If you can't find design information, you can also use the "cut and try" method. Just wind a coil then measure its inductance and iterate from there. Of course, this means you have to have an easy way to measure inductance, but this can be very simple if you have a sine oscillator and an oscilloscope or AC voltmeter. Just setup the oscillator to output a sine wave at a known voltage and frequency, put a known resistor in series with the unknown inductor so you have a simple series circuit of oscillator, resistor, inductor. Then measure the AC voltage across the inductor or resistor. You can then calculate the impedance of the inductor using simple ohms law. From this you can simply calculate the inductance knowing the frequency of the AC signal. Watch out for errors such as mixing peak vs RMS ac voltages (use either but be consistent). Go ahead and vary the frequency and resistor value in order to get a practical voltage drop across the inductor, but keep the frequency as low as is practical to avoid errors due to hookup. Also, be sure to include the oscillator's equivalent output resistance in your ohms law calculation.