Please note: The graphics in the early part of the document are the best I can do for now. I hope they get the point across!
A Kite Line Capstan With Winder Adaptors.
Motivation
In the summer of 2009 I decided I wanted to get into Kite Aerial
Photography, and quickly became dissatisfied with the tedium of
winding in kite string; especially with a lot of wind.
So, I went looking on the internet for kite winders and was
unimpressed by what I found since I did not want to limit myself to
just one line weight per bulky and heavy-weight winder. I really like
flying from a halo spool; thank you very much.
But! One cannot wind lots of line under significant tension onto a
lightweight halo. The halo tends to collapse or
explode
due to the accumulated stress. The heavy-weight winders are heavy
because they are built to take that stress.
One comment on the page about a halo winder
exploding
got me thinking:
I would think that the right approach
would be to have the cord wind around a shaft a few times before
going onto the spool; the shaft would thus supply most of the tension
for pulling in the kite; the spool could be left a little bit to
avoid an overly-loose wind, but would not have the huge force pushing
on it.
That sounded like a capstan and take up reel to me!
Sailing Winches, Capstans, and Take-up Reels
Now, my other summertime hobby is sailing, and there we deal with
lines (ropes) under horrific tension and make them tighter with
sailing winches, or capstans as they are properly called. The lines
to be tensioned is wrapped clockwise around the barrel of the winch 2
or 3 times and pulled taught so the loops are tight against the
barrel. Manually operated capstans have pawls inside (somewhat like
a bicycle freewheel) that allow it to rotate clockwise only and snug
winds of the lines have a lot of grip against the textured barrel; so
the line will not slip back out again as long as a light tension is
maintained on the tail ( that is the bit of line that is already
'past' the winch)
Usually it it possible to plug crank handles into the top of the
capstan and use them to crank the barrel around to pull in more rope.
The handles swing out 2 or 3 times the radius of the barrel so there
is some mechanical advantage working for the cranker even with direct
drive. For situations needing even more pull there are winches that
use a lower gear ratio if you crank the handle counter-clockwise, and
even fancier units that will gear down again if you crank clockwise
again. Some sailing winches have an additional rope gripper that
handles the tail automatically to avoid dedicating one person to
tailing while another hefty soul grinds
away on the winch handle.
Of course the hefty soul could be replaced with a motor. But
motors are heavy and illegal in wind-power-only competition. And
sailing is all about competition.
What happens to all that line when it has been cranked in?
Generally it gets dumped on the deck because the lengths are
manageable: meters only, not tens of meters. Its usually too long
(and too thick) to wind onto the capstan of the winch, but O.K. to
sit on or coil up a bit after the fact. Quick access may be more
important than utter neatness all the time.
But if there is a lot of line, it should get wound up on a reel
under just enough tension to keep it neat. That means the drum can be
of lightweight construction (even cardboard!) because the windup
effect is not going to happen once the winch/capstan has dealt with
the tension..Managing the tension difference is a detailed subject I
don't want to completely understand; I just want to preserve my halo
kite string reels so I can take aerial photographs of racing!
My kite string winder wish list
- Make it possible to use a halo as a take up reel
- quick changes of take up reels so:
- I can fly a a kite on the halo alone, and retrieve it on the
winder.
- several kite lines on compatible reels can fly and pulled
down with the winder
- I can chain several reels worth of line together.
- handy enough to be used on a boat, especially a sailboat.
- provide some mechanical advantage for high pull situations
- have a speed handle for low pull situations
- lightweight, but robust enough to go in a backpack, be used
on a boat, and by a child.
- home build-able from cheap material
The Basic Ideas
I started with the basic capstan to reel idea ( the reel is on a
slipper clutch to control the winding tension):
and put the winch and reel slipper clutch on the same axle to ease
construction and save space. This required a pair of fair leads to
direct the line from the capstan to the reel
This is a schematic of the top view:
One Real World KAPstan
Winch
Here is an operators view of one real world implementation:
- The spine of the winch is made from 3/4 inch dowel with a
simple hole drilled crosswise for the 1/4 inch bolt axle.
- The top and bottom cross pieces are also dowel, glued and
screwed onto the spine where it was cut with a 3/4 inch drill for a
flush fit. The top cross piece forms a handle for the left hand, and
the bottom rests against the gut or hips to support the whole for
the right hand to operate the crank.
- The white capstan is made from the plastic hub of a lawnmower
wheel, the ribbed texture is a neat bonus I only discovered after
cutting off the tire!
- The green 50 pound test fishing line is being wound on the
reel it was sold on with the spider cut out to make it small halo.
- The 3 fair leads are eye-bolts with their eyes twisted a bit
out of true so the line can be slipped in from the side at treading
time.
- The pink stuff just visible to the right of the reel is
'rubber' packing foam cut into a disk to support the reel from the
inside with a hole in the center for the axle to go through.
- The wing nut just visible to the left is on the end of the
1/4” x 4” bolt that forms the axle. The axle passes though the
slipper clutch/reel holder, spine, and capstan to a double ended
crank on the far right.
- The line is threaded in from the bottom of the reel to the
kite as follows:
- it feeds up from the bottom of the reel
- to the reel-side fair lead
- to the capstan takeoff fair lead,
- around the capstan 4 times in the same direction as the
takeoff reel,
- then through the capstan fair lead
- to the kite.
Here is a capstan-side view with an Premier Kites 8 inch winder
mounted. Only the foam insert was changed to fit the larger reel.
Note the path the line is threaded through the fair leads and around
the capstan and reel.
The crank bar is made from hardware aluminum
1.25” by 1/16 bar stock, the knobs are plastic drawer pulls. The
frame is made from 3/4” dowel. I cut the spinal dowel with a 3/4”
drill to make clean T-joints at the head and tail ends.
The head of the axle bolt is visible here, clamped to the crank by
crimping it around the bar with a bench vise after starting the bend
with a hammer.
The black backing disk on the other side of the spine is made of
1/8” expanded PVC board sometimes sold under the name 'Sintra' in
Canada and the United States. This stuff is nice to work with: I cut
that circle out with aircraft snips after drilling a center hole and
scribing a big circle as a guide.
Here is
the whole winder from the other side with the 8 inch halo mounted and
tow other reels with their inserts to show the range of what sizes
work. The holes were punched though the foam with thin walled 1/4”
brass tubing because drills just don't work on this foam. I cut the
outlines with scissors and I did not try to be precise at all. There
is a lot of room for eccentricity and run out here since the rotation
speeds are so low.
The black retaining disk for the foam is also made from Sintra.
This was cut with the biggest hole saw I had and it fits nicely
inside the smallest reel while working well with this big one.
Here is
another view from the reel side with the fishing line mounted to show
the big backing disk along with the foam insert, insert retaining
disk, and the axle hardware (a jammed pair of nuts) that keeps the
business from spinning off while slipping.
The foam insert allows the reel to be aligned to the fair lead
that feeds it. Level winding can be approximated by nudging the line
to the appropriate sides with the thumb of your hand on the top
crossbar while cranking with the other.
Details
Slipper Clutch and Reel Holder
Here is the winder, upside down, with the reel support and slipper
clutch removed from the crank axle.
The big backer disk would go on the axle first, then the foam reel
adaptor, then the small disk, the washer, the hex nut and lastly the
wing nut.
The hex nut is finger tightened enough to squeeze the backer plate
against the hairpin clip just visible in this photograph. The tighter
this pressure, the tighter the line will wind on the reel since this
is the slipper clutch that controls that tension.
The wing nut is necessary to hold the hex nut at the position
selected since normal operation will either tighten the nut (right
handers) or loosen the nut (left handers) as the clutch slips. Just
tighten the wing nut enough to jam the two nuts together. Remember
you will have to un-jam them with your fingers at some point!
Crank Axle Through Spine and Retaining hardware
Here the
crank axle has been removed from the spine and the retaining hardware
laid out in order of assembly. The two washers on each side reduce
friction and slop between the capstan, spring clip, and the spine
between them.
The spring clip is threaded through a hole cross drilled in the
axle far enough away from the capstan to leave room for washers.
The spine is cross drilled with a hole (barely visible here) big
enough to allow the crank axle to turn freely without slop. Start
small and work up in the smallest increments you can until things run
freely. If needed lubricate with candle wax later, but will swell the
wood and make things tighter.
Attaching the Capstan to the Axle
I used a piece of plastic hose to re-size the bore of the
lawnmower wheel hub to fit tightly on the bolt. This is where most of
the kite line strain and leverage from the crank racks the capstan so
it must be strong and solid. Fortunately that is not hard to
accomplish.
The hose was picked to be a tight fit for the wheel bore, inserted
and cut to length, then drilled out for a tight fit on the 1/4 inch
crank axle.
With the axle pressed in (and the crank installed, see below) I
drilled through the face of the capstan, through the hub, hose, and
axle to install a cross pin that fixes the wheel rigidly onto the
axle. I use coat hanger wire for the pin; I will use a rolled spring
pin for a cleaner look next time.
The Crank
The crank is a bit of aluminum bar stock with drawer pull knobs
for handles. The bolt of the crank axle is threaded through the a
hole at about the 2/3 vs 1/3 point and the bar bent up to pinch the
hexagonal head of the bolt. Note: the gaps between the crank handles
and the capstan are excellent traps from stray kite line. So
eliminate them in your editions!
Obvious Possible Improvements
These have been left as an exercise for the reader.
- The hex nut jammed with the wing nut lacks class but that is
the best I have for now.
- The wire pin through the capstan and axle should be a rolled
spring pin.
- The length of the spine should be adjustable to the body of
the user.
- The sloppy nature of my crank handle leaves space for the
line to get wound between it and the capstan when threading or
winding out (see below). This is just a teething pain until someone
comes up with a better construction technique.
- Clean up all the places the line gets caught while threading.
- Add a holding strap for the crank.
Advantages
I managed to accomplish most of my wish list and have hopes for
the rest. It is light and easy to transport, the parts are cheap to
buy, alter, and assemble. It is fairly handy to use, and gets out of
the way easily when it is not wanted.
The mechanical advantage of the long throw handle is amazing to
use, especially when the line is being reeled in so nicely. The small
size of the capstan wheel helps a lot.
The high speed, short throw handle works well too and its amazing
how fast the line comes in when all one has to do is crank; instead
of swinging the arms all over to dump line on the ground for later
low-tension pickup or for the slow one wind at a time spooling
directly onto a halo.
A small capstan can wind onto many (larger) sizes of reels. The
example 8 inch halo seems to be about the workable limit. Larger
capstans would match better with larger reels for ease of operation,
and a longer crank handles would preserve the mechanical advantage.
The cranking speeds are low enough that sloppy construction will
still work. The critical fits are all along the axle, but most are
self aligning or decreed by the drill bit for the axle hole. I don't
think I measured any linear dimension on the prototype; it was all
done 'by eye' and 'to fit'.
This thing should scale up to handle strong pulling kites easily.
I suspect a heavier spine, a back strap, bearings on a thicker axle,
and a heavier crank will be most of the changes. The wheel hub
should be able to handle a lot of pull as it is.
Disadvantages (with some suggested fixes)
When the reel is bigger than the capstan, then unwinding line
while threaded is a tricky business. The problem is that the reel
lets out more line per revolution than the capstan will wind out; and
the extra line usually bunches up between the reel and the last fair
lead before jamming between the backing plate and the spinal column.
Retarding the reel with a thumb is usually enough to prevent this
from happening, but it is a pain. I hope to add a one way retarder
between the spine and the back plate to do this automatically. For
large line releases it is usually nicer to un-thread the line and use
the reel free-hand anyway.
This winch does nothing for twisted line. It leaves the twist as
it finds it as long as there is some tension. If there is a lot of
twist and the line goes slack, then the line will twist on itself and
probably tangle somewhere inconvenient.
The free-hand reel technique used to let out line will affect how
much twist added or removed from the line so pay attention and
alternate sides when letting the line rip off the reel.
Threading and un-threading the line under tension is tedious but
not horrible. I worry more about teaching others how to do it than
the personal time and attention needed this ritual.
The capstan has to be smaller than the winding diameter of the
reel for the slipper clutch arrangement to work. If the capstan is
bigger than the winding diameter, a gearing up mechanism is needed
and that seems too complicated to be worthwhile.
Further Work
Addressing the obvious improvements is a priority, but I see other
riffs on the basic concept.
Cordless Drill Power
I have made an electrically powered version. In fact that was
first! I learned just enough to tease you with.
It turns out that a cordless drill, the rubber core from a sanding
drum, some O-rings, the top of a soup can, plus some coat hanger wire
can develop enough pull to snap 50 pound test fishing line while
leaving the winds on the reel loose enough to fall over. Fine trigger
control is necessary with that monster.
I hope to refine this beast for wider consumption later. It seems
to be the perfect use for a cordless drill whose batteries have died.
Replacing those expensive batteries with a heavy sealed lead acid
battery means that the unit can be left on the ground with a few
traction spikes to haul down kites with no cranking!
However, that is a story for another day. The existing kite
fishing winches are safe for now.
Bicycle Powered
I usually am on my bike when I am kite flying so using my legs via
gearing would be nice. Even better would be to use my 3 year old's
boundless energy.
Wrap-up and Challenge
Kite fliers tend to be inventors and hackers. My goal with this
missive was to throw a challenge out so others will improve on the
basic concept and construction insights that struck me this summer.
If someone wants to construct and sell winders based on this, go
ahead! I hope you have competition! I want a sample, and some form of
credit, but I don't want to block real innovation in a pastime I
enjoy.
Contact Info
Albert den Haan
albert.denhaan@gmail.com
Ottawa, Ontario, Canada.
A
Kite Line Capstan With Winder Adaptors. by Albert
den Haan is
licensed under a Creative
Commons Attribution-ShareAlike 3.0 Unported License.
