Tuesday, 9 October 2012

In the Heat of the Moment - a Brakedown

Spookworks Boffins take a brake to talk about heat and er....the Sun

Those big shiny things behind the wheel are called brakes.  They make the car stop. 

We have let one of the Spookworks Boffins out of the labratory and asked him to come and talk to you about brakes and heat and how the Spookworks Impreza brakes cope with heat.  Fascinating stuff, so I suggest you either grab a  pillow and some strong coffee and sit back and enjoy....

Thank you, well the first thing we need to do is become familiar with the partial differential equation.  Using the Cartesian co-ordinates against a time variable you can see the laplace variator and its corresponding thermal diffusivity.   

You put the coffee in first, then add the milk and sugar; then stir...

It is the prototypical parabolic partial differential equation and is connected through probability theory to the Brownian motion and the Fokker Planack equation. Now taking into account "donk"...

Mark 1 hammer - useful for so many things.

Sadly the Spookworks technical boffin has had to take a brake so I will carry on on his behalf...

Spookworks is fortunate to have Alcon on board as part of the team, and as we all know they simply make the best brakes in the business.  Here at Spookworks we have been having a bit of an issue keeping the brakes cool and every 3 or 4 events we end up cooking the brakes and warping the discs. 

Only to be expected in a 1300kg rally car hammering the brakes for 50 -60 miles each event. So in conjunction with Alcon we set about trying to measure how hot brakes actually get and having conducted measurements during a live event we though we would share the data with you. 

First thing is you need a new set of discs with some of this really cool heat temperature paint on them. You can see it on the top of the disc in green, orange and red. These colours change with heat and therefore you can tell how hot the disc is getting by the different colours.  Easy! You will notice 3 stickers on the top of the caliper, the side of the caliper and the disc bell.  

Nice new Alcon disc with temp paint at top of disc and temp stickers on caliper (top and side) and on the disc bell.

After each stage the crew would immediately jack the car up and record the colours of the paint and the temps indicated on the stickers.  The green turns white at 460 degrees, the orange turns yellow at 550 degrees and red turns white at 630 degrees. If it gets any hotter than that, the indicators are the car is on fire or a liquid metal puddle underneath where the brakes used to be.

So after 4 stages here are the results:

So what can we make of this information.  The brakes get pretty hot at 550 degrees Celsius.  For example the front brakes on the Spookworks Impreza are:

89 degrees hotter than the hottest planet in the solar system (Venus 462 degrees C)

1/10th the temperature of the Suns surface and 1/27,000th the temp of the Suns core. 

16 times hotter than the hottest place on earth (Dallol, Ethiopia)

15 times hotter than a human being

Just under half the melting point of steel (1370 degrees)

1/1,000,000,000 of the hotness of Sky News Presenter Sarah-Jane Mee

 Here are some pics of the brakes and you can see the colour changes of the paint and the temp strip on the caliper.  These will now be monitored for the next few events to determine why we seem to be warping brake discs.

The sun - only 10 times hotter than Spookworks brake discs after 11 miles.  That's actually pretty cool...