Winter project, tow out gear - wing wheel

I have to refurbish/replace my wing wheel assembly and need some
suggestions/insights. The current one is the typical aluminum wing
cuff and bicycle wheel. It wasn't well made to start with and it's
falling apart. I want to take this opportunity to improve the thing.

One of the biggest issues I see is that if the cuff isn't perfectly
aligned on the wing, the wheel will try to track sideways and cock the
cuff risking wing damage. Further, it's a big chunk of "stuff" that
takes up space in the trailer or retrieve vehicle.

My first thought is that there are already wing cuffs used as wing
supports in the trailer. One of these might serve a second purpose as
a wing cuff for the tow out gear if I made it a little wider and added
attach points for a wheel. This would eliminate the need to find
extra space for it.

My second thought is to use a castering wheel instead of a fixed one.
This would prevent lateral and twisting forces from being transferred
to the wing. Even if the wing cuff wasn't perfectly aligned, it
wouldn't matter. The wheel/fork/steering head from a child's bicycle
might be adapted. I'm thinking that the typical ~20" wheel is much
larger than it needs to be.

Further thoughts about wheels leads me to think a bicycle tire is
designed for traction which isn't really needed in a wing wheel. In
fact, it would probably be better if it would slide sideways more
easily than a rubber tire. Pneumatic tires also can go flat. Maybe a
solid plastic wheel from some other source would be better.

Any thoughts?

On Nov 5, 11:06*am, bildan wrote:
I have to refurbish/replace my wing wheel assembly and need some
suggestions/insights. *The current one is the typical aluminum wing
cuff and bicycle wheel. *It wasn't well made to start with and it's
falling apart. *I want to take this opportunity to improve the thing.

One of the biggest issues I see is that if the cuff isn't perfectly
aligned on the wing, the wheel will try to track sideways and cock the
cuff risking wing damage. *Further, it's a big chunk of "stuff" that
takes up space in the trailer or retrieve vehicle.

My first thought is that there are already wing cuffs used as wing
supports in the trailer. *One of these might serve a second purpose as
a wing cuff for the tow out gear if I made it a little wider and added
attach points for a wheel. *This would eliminate the need to find
extra space for it.

My second thought is to use a castering wheel instead of a fixed one.
This would prevent lateral and twisting forces from being transferred
to the wing. *Even if the wing cuff wasn't perfectly aligned, it
wouldn't matter. *The wheel/fork/steering head from a child's bicycle
might be adapted. * I'm thinking that the typical ~20" wheel is much
larger than it needs to be.

Further thoughts about wheels leads me to think a bicycle tire is
designed for traction which isn't really needed in a wing wheel. *In
fact, it would probably be better if it would slide sideways more
easily than a rubber tire. *Pneumatic tires also can go flat. *Maybe a
solid plastic wheel from some other source would be better.

Any thoughts?

I think all of the points you raise are on target. I have a
"factory" Anschau (Komet) wing wheel with the padded fiberglass
cuff. It does suffer from the twisting issue you describe. I made
two modifications to mine:

1. Replaced the existing pneumatic tire with a 14" solid tire with a
spoked plastic wheel. I had nothing but trouble with the pneumatic
tire, especially with the bead being pulled off the tire when the
lateral loads were applied. I must have replaced the tube 5 times
over 2 years. I think you do want to account for the loss of some
shock absorbtion if you go with a solid wheel; the factory unit I
have has a gas strut that allows the unit to collapse slightly under
load.
2. Added 8 pounds of weight to the bottom of the cuff. This
counteracts the tendency to sometime drop the opposite wing if there
is a wind gust or some other upset. I've seen guys split an aileron
when the wing falls at just the wrong moment, especially when towing
the glider with water in the wings.

FWIW, I think a well-made aluminum cuff (i.e. properly shaped to match
the wing profile and well padded) is much easier to pull off than a
home-built fiberglass version.

P3

One of the biggest issues I see is that if the cuff isn't perfectly
aligned on the wing, the wheel will try to track sideways and cock the
cuff risking wing damage. *Further, it's a big chunk of "stuff" that
takes up space in the trailer or retrieve vehicle.

My first thought is that there are already wing cuffs used as wing
supports in the trailer. *One of these might serve a second purpose as
a wing cuff for the tow out gear if I made it a little wider and added
attach points for a wheel. *This would eliminate the need to find
extra space for it.

My second thought is to use a castering wheel instead of a fixed one.
This would prevent lateral and twisting forces from being transferred
to the wing. *Even if the wing cuff wasn't perfectly aligned, it
wouldn't matter. *The wheel/fork/steering head from a child's bicycle
might be adapted. * I'm thinking that the typical ~20" wheel is much
larger than it needs to be.

Further thoughts about wheels leads me to think a bicycle tire is
designed for traction which isn't really needed in a wing wheel. *In
fact, it would probably be better if it would slide sideways more
easily than a rubber tire. *Pneumatic tires also can go flat. *Maybe a
solid plastic wheel from some other source would be better.

Any thoughts?

Study the Sparrowhawk wing wheel. It is a beautiful exercise in
minimalism. The cuff is somewhat traditional (although would only fit
a 'normal' sailplane's tailplane...), but rather than a fork it uses a
thick and somewhat flexible fiberglass bow with 2 rollerbade wheels
and indeed casters. It is really light (obviously, it was designed by
Greg Cole!) While I myself would like bigger wheels, it is a very
elegant solution with castering the fiberglass bow.

I am making a new one for my ship, but more traditionally constructed.
A hinged (well fit...) fiberglass cuff and a bike fork for a 20"
wheel. My fork will be easily removable though, as it will be attached
via a gooseneck (the part of a bike that attaches the handlebars to
the forks). I am a bike fan with a BMX background so chose 'cool' bmx
parts (FMF fork, Spin wheel...ebay). My 20" bike wheel (oversize for
smooth fields, perfect for rough ones with badger holes etc) is a
sylish composite 3 spoke jobbie that looks really cool, and your right
traction is not necessary. I myself wouldn't use less than a 16" bike
wheel (Cobra wing wheels are 16") since I do visit fields with sizable
badger/chuckholes (probably prairie dog holes for you!) I use a Tioga
Pool Comp tire (a fully slick tread) and have a kevlar tire liner. If
I run into problems with repeated flats (my field is a goathead
factory...) I will pay the few extra bucks to have the tube expandy-
urethane foam-filled for a permanent solution. I like the shock
absorption that pneumatic/foam-filled wheels provide myself, and the
larger the diameter of the wheel the lower the rolling resistance is
over obstacles. My wheel attaches via a quick release skewer so is
very easily removed. The fork also easily removes if I really need to
break it down.

I chose not to make mine quite as light as possible though, as I like
my wheeled wing to stay on the ground. I may even make a provision on
it to accommodate a 5-10# weight for breezy days because it is lighter
than average.

-Paul

On Nov 5, 9:58*am, sisu1a wrote:
* One of the biggest issues I see is that if the cuff isn't perfectly



aligned on the wing, the wheel will try to track sideways and cock the
cuff risking wing damage. *Further, it's a big chunk of "stuff" that
takes up space in the trailer or retrieve vehicle.

My first thought is that there are already wing cuffs used as wing
supports in the trailer. *One of these might serve a second purpose as
a wing cuff for the tow out gear if I made it a little wider and added
attach points for a wheel. *This would eliminate the need to find
extra space for it.

My second thought is to use a castering wheel instead of a fixed one.
This would prevent lateral and twisting forces from being transferred
to the wing. *Even if the wing cuff wasn't perfectly aligned, it
wouldn't matter. *The wheel/fork/steering head from a child's bicycle
might be adapted. * I'm thinking that the typical ~20" wheel is much
larger than it needs to be.

Further thoughts about wheels leads me to think a bicycle tire is
designed for traction which isn't really needed in a wing wheel. *In
fact, it would probably be better if it would slide sideways more
easily than a rubber tire. *Pneumatic tires also can go flat. *Maybe a
solid plastic wheel from some other source would be better.

Any thoughts?

Study the Sparrowhawk wing wheel. It is a beautiful exercise in
minimalism. The cuff is somewhat traditional (although would only fit
a 'normal' sailplane's tailplane...), but rather than a fork it uses a
thick and somewhat flexible fiberglass bow with 2 rollerbade wheels
and indeed casters. It is really light (obviously, it was designed by
Greg Cole!) While I myself would like bigger wheels, it is a very
elegant solution with castering the fiberglass bow.

I am making a new one for my ship, but more traditionally constructed.
A hinged (well fit...) fiberglass cuff and a bike fork for a 20"
wheel. My fork will be easily removable though, as it will be attached
via a gooseneck (the part of a bike that attaches the handlebars to
the forks). I am a bike fan with a BMX background so chose 'cool' bmx
parts (FMF fork, Spin wheel...ebay). My 20" bike wheel *(oversize for
smooth fields, perfect for rough ones with badger holes etc) is a
sylish composite 3 spoke jobbie that looks really cool, and your right
traction is not necessary. I myself wouldn't *use less than a 16" bike
wheel (Cobra wing wheels are 16") since I do visit fields with sizable
badger/chuckholes (probably prairie dog holes for you!) *I use a Tioga
Pool Comp tire (a fully slick tread) and have a kevlar tire liner. If
I run into problems with repeated flats (my field is a goathead
factory...) I will pay the few extra bucks to have the tube expandy-
urethane foam-filled for a permanent solution. I like the shock
absorption that pneumatic/foam-filled wheels provide myself, and the
larger the diameter of the wheel the lower the rolling resistance is
over obstacles. My wheel attaches via a quick release skewer so is
very easily removed. The fork also easily removes if I really need to
break it down.

I chose not to make mine quite as light as possible though, as I like
my wheeled wing to stay on the ground. I may even make a provision on
it to accommodate a 5-10# weight for breezy days because it is lighter
than average.

-Paul

One of my frustrations is that glider makers don't offer an option for
threaded hard points on the lower wing surface. These, with an I-bolt
would serve as tiedown points, wing wheel attachment points, one-man
assembly dolly attachment points and maybe trailer attachment points.
They could eliminate the need for cuffs entirely saving huge amounts
of room for "stuff". They could just be taped over when not needed.

I'm thinking of two wing wheels if they can be made simple/light/small
enough. (Yeah, I know - more "stuff") Two would totally eliminate the
tip over problem. If I can use the trailer wing saddles/cuffs, the
additional "stuff factor" might not be too bad.

I'm not sure that shock absorption is necessary. The only vertical
load is the tip over force which is tiny compared to the weight of the
glider. The current wing wheel is very rigid and causes no problem.
If they're rigid, they might serve double duty as wing stands.

On Nov 5, 12:54*pm, bildan wrote:


I'm not sure that shock absorption is necessary. *The only vertical
load is the tip over force which is tiny compared to the weight of the
glider. *The current wing wheel is very rigid and causes no problem.
If they're rigid, they might serve double duty as wing stands.

I think that shock absorbtion is a good idea. I'm not so worried
about the load on the spar or even on the wing skin under the cuff
(pretty insignificant) as I am about two scenarios:

1. If you get a strong vertical jolt (say running over a lip of a
taxiway), you run the risk of twisting the glider to the point where
either it rotates and catches the other wing on the ground or puts
twisting loads on the aft fuselage that may not be insignificant
(depending on your your glider is secured to the tow-out bar).
Especially if you have a slight unballance with water, this could be
serious.

2. If you get a strong longitudinal jolt (catching the wheel on a
chuck hole) what happens to the trailing edge of the wing if the cuff
shifts suddenly?

I'm thinking that some amount of give in the system is useful. Just
my 0.02.

P3

I have a "Swan" trailer (from Germany) and "Swan" towout gear.

The wing wheel is the typical cuff around the wing and bicycle wheel.

A bit ingenious is the "suspension" they built into the setup. The
two vertical square tube aluminum forks that connect the cuff to the
wheel axle do not connect directly to the axle, but to an offset from
the axle that allows some pivoting movement. I think I have some
digital photos somewhere and if anyone is interested, I might be able
to dig them up and e-mail them. No, I don't have ready access to the
wing wheel itself at the moment.

The Swan wing wheel cuff fits over the wing at the very end of the
wing. It is a hinged cuff made of aluminum and padded with felt. All
frame members are made from aluminum. The wheel is a spoked steel rim
bicycle wheel. I don't know the diameter, but it may be 20"
Maybe... I've used it only a few times and it worked well. I've only
seen it work from the mirror of my car and not from walking behind my
car to see if it's twisting and popping the wing. I'm sure a
castoring wheel would work much better for most setups.

Ray Lovinggood
Carrboro, North Carolina, USA

I would like to see the pictures, if possible.
Fred
"rlovinggood" wrote in message
...
I have a "Swan" trailer (from Germany) and "Swan" towout gear.

The wing wheel is the typical cuff around the wing and bicycle wheel.

A bit ingenious is the "suspension" they built into the setup. The
two vertical square tube aluminum forks that connect the cuff to the
wheel axle do not connect directly to the axle, but to an offset from
the axle that allows some pivoting movement. I think I have some
digital photos somewhere and if anyone is interested, I might be able
to dig them up and e-mail them. No, I don't have ready access to the
wing wheel itself at the moment.

The Swan wing wheel cuff fits over the wing at the very end of the
wing. It is a hinged cuff made of aluminum and padded with felt. All
frame members are made from aluminum. The wheel is a spoked steel rim
bicycle wheel. I don't know the diameter, but it may be 20"
Maybe... I've used it only a few times and it worked well. I've only
seen it work from the mirror of my car and not from walking behind my
car to see if it's twisting and popping the wing. I'm sure a
castoring wheel would work much better for most setups.

Ray Lovinggood
Carrboro, North Carolina, USA

On Thu, 06 Nov 2008 16:59:54 -0800, Papa3 wrote:

I think that shock absorbtion is a good idea. I'm not so worried about
the load on the spar or even on the wing skin under the cuff (pretty
insignificant) as I am about two scenarios:

I'd add a third:

3. Personally, I'd be more worried about the twisting effect that will
drive the wing LE against the fuselage and possibly damage the pickup
pins and/or upset their shims if the wheel hits anything. The loads
applied at this point will be FAR greater than any forces at the tail
dolly or on the far wingtip.

Thats why you NEVER push a glider by its wingtips.

I'd suggest that your best protection against these forces is twofold:

1) use the biggest possible bicycle wheel on your tip dolly. A big wheel
will ride over a higher obstacle without catching on it than a smaller
one.

2) take care not to run the tip wheel over anything that it won't ride
over easily.

Picking up on other comments in this thread:

- a fore/aft pivot on the fork that carries the wing dolly wheel and
a gas strut suspension can't hurt, but personal observation suggests
that the load even the smallest gas strut can support is so much greater
than the weight on the wheel that the strut won't cushion anything
unless its so old and knackered that its about to collapse completely.

- If you carefully align the tip dolly wheel so its parallel with the
fuselage centre line it will never drag sideways. Its axle is so close
to being inline with the main wheel axle that there's never a noticeable
side force on a properly aligned dolly wheel even when you pivot the
glider round its main wheel.

- A typical tip dolly isn't particularly light if you make it with an
old touring bicycle front fork and wheel.

At a guess mine weighs 7 kg (15 lbs) or so. I don't think I've seen it
come close to lifting, even towing crosswind in a strong breeze with
the dolly on the windward side. I fly a Libelle, which isn't exactly
heavy AND has the dolly on its lightest wing. Murphy guarantees that!


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Martin Gregorie wrote:
On Thu, 06 Nov 2008 16:59:54 -0800, Papa3 wrote:

I think that shock absorbtion is a good idea. I'm not so worried about
the load on the spar or even on the wing skin under the cuff (pretty
insignificant) as I am about two scenarios:

I'd add a third:

3. Personally, I'd be more worried about the twisting effect that will
drive the wing LE against the fuselage and possibly damage the pickup
pins and/or upset their shims if the wheel hits anything. The loads
applied at this point will be FAR greater than any forces at the tail
dolly or on the far wingtip.

Thats why you NEVER push a glider by its wingtips.

I'd suggest that your best protection against these forces is twofold:

1) use the biggest possible bicycle wheel on your tip dolly. A big wheel
will ride over a higher obstacle without catching on it than a smaller
one.

2) take care not to run the tip wheel over anything that it won't ride
over easily.

My personal practice is to *never* exceed 5 mph when towing. I read an
article some time ago (Soaring magazine?) where an insurance company
reported that most damage incidents while towing were due to towing too
fast. Or the damage could have been avoided by towing more slowly.

Never stop quickly (don't ask).

The other thing I do is to use small/short screws for the wing cuff
clasp attachment. Any excessive loads will result in the screws letting
go: in effect they are like shear pins, so the wing is protected. I
have "tested" this safety when attempting to tow with a flat glider main
wheel (a bad idea!). The safety worked.


- If you carefully align the tip dolly wheel so its parallel with the
fuselage centre line it will never drag sideways. Its axle is so close
to being inline with the main wheel axle that there's never a noticeable
side force on a properly aligned dolly wheel even when you pivot the
glider round its main wheel.

Agreed. My practice is to frequently glance at the wheel while towing.
If it starts to skip or lean then I stop the car, get out, and
straighten the wheel. With practice one quickly learns how to put the
wheel on straight at first try.

Regards,

-Doug

Martin Gregorie wrote:


* * * "Thats why you NEVER push a glider by its wingtips."

From DG:

Pulling an aircraft
von friedelweber am Do Okt 25, 2007 1:36 pm
Is it okay to pull an aircraft on the wingtips?

The question tends to pop up in the gliding society. There is always a
concern that wings could suffer damage if the ground crew pulls on the
wingtips. Therefore we’d like to give you a short insight – without
going into too much detail – on the force that can be applied in a
longitudinal direction. Water tanks and other specific items are left
out in this abbreviated description. The length of the lever enable to
calculate the max. force a wing has to withstand without suffering any
damages.

The building describes a force of 400N as specification for every
glider. This will result in a force of 40kp (longitudinal). A normal
adult will commonly not be able to develop a force of 40kp in a
longitudinal direction without any problems. In other words – it is
save to pull a plane on its wingtips.