Winter project, tow out gear - wing wheel

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

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

Fred and all,

After I posted my reply and stated "I have photos", I looked for the
photos and haven't found them yet. Without ready access to the wing
wheel (it's at the airport and, unfortunately, I'm not), I won't be
able to run out and snap a photo right away. But in the meantime,
I'll keep looking. I KNOW I took the photos. I just don't remember
where I might have put them. Maybe I just need to search for ALL jpeg
files on my computer.

I regret my hasty posting.

Ray Lovinggood
Carrboro, North Carolina, USA

Roger on the SPEED, I have repaired several gliders over the years
that were damaged in towing and they were all towing too fast. I tow
at about 5 mph, on some vehicles I need to ride the brake a tad to
keep it slow. I also adjust the mirror to show the wing wheel which I
put on the left wing. I once saw an idiot towing at a good 30 mph!
While turning, the wing dolly twisted and ripped open his
alieron................put him out of the contest.
JJ

rlovinggood wrote:
Fred and all,

After I posted my reply and stated "I have photos", I looked for the
photos and haven't found them yet. Without ready access to the wing
wheel (it's at the airport and, unfortunately, I'm not), I won't be
able to run out and snap a photo right away. But in the meantime,
I'll keep looking. I KNOW I took the photos. I just don't remember
where I might have put them. Maybe I just need to search for ALL jpeg
files on my computer.

I regret my hasty posting.

Ray Lovinggood
Carrboro, North Carolina, USA

At 12:36 07 November 2008, Doug Hoffman wrote:
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

Hi Doug,
I have used a trailing arm design successfully for over 12 years
on various gliders . There attribute: it makes the wing /
wheel combination very stable even in rough grass. Here is a picture.
http://www.ssa.org/myhome.aspmbr=825...5&show=gallery
Udo

Check your tail dolly's also. Mine had the wheel attached to the cuff
with screws, not through bolts. One day this spring they separated
while towing behind my truck and the rudder hit the bumper and was
damaged.

The new design has a much more secure attachment.

Todd Smith
3S

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.

On Nov 6, 8:16*pm, Martin Gregorie
wrote:

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

I have seen the question of if it is OK to pull/push by the wingtips
asked many times. This exact question was asked of the DG/LS folks
years ago. Their answer was "Yes, it is!". I searched my mail
archives and found the reference to this in the DG Newsletter #69,
June 2004. Unfortunately, the link in the newsletter email is no
longer valid. Here is what I have from the email...

12. Pulling an aircraft: Is it okay to pull an aircraft on the wingtips?

Yes, it is!

http://www.dg-flugzeugbau.de/faq-e.html#pulling

Sorry, that I didn't keep the web page info. As I remember the FAQ,
it had a technical discussion on why this was valid. Does this apply
to all gliders? Hmmmm.

My $0.02.

- John DeRosa

Looks like "BrianDG303" came up with the reference I spoke of.
Thanks.

The question still stands, is it ok for every glider or just
DG's? ;-)

- John DeRosa

Try this for the pictures
http://www.ssa.org/myhome.aspmbr=825...5&show=gallery