Tim - I did this a while back.
I drilled a small hole in a fin closest to the plug and as low as possible.
I then secured an iron-constantan junction (J-type) to the fin with thin copper wire and coated it with transistor heat-sink compound.
As I recall (40 years ago) the temperatures were around 250 degrees F.

  Bob Z.

U.S.Sensors makes temperature sensors up to 450 °C, bolt-on and threaded.

I use a laser thermometer when running new engines on my test stand, but it's a bit tricky to aim at the narrow side edge of the head, or the top of the cylinder head. Anywhere on the cylinder won't work well, because it will give you a large range of readings from top to bottom!

Bill

I was thinking of something that I could run in flight, recording with a TUT.

  I just started working for a plastic molding company this past spring, and in working on the MANY different type of molds, there are lots of ways of heating things and this requires small thermocouplers. They are held in place on the various cores with sheet metal clamps and small machine screws. Should be easy to figure a way to secure the end to an engine cylinder. I would put it against the cylinder right above the exhaust, or in the path of the exhaust flow. When I get to work Monday I will get the names of some of the suppliers, but that may be easy enough with a google search of injection molding suppliers.
  Type at you later,
   Dan McEntee

Horizon sells temp sensor for their telemetry packages

Helicopter and jet folks use the engine temp sensors quite a bit and from what I see the RC set up through the Rx back to the Tx is using a RS232 data standard

perhaps a el cheapo Hobby King system can be used to backwards engineer it to use with the TUT

Tim,
I would think you need as instantaneous response as possible, not sure where geographically on the engine that would be, but suspect perhaps that two regions would be valuable
something like an exhaust temp would be a valid number, and you would want measure someplace as close to the temp generation as you can. admittedly aluminum transfers heat rapicly,but depending on what you are trying to accomplish would dictate where to place the temp sensor right?

Tim,
I would think you need as instantaneous response as possible, not sure where geographically on the engine that would be, but suspect perhaps that two regions would be valuable
something like an exhaust temp would be a valid number, and you would want measure someplace as close to the temp generation as you can. admittedly aluminum transfers heat rapicly,but depending on what you are trying to accomplish would dictate where to place the temp sensor right?

I'm making the (possibly erroneous) assumption that head temperature would be a pretty good reflection of how the temperature of the engine is affecting the run -- i.e., running away, dogging down, etc.

I'm mostly interested in the relationship between engine overheating (or overcooling) and the run, and in how jiggering the cooling ductwork affects engine temperature.

Using a strip of thin copper I made a plug washer with a short tang on one side bent up to clear the head fins where the thermocouple was attached to. My figuring was that all engines have a virtually identical thickness of metal above the combustion chamber so should give reasonably good comparative readings.

That's a good idea. After-market CHT gages for full size aircraft are the same: Replace the plug gasket.

I installed EGTs on an VW aero conversion and found the max heat was not close to the head...but approx 8" toward the exhaust tip (it had open exhaust pipes with a sensor on each pipe). It took a few tries to find the sweet spot but lesson learned was not to place the sensor close to the engine.  EGTs worked fine on the spark plugs. I think it should work the same on glow engines. If I did it again I'd probably try shooting an infrared at it to get the hot spot.

You can easily make your own from a 1/4" ring terminal.  Solder or crimp the thermocouple to the ring terminal flange.  You might have to bend to fit .....

Tim,
you could just bond the TC to the head at whatever spot you want using JB Weld. We use a hysol product at work but it is pretty much the same thing.

What TC amplifier are you planning on using on the TUT? I have had good luck with the MAX6675 for K type TCs.

Not to side track too much but I would be curious to hear your thoughts on using a pitot tube air speed sensor as one of the gain factors.

There are groups out there that are basing autonomous piloting on the use of the new 5 dollar Linux single board computer RasberryPi Zero. One of the parameters they can watch and react to is sir speed.

http://erlerobotics.com/blog/home-creative/

Mark

Very interesting Tim.

I have a bag of K type thermocouples here from previous projects. I will send you some of them if they look useful. You can pick up a MAX6675 (or the TC amp of your choice) breakout board on ebay, Adafruit, or Sparkfun, for about 10-20 bucks.

The thin ones are welded tips. I think there are three in there. The thick one has a fiberglass braid over the wires. It has not been welded. You can twist the ends together to form the junction though.

Pics attached of TCs