Jake Anderson wrote:
> 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.
> 
> 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?

But that's only the very last step in the process. How long does it take
from when you receive the electrical trigger signal to when you actually
have the pads against the blade with 3000 PSI behind them?

-- Dave Tweed
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