On 13/07/10 12:09, Vitaliy wrote:
> Jake Anderson wrote:
>    
>> The field of stopping a rotating metal disk is a fairly thoroughly
>> explored field, they are called car brakes.
>> I'd wager with a hydraulic accumulator, shop air, and some ABS/brake
>> components you could stop the blade near arbitraily fast.
>> damage to the blade would be minimal, though you would want to check it
>> for warping if it got used often.
>>      
> I don't think that car brakes are designed to stop "arbitrarily fast",
> compared to the time scales in question.
>
> Vitaliy
>
>    
brembo 6 piston caliper, 55 square centimeters worth of piston area
decent brake pad CF is ~.8
push the pressure to 3000PSI say.

a 10" blade is say .1" thick
weight is ~1kg, KE is 1500J

converting to a linear motion to make life simple
KE = .5MV^2
sqrt(KE /.5M) = V

V=54m/s
~=200km/h which seems to be ~ the tip speed of the blade as calculated 
by others so it seems good.

clamping force on the disk is 8.5 square inches * 3000PSI = 25500 pounds 
= 11590kg = 113590N
deceleration force = .8 * clamping = 90872N
acceleration = F/M = A = 90872M/s/s (~9000G)
v^2/2a = s
57^2/2*90872 = 0.017876794 meters
so about 20mm give or take.

seems fast enough for me?


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