>There is a much lower power
requirement for 16mm than there is for >any video ormat
I've often wondered what it would take to produce a spring wound accessory
motor for the Arri S or the A-Minima. Using negator springs (as in the
K100), such a motor would be very light and could probably be made to
run for at least 90 seconds. If it could be electronically governed at
sync speed (which would use VERY little power -- probably a 9V alkaline
battery could do it), that would be fantastic.
J-P, are you there? Is this a completely crazy idea?
Another approach might be a small spring wound, belt-worn generator that
charges a small "buffer" battery to stabilize its output voltage.
Though much less efficient, it might be a more practical and universal
solution, since it could power 16mm and DV cameras as well, and would
not have to be sync sensitive. Also, several spring-winds worth of energy
could be stored in the battery, allowing longer continuous runs. One of
these units could be shooting, while another is being wound up.
(PS: A negator spring is not like the ordinary clock spring you find in
most windup cameras. A clock spring is wound in a single spiral; when
you wind it up, you simply tighten the spiral. But a negator spring works
between two spools. At rest, the spring is wound fully onto one spool.
To wind it up, you wind the spring onto the second spool, where it's curled
in the opposite direction, thus storing its mechanical energy. In other
words, it wants to return to its original spool. The arrangement is roughly
like a displacement magazine in which the take-up spool winds the film
emulsion-out. This takes up a bit more space than a clock spring, but
has several advantages: Unlike a clock spring, its output is extremely
uniform from start to finish, so it puts less stress on the speed-governing
mechanism. Likewise, winding the spring is very easy and doesn't get harder
as you approach full wind. You can pack a lot of run-time into a small
negator spring, and I don't think there's any theoretical limit to it.
Do a Google search on <negator spring> to find out more
than you ever wanted to know....including an excruciatingly detailed analysis
of Abraham Zapruder's 8mm B&H camera!)
Marin County, CA
Dan Drasin wrote :
>I've often wondered what it
would take to produce a spring wound >accessory motor for
the Arri S or the A-Minima.
Given that the A-Minima can be run from relatively cheap, tiny, and disposable
lithium cells that are tiny and can be purchased at WalMart for about
$20/set (and a set is good for 1600-2000 feet) it seems pretty silly to
add noise and bulk and mechanical problems to solve a problem that doesn't
exist. The weight and space these batteries take up in comparison to the
amount of film they'll pull through the camera makes their size and weight
and cost truly negligible for remote location shooting. The four batteries
end up being slightly bigger than two AA cells.
If you can shoot 2000 feet for $20, that's a penny a foot. Given what
stock and processing and transfer/printing costs, that's pretty cheap.
And on a long camping trip, the added weight of the food you'd need to
carry to cover all the extra calories consumed by all that cranking would
probably be worse than the weight and cost of the lithium cells!
Of course, you could just bring a Bolex... and be cranky.
Jeff "and we can bring my spring wind, tube electronic Nagra II"
>cheap, tiny, and disposable
lithium cells that are tiny and can be >purchased at WalMart
for about $20/set (and a set is good for 1600->2000 feet)
Well, if it takes that little power, it should be possible to run it off
one of the wind-up battery replacements which have resulted from the famous
wind-up radio, or a solar panel trickle charging batteries.
If you're in the burning desert, solar panels work well. Even a biggish
25-watt one, which would run my video camera without having to accumulate
to batteries, is something you could sling over your shoulder and work
with the sun to your back!
London…where for some unaccountable reason solar panels don't
work very well.
Dan Drasin wrote :
> Another approach might be a
small spring wound , belt-worn generator
You almost had me interested until this. One of my new years resolutions
2003 : Just say no to battery belts !
Jeff Kreines writes :
>the added weight of the food
you'd need to carry to cover all the extra >calories consumed
by all that cranking would probably be worse than >the weight
and cost of the lithium cells!
Takes a bit of helium out of THAT trial balloon ! But can you back this
up with charts, please ?
Bolex shopping in fact for like reasons.
Sam Wells wrote :
>Takes a bit of helium out of
THAT trial balloon ! But can you back this >up with charts,
Walter has them on his web site, I think.
>Walter has them on his web site,
You'll also be able to find them on page 1,432 of the new edition of the
Director/DP, Downstream Pictures
Dan Drasin wrote :
>If it could be electronically
governed at sync speed (which would use >VERY little power
- probably a 9V alkaline battery could do it), that >would
be fantastic. J-P, are you there? Is this a completely
'negator spring'…yes we considered this idea but it's bulk, weight
and noise added to the camera. For remote locations we preferred to make
the A-Minima a low power machine able to run from a set of disposable
lithium cells (and in the near future out of a fuel-cell).
BTW : you probably would never amortize the cost of a mechanical generator
compared to the few lithium cells you will ever burn-out.