REFLECTOR: The law of conservation energy.

[Ron Brown]

I have the XT upgrade to my MATCO's and have worn out one set of pads.  They wore out evenly - both sides and no tapering.  Perhaps the weakness existed in the original design but I don't believe that is the case with the XT's.

Again, I have had good luck with my MATCOs on a 173 Elite RG and I fly off a "short" runway and have to use the brakes more heavily than most folks.  In fact, I had a recent landing where I came in high and hot with shifting winds and wound up touching down half way down the runway.  I had to get on the brakes pretty hard - enough to hear the tires squeal (but not lock) and there was plenty of stopping action and no fade.

If you generate too much heat back there, you'll wind up installing the $800 aluminum main gear boots!!!

Ronnie
  ----- Original Message ----- 
  From: Brainard, Jerry 
  To: Velocity Aircraft Owners and Builders list 
  Sent: Tuesday, March 18, 2008 1:38 PM
  Subject: Re: REFLECTOR: The law of conservation energy.


  I think there another huge difference.  That's the stiffness of the caliper assembly.  The mass of the rotor does not appear to be enough different to account for the braking difference.  If it were just the mass cooling of the rotor, it would be a brake fade problem.  That does not appear to be the case.  The Matco's seem to be weak in initial and extended braking.  As you pointed out Larry, the arm is not the important difference, it should be the amount of the heat absorbed and dissipated.  Of course all of that assume that you have correct pad contact.  The Matco's do not appear to have sufficient strength across the caliper.  The beautiful piston side looks plenty strong, but the same cannot be said of the opposite side.  The bolts might be enough, but the backing plate looks to light weight to stay in contact as pressure increases.  That would lead to a hot spot on the inside edge that would quickly lose braking effectiveness due to gasification of the hot spot.  If you look at other braking systems, they have a more robust caliper on both sides of the rotor and a very stiff junction between the two side.  The objective is to keep both pads in even pressure on the rotor.  Obviously, it would take a brake dyno and some creative testing to confirm my hypothesis.

  - jerry




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  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Laurence Coen
  Sent: Tuesday, March 18, 2008 1:05 PM
  To: Velocity Aircraft Owners and Builders list
  Subject: REFLECTOR: The law of conservation energy.


  Any vehicle, (plane,train, auto) that uses friction breaks to stop converts kinetic energy, (speed x weight) to heat.  Therefore, Cleveland or Matco, the same plane at the same speed will make the same heat.  Why then do the Clevlands stop better than the Matco?  The Clevlands larger diameter disk provides greater braking torque for the same friction due to the longer moment arm but the increase in diameter also increases the surface speed at the same wheel rotational speed and therefore the same heat (no free lunch).  The larger disk has two things going for it.  A larger thermal mass to absorb heat and greater surface area to reject heat.

  Larry Coen
  N136LC
  SE/RG Franklin/IVO, Stops fine Matco

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