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In lugnet.technic, Bob Kojima writes:
> i will be showing this at a talent show on may 10th. i just finished it
> yesterday. it was such a nice day outside and i don't really have a flat
> surface long enough to set it up in my house, so i set it up outside. i
> made this bridge from pictures of the real bridge and a little inspiration
> from TJ Avery. the hawthorne bridge is about a mile away from my office so
> i spent a lot of time just looking at it.
I hope my bridge design spreadsheet worked okay for you. Your trusses look
good! Nice work. Very nice!
> you are right about synchronizing the motors. one of the motors runs
> faster than the other. i made the string a little longer on one side. so
> when the bridge starts to go up it is a little lopsided, but by the time it
> reaches the top it evens out. not a very good solution but it works.
I've hit a similar problem in planning out a crane. I've contemplated using
two separate winches to lift the main hoist, but just like your drawbridge,
one side can lift faster than the other. This depends on individual motor
speed and the specific diameter on the winch drum (which varies as string is
winched in or out).
I'm not sure how to solve this effectively. The simplest way is to control
each side independently, but that adds a lot of controls the user has to
manage. You could use a RCX and two rotation sensors to keep the amount of
string let out equal on both sides. But I've yet to try this.
-TJ
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Message has 3 Replies:
 | | Re: drawbridge
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| I just got through purchasing 4 rotation sensors for that very reason for my lift bridge ((URL) - in Creations). I will be adding the 4 rotation sensors and an additional rcx to my bridge sometime this year. Out of 32 motors, I could never get 2 (...) (21 years ago, 29-Apr-03, to lugnet.technic, lugnet.trains)
| | | Re: drawbridge
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| (...) In my view one of the simpler ways is to shaft connect the two motors if you can... You can hide it if you have the sort of lift bridge that has an upper connection between the two towers. It may not always work though. (21 years ago, 29-Apr-03, to lugnet.technic, lugnet.trains)
| | | Re: drawbridge
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| (...) 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 (...) (21 years ago, 29-Apr-03, to lugnet.technic, lugnet.trains)
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Message is in Reply To:
| | Re: drawbridge
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| (...) yes thank you for fixing the link. some how some extra characters got added in to the link. i will be showing this at a talent show on may 10th. i just finished it yesterday. it was such a nice day outside and i don't really have a flat (...) (21 years ago, 28-Apr-03, to lugnet.technic, lugnet.trains)
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