competent when it is inspected.

 bob

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 20, 2020 7:54 am Post subject: heat probe

At 05:31 AM 11/20/2020, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com>



 the chip detecter looks like a good idea but i don't have a place to mount it. it is way over my head to drill and tap a hole in the gearbox case.

  maybe down the road it would be a job for someone competent when it is inspected.

  	


    Adding a pipe-thread hole in the casting is

    probably the easiest of tasks. Straight thread

    taps are not 'self aligning' and it's too easy

    to have your tap start cutting on a slightly

    axially mis-aligned orientation. Pipe threads are tapered

    and they start cutting with a minimum of attention

    to position and force . . . you can concentrate

    on axial alignment and the tap takes care of the

    rest.



    This thread begs some questions:



    Is this a flooded, pressurize gearbox?



    Fed with engine oil?



    Are there any instances of field failures due

    to degraded gearing?



    Were these judged to be conditions long-in-the-

    making that MIGHT have telegraphed impending

    failure by increased temperature, metal

    chips in oil, noise, etc?



    What are the recommendations of the manufacturer

    for monitoring gear box condition?



    If it is judged that addition of any sensors

    by penetrating the gearbox case is a good thing

    to do, where is the best place for locating

    those sensors. There will be optimum locations

    after consideration of structural issues, temperature

    gradients, optimal chip-congregation points, etc.



    If this box is lubricated with circulated engine

    oil, then I'm skeptical of the value of adding

    any single temperature sensor. You've got hot

    oil coming in. You'll want to know TEMPERATURE

    RISE attributable to gear box wear.



    What is the experience of the user community

    with respect to this topic? It naturally seems

    like a cool thing to add such sensors but

    before you venture forth, it would pay to know

    if such sensors are KNOWN to be effective along

    with protocols for interpreting what a temperature

    gage is telling you.



    I seem to recall a similar discussion many moons

    ago on another forum . . . perhaps Compuserv AVSIG

    . . . wherein a reader suggested that the best

    harbinger of impending gearbox doom was a dial

    indicator he could firmly affix to some part

    of the airplane to measure backlash in the gearing.



    The observed number would rise noticeably long

    before the gearbox trashed.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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Bill Allen

Joined: 24 Aug 2009
Posts: 42
Location: UK

Posted: Fri Nov 20, 2020 9:21 am Post subject: heat probe

Most chip detectors fit where the drain plug goes. You can get them from

salvage yards where they break helicopters. That’s where I got mine

yellowduckduo(at)gmail.co
Guest

Posted: Fri Nov 20, 2020 10:00 am Post subject: heat probe

A few folks have made their own chip detector.  A pair of metal probes 

with a magnet epoxied into a pipe plug. Where possible expose it to oil 

flowing in a line going to a filter.  It's important to catch bearing 

failures before they progress too far and periodic oil and filter 

changes may not be frequent enough.

Ken



On 20/11/2020 11:47 AM, Bill Allen wrote:

 	  Quote: 	
		   Most chip detectors fit where the drain plug goes. You can get them 

 from salvage yards where they break helicopters. That’s where I got mine.



 On Fri, 20 Nov 2020 at 11:42, bobnoffs <icubob(at)gmail.com 

 <mailto:icubob(at)gmail.com>> wrote:



     

     <icubob(at)gmail.com <mailto:icubob(at)gmail.com>>



     the chip detecter looks like a good idea but i don't have a place

     to mount it. it is way over my head to drill and tap a hole in the

     gearbox case.

      maybe down the road it would be a job for someone competent when

     it is inspected.

      bob





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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Fri Nov 20, 2020 4:29 pm Post subject: Re: heat probe

I admit adding a chip detector is a stretch but I think a temp probe could be valuable. You are not looking for absolute temp  but a trend compared to engine oil temp. 

 If I had a gearbox with a hx of failure I would probably be looking for another gearbox. Kind of like having an engine oil analysis. Maybe I will see something coming

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