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    Carbon dioxide rocket cars

    I think you've isolated the factors impacting performance. As to a computer model it is only as good as the assumptions and data. If you want a good model and know anyone with data acquisition equipment I suggest measuring (sampling) the force output from several co2 cylinders. I offer a couple...
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    Carbon dioxide rocket cars

    So a less massive lower inertia car could accelerate faster due to a(t) = F(t)/mR. But then it would be less effective at pushing air and overcoming axle/tether friction due to have less equivalent rolling mass mR! In other words it would have a lower ballistic coefficient with regard to the...
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    Carbon dioxide rocket cars

    I've seen small teflon and delrin flange bushings in catalogs, similar to this: http://www.graphalloy.com/html/type_317.html and it would reduce the inertia contributed by the ball bearings but might be worse in terms of friction at speed. I've been searching for some friction curves for...
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    Carbon dioxide rocket cars

    I only recently learned that Tribology is the study of rubbing/friction and the keyword appears to be Stribeck curve. Are you running ball bearings? I think a commercial plastic sleeve bearing is the proper choice to eliminate extra bearing inertia in these small machines but its just a hunch...
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    Carbon dioxide rocket cars

    Here's one simplified formula for acceleration: a(t) = \frac{F(t) - cv^{2} - bv}{m_{R}} where I define the equivalent rolling mass: m_{R} = m + \frac{J}{r^{2}} in which F(t) is thrust, c is quadratic drag coefficient, b is linear friction coefficient, m is the mass of the car, J is...
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    Carbon dioxide rocket cars

    Bob, Thanks for the links. This link includes a Macromedia flash animation showing 0.3 seconds of thrust: http://www.science-of-speed.com/competition.asp?id=91 and mentions speeds up to 45 miles per hour which of course would be peak speed at the end of the thrust period. Ideally you'd...
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    Carbon dioxide rocket cars

    Breaking due to bending moment is interesting. Is the thrust vector downward at the rear to keep the front wheels pushing down, thereby generating the bending moment? The Estes rocket cars practically fly down the tether line in some internet videos. Lots of things could happen depending on the...
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    Carbon dioxide rocket cars

    Bob, Could you point me to a supplier of the firing mechanism and standard co2 tanks? Or provide a technical information link? I may wish to do some local activities with small rocket cars. To run a good model you'd need the thrust-time curve, drag coefficient, frontal area, friction...
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    Carbon dioxide rocket cars

    I did an engineering simulation of the Estes Dragster over a 90 foot run: http://www.hobbylinc.com/htm/est/est9114.htm where to reduce elapsed time you clearly want to reduce mass, maximize thrust, reduce friction in the rolling axles and tether line, and finally reduce inertia in the...
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