- ratios: 11.6, 29.8, 76.5, 196.7, 505.9, 1300.9
Motor = Mabuchi RE-260RA-2295 (data sheet) -- 2670
(another data sheet) -- 2670
- nominal no-load motor speed: 6300 rpm = 659.7 rad/sec
- nominal no-load current (mA) 160
- nominal stall current @1.5V 2560 mA
- nominal stall torque @1.5V 0.69 oz-in = 4.90e-3 Nm
- see datasheet above for nominal speed, current torque, at max efficiency
Metric gear module: http://www.metrication.com/engineering/gears.html
- Module = pitch_dia/N where pitch diameter is in mm, N = teeth
- As usual, addendum diameter = pitch diameter for N+2 teeth
- For the large blue gears in the gearbox, N=36
- Measured with calipers: addendum diameter ~ 19mm, which would be the pitch diameter for a gear with N+2 teeth. So module = 19/38 = 1/2
- Face width = 3mm
- Material = nylon. Flexural yield stress ~ 60Mpa or perhaps somewhat less for endurance (see links below).
Encoder for testing the motor:
- Helps to put a capacitor across the sensor to reduce false spikes
Some useful links for nylon gears:
- http://www.substech.com/dokuwiki/doku.php?id=thermoplastic_polyamide_nylon_6 Nylon 6 properties
- Flexural strength ~91MPa (130ksi)
- They suggest 62 N/mm^2 = 62MPa for injection molded gears. Other sources (e.g. Davis2005) suggest more like 45MPa so it may depend on the quality of nylon or it may be the latter is a safe endurance limit.
- http://sdp-si.com/plastic/design-of-plastic-gears.php - suggests 20deg pressure angle most common and has some simple adjustments for speed, temperature, etc.
- refers to formulas in the Gear Durability section: http://www.sdp-si.com/resources/elements-of-metric-gear-technology/page10.php. (scroll down to Section 18.2)