At 06:08 AM 27/02/2010, saab wrote:
>I am a long time lurker desirous of building a small launch to use
>on a very quiet local river. Two questions that haven't been
>answered by the search facility:
>
>1. Why wouldn't an auto starter motor provide a low tech solution
>for short distance cruising?
Well, that depends on *how* short. The actual answer is - very badly.
Starter motors are designed to provide a lot of torque for a very
short time - they are really a 3 volt (or so) motor being grossly
over-driven. I have used a starter motor as the motor for a 12V air
compressor and also for a fire hose reel. The hose reel only took
about 20 seconds, the air compresor about 40 seconds. The motor on
the air compressors were too hot to hold you hand on by the time it
cut off, but since they were only needed now and then, wasn't a problem.
As well as the very short designed run time, starter motors are
designed for very short overall life - but in typical automotive
application, this is often many years, a decade or more. But stop and
think about that - typical start time is a few seconds, so a few
starts per day may be 30 seconds of run time. 5 days per week, 50
weeks a year may be typical, so 125 min of run time per year, maybe
total life of 10 to 15 hours.
If you want a cheap motor, haunt the scrap dealers until you find a
wrecked battery forklift or floor sweeper, etc., the power steer
motor or the hydraulic from the forklift, traction or brush drive
from the sweeper, etc., may be a good candidate (but all depends on
the design).
>2. Has anyone looked at the arduino micro-controller as an
>inexpensive motor controller? The computer itself is around $20.00
>and a diy motor controller is (supposedly) available as a kit for
>$15. This would control 36 volts and 8 amps.
I do not know that one, there are a bunch of cheaper pre-built
scooter, etc., controllers out there at 30 to 70 amps peak, they'd be
fine at up to 20 amps continuous - there are also kits, but a kit is
only as good as the builder.
http://www.jaycar.
as it is, but I believe a change to the circuit will let it go higher
- we've used these with a better Fet to do 50A (peak, 20A continuous).
http://www.jaycar.
adventurous, but never used that one.
Hope this helps
Regards
[Technik] James
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