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  #21  
Old January 9th 04, 03:48 AM
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The control linkage that actually tilts the head is mounted 90 degrees
away from the actual intended movement. It appears that BJ took
gyroscopic precession into consideration when he designed this head.

But, like I said, nobody, not even BJ, would ever consider this
approach for a new design. He used this design because it was the
best he could come up with at the time that didn't violate anybody's
patents.

I'm going to change it myself as soon as is feasible.

Dennis.

"Andrew Crane" wrote:

OK - silly question. On the face of it, it seems to make a lot of sense to
do it this way

- simple connection - you could probably lose the swashplate somehow too
- fewer cyclical forces on components
- less chance of mast bumping

What are the downsides other than potentially odd handling?

I should imagine that the control forces would be enormous and pushing the
rotor head forwards would cause the fuselage to pitch backwards for a
start-off.

Regards
Andrew

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Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."

To find out what an H-1B is and how Congress is using
them to put Americans out of work, visit the following
web site and click on the "Exporting America" CNN news
video: http://zazona.com/ShameH1B/MediaClips.htm

  #22  
Old January 9th 04, 09:52 AM
PW
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"Andrew Crane" wrote in message
...

wrote in message
...

To avoid this problem, BJ tilted the entire rotor head rather than
changing the pitch cyclicly. In fact, the pitch on the blades only
changes when the collective is moved and not the cyclic. This results
in the grease being retained for a longer period of time. It still
needs frequent regreasing, but at least you don't need a new set of
bearings after each hour of flight.


OK - silly question. On the face of it, it seems to make a lot of sense to
do it this way

- simple connection - you could probably lose the swashplate somehow

too
- fewer cyclical forces on components
- less chance of mast bumping

What are the downsides other than potentially odd handling?

I should imagine that the control forces would be enormous and pushing the
rotor head forwards would cause the fuselage to pitch backwards for a
start-off.


Not if you do it right.

Dennis,

I had no idea BJ did that. If you remember, I wanted to "rid" my coaxial
of the swashplate. Reading the above post, I got excited about the loss of
the swashplate but how did BJ keep collective control without one. Or did I
misunderstand?

Phil


Andrew,

I'll guarentee that if you tilt the mast "my way", the tail doesn't pitch
down. I'm tilting a mast at a very low CG....PLUS.... I'm moving it forward
to slightly change to a forward CG. Same for left, right and to the rear.
Sounds weird but works. It add control complexity, but at least it's not up
in the head spinning.

Phil

Back to lurk mode.


  #23  
Old January 9th 04, 04:22 PM
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Actually, I think you misread it. The scorpion DOES have a
traditional swashplate. The linkages to and from it are a little
different, but that's all. It has only two control rods to it. There
is a pivot mechanism at the rear to hold it at a third point. It does
not slide up and down on the shaft. On the top side, there is only
one linkage which is connected to the hub itself and not the blades.
This linkage is what tilts the rotor head.

The collective is totally separate. It is a cable that runs from the
collective control, through the shaft, and out to a sissors joint on
the hub that changes the pitch on the blades. On this design, the
blades only change pitch when the collective is moved and not cyclicly
as in a regular helicopter.

So, with the Scorpion design, the swash plate is not used for the
collective control and is only used for the hub tilting mechanism.

There are other swash plate designs that use a pivoting rod inside the
rotor shaft that are not as reliable. The Mini-500 uses this
approach. Personally, I would not fly in a helicopter that had this
kind of swash plate mechanism as there is no way to inspect it to make
sure its still connected properly. Such a critical component needs to
be out where you can shake it.

Dennis H.


"PW" wrote:

Dennis,

I had no idea BJ did that. If you remember, I wanted to "rid" my coaxial
of the swashplate. Reading the above post, I got excited about the loss of
the swashplate but how did BJ keep collective control without one. Or did I
misunderstand?

Phil


Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."

To find out what an H-1B is and how Congress is using
them to put Americans out of work, visit the following
web site and click on the "Exporting America" CNN news
video: http://zazona.com/ShameH1B/MediaClips.htm

  #24  
Old January 10th 04, 12:17 AM
Ryan Ferguson
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wrote in message ...

I don't mean to sound argumentative, but I need cold, hard facts and
not general rumors that the ship is dangerous. What is specifically
bad about the Scorpion? I realize that there are many unorthodox
things being done, but is that really bad?


I am basing my remarks on comments you made about the age and
condition of the kit.

I have not flown a Scorpion, nor do I intend to fly one. 'Unorthodox'
homebuilt helicopter design appeals to me about as much anal warts.
How many of these things are flying around? How experienced are the
owner pilots who fly them?

But getting back to the main point, I really do want to hear about
specific problems with the Scorpion. I want to correct these problems
as much as possible.


Forget the Scorpion design for now. The specific problems a

a) You are a neophyte helicopter pilot.
b) You are 'rebuilding' what sounds like a defunct homebuilt kit that
someone else gave up on.
c) You are trying to maximize your training dollar by considering,
even if by the longest stretch of your wildest late night fantasy,
flying your Scorpion to meet some of the aeronautical experience
requirements of your desired pilot certificate.
d) You intend to build, then fly, then maintain your homebuilt
helicopter with your current level of experience.

You sound like you're pretty mechanically inclined. I'm not. I'm
just a pilot. Yeah, I put a little time in on my own airplane and
help out on the annual. But that's airplanes. Helicopters are a
different story. The more I learn, the happier I am that I have
qualified, knowledgeable, and experienced mechanics around who give
our training fleet the TLC they need to be the safe and reliable
workhorses they are. These contraptions are amazingly complicated in
many respects, and surprisingly simple in others. Have you ever flown
test flight trying to gauge blade tracking? Can you track down a
vertical vibration problem? Can you even discern a normal vibration
from abnormal? Honestly, how could you? I say these things not to
belittle. I say them just to make you think. You want to be a test
pilot at 10 or 20 or 30 or whatever hours. I don't want to be a test
pilot at 1,500. Thanks, but no thanks.

My last word. If you pursue the path you're on, you must accept the
fact you'll be facing a vastly increased level of risk. There is a
very significant, very real chance that you will injured or, god
forbid, killed by this dream. Are you willing to forfeit your life
for a homebuilt helicopter?

I won't pound you any further on this. The decision is now yours.
Best of luck to you.

-Ryan
  #25  
Old January 10th 04, 01:10 AM
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Thanks for your comments, however, I would like to add one thing about
what you said....

(Ryan Ferguson) wrote:

b) You are 'rebuilding' what sounds like a defunct homebuilt kit that
someone else gave up on.


The Scorpion was originally supplied as a kit made by Rotorway
Aircraft. It looks like this one is one of the earlier ones. The
basic design is almost exactly the same as the Rotorway Exec's
currently being sold. The Exec has a bigger engine, two places, a
beefed up frame and a better control system. However, it still uses
belts, chains, and the same basic hub design.

For this particular one, it apparently sat in the crates until about
10 years ago when it was finally assembled. There is plenty of
cosmetic stuff, but I do plan to strip it down to the frame, test and
rebuild everything.

Again, I appreciate your words of caution and rest assured that I
won't be taking any unnecessary risks. The ship will be balanced
before it gets to leave the ground. The necessary instructions came
with the kit.

Dennis H.



Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."

To find out what an H-1B is and how Congress is using
them to put Americans out of work, visit the following
web site and click on the "Exporting America" CNN news
video:
http://zazona.com/ShameH1B/MediaClips.htm

  #26  
Old January 10th 04, 05:02 AM
helicopterandy
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wrote in message ...
The R22 is a fine helicopter. However, there are those that fly jet
rangers that would call the R22 a "Death Trap". You suggested that
the Scorpion is not safe. However, you did not specify 'why' you
don't consider it safe.

I don't mean to sound argumentative, but I need cold, hard facts and
not general rumors that the ship is dangerous. What is specifically
bad about the Scorpion? I realize that there are many unorthodox
things being done, but is that really bad?

Take the cable-in-shaft control head for example. The entire rotor
head tilts on a U-Joint rather than cyclicly changining the pitch as
does a traditional helicopter. You might look at that and wonder why
BJ Shramm did it that way.

Here is the answer. At the time, the patent on elastomeric bearings
was still in effect. BJ could not use them. He elected to use
traditional thrust roller bearings. The problem with using these
bearings is that if they are under a load and are used cyclicly
(rocking back and forth with every revolution), the grease rolls out
of the way after a few minutes of operation and the bearings have to
operate without lubrication. This results in a failure.

To avoid this problem, BJ tilted the entire rotor head rather than
changing the pitch cyclicly. In fact, the pitch on the blades only
changes when the collective is moved and not the cyclic. This results
in the grease being retained for a longer period of time. It still
needs frequent regreasing, but at least you don't need a new set of
bearings after each hour of flight.

But getting back to the main point...



Dude, your own statements here are full of "cold hard facts". Read
what you are posting. If you are being truthful, you're trying to
cheaply (forget about it!) find a way to get an obviously terribly
designed aircraft running AND flying yet you cannot fly yourself.
That's like telling a little leaguer that he's gonna start for the
Rams! He'd get killed. DO NOT believe everything you read posted here
from some of the other folks here.
Just go back and reread your own posts and ask yourself why anyone w/
a grain of average IQ would even consider trying to piece together a
chopper from a pile of inferior parts. This isn't "Flight of the
Phoenix". It could wind up very badly.
Save up some $$, finish your instruction in a Robbie or Schweitzer and
then either lease or buy outright.
If you are looking for an inexpensive way to fly helicopters, forget
it. Find another hobby. This one is not for poor folks. Go learn how
to make a higher income.
No disrespect intended, just telling it like it is.
Take care.
  #27  
Old January 12th 04, 07:48 AM
Bob
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Dennis...
I will admit that I've only seen ( up close and personal) a Scorpion ONCE
in my 20 year career as a heavy helicopter mechanic, inspector, chief
inspector etc. etc., and that one look was MORE than enough for me. I don't
even have enough imagination, nor do I care to, picture cyclic change
without blade pitch change. Maybe Sikorsky and Bell, and Boeing et.al. are
missing something important all these years, huh? I never saw ANY real
helicopter that slings grease the way you're talking about unless something
is RADICALLY WRONG. Therein lies clue #1. I always thought they should
just put servos in the thing, hand ya a radio and let you keep your
distance.
I could make better rotor head parts in my cellar, and you strap your ass to
that thing? I STRONGLY suggest a have look a a few REAL helicopters for
some good design comparisons any of which can be done before or after you
have your head examined.

Good Luck!
Bob V.


  #28  
Old January 12th 04, 03:55 PM
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The scorpion head is not the best design in the world. However, as
far as the tilting, an R22 doesn't really tilt on a U-joint, but an
optical illusion makes it look like that. The scorpion really does
tilt.

I have looked at the R22 head and this looks like a nice one. I am
planning some kind of hybrid between the R22 and Bell using
elastomeric bearings. There is no grease in an elastomeric bearing.

This, of course, assumes that I don't find a cheap one on ebay.

Dennis.

"Bob" wrote:

Dennis...
I will admit that I've only seen ( up close and personal) a Scorpion ONCE
in my 20 year career as a heavy helicopter mechanic, inspector, chief
inspector etc. etc., and that one look was MORE than enough for me. I don't
even have enough imagination, nor do I care to, picture cyclic change
without blade pitch change. Maybe Sikorsky and Bell, and Boeing et.al. are
missing something important all these years, huh? I never saw ANY real
helicopter that slings grease the way you're talking about unless something
is RADICALLY WRONG. Therein lies clue #1. I always thought they should
just put servos in the thing, hand ya a radio and let you keep your
distance.
I could make better rotor head parts in my cellar, and you strap your ass to
that thing? I STRONGLY suggest a have look a a few REAL helicopters for
some good design comparisons any of which can be done before or after you
have your head examined.

Good Luck!
Bob V.



Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."

To find out what an H-1B is and how Congress is using
them to put Americans out of work, visit the following
web site and click on the "Exporting America" CNN news
video: http://zazona.com/ShameH1B/MediaClips.htm

  #30  
Old January 13th 04, 05:56 AM
Cam
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Good on You Dennis! Just remember, It's just a machine, there's NO
Magic!!!!!!

Cam..


 




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