REFLECTOR: Brake performance

Mark Magee edjonesbrady at gmail.com
Sun Mar 17 06:56:20 CDT 2013


Commercial aircraft braking systems are where anti-lock braking systems were born. Maybe the math on our non-computerized, non anti-locking brake systems are tuned to where we can stop, but not enough force on the rotors to lock them. Locking them normally can cause a runway departure on either landing or aborted takeoff.
On wheel panted FG's, heat fade can become an issue particularly on short field landings, that's the most serious problem many will encounter.
FWIW.

Mark B. Magee
N32XL XLFG
Sent from IPhone 4S

On Mar 16, 2013, at 12:45 PM, Velocity <velocityxl at fastmail.fm> wrote:

> I modified my Brake caliper form 1.25 Dia to 1.5 dia pucks . I also checked to see I was getting 450 psi out of my master cylinders and I am still yet to be able to lock the Wheels.
> Matco said I should have more than enough to lock the wheels I tend to think there is some fussy math going on here. I feel I have plenty of stopping power right now but like engine HP there is never enough power and I would really like to be able to lock the wheels in  a pinch.
> 
> Ron
> 
> 
> On 3/16/2013 10:26 AM, Brian Michalk wrote:
>> 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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