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Iain Hendry wrote:
>
> You know, I think I've already stressed to Calum enough how tired I am of
> hearing people in line, when they first join the queue, and they all turn to
> one another and ask "Does it go all the way around?" :)
>
> (Going all the way around isn't really viable and hasn't been done on rides
> without counterweights, the acceleration you get without a counterweight is
> devestating, results in something like 12 g near the bottom. It's why
> roller coasters don't have circular loops*)
Huh, good point, hadn't thought about the gmax at the bottom :)
Mind you, 7 or 8 G sounds like fun...
>
> This, itself, is the problem I was trying to get around by using a flywheel.
> The only way in a scale model to get the pendulum to go slower really is to
> put a counterweight on it, but since that is out of the question I am trying
> to put a high-speed flywheel in line with the drive so that it is a "Forced"
> swing, that is, it is not a pendulum for hte model anymore it is just a
> driven arm, that is being driven by the acceleration and deceleration of the
> flywheel.
>
> It should, in theory, work, however since friction is naughty on things like
> this I have a feeling even this won't work smoothly. And I dont know how to
> do nice smooth sinusoidal accelerations of motors wiht NQC...
>
> If I can't get past the drive head issue and geting it to swing smoothly
> then I will not proceed any further with this, if I am going to build a
> model of this then it has to run very smoothly and true to life.
I'd point out that circular motion and sinusoidal motion are
interrelated... if you use a cam or off-centre gear drive, you could get
a very convincing pendulum motion. The trick would be finding enough
torque to run it...
>
> And yeah, Revolution is so large that the period of swing is something in
> the order of 10 seconds. It's really, really, really incredible to watch.
> It seems to stay up in the air forever.
>
> (I can't remember how to calculate swing - did you, and thats how you got 10
> sec. for 25 m pendulum?)
>
> Iain
T = 2 x PI x sqrt( L / g )
T = period (s)
PI =~ 3.1415
L = length of pendulum (m)
g = acceleration of gravity (m/s/s) =~ 9.8 m/s/s
So it'd take about 10s to complete a full back and forth cycle.
Actually, come to think of it, that rule only applies for small swings;
there's a error factor of (1 + 1/16 A x A + 11 / 3072 A x A x A x A) for
large angles A.
So that'd make it more like 13s.
Jeff
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Message has 1 Reply:
 | | Re: Decagon?!
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| "Jeff Elliott" <jeffe@telepres.com> wrote in message news:3D7672F8.7B6150...res.com... (...) Moonsault Scramble which operated from 1983 until very recently at Fujiku Highland in Japan had the record for the highest force of any ride, it was around (...) (22 years ago, 5-Sep-02, to lugnet.org.ca.rtltoronto)
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Message is in Reply To:
| | Re: Decagon?!
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| (...) 40! Crap. I'll have to see what I've got when I get home. (...) You know, I think I've already stressed to Calum enough how tired I am of hearing people in line, when they first join the queue, and they all turn to one another and ask "Does it (...) (22 years ago, 4-Sep-02, to lugnet.org.ca.rtltoronto)
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