trailer sway mitigation TSM

Having avoided bias ply on cars and trailers for the last 40 years, I wonder if they hold a nail or screw better than they used to?
Jim

On Saturday, December 21, 2019 at 7:56:08 AM UTC-8, Eric Greenwell wrote:
wrote on 12/21/2019 6:39 AM:
Note that Nelson Funston's Trailer Dynamics paper was written in 1987. I would bet that tire technology has changed somewhat in the intervening 32 years. Still, the paper is interesting and informative.

The steel belted radial was well-established in 1987. I've discussed tires,
particularly trailer tires, with Nelson many times since then, including recently
about the specific tires to get for my trailer. He has never mentioned any changes
to tire technology that would affect us, nor have I heard of anything.

Also, there is nothing in his paper that depends directly on tire technology. It's
the lateral stiffness of the tire tread that is important; then and now, radial
tires have significantly more stiffness that a comparable bias ply tire.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Light truck tires are not available in a size that fits Cobra trailers. Found that out this last summer when I had to replace a blown tire.

Tom

On Saturday, December 21, 2019 at 5:51:26 PM UTC-8, 2G wrote:
On Saturday, December 21, 2019 at 7:56:08 AM UTC-8, Eric Greenwell wrote:
wrote on 12/21/2019 6:39 AM:
Note that Nelson Funston's Trailer Dynamics paper was written in 1987.. I would bet that tire technology has changed somewhat in the intervening 32 years. Still, the paper is interesting and informative.

The steel belted radial was well-established in 1987. I've discussed tires,
particularly trailer tires, with Nelson many times since then, including recently
about the specific tires to get for my trailer. He has never mentioned any changes
to tire technology that would affect us, nor have I heard of anything.

Also, there is nothing in his paper that depends directly on tire technology. It's
the lateral stiffness of the tire tread that is important; then and now, radial
tires have significantly more stiffness that a comparable bias ply tire..

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Light truck tires are not available in a size that fits Cobra trailers. Found that out this last summer when I had to replace a blown tire.

Tom

The curious thing in the LT vs ST debate is WHY would a tire company design a BETTER trailer tire intended to be put on a truck than a tire SPECIFICALLY and EXCLUSIVELY to be used on trailers? Just doesn't make any sense. Note that is a different question as to is it ok to use an LT tire on a trailer.

2G wrote on 12/21/2019 5:51 PM:
On Saturday, December 21, 2019 at 7:56:08 AM UTC-8, Eric Greenwell wrote:
wrote on 12/21/2019 6:39 AM:
Note that Nelson Funston's Trailer Dynamics paper was written in 1987. I would bet that tire technology has changed somewhat in the intervening 32 years. Still, the paper is interesting and informative.

The steel belted radial was well-established in 1987. I've discussed tires,
particularly trailer tires, with Nelson many times since then, including recently
about the specific tires to get for my trailer. He has never mentioned any changes
to tire technology that would affect us, nor have I heard of anything.

Also, there is nothing in his paper that depends directly on tire technology. It's
the lateral stiffness of the tire tread that is important; then and now, radial
tires have significantly more stiffness that a comparable bias ply tire.



Light truck tires are not available in a size that fits Cobra trailers. Found that out this last summer when I had to replace a blown tire.

Yokohama Supervan Y356 LT195/75R14 fit my ASH 26 E trailer. I got them from
Tirerack.com, and they still carry them. Walmart has them, too, but you might have
to order them first if you want to pick them up locally.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

2G wrote on 12/21/2019 6:23 PM:
On Saturday, December 21, 2019 at 5:51:26 PM UTC-8, 2G wrote:
Light truck tires are not available in a size that fits Cobra trailers. Found that out this last summer when I had to replace a blown tire.

Tom

The curious thing in the LT vs ST debate is WHY would a tire company design a BETTER trailer tire intended to be put on a truck than a tire SPECIFICALLY and EXCLUSIVELY to be used on trailers? Just doesn't make any sense. Note that is a different question as to is it ok to use an LT tire on a trailer.

LT tires make fine trailer tires; after all, they can handle the more demanding
life on a truck. But! They cost more - often much more - than a trailer tire, due
in part to the much higher speed rating, and that's why the tire companies make
trailer tires. Who would buy a $124 LT tire when they can get an ST tire for $80?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Because it's cheap insurance?Â* (Cheap glider pilots notwithstanding...)

On 12/21/2019 9:27 PM, Eric Greenwell wrote:
2G wrote on 12/21/2019 6:23 PM:
On Saturday, December 21, 2019 at 5:51:26 PM UTC-8, 2G wrote:
Light truck tires are not available in a size that fits Cobra
trailers. Found that out this last summer when I had to replace a
blown tire.

Tom

The curious thing in the LT vs ST debate is WHY would a tire company
design a BETTER trailer tire intended to be put on a truck than a
tire SPECIFICALLY and EXCLUSIVELY to be used on trailers? Just
doesn't make any sense. Note that is a different question as to is it
ok to use an LT tire on a trailer.

LT tires make fine trailer tires; after all, they can handle the more
demanding life on a truck. But! They cost more - often much more -
than a trailer tire, due in part to the much higher speed rating, and
that's why the tire companies make trailer tires. Who would buy a $124
LT tire when they can get an ST tire for $80?


--
Dan, 5J

On Monday, December 16, 2019 at 2:03:02 PM UTC-6, princiar wrote:
Anyone has experience towing a trailer with a car with the trailer sway mitigation installed?

Check out this technical paper (https://purehost.bath.ac.uk/ws/porta...JAUTO981.pdf); it is really pretty easy to digest.

Figures 9-14 provide the important results. Figure 10 shows that minimizing the yaw inertia of the trailer provides the largest impact on damping ratio, and thus the safe towing speed. Figure 9 shows that adding tongue weight above about 6-7% does not really improve the speed very much. Figure 11 shows that changes in the overall trailer mass do not greatly impact the safe towing speed. Figure 13 shows that making a large change in tire pressure (from 30 to 40 psi) only changes the speed for the same damping ratio by a couple of mph. Figure 14 shows that adding a friction stabilizer likewise only changes the speed a couple of mph.

Most composite glider since the 1970s load the wing roots to the front of the trailer, and this directly helps lower the yaw inertia of the trailer. However, many older wood gliders with large root chords load the wing roots aft. For these trailers, the axle must be mounted further aft to help control the yaw inertia so that the trailer can be pulled at highway speeds. Trailers that load over the tongue should have the wing roots forward, and these should be similar to more modern trailers. I have one of these for a Ka-6, and it is a real detriment for drag with the big flat door directly into the wind, even behind a full-size van.

As for tires, if one wants to travel above 65 mph, trailer tires are probably not what you want, since it is above their speed rating. If you drive on Interstate highways, this could be an issue, unless you are comfortable backing up traffic. I myself prefer the radial tires that are not speed limited (at least to normal road speed limits) and are likely to give a smoother ride for my glider as well.

As long as I load the trailer to have a safe margin with damping ratio and I have reasonable pressure in the tires, I have towed single-seat trailers with my Ford E-150 passenger van, my wife's 1999 Volvo V70, my 2003 Ford Focus, or even years ago, my old 1981 Volvo 245. Towing with the 245 (108 hp max at SL) limited my speed significantly when climbing over mountain passes in Oregon, but it did okay on the level, albeit normally not using overdrive. One should also respect the max speed when towing with a smaller car though, because of the time, distance, and stability to do a panic stop with the increase in total weight.

Read the paper and try not to overthink this topic. Load your trailer properly, air up whatever tires you choose, and drive safely.

... Neal P.

At 05:42 23 December 2019, wrote:
On Monday, December 16, 2019 at 2:03:02 PM UTC-6, princiar
wrote:
Anyone has experience towing a trailer with a car with the trailer
sway
m=
itigation installed?

Check out this technical paper
(https://purehost.bath.ac.uk/ws/portalfiles/=
portal/147993632/JAUTO981.pdf); it is really pretty easy to digest.

Figures 9-14 provide the important results. Figure 10 shows that
minimizin=
g the yaw inertia of the trailer provides the largest impact on
damping
rat=
io, and thus the safe towing speed. Figure 9 shows that adding
tongue
weig=
ht above about 6-7% does not really improve the speed very
much. Figure
11=
shows that changes in the overall trailer mass do not greatly
impact the
s=
afe towing speed. Figure 13 shows that making a large change in
tire
press=
ure (from 30 to 40 psi) only changes the speed for the same
damping ratio
b=
y a couple of mph. Figure 14 shows that adding a friction stabilizer
likew=
ise only changes the speed a couple of mph.

Most composite glider since the 1970s load the wing roots to the
front of
t=
he trailer, and this directly helps lower the yaw inertia of the trailer.

=
However, many older wood gliders with large root chords load the
wing
roots=
aft. For these trailers, the axle must be mounted further aft to
help
con=
trol the yaw inertia so that the trailer can be pulled at highway
speeds.
=
Trailers that load over the tongue should have the wing roots
forward, and
=
these should be similar to more modern trailers. I have one of
these for
a=
Ka-6, and it is a real detriment for drag with the big flat door
directly
=
into the wind, even behind a full-size van.

As for tires, if one wants to travel above 65 mph, trailer tires are
probab=
ly not what you want, since it is above their speed rating. If you
drive
o=
n Interstate highways, this could be an issue, unless you are
comfortable
b=
acking up traffic. I myself prefer the radial tires that are not speed
lim=
ited (at least to normal road speed limits) and are likely to give a
smooth=
er ride for my glider as well. =20

As long as I load the trailer to have a safe margin with damping
ratio and
=
I have reasonable pressure in the tires, I have towed single-seat
trailers
=
with my Ford E-150 passenger van, my wife's 1999 Volvo V70, my
2003 Ford
Fo=
cus, or even years ago, my old 1981 Volvo 245. Towing with the
245 (108
hp=
max at SL) limited my speed significantly when climbing over
mountain
pass=
es in Oregon, but it did okay on the level, albeit normally not using
overd=
rive. One should also respect the max speed when towing with a
smaller
car=
though, because of the time, distance, and stability to do a panic
stop
wi=
th the increase in total weight.

Read the paper and try not to overthink this topic. Load your
trailer
prop=
erly, air up whatever tires you choose, and drive safely.

... Neal P.

What is worth remembering is that the cause of the sway is
aerodynamic. Loading, tyre pressure, fiction dampers can only
ensure that the sway is damped out and does not increase. Trailers
with less vertical surface area aft of the wheels suffer less from
snaking than those with equal or greater vertical surface area behind
the wheels. You may not be able to change the aerodynamics of the
trailer but a good friction damper and proper loading will normally
ensure that the snaking is damped.
I have been a passenger in a car towing a Cobra trailer at over
100mph, scared the crap out of me but it was completely stable, but
only when loaded with the glider. Empty it was a different story.

This radial vs bias ply tire discussion has caught me off guard.
I always in the past read bias ply was the way to go on trailers, due to stiffer sidewalls.
Maybe not...
I've got 2 new bias ply tires on my Cobra now, they seem to do OK, I typically cruise 75-80, on the straights, out west with that thing using a F150 or full size GMC van.

On Monday, December 23, 2019 at 7:11:41 AM UTC-8, Nick Kennedy wrote:
This radial vs bias ply tire discussion has caught me off guard.
I always in the past read bias ply was the way to go on trailers, due to stiffer sidewalls.
Maybe not...
I've got 2 new bias ply tires on my Cobra now, they seem to do OK, I typically cruise 75-80, on the straights, out west with that thing using a F150 or full size GMC van.

You better check the speed rating on those tires; most ST tires are limited to 65.

Tom