Steering multiplier plan

Steering multiplier plan

Post by Peter Ulfhede » Wed, 21 Dec 1994 17:44:45


Some time ago there was a thread about steering large kites. There
were several solutions discussed the solve the problem with long arm
movement to turn the kite.

So, I've been thinking (well... sort of) about this. I have come up
with this idea. I've built one, but I have not tried it on a kite yet.
I have done some ground testing though and it seems to work. It will
effectivly double your arm movement. A 50cm difference in the
positions of the handles will give a 100cm difference at the flying
lines.

Andrew B. has politely pointed out that there is a drawback with this
design. The force difference on the lines can't exceed 25/75% This
means that the pulley system will stop letting out line on the slack
side when the force in that line drops below 25% of the total pull.
How much of a practical problem this is will have to be determined by
practical tests.  My guess is that it will also depend on which kite
that is used.

I will of course try it out myself as soon as weather permits.  We are
kind of out of kite season here in Sweden this time of the year. This
reminds me to wish you *ALL* on rec.kites a Merry Christmas and a
Happy Windy New Year.

Tight Pulleys

Peter

                2 x Multiplier by Peter Ulfheden
                ================================

   K             K                 K     = Line to kite
   |             |                 A,B,C = Pulleys
   |             |                 e,f   = One line running in pulley A
   &             &                 a,b   = One line running in pulley B
   |\           /|                 c,d   = One line running in pulley C
   | \         / |                 &     = Knot
   |  \       /  |                 H     = To handles
   |  e\     /f  |
   |    \ A /    |
   |     \O/     |
   |a     |     d|
   |      &      |
   |     / \     |
   |   b/   \c   |
   |   /     \   |
   |B /       \ C|
   \O/         \O/
    |           |
    |           |
    |           |
    H           H

--

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 | S-191 44 Sollentuna   |  Phone: +46 8 751 02 15 |
 | SWEDEN                |  Fax:   +46 8 35 04 29  |
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Steering multiplier plan

Post by Ronald van der Putt » Thu, 22 Dec 1994 16:34:15

Hi Peter,

Unfortunately, I didn't follow the threat about steering large kites, and
therefore this is the first time I see you steering system.
There are a few things I don't understand, you are (in fact andrew did)
talking about a force difference on the lines that can't exceed 25/75%, any
reason for that? My guess is that as long the kite generates enough pull
you will NOT encounter this 'drawback'. Which brings me to the following;
What if you have to let go? This system not only carries the weight of the
handles, but also the weight of the Pulleys. furthermore, the system has a
closed loop at the bottom, which of course is VERY dangerous if you have
to let go of the kite.
Perhaps there is a possibility to release the kite at point Q?

Quote:

>    K             K                 K     = Line to kite
>    |             |                 A,B,C = Pulleys
>    |             |                 e,f   = One line running in pulley A
>    &Q           Q&                 a,b   = One line running in pulley B
>    |\           /|                 c,d   = One line running in pulley C
>    | \         / |                 &     = Knot
>    |  \       /  |                 H     = To handles
>    |  e\     /f  |
>    |    \ A /    |
>    |     \O/     |
>    |a     |     d|
>    |      &      |
>    |     / \     |
>    |   b/   \c   |
>    |   /     \   |
>    |B /       \ C|
>    \O/         \O/
>     |           |
>     |           |
>     |           |
>     H           H

Are there any length restrictions in lines a, b, c, d and f? and how about
the strength of these lines. I'm not a expert in mechanics, but I think, if
you gain a bigger line length difference you have to pay somewhere else.

Ronald

PS: Is this system great to use with a buggy, or what?

_______________________________________________________________________________

DoubleSpace.....,
        Beyond the final frontier,
        To boldly go where no one has gone before.

 
 
 

Steering multiplier plan

Post by Andrew Beatt » Fri, 23 Dec 1994 15:04:53

Quote:
>There are a few things I don't understand, you are (in fact andrew did)
>talking about a force difference on the lines that can't exceed 25/75%, any
>reason for that?

Let's look at the thing under full turning:

Quote:
> K             K
> |g           h|
> |             |
> &             &
> |\           /|
> | \         / |
> |  \       /  |
>  \ e\     /f  |
>   \  \ A /    |
>    \  \O/     |
>    b\  |a    d|
>      \O&      |
>       | \     |
>       |  \c   |
>       |   \   |
>       H    \ C|
>       B     \O/
>              |
>              |
>              |
>             DH

Let's say that we've got 4kg pull on handle D and 0kg pull on handle B
(we're trying to pull as hard to the right as we can).  Because C is a
free-running pully, the tension in line c and line d must be equal. c
is 2kg and d is 2kg.  The pull on B is Zero, so b hangs slack.  The pull
on a is all of c, plus half of the zero pull on B, so the tension in
a is also 2kg.  The pull on A is split 50/50 between e and f, 1kg each.

The total tension on g is e(1kg) + b(zero) = 1Kg
The total tension on h is f(1kg) + d(2kg) = 3kg

This isn't just a limitation of Peter's implementation.  It can be proven
mathematically that you can't beat it.  You can't get better than this
without a *compressive* member in the system to push the "slack" side
forward.  You reach the 75% turning faster but you can't get past it
and believe me, you want the full 100% to get a Peel out of a tip-stand.

You owe the Kite Oracle a perpetual motion machine.

Andrew
--
Kite FAQ's: ftp.hawaii.edu:/pub/rec/kites/faq)        o  /\ Kite Jumping
For sale: 10' Flexis with std & UF Spars.             |_ \/   is for


 
 
 

Steering multiplier plan

Post by Peter Ulfhede » Sat, 24 Dec 1994 03:13:30


: reason for that? My guess is that as long the kite generates enough pull
: you will NOT encounter this 'drawback'.

I guess this is true.

: closed loop at the bottom, which of course is VERY dangerous if you have
: to let go of the kite.
: Perhaps there is a possibility to release the kite at point Q?

I'm sure too, that it would be dangerous to fly one built with no
thought of the safte aspects. This is perhaps something you people, at
rec.kites, can help me figure out how to solve.

: >
: >
: >    K             K                 K     = Line to kite
: >    |             |                 A,B,C = Pulleys
: >    |             |                 e,f   = One line running in pulley A
: >    &Q           Q&                 a,b   = One line running in pulley B
: >    |\           /|                 c,d   = One line running in pulley C
: >    | \         / |                 &     = Knot
: >    |  \       /  |                 H     = To handles
: >    |  e\     /f  |
: >    |    \ A /    |
: >    |     \O/     |
: >    |a     |     d|
: >    |      &      |
: >    |     / \     |
: >    |   b/   \c   |
: >    |   /     \   |
: >    |B /       \ C|
: >    \O/         \O/
: >     |           |
: >     |           |
: >     |           |
: >     H           H
: Are there any length restrictions in lines a, b, c, d and f?

Not really, as long as the knots doesen't enter the pulleys
at full arm movement.

: and how about
: the strength of these lines. I'm not a expert in mechanics, but I think, if
: you gain a bigger line length difference you have to pay somewhere else.

You pay by having to exercise a bigger force *difference* in your arms
while turning.

: PS: Is this system great to use with a buggy, or what?

Yes, why not? I think it can be useful when you see your self standing
like a scarecrow with any kite.

Peter

--

[]-------------------------------------------------[]


 | S-191 44 Sollentuna   |  Phone: +46 8 751 02 15 |
 | SWEDEN                |  Fax:   +46 8 35 04 29  |
[]-------------------------------------------------[]

 
 
 

Steering multiplier plan

Post by Philip B. Cha » Sun, 25 Dec 1994 00:56:05


Quote:

>Subject: Re: Steering multiplier plan
>Date: Wed, 21 Dec 1994 08:34:15 +0100
>PS: Is this system great to use with a buggy, or what?

yes, it looks very interesting aside from Andrews  point on the 75% limit and
the safety concerns.  As for buggying, I have a trick that I have been meaning
share with the list.  So far I have only circulated this privately for fear of
getting flamed for idiocy, but I have tried it and *it works*.

If you have tried buggying with kites that require a lot of displacement to
turn you frequently find that you cannot move your arms far enough for an up
turn.  Meanwhile you can easily get the displacement for a down turn, but
monsters like the big peels sometimes don't have the room to turn down.  You
want to do up turns more often than down turns.

The solution to this problem is to switch the handles so that you left hand
pulls the right handle the right hand pulls the left handle.  The hard part is
that you have to learn to fly the kite backwards.  I DO NOT advise doing this
around people, light poles, trees, or any other object that you would not want
to hit.  A good drop zone is also valuable and make sure you use quick
release, because you will want to release when the kite is in a dive and you
get confused.  

Once you have learned to fly backwards, get into the buggy (remember, *LOTS*
of room) and try it.  Once the fear is gone you will find that upturns are
much easier and down turns are still easy.  For my 10m2 peel it really
balanced the required displacement with the available displacement.

Anybody ever try this trick?  Anybody kill a kite doing it? ;-)

I swear it works!

Philip


NetWare help >>>>>>>>>> http://grove.ufl.edu/~pbc <<<<<<<<<< NetWare help

 
 
 

Steering multiplier plan

Post by Joachim Wiechma » Sat, 24 Dec 1994 06:31:00

Hello Peter,

[some stuff about minimizing steering movements deleted]

I could imagine another drawback concerning force vectors: As all forces point
either in the direction handle-kite or somewhat to the center pulley there will
probably occur a resulting force dragging the lines towards each other. You
might test that using longer flight lines in your kite simulator.

I wish you (and all rec.kiters) a Merry Christmas and a Happy New Year, too.
o<:-)}   (no convincing Santa Claus, I'm afraid...)

Joachim