Aardwolf

Has anyone put a Pyrometer on their rotors? Would this be helpful for detecting fade ahead of time? I was just thinking about it. Is there a different type of monitor for this purpose? There would have to be some type of swivel because of the rotor turning, that might wear out or clog. I am just wondering though. Thanks.

Andrew

AU N EGL

Rotor paint. put some on the edge of the rotor. Paint turns color to what the highest temp attaned

davidfarmer

too hot, use rotor paint.

you can use an infrared pyro on the "hats", but the rotor surfaces get too hot. Measuring the hats can give you a ballpark idea of the relative temps, front to rear, for instance, but not actuall friction temps.

Paint on the outter lip of the rotors is the right way. Don't get the all-in-one paint, get the kit with multiple colors.

Slalom4me

As for mounting, the pyrometer sensor can be effective operating in
proximity. Here are probe and a ring-style Type-K probes as sold for
the G2X data logger. It isn't a high priority, but I'd like to add oneor two to get traces to complement the line pressure sensor I have now.





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John Shiels

Wilwood or AP sell tape which tells the temperature where you place it like on the calipers or hub. Ten bucks or so.

Aardwolf

How does your line pressure work? One on each corner? I thought of tape or paint but this wouldn't help while on the track. If I work the brakes real hard, I know there will be fade at a corner, but I can't really tell without trying the brakes. If I could see the temps on the dash I could at a glance see how the brakes are doing. It seemed like a neat idea anyways. That is interesting the sensor can work in proximity. A dual pyrometer could monitor both front calipers or monitor one side of the pad, rotor, or caliper.

Solofast

Putting a thermocouple on the rotor isn't difficult, it's just expensive. You need what is called a slip ring, that will allow the transmission of thermocouple junction data from the rotating hub to the spindle. Won't go into the details here, but suffice it to say that the technology is there to do either with slip rings, telemetry or optical temperature sensors.

While brake rotors get really hot, fade is primarily a result of either pads going away (too hot) or fluid boiling, and caliper temps are really the the most reliable indication of both of those situations. Once calibrated you can see fade coming and could likely back off a bit on braking and get temps back under control.

You can easily put a thermocouple on the caliper, I did it for some engineering consulting to win a lawsuit against one of those "dust shield" manufacturers. (The "Kleenwheels" resulted in what they call in rally speak a "straight at T" incident...... and totaled a Bimmer when the brakes faded). We imbedded the TC in the caliper, to get away from the surface temperature effects. If you are blowing a lot of air over the caliper you will be reading the surface temp and not it's core temperature (which is what is important). The temps inside the calipers didn't respond all that quickly, which is why you can kid yourself by looking just at caliper surface temperatures, even with thermocouple on the caliper. Putting heat tape or paint on a caliper is pretty much worthless if you are blowing much air over it, you need to be putting it where it doesn't get much airflow if you are going to get any good information.

Still it is all just a energy balance, if you don't take out as much heat as you are putting in each lap, the temps keep rising until things go soft.

davidfarmer

I'm sorry, I thought you were looking for setup purposes, not real-time readings. For what you'd spend in a setup like above, you could put on a set of larger brakes and wheels, and with propper cooler, wouldn't have heat related problems.

Aardwolf

Well Thunder racing has the gauge and probe on sale for $136, so not so bad in price. The key would be finding a place to read that would actually help.

Imbedded in the caliper, did you have to drill a hole?

Solofast

In that case we did because we were trying to compare their data (that was measured on the surface and said that the temps didn't go up significantly) with what was really happening in the caliper (fluid boiling). I haven't looked carefully at our calipers to see if there is a good place to put a thermocouple that would get you any data that is of any use. If you can put it outside of the breeze, back near the piston that might work pretty well. The best spot would actually be to put the TC on the piston in the recess behind the pad. Then you are reading basically the fluid temperature. If you put a small groove in the back of the pad you could put a high temp thermocouple lead in the piston cup and tack weld it down with a strap of .002 shim stock and that would work. That is what we do to instrument turbine engines and it is pretty much "industry practice" for us.

As an aside, I am suprised that somebody making the brake pad shims hasn't put a TC on the piston or in that area and compared a before and after so that they could advertise how much good it did to cut the heat transfer to the pistion.

robvuk

Are you saying that those dust shields actually caused the brakes to fade on the street? That Bimmer must have had the littlest brakes ever or the guy was driving waaaay beyond street legal speeds.

Slalom4me

While that is possible with four sensors plumbed into the lines for the
respective corners, I have a single sensor. With adapters, I install it in
the front circuit at the master cylinder. With different sized fittings,
the sensor can be switched to the rear circuit. The OEM line fittings
remain intact.

Here is the G2X Brake Pressure sensor


Regarding probe placement. For my purposes and budget, I am confident
that a probe in near proximity to the caliper and rotor will provide me with
enough information to make useful judgements. I understand that others
will need/want more precise readings and have the budget to obtain these.
I enjoy seeing/reading about how that is done but it is beyond my needs.

Or monitor fore & aft brakes.

Of course, with TWO dual reading gauges ...

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Slalom4me

Actually, the sensor shown above is an oil pressure unit. The
G2X Brake Pressure sensor has a different body shape - but
the image conveys the idea.

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Aardwolf

This sounds like a decent idea? I think I will put it on my bench as a new project.

Your are thinking of putting a temp probe on the caliper to? What are you looking for in the pressure gauge? Is that for seeing air in the line or that the booster is working correctly?

AUTO_X_AL

The racer I mentioned above had his square in the middle of the pad. I can't remember if it was inside or out but he had drilled a hole into the pad and threaded a thermocouple right in the center of it. It was amazing to see the variance in temps in real time.

Slalom4me

The ideas behind pressure gauge were to quantify things like fr:rr bias,
line pressure relative to braking G's and so on.

The datalogger has unused channels. Adding traces for brake heat seems
interesting. It is easy enough to do but it will wait until other matters
are caught up.

.

Aardwolf

I see, interesting! It would also be nice to know there is pressure and there wasn't a failure. I will try the idea and see how it works. It won't waste much money if it doesn't help. Perhaps the gauge can show how much the ducts help to, or where directing the duct helps the most. I can think of many uses for this!

Solofast

Well, no they weren't really driving at normal speeds or conditions, they were "Cannonballing" an SCCA TSD night rally. That's where you and a few people decide not to go for the real cast speeds, but go for "lowest ET" of the night......

They were ok untill the got hung up at a checkpoint that was right after a section that was braking intensive... without any cooldown the fluid boiled and they left the checkpoint, came over a rise at speed and found they had no brakes at all. Hence the "straight at T" into a farmers field. Fortunately they missed the barn, but the Bimmer was a write off... I think it was a BMW 325 about circa 1985 and I simply don't recall if it had vented rotors or not....

What was suprising was how much faster the dust shields resulted in fade. With a normal car the air from under the chin is pulled by the low pressure air thru the wheel well and out thru the wheels. If you block that off things cook pretty fast. I would have to look at the old stuff that I did for the lawyers, but I seem to recall that it only took about 10 or so stops from 60 to fade out the brakes with the dust shields on, and more than 20 without them. (I was the taking the data during the testing and was about carsick by the time we were done accelerating to sixty and immediately hitting the brakes and then doing it again and again). While they did it in a really big way, I would think that a spirited run down a mountain run with the dust shields could easily get you in trouble.