Muller Dynamo replication (updated 11 June '11)
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<General thoughts>
<Variations>
<Platform>
<Motor>
<Generator>
<Research>
GENERAL THOUGHTS
i was wondering if we could get away with less coil/rotor mags straight off, to reduce coil winding & mag costs - however, i THINK that the more coil positions then the less 'cogging' there will be
also, more gen coils means better approximation to DC of the rectified o/p - needing a smaller buffer capacitor
if i use a DC motor drive then the trade-offs will be:
- motor efficiency
versus
- faster route to testing generator (no timing sensors, no drive cct make/test) - can retain 7 gen coils, but only need 6 mags
is there any benefit from having coils on outer sides of their shelves? - so that the inner edges of the two shelves are aligned with the core-ends nearest the rotor? - more aerodynamic for rotor?
not very confident about my mech skills wrt to getting low-loss rotor support & action; so i need to keep it very simple but reliable - not requiring too much alignment or special tooling
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VARIATIONS
since there seem to be so many rep attempts underway, and i guess the majority will be keeping pretty closely to Romero's details, i'm inclined in a perverse sort of way (as usual) to try a few variations for my own attempt:
- use smaller diam rotor & less coils/mags;
- use smaller mags;
- use dense 'wood' for rotor & stator 'shelves';
- construct 'slim' rotor;
- try to use nylon studding & nuts;
i can see the sense in building a close replication 1st and then trying different things from there - and i'm not completely sure i'm doing the right thing
i guess i'm taking a gamble on how 'robust' the excess energy seems to be on Romero's build, when he does things like hand-start it with no battery, or vary the drive voltage between 12V to 4.5V and back, and it still self-runs
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PLATFORM
2 Qty stator shelves - 8mm board (laminate flooring);
1 Qty rotor - (as above);
1 Qty base - Heava wood bread board;
3 Qty nylon studding - inter stator support (1"-2" separation);
6 Qty nylon studding - stator to base support
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MOTOR
initial config will use an MFA RE-170 3V DC motor;
approx 80% Eff at max torque - 1A 8900rpm;
first run-up with rotor (preliminary octagonal cut-out), no mags:
start-up current approx 1.5A, decreasing to approx 0.85A
run down time approx 55s
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GENERATOR
14 Qty 6 x 20mm 4B1 ferrite cores
14 Qty 7 x 0.09 enamelled multi-strand solderable copper wire coils
7 Qty FWBRs using paired & individual schottky diodes
14 Qty mild 2 x 20mm steel washers at outer ends of cores
14 Qty 2 x 15mm Neo mags on the washers
all coils/cores mounted outwards from their respective shelves;
FWBRs mounted under lower stator shelf
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RESEARCH
i found these images of an actual motor design by the Muller company...
click on images below to enlarge, if required
use brower 'Back' button to return here
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