Subject:
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Re: New Model: Sikorsky MH-53 E
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 24 Jul 2001 22:08:14 GMT
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Viewed:
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1309 times
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In lugnet.technic, Simon Bennett writes:
> You've done a great job here Reinard, I'm most impressed that the attitude
> of both rotors is adjustable and I love the folding tailplane. You
> certainly didn't choose an easy helicopter to model! Well done.
>
> Two questions:
>
> I couldn't see any real close up of how the main rotor is adjusted, it looks
> like there's a sort of annular ring with six steering arms attached between
> it and the blades, does this rotate to alter the pitch?
Ooops, you got a weak point here.... Let me explain:
I designed it as an extension of the old, old, 852 technic helicopter. What
is the same is the 'swashplate' concept: two normal plates
with the 'smooth' side against each other. Trough a specific construction
(using some effects caused by friction) one guarantees that
the two plates remain in contact with each other and therefore allow you to
control the pitch as in the real thing. The only problem
then becomes how to alter the position of the bottom part of the swashplate.
(As you read this, I have put on the site some pictures
showing the rotor head construction in detail. When I take the model apart
I'll also show in detail the pitch control mechanism) I
could not use the concept proposed by Leo Dorst, because 1) I did not have
enough room in the fusilage, and 2) I had to strenghten
the rotor axle, so that it could cary the rotor assembly under the specific
angle (about 9 degrees). The rotor axle is actualy made up
out of round 2x2 bricks with an axle in the middle. Leo's construction needs
a simple technic axle, not an axle with the dimension I
used.
But...
Due to the length of the blades, the stress and weight put on the
blade-turning points in the heart of the rotor; the friction got so high,
that the whole mechanism does not work properly...
So end result is, that it looks real cool, but does not work. I discovered
this when I was halfway trough, and didn't have the heart to
break everything down again...
Everything else on the model works...Tail rotor also. (but that one was
easy, copied basic concept from http://homepages.tesco.net/
~andrew.bissell/models.htm (look at the cobra) and altered it a bit)
>
> This is a pretty big model, how did you decide what scale you would use?
I wanted to make a big model in the first place, so the only question would
be how big... There is one building part whose size you
cannot alter: wheels. I took all the wheels-sizes I had and calculated the
size of the model when this particular wheel was going to
be used for the landing gear. I then settled for the 2994 wheel (30.4 x 14
VR). Then all other sizes followed from the scale taken
using this wheel. (of course, in approximation)
greetings,
---Reinard
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Message is in Reply To:
 | | Re: New Model: Sikorsky MH-53 E
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| (...) You've done a great job here Reinard, I'm most impressed that the attitude of both rotors is adjustable and I love the folding tailplane. You certainly didn't choose an easy helicopter to model! Well done. Two questions: I couldn't see any (...) (23 years ago, 23-Jul-01, to lugnet.technic)
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