REFLECTOR: Brake performance
Brian Michalk
michalk at awpi.com
Sun Mar 17 12:55:25 CDT 2013
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 <mailto:michalk at awpi.com>
> *Sent:* Saturday, March 16, 2013 10:26 AM
> *To:* Velocity Aircraft Owners and Builders list
> <mailto:reflector at tvbf.org>
> *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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