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At 08:33 AM 10/6/2003, you wrote:
> I guess I was curious why you used pneumatics. I would think a
> motor/gear/rotation sensor would give you very fine angular resolution and
> variable speed. You also would only need to control either the front or the
> back, but not both.
Two reasons. One, using a motor didn't occur to me. ;) Two, I don't have
any rotation sensors either. I'm also unsure how I could use a motor to
tilt and raise at the same time, though I don't think that's a movement
needed very often. I could always stack a book or two under the baseplate.
I had also been toying with the idea of using a pneumatic tilt system for a
while.
> By using a motor/rotation sensor, you could have the RCX compute the desired
> tilt angle from some kind of camera script that describes certain way
> points at
> specific frame numbers (key frames?) or time.
Or even just a certain amount of movement per frame. A 'next frame' button
could be incorporated into the design easily. For that matter, even just a
motor, heavily geared down (ie without the rotation sensor), would work if
you programmed it to only tilt for some small fraction of a second. Larger
increments could be worked with multiple button hits.
Another advantage to this system is that it would inherently be more
stable. The way the platform is connected to the pistons, and indeed just
the general design, does allow some shaking to get in. A fully technic,
geared design could be built so as to be literally rock-solid.
Hmm, I see Motorized Camera Tilt Unit coming soon. :)
> You could provide a similar mechanism for pan.
Pan, IMO, is a little trickier. The idea of a calculated rotation period is
good, but the technicalities of how to build a pan platform are harder.
There are two major problems:
1) the platform must be very close to the ground. Preferable height is 1
stud or less.
2) turntables, especially the technic premolded, are rather shaky and can
be tilted to one side or the other, just by the way they are designed.
I haven't bought the Hailfire yet, so perhaps I'm missing something with
those wheels. Has anybody experimented further with using them as a
turntable? I saw pictures at some point showing how certain tyre hubs fit
well inside there but I don't know if experimentation went farther than
that. Seems to me that with the right mechanism some serious control could
be gained.
> Tecno-stuff sells pressure sensors. I just bought one.
I'll look them up, thanks.
> > > The airtank (yours and the LEGO version);
> > > Does it really need an in and out? Would not an in be enough since it
> > > would act
> > > as out as the preassure in the rest of the system drops?
> >
> > I think you're right, except for one thing: you would not be able to use
> > the system while you're pumping. Air would constantly be pumped IN and
> > there would be no way for air to get OUT. With a compressor, for instance,
> > this would be impossible to use.
>
> Hmmmm. I'm not sure this is true. The pressure wave that is created by you
> pumping will get distributed to both the tank and the platform lift pistons.
Hmm, I think you're right. This didn't occur to me.
You would have to be careful, though, that the pressure wave doesn't create
uneven flip patterns with the pistons. Having a direct connection with a
partly pressurized airtank may create a high-pressure surge when you hit
the pump. I don't know, maybe it would balance out...one more thing to try.
> Light Sabres work well too.
Ah, and I just *happen* to have four of those around here somewhere from a
previous film... :-)
~Mike
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