REFLECTOR: Brake performance

Tue Mar 19 08:20:30 CDT 2013

Kevin, I am not sure about your question but I will give  you my experience. When I first got my aircraft, the second one built by factory, it had Cleveland brakes. I upgraded them because of brake fade. That made a big difference, and no fade. A couple years back I converted to the toe brakes which had the master cylinders attached to the pedals and one reservoir. That made landing without having brakes on but I didn’t see any difference in stopping power.

From: Kevin Baker 
Sent: Tuesday, March 19, 2013 1:26 AM
To: Velocity Aircraft Owners and Builders list 
Cc: Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: Brake performance

For those folks that had original pedels that upgraded to the toe brakes did you notice any diff utilizing the same calipers?

Thanks
Kevin Baker

.

On Mar 18, 2013, at 11:26 PM, Kurt Winker <nmflyer1 at aol.com> wrote:

  I find this brake exercise interesting. I have been watching brake posts for some time. Consequently, when an upgrade was announced for the 173FGE Matco brakes, I sent them in for an upgrade. 
  These things are Huge! 
  The interesting thing is, the brakes on my Cherokee 235, are comparatively tiny. In fact, the calipers are the same size as the ones on my J-3!

  I do not have toe brakes in my 235, just the old hand brake. I have always found it sufficient, and in fact I can lock them up at 2900 lbs, if I want to. 

  The J3, no way will they lock up, even though it weighs under 1000 lbs...(but if you aren't careful you can raise the tail uncomfortably high. Standard heel master cylinders on this, with small Cleveland brakes and big tires. 

  Soon we shall see how my setup works. I did change out my master cylinders (as previously posted) to billet aluminum racing cylinders that don't leak! 

  More upon testing. 

  Kurt. 

  Sent from my iPad

  On Mar 17, 2013, at 11:55, Brian Michalk <michalk at awpi.com> wrote:

    Thanks.
    That brings the horizontal braking force down to 716lbf per wheel.  Just under my estimated 750lbf vertical force.  With a surface/tire friction number below .95, I should still be able to lock up the wheels.

    I used to direct the skid number data collection program at TxDOT, and we also measured a lot of runways.  Skid numbers below 32 (.32 friction number) were generally considered low and in possible need of a resurfacing*.  Non-polished surfaces (like shoulders) could easily score into the 80's, and runways would score pretty well unless they had a lot of rubber buildup.

    * This is a gross generalization.  Lot's of other factors came into play like braking requirements, data distribution, accident statistics and so forth.

    On 03/16/2013 12:18 PM, Laurence Coen wrote:

      Brian,

      A 600x6 is 18" in diameter for a 9" radius.  6" diameter wheel plus two 6" sidewalls.  The RG has a smaller tire that is 15" diameter and a 7.5" radius.

      Larry Coen
      N136LC

      From: Brian Michalk 
      Sent: Saturday, March 16, 2013 10:26 AM
      To: Velocity Aircraft Owners and Builders list 
      Subject: REFLECTOR: Brake performance

      I just looked up the Matco specifications for the WHLW600XTE
      http://www.matcomfg.com/WHLBRKASSY600X6TRPLeXtraTorqueEnergy-idv-3801-4.html

      I don't know how the number match dimensionally, but I assume a 6.00-6 wheel has a six inch radius?

      Assuming the wheel above, a 5/8 bore master cylinder and their specs of:
            Static Capacity 1860 LBS 
            Load Limit 5580 LBS 
            Maximum Accelerate/Stop Kinetic Energy 450500 ft-lb 
            Torque Rating (@450 PSI) 6441 in-lb 

      For 450 PSI, I would need to press on the master cylinder a force of 138lbf, which I am certainly capable of, and feel that I can generate this much force without too much effort.  There is perhaps a 3X mechanical advantage in the pedal arrangement.

      Their torque rating, with the wheel above shows that it could provide 1074lbf to a wheel weighted to approximately 750lbf.  Horizontal force is higher than vertical force, indicating a friction number greater than 1.0 is needed.

      This tells me that with very little effort, one should be able to lock up the wheels while taxiing in their airplane.  I have the original brakes, the W600XT, which have identical torque performance, but different kinetic energy numbers.  I don't need higher energy, I want better torque.  I do not think I am getting the performance indicated in these specifications.  Is my math wrong?

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