HOT HEADS CAUSE TROUBLE-KNOW WHEN TO COOL IT: K thermocple DIY

[motoman]

HOT HEAD DIY...K WIRE JOINT TERMINATION

Apparently the manufacturers join the K wires "hot end" with an electric weld. Not tried ,but you may read about hooking up car batteries to produce the "ball." Sounds risky. The metal of the two K wires is slightly different versions of nickel alloy ; one is magnetic (-). Termination techniques vary from twist (seems weak), peening, crimping, and gas weld. The ball is the instant temp pickup contact, and can be configured for surface, gas or fluid measurements. Tin/lead solder may work , but may loosen due to reflow temps at head. Silver solder and braze should work, but fluxes must be removed.

 

[motoman]

HOT HEAD DIY...SPARK PLUG CONNECTOR

Cut off your plug sealing washer. What follows is Intek 24 , my only ref. Measurements for this effort: (1) washer seat .830" OD, width .165" NOTE: the washer seat is counter-bored with a ridge at .831" (2) Plug thread OD .548", plug washer thickness .059". (3) K washer material (here) plain or stainless steel . Pictures online look like copper.

A note on the pics below which may confuse. First attempt was wire rivet butt- brazed to washer. This did not work out. Too weak. The picture series is included because it contains other useful views. (pics lost in cyberspace and reappeared). Tractor has gas weld version.

Start with a washer OD large enough for a 1/8" by 1/4" grip pop rivet hole at the outer radius (1/8" drill). The washer is drilled for the pop rivet as a wire barrel. Blue (marker pens work) and scribe the desired OD and barrel tab. Then reduce the OD to .830" except for the tab. Drill tab.

More clarification: In third pic a solid ("chinese") K wire setup is shown Two wires inside the white jacket. As you may know I did not use this style, rather the cable with stranded wire. But this shows how the "purchased" solid wire comes to you with a male K connector. The balled end is not shown. As noted someone should try this style to see if it can take the vibration and (possible) external noise interference. Geeze what a patchwork I created.

 

[motoman]

HOT HEAD DIY...GAS WELD, CRIMP, ROUTE

Used big oxy/acetylene torch. Smallest tip with 3 psi oxy-acetylene. Flame tiny, just enough so it does not "pop out." Make the K wire ball contact now if you need to. (either stranded wire or solid), and the barrel to washer weld. Did not fuse weld. Grind down a 1/16" steel rod end to a small diameter. A little dab will do 'ya. Get in and get out asap both tasks. I used a vise to just expose the wire ends for the ball contact. ( A jeweler's torch is perfect here).

Your washer must seal the plug. Blue it and torque lightly (12 ft lbs) . Read contact both sides. Improve it if necessay. RE blue .Retorque full (15-20 ft lbs) read , correct if necessary. The wire barrel may be bent away slightly to clear boot. No leakage permitted at seal!! FIRE hazard and lost power. Slide heat shrink onto wire above crimp. Crimp the balled K wire into the wire barrel. If you route wire from plug to cowl thru a SMALL HOLE you must connect the K connector from the tractor seat. With solid wire should be no problem. With stranded wire this is difficult. The left pic does not show K wire, just mock up.

Again and to answer panabiker question about wire shown on head pic below. Sorry , folks, bad choice for DIY. That wire is NOT K wire. The K wire is shown in other pics as red/yellow and welded ball. Panabiker is right about extending K wire- regular copper apparently can be used , but only to "cold" end which is thermometer. Sometimes long runs require this e.g., VW bus. Not on our stubby tractors. OK?

 

[panabiker]

From the picture on the left, did you just make the K junction from two regular, plastic shield copper wires? My understanding is that you have to use the special K thermocouple wires to form the junction.

 

[motoman]

From the picture on the left, did you just make the K junction from two regular, plastic shield copper wires? My understanding is that you have to use the special K thermocouple wires to form the junction.

Please see edited correction above.

 

[motoman]

OK, Initial 3-temp readings with the installed Bedee oil temp gauge (sump), sump K, and head K.

Ambient 78F
Bedee, Sump K, Head K, Activity
195F 176F 215F lite haul
225F 208F 268F cut weeds out chute
230F 216F 260F dry leaves bagged

 

[motoman]

T HEADS DIY...MISCELLANEOUS

CONDUIT Brake line should work as a conduit for the white, solid K wire. This line may also work for (electronic) shielding. The ends would require foil or ? It is easily formed for routing.

CHT GAUGES Reality check. Why go K thermocouple and not the kits for $80-$100? Latter are resistive type, non linear and may be wildly inaccurate. Classic bench tests show error of up to 60 F.

DUAL INPUT Want to look at two areas at once, like both cylinders? Two channel thermometers are available at low cost..

KITCHEN CALIBRATION Check accuracy of your set up with ice water (32F) or boiling water (212F)

PLUG RING CARE When the spark plug is tightened or loosened hold the ring in place, square, during swivel action. Should not follow plug around. If it hangs up open the ID slightly.

READING Curious about the effect of 300 F plus on the head (s)? Try:

aagaskets.com; liquidcooledairpower.com; enginehistory.org; sut.ac.th;
en.wikipedia.org/wiki/refractory_metals; afsinc.org;

 

[panabiker]

...
CHT GAUGES Reality check. Why go K thermocouple and not the kits for $80-$100? Latter are resistive type, non linear and may be wildly inaccurate. Classic bench tests show error of up to 60 F.
...

I thought most CHTs do use thermocouples, either K type or slightly more expensive J type. The problem may be that the meter they sell in the kits lack the ambient temperature compensation circuitry to display the hot junction temperature accurately.

 

[RobertBrown]

Very interesting and very relevent.
Since you have collected, and have the technology to collect data, it seems to that determining the effect of ambient temp on engine temp is something we could all use.
Can you graf the effects of engine temp rise as it relates to ambient temperature rise????

 

[motoman]

I thought most CHTs do use thermocouples, either K type or slightly more expensive J type. The problem may be that the meter they sell in the kits lack the ambient temperature compensation circuitry to display the hot junction temperature accurately.

I am not an expert, but I have spent a lot time on line. The motorcycle sensors must be resistive as their sensor heads resemble coolant sensors (brass tubes) and there is no talk of K or or temp compensating features ( the digital K thermometers have a Tc button to push which adjusts the cold end to ambient rather than some estimate like 72F ambient. I guess some aircraft ( at least some, maybe all) use the K . What is a little confusing is that a lot of the $280-$3000 units show 28v, but that could be back lighting. I have seen that resistor sensors can be very accurate, but very expensive. Amusing and impressive is the widespread use of the K on the new wave of scooters and of course the go cart guys have used the K for years.