Subject:
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Re: Vertical lift spans (was: Re: drawbridge
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Newsgroups:
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lugnet.technic, lugnet.trains
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Date:
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Wed, 30 Apr 2003 02:53:00 GMT
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Viewed:
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253 times
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> > In lugnet.technic, Steven Lane writes:
> >
> > > Ok, here's my idea for a solution for a vertically lifting bridge.
> > >
> > > All you need is one winch connected to one lifting line. You also need one
> > > control line(running off the same motor but geared down 2:1).
> > >
> > > The lifting line goes up the first tower down to the lift span, turns 90
> > > degree's around a free running pulley, across the span, round another pulley
> > > and up the other span where it goes over two more pulleys and then goes back
> > > to the winch via a mirror image route back to a second winch drum on the
> > > same winch axle.
OK, this is similar, but first take a walk down to the local auto repair
shop and see if you can look at a 'cats cradle' type auto hoist.
Here is my description. It involves one string to lift one end of the span
and another string, which is fixed at each end, to keep the span level.
Rig a line with pullies or whatever to lift ONE end of the span.
Fasten another line to the foot of the tower at this same end, run this line
up to the span and OVER a pulley fixed to the span, continue the line across
the span and UNDER a pulley on the other end of the span, fasten the line to
the top of the second tower. The string follows a sort of laying-down 'Z'
path from the bottom of one tower to the top of the other, there is now
winching or winding required on this second string.
As the end lifts an equal amount of line is drawn across the span and lifts
the other end of the span.
This configuration avoids a lot of problems with trying to match winch drums
etc and does not need an excessive amount of string. Lego string is so hard
to find nowadays!!! It might be difficult to get a string that does not
cause problems with stretching etc, maybe metal fishing trace could be worth
consideration, or how about guitar strings?
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Message is in Reply To:
 | | Vertical lift spans (was: Re: drawbridge
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| Not sure where to chime in, so I'll jump in here. Regarding the lifting of vertical lift spans: I've built many of these over the years and my latest version (yet to be published on the internet) takes advantage of an engineering survey done on one (...) (22 years ago, 30-Apr-03, to lugnet.technic, lugnet.trains)
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