Subject:
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Re: My Latest MOC: 1.4m Boom Crane
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Newsgroups:
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lugnet.build, lugnet.technic
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Date:
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Thu, 8 Feb 2001 22:58:32 GMT
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Viewed:
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249 times
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In lugnet.build, Jeff Elliott writes:
> Hi all,
>
> Thought I'd post a photo of my latest creation, a technic boom crane.
>
> http://www.brickshelf.com/cgi-bin/gallery.cgi?i=31827
Hi Jeff, great crane!
Here's some preliminary shots of my crane
http://www.lugnet.com/~469/projects/towercrane
> The main boom is about 1.4m from tip to hinge. The counterweight is a
> 1.5kg SCUBA lead weight (wrapped in plastic, of course), but that can be
> doubled if I'm lifting heavy loads.
I've had mine running to 1.8m, but while building it's been considerably
shorter. I used fishing sinkers, contained in a Lego "box". The problem with
that is the gap between sinkers means less weight / volume, and if the
container breaks...
> There are four controls for the crane:
>
> 1 - Turntable rotation (1:3, 1:56)
> 2 - Counterweight positioning (1:24)
> 3 - Boom up/down (1:24, medium spool, 1:4 pulley reduction)
> 4 - Hook up/down (1:24, large spool, 1:2 pulley reduction)
Mine's a bit different. I use 2 RCXs. 1 controls the counterweight
automatically - the entire platform tilts as weight distribution changes, and
sensors detect it & move the counterweight. The other RCX is basically just so
I can use the Mindstorms remote control to operate it! Note that the
interaction between the two is now very different than explained on the page
currently. I'm just putting finishing touches on the programs, I'll probably
update the page in a couple of weeks.
> All motive force is from single 'new' 9v technic motors, powered from a
> polarity-switch / train controller setup, except the hook which is
> driven off a battery pack 'cuz I ran out of polarity switches :).
One advantage of using the RCXs! I'm using new 9v motors for all except
rotation as follows:
1 - Rotation 2x old 9v motor via 1:24, 1:24, 8:56
2 - Counterweight 1x new 9v via 1:24, 1:3, using chain on 16 tooth gear
3 - Boom 2x new 9v via 1:24
4 - Hook 1x new 9v via 1:24, 1:3
I need 2x old 9v for rotation, as these motors seem a lot "weaker" for the same
speed than the new ones (this may be friction related). Because of the weight
of the platform, the friction generated at the edges of the turntable was
excessive, especially when it's slightly off-balance, so I used some margarine
to help it along!!
> Manual control of the counterweight is essential to not tipping the
> crane; if you try to lift a heavy weight with the boom out, it requires
> the counterweight to be moved all the way out, etc.
Movement of hook is now stopped while counterweight is being adjusted. Boom can
still move, as it only moves very slowly, and doesn't cause major weight
redistibution while moving (ecxept if you try to lift by raising the boom -
this has to an education thing!)
> You also have to be cautious not to collide the erect boom with the
> ductwork under the ceiling :)
I also have that problem, although my tower is not nearly as high as yours!
> I've trained two folks at the office in how to operate it; I've
> sabotaged the controls and gearing so that you need inside knowledge in
> order to move it from its rest position :)
I haven't let anyone get their hands on my remote yet! I displayed it pretty
much as it currently is at LegOz 2001.VIC.1
<http://news.lugnet.com/loc/au/?n=4256>, but no-one else got a go, as the RCX
programs were still in their infancy, and I wasn't 100% confident with the
automatic counterweight movement.
> I'd be interested in discussing power and gearing solutions with others
> who have developed high-load cranes... I notice that some of my gear
> boxes are creating plastic dust with heavy usage, a sure sign that I
> need to reconsider the gearing that I'm using.
Hmmm. I may have to check mine. I haven't noticed any shavings.
> I'm afraid I don't have much background knowledge of how cranes really
> work, so I just slapped together something which functioned through
> trial and error, but I'm pretty happy with the result. If anyone has
> comments on things I'm obviously doing wrong, let me know...
Well, I got lucky. My local TAFE had a crane they were using to build an
extension, and were also using it as a "training" crane for some of the
students. I went & asked if I could observe, and they said yes! Unfortunately
it was only a small one - using hydraulics to lift the boom, but it's probably
the only such chance I'll get for a while, so enjoyed it immensely!
> Two Lego pieces were modified in the construction of this crane
> (something I usually abhor): I redrilled the two uptake spools (technic
> wheel hubs) so that the threading hole would accept the heavier cord I
> used. The original hole was only large enough for thread; I widened it
> to 3/32". I guess I have so many wheels that I don't feel *really* bad
> about doing this :(
I used the wheel hubs <http://img.lugnet.com/ld/32007.gif> that came in the RCX
for the boom. They have no hole, so I have the string going over the side to a
1/2 width wheel <http://img.lugnet.com/ld/4185.gif> where it's tied on. The
hook spools directly onto a #8 axle, with two of those 1/2 width wheels to
contain it.
Regards,
ROSCO
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Message has 2 Replies:
 | | Re: My Latest MOC: 1.4m Boom Crane
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| (...) <snips galore> (...) (URL) my chief inspiration when I built my crane. Hats off to both of you! (...) I thought seriously about using the RCXs to auto-control the counterweight, but I wasn't sure exactly how hard it was to control, and I have (...) (24 years ago, 9-Feb-01, to lugnet.build, lugnet.technic)
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Message is in Reply To:
| | My Latest MOC: 1.4m Boom Crane
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| Hi all, Thought I'd post a photo of my latest creation, a technic boom crane. (URL) genesis of this MOC is that I'm building a Lego cubicle divider at work. Naturally, for such a large scale project, a large crane is needed (duh! :D) So I set about (...) (24 years ago, 8-Feb-01, to lugnet.build, lugnet.technic)
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