XML Brake TEMP?

[Engjell Berisha 1]

Does it even exist I've been looking for the code for ever and I still got nothing. I'm just trying to get a string to show me brake temperature, thats all, nothing more but IDK how to do it in any other way then XML.

[WarpD 824]

I don't think there's a variable in FS that provides brake temp.

[Engjell Berisha 1]

Anyway I would go about this? Is there a wheel temp variable or something related to the brakes that would give me a temp close to the brake temp.

[Chuck_Jodry-VJPL 663]

Perhaps you could measure the time brake is applied and wheel rotation ,and link that to an animated needle or a dialface , putting a fair bit of lag on the rotational animation , if you were to link this node to another that read the OAT it would baseline there.basicly you fake it , mind you i am thinking modelled gauges in the vcand you are talking string values for a gauge

[taguilo 33]

No there is no wheel temp var in FSX, a reasonable thing because it's not something that could be simulated in a generic form.Does your aircraft measure direct temp or instead an index like 0 to 5, as some airliners use (ie 757/767) ?Tom

[Engjell Berisha 1]

The aircraft I'm trying to do this for is the C-17 and it gives the actual Celcius reading.

[WarpD 824]

heat=fpV, where f is friction coef, p is pressure, and v is velocity.

[Engjell Berisha 1]

Does that mean that I can get it to give me a brake temp reading? And if so how I didn't quite understand what you said mate.

[WarpD 824]

That's the formula... it's basic physics. It's not part of FS, as I said FS doesn't supply brake temp.Pick a friction coefficient of a known brake pad in the real world (just find one on the internet)... determine braking pressure based on max hydraulic pressure versus amount of brake applied (just a value to use)... get velocity from ground speed. That should give you something to work with.

[WarpD 824]

Assuming the following:f = friction coefficient of the brakes = 0.50p = pressure of the brakes = 3200 psiV = velocity = 250kts250kts = 128.6 meters per second0.50 * 3200 * 128.6 = 205760 joules205760 joules = 108 degrees C = 227 degrees FThat make it clearer?

[Engjell Berisha 1]

Awesome mate!!!Now can I put that into code so that flight simulator could do the formula and give me a figure on the brake temp? And if I did the Friction Coefficient of the brakes and the Pressure would be constants right? The only thing that I would put as a variable for FS to understand would be the V and it would plug that in with my GS?

[mgh 89]

The formulas are wrong.0.50 * 3200 * 128.6 = 205760 joulesGiven that the friction coefficient (0.5) is dimensionless the LHS of your equation is:pounds/square inch * Metres/secThat is an incompatible mixture of Imperial and SI units and doesn't give Joules which are Newton*Metres and represent work/energy/quantity of heat. Even converting pound/sqare inch to SI units (Newtons/sq metre) the LHS becomesNewtons/sq Metre) * (Metres/sec) = Newtons/(Metre*Sec)which is still not Joules.205760 joules = 108 degrees C = 227 degrees FTemperature is different unit to a Joule and there is is no universal relationship between them.

[WarpD 824]

>The formulas are wrong.>>0.50 * 3200 * 128.6 = 205760 joules>>Given that the friction coefficient (0.5) is dimensionless the>LHS of your equation is:>>pounds/square inch * Metres/sec>>That is an incompatible mixture of Imperial and SI units and>doesn't give Joules which are Newton*Metres and represent>work/energy/quantity of heat. Even converting pound/sqare inch>to SI units (Newtons/sq metre) the LHS becomes>>Newtons/sq Metre) * (Metres/sec) = Newtons/(Metre*Sec)>>which is still not Joules.>>205760 joules = 108 degrees C = 227 degrees F>>Temperature is different unit to a Joule and there is is no>universal relationship between them. To be blunt, you've just jumped into something as if you're the world's foremost expert on the subject. Well, you're not... and you're wrong. End discussion. Seriously.

[martinboehme 492]

> End discussion. Seriously.Erm... why? He has a number of good points.First of all, your equation is for power, not heat (which is power times time). That's why the units don't work out.Second, the "pressure" in your equation is kind of misleading, because "pressure" in physics is usually force per unit area; what you mean is the force applied to the brake pads. That, multiplied by the coefficient of friction, gives us the retarding force. That in turn, multiplied by the velocity (of the brake disc going past the brake pad) gives us "power" (i.e. the amount of kinetic energy we're dissipating per second), as per your equation. We would have to multiply this with the length of time that the brakes were applied to get the amount of energy dissipated, or heat.Third problem is, this amount of energy still doesn't tell us how hot the brakes are going to get. First of all, this would depend on the specific heat capacity and the mass of the components that we're heating; additionally, we're losing a lot of heat to the environment, and this effect depends on the speed of the air going past the brakes. I would say that it's very hard to model / calculate all of this accurately from first principles... I would guess that addons that simulate brake temperatures do this using data that was measured on the real aircraft.Cheers,Martin

[ozbeowulf 0]

Might I suggest that too much effort has been invested in the straining of gnats?Don't overwork the physics; look at the desired output and work with the cause and effect relationship. When the cold and dark aircraft is sitting on the ramp, the brake temperature is the ambient temperature as shown on the OAT gauge. Let the code change the temp variable by a small percentage each time it refreshes. Adjust the variable pos/neg value and the gauge refresh rate so the temp increases slowly whenever brakes are applied and decreases slowly (but never below ambient) when brakes are off. If you want to get fancy, introduce an aircraft speed variable to the process. Test-taxi the aircraft (including aborted takeoffs) and adjust values as necessary.In the end, you'll have a gauge or gauges that follow the dynamics of the brake heating/cooling cycle. It won't be perfectly accurate, but sometimes we have to accept that FS9 cannot model reality to the nth degree.Cheers,Glenn