[PilotjohnS]

I want to put a thermal couple on each brake caliper. With the g3X system, I can have a readout of brake temps using the aux temp sensor input on the GEA24.

What location on the brake caliper is best? I plan to just attach with JB weld.

 

[Bsquared]

I don’t think it will make much difference where you put it on the caliper. The heat is generated due to the friction at the pad/rotor interface and it will take some amount time for the heat to soak through to the caliper. The caliper temp will normalize pretty quickly once the heat gets to it so just about any location should should provide similar results. I worked for a company that made brake temp sensor systems for Boeing and some biz jets and brake temp lag was always an issue. I believe most airliners use brake temp to determine if the wheels are too hot to depart on the next flight and not something you react to during landing.

 

[lr172]

I don’t think it will make much difference where you put it on the caliper. The heat is generated due to the friction at the pad/rotor interface and it will take some amount time for the heat to soak through to the caliper. The caliper temp will normalize pretty quickly once the heat gets to it so just about any location should should provide similar results. I worked for a company that made brake temp sensor systems for Boeing and some biz jets and brake temp lag was always an issue. I believe most airliners use brake temp to determine if the wheels are too hot to depart on the next flight and not something you react to during landing.

+1

If you are looking to observe whether or not you brake will hold out during a stopping event, that is never going to happen. no sensor is going to predict that as the heat is between the pads and the rotors contact area and there is no real way to get sensors in that area. If looking to whether or not take off is safe after landing, It would take A LOT of testing to correlate caliper temp relative to pad/rotor temp and then you need the critical temp for brake fade as well as cooling profiles for various components. You'll also need the thermal coefficiency of the JB weld. They make special epoxies for use in thermally conductive applications. For general long term trends that is no big deal, but it is if you are looking for quick sensor reaction.

 

[skypilot737]

Brake temp sensors

I put them on my RV-7a on the open threaded hole on the Matco brake actuator. I purchased a thermocouple that was designed to go under a bolt and bolted it to the brakes. I then ran the wires up the gear leg and then to my display. I have a dynon system that allows thermocouple connections. You do need to make sure that you have the right kind of thermocouple type and wire for your display. I bought mine from Amazon for under thirty dollars if memory serves.
My goal was simply to know if my brakes were getting too hot for my fluid o ring combination. I heard a few stories of people over heating their brakes and loosing their fluid out the bottom of the brakes. So far the most I’ve seen was 150 degrees when I was doing stop and goes. I recommend it so you know how hot your brakes are vs guessing. BTW my company didn’t spring for the brake temp gauges at work and it is a complete guessing game.

 

[rdamazio]

Just a thought: while a thermocouple wouldn't work, you *could* use an IR-type sensor inside the wheel fairing that's aimed at the disc (at a point just after it loses contact with the pad?) and measures actual disc temperature. Getting it right and properly calibrated will be a good amount of work, but could be a fun project.

One such sensor: https://www.texense.com/en/infkl-800degc-ir-brake-temperature-sensor-33.html

 

[rv8ch]

Having this temperature would be very interesting, but not sure how useful it would be.

IIRC, DanH did some calculations that showed that the RV disks are sized for one full braking event before they need to be cooled down. So, if you land and brake hard, or have an aborted takeoff that requires hard braking, go shut down and have a coffee.

If you plan some T&Gs, you need to consider how much you use them and how much time you give them to cool off before the next landing. Don't underestimate the amount of heat generated when taxiing if you use brakes.

Keep us posted on your progress.

 

[PilotjohnS]

Purpose?

I guess I need to decide on the purpose for the temp sensor. I was thinking about info just to know how hot the brake fluid is getting to avoid destruction of the seals and a brake fire. I guess I dont care about how hot the disc gets because that doesn't lead to any kind of failure or fire. (Unlike an airliner, I have never heard of a tire failure due to brake temperatures on our small planes).
I think I will put them on the caliper with JB weld. Someone mentioned using a special thermal glue; I dont think that is necessary, and I can show the math why.

I’ll report back in a few months after my first flight.

( and thanks for the data, very helpful) maybe i will glue some shinny foil on the wheel pants where they are closest to the brake rotors)