Subject:
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Re: 1:20 scale Apache Helicopter
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Newsgroups:
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lugnet.technic
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Date:
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Sun, 23 Oct 2005 19:07:02 GMT
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Viewed:
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6495 times
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In lugnet.technic, Mark Bellis wrote:
> In lugnet.technic, Ross Crawford wrote:
> > In lugnet.announce.moc, Mark Bellis wrote:
> > > Here's my MOC of an Apache helicopter, built to 1:20 scale, compatible with
> > > Technic figures. http://www.brickshelf.com/cgi-bin/gallery.cgi?i=1437017
> >
> > Looks like it's going well! Can't wait to see the finished model! But...
> >
> > > It features the first ever fully working Lego helicopter rotor with collective
> > > and differential rotor blade pitch control.
> > > http://www.brickshelf.com/cgi-bin/gallery.cgi?i=1437013
> >
> > Sorry mate, but I already had that in 2000 with my first model after my "dark
> > ages": http://www.br-eng.info/about/lego/mocs/huey.htm
> >
> > Implementation is a little bulkier, but I didn't mod any parts ;)
> >
> > Regards
> >
> > ROSCO
>
> Sorry, the rotor was done in 1996 - TLG have the pictures! So mine was the
> first after all! :-)
>
> Mark
Anyway, I'm glad I'm not the only one to have tackled this problem. As soon as
I bought an 8856 helicopter http://www.brickset.com/search.aspx?query=8856 I
thought "That's not how a real helicopter works" and began thinking how to do it
properly. This was the main reason I sent TLG the photos, as if to say "Come
on, you've made the parts, now give us a proper helicopter!". At the time, I
sent a whole film of various train and technic stuff, including the pick and
place robot, now well documented on my Brickshelf, and a roverbot powered by two
12V train motors, then the most powerful LEGO motors available.
I'm not sure whether I will finish the Apache, since I built it as a demo for
the rotor mechanism, expecting that no-one would understand the mechanism
without the rest of the helicopter! I need more of the new RC car motors before
I can continue, due to the power required to rotate the blades, but I have so
many other projects on the go that it's not the greatest priority. The model
has been in its present form for a few years as I've been busier with trains!
Originally, back in 1996, had intended to build a Chinook, thinking "why not
make another rotor the same now that it works well", but a Chinook has only 3
blades per rotor, not compatible with the 4-way swash plate, and in a mock-up I
found that it was difficult to put the strength in the body, so the Apache was
more feasible, particularly as I found a leaflet about it, with good pictures,
in a magazine. It still didn't have scale drawings though, but I can't expect
to get those since it's a military vehicle!
I found with the 8856 helicopter that the splined ball piece didn't have as much
grip on an axle as most other parts with axle holes, so I thought I'd weaken its
grip a little further - enough to allow it to slide to achieve collective pitch
variation. This worked well on the main rotor so I made another one for the
tail rotor.
The weight of the rotor with trial blades is so great that the swash plate
bearing certainly needs its wishbone pieces on all four sides, rather than just
one and a flex cable like the 8856 set.
http://www.brickshelf.com/cgi-bin/gallery.cgi%3Fi%3D1437013
I remember that, as soon as I had two 8856 helicopers and an 8865 Test Car, I
built a four wheel drive car, but the swash plates weren't strong enough to hold
the front wheels on round corners! I guess TLG had the same problem, which is
what led them to make different parts for the VX4 Supercar 8880.
Another problem to overcome in the Apache was the weight of the blades and the
consequent centripetal force as they rotated even at a modest speed. That's why
the pivots for the blades are so far from the centre of the rotor.
I had thought the steering parts from the smaller trucks with suspension, such
as the Dakota Wrecker, were pretty useless till I found this application for
them - four to link the swash plate to the blades.
There's plenty of ability to pivot the whole rotor just with flexing of the main
axle, so a separate pivot wasn't necessary. It should only pivot to hang the
weight of the body below it when flying (which a LEGO one without custom parts
never will!)
Following the example of a motor glider in one of the Technic ideas books, and
the sails in various ship sets, I could look into making paper or acetate blades
to save weight and increase aerodynamic efficiency (LEGO plates weren't designed
for that!), but I was reluctant to use non-LEGO parts.
I like your Huey Ross, it is well deserving of the prizes it won.
Mark
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Message has 1 Reply:
 | | Re: 1:20 scale Apache Helicopter
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| (...) D'oh! But I can still say at least mine didn't have any modified parts ;) (...) Actually, the swash plates on a chinook are a bit simpler - they only require collective and roll control, pitch is handled by differential collective on the 2 (...) (19 years ago, 23-Oct-05, to lugnet.technic)
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