Recent content by CraigH

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    Mechanism that only rotates when driven from one side

    The problem with this theory is that when I stick my fingers through the vent in the back of the motor, and turn the fan looking thing, (http://i01.i.aliimg.com/photo/v0/1961143857/12v_rs_770_775_dc_drill_motor.jpg), I can turn the other end of the drill even when power isn't applied. It is...
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    Mechanism that only rotates when driven from one side

    I don't have a wrench on hand at the moment. But I did accidentally apply a lot of force during an experiment today. We were running the motor with a fly wheel attached, ramping the speed up and down in both directions. We put it up to full speed, and then suddenly turned the power off. The...
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    Mechanism that only rotates when driven from one side

    I have a geared DC motor taken from a hand drill. When I manually turn the internal motor, the drill bit rotates. This can be done in both directions. However If I try and turn the drill bit it does not rotate. What is the mechanism called that achieves this? My friend says it is a sprag...
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    Speed limitations of pot & arduino for angle measurement?

    Can you please link me to where I can buy these encoder shields? Also, where can I find a library written for it? Thanks.
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    Speed limitations of pot & arduino for angle measurement?

    Discrete readings are acceptable, if I can achieve a precision of 1 degree. The pot will be attached to a pulley, driven by a high torque DC drill motor running at 450 RPM. It is part of the control system for a (fairly heavy) robot arm. Wear is certainly a issue, but the main concern for our...
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    Speed limitations of pot & arduino for angle measurement?

    If I am using a continuous rotation potentiometer on a pulley, and I want to use an Arduino to convert this reading into an angle as part of an angle control system, then what are the limitations for how fast the pulley can turn? Specifically, if the pulley is turning at 450RPM, will a...
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    Relationship between size and frequency of an oscillator

    I've almost found the answer. http://www.ieee-uffc.org/frequency-control/learning/pdf/Piazza-MEMS_Resonators_for_Frequency_v1.pdf says the answer is: ##f_0 \propto \frac{T}{L^2} \sqrt{\frac{E}{\rho}}## I now just need to know what the symbols are. Any ideas?
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    Relationship between size and frequency of an oscillator

    I've always just accepted that as you scale down a mechanical system the frequency and Q factor both increase. For example, this Wikipedia page simply says that "Small bells ring at higher frequencies than large bells". But for a driven damped harmonic oscillator, what is the exact relationship...
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    Variable resistor & inductor connected to alternator

    A simple 2 pole alternator (a synchronous generator), is powered by a steam turbine. The amount of steam to the turbine is kept constant with a constant pressure ##p##, flow rate ##\dot{q}##, and power ##P##. If a variable resistor, inductor, and capacitor are connected in series to the...
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    Force on a magnet inside a short coil

    Find a cylindrical piece of iron (or other material that retains a magnetic field), drill a whole through it (like this), and then apply a strong external magnetic field. The magnetic domains in the material should align creating a magnetic annular prism (i.e a hollow core magnet)
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    Force on a magnet inside a short coil

    The equations are incredibly difficult, so I'm just after a general idea of how the force on a magnet bellow a coil changes with the distance to the coil. Shown bellow: Axial symmetry: o x o x cross section of coil o x o...
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    Calculate force to lift piston from a given closing pressure

    Is there a name for this principle? e.g "hydraulic leverage"
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    Calculate force to lift piston from a given closing pressure

    Am I also correct in saying that because the fluid is incompressible, and the volume out of the smaller piston equals the volume into the bigger piston; then the smaller piston will move more than the bigger piston. Is this just the basic principle to why hydraulics can provide such huge force...
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    Calculate force to lift piston from a given closing pressure

    That's true, but for the valve I am looking at the forces calculate at values between 2.5 and 4.0 Mega Newtons. This is ridiculous isn't it? I've never really studied hydraulics, so I can only compare it to an electric motor. For a motor to provide 4.0 Mega Newtons it would have to be geared...
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    How to calculate the angles that define the position your arm is in

    Ah okay I see what you mean, in my case ##S## is the origin. So I am looking for the angle between the line ##S E## and the vertical. I'll edit the original post and clarify this.
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