• Lilla Lisa Specs

    2013-11-02 Author: Mikael Tulldahl
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    Motors

    Turnigy L3040A-480G Brushless Motor

    Model: Turnigy L3040A-480G Brushless Motor

    Specs: kv :480 rpm/V

    max current: 52A.

    suitable for 6s system (22.2V)

    You can calculate the torque constant, Kt, given the kv:

    Kt=9.5/Kv=9.5/480=0.02Nm/A

    at 52A: M=I*Kt=52*0.02=1.04Nm

    gear ratio of 10:35 gives:

    Mout=1.04*3.5= 3.64Nm

    M=F*r –> F=M/r=3.64/0.02=182N

    two motors: 2*182N=364N

    so it is able to push forward with about 364N at full current at both engines. however we dare to push much more current for a short duration

    Transmissiontransmission

    the motors have a 5mm axle, we picked regular rc buggy pinion steel gear for use on the motor shaft, 10t and mod1 the motor gear has a direct drive on the wheel gear, a 35t mod1 gear from sdp-si of stainless steel. the wheel gears were modified (not the teeth)with cnc to minimize weight and to fit nicely with the rims. the rims are cnc cut from both sides from a piece of Nylon. nylon turned out to be very hard to work with and i had some failed pieces before I figured out a good manufacturing method. the wheel gear is slided on the hub, and fastened with a handful of m3 screws threaded into the nylon. a mold was milled from 8mm sheets of PC and used to mold polyurethane on the rims. a wheel diameter of 41mm was used. with a 4.5mm thick polyurethane tire. the tire is expected to compress about 1mm as they touch the doyho.

    wheel curing polyurethane tires SAMSUNG

     

    Batteries

    1.3 Ah 6s nano-tech

    we have one individual battery pack for each motor, each is a 1.3Ah 6s(22.2V) 45c – 130c turnigy nanotech

    http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=22907

    Motor controllers (ESC)

    the motor controllers are a custom design by Benjamin Vedder. they turn out to run our motors perfectly sensorless, but we will anyway probably

    put in sensors in the motors, by putting hall-sensors between the coils.

    MagnetsSAMSUNG

    magnets were sourced from http://www.magnetvaruhuset.se/

    we chose the type “super-flatgripare” with threaded tap. these are high quality and very strong!

    diameter: 16mm

    rated attraction force: 10kg

    depth:4.5mm

    treads: M6

    price:28SEK each

    after experimentation i’ve evaluated them to give a force of up to about 7 kg each on the dohyo. however, the force is drastically decreasing with increasing distance, e.g. 0.1mm apart from dohyo might just be about 2-3 kg force left. there is space for up to 35 magnets, but in reality about 10 slots are not used ( could be used if more magnetic force is found needed). The “center” of magnets lie about 1/3rd of the distance between wheels and plow, measured from the wheels