trailer sway mitigation TSM

I have a newish VW Golf that has trailer-assist option. It has electronic stability system for trailer towing, including fancy servo steering that points the trailer directly to direction you want when reversing.

All I can say is that it goes like a train on rails and I have never had slightest indication of swaying.

At 07:35 18 December 2019, krasw wrote:
I have a newish VW Golf that has trailer-assist option. It has
electronic
stability system for trailer towing, including fancy servo steering that
points the trailer directly to direction you want when reversing.

All I can say is that it goes like a train on rails and I have never had
slightest indication of swaying.
Hi,
You should have a look at this, I think it explains a lot.

At 07:35 18 December 2019, krasw wrote:
I have a newish VW Golf that has trailer-assist option. It has
electronic
stability system for trailer towing, including fancy servo steering that
points the trailer directly to direction you want when reversing.

All I can say is that it goes like a train on rails and I have never had
slightest indication of swaying.

At 07:35 18 December 2019, krasw wrote:
I have a newish VW Golf that has trailer-assist option. It has
electronic
stability system for trailer towing, including fancy servo steering that
points the trailer directly to direction you want when reversing.

All I can say is that it goes like a train on rails and I have never had
slightest indication of swaying.
Hi,
You should have a look at this, I think it explains a lot.

At 07:35 18 December 2019, krasw wrote:
I have a newish VW Golf that has trailer-assist option. It has
electronic
stability system for trailer towing, including fancy servo steering that
points the trailer directly to direction you want when reversing.

All I can say is that it goes like a train on rails and I have never had
slightest indication of swaying.


Have a look at these clips.

https://www.youtube.com/watch?v=w9Dgxe584Ss

https://www.youtube.com/watch?v=6mW_gzdh6to

BG wrote on 12/17/2019 9:54 PM:
On Monday, December 16, 2019 at 12:03:02 PM UTC-8, princiar wrote:
Anyone has experience towing a trailer with a car with the trailer sway
mitigation installed?

I used to tow a DG 800 with a single axle trailer with a 4 Runner and found it
got to be quite a adventure. Any rapid turning would end up with a sway side
to side. I now tow with a Range Rover with 20" wheels with low profile tires.
The difference is night and day. IT was easy to understand the the major
difference is the tires. The 4 Runner had a high profile tire that flexed if
you pushed side to side on the rear of the car. The low profile tires have
virtually no sidewall flex. The suspension in the 4 runner was solid with
great sway bars, they however could not over come the flexing in the tire
sidewalls. In the Rover I can easily go any speed I desire with zero sway and
can change lanes at will. Push your car sideways at the rear and observe what
you see. Any motion will reveal why you have sway. I have seen many work
arounds with friction tuning to dampen sway, but none work better than
addressing the root cause.

The tire stiffness that is important is the lateral tread stiffness - how much the
tread deflects under side load. For this reason, radial tires are better than bias
ply tires, even though the bias ply tire might feel "stiffer" in your hand push
test. There are things that tend to increase tread stiffness and "side push
stiffness" at the same time, such as lower profile tires or higher pressure, so
it's easy to mistake what causes the improvement, and what is by-product of the
change.

There are likely other differences between the 4 Runner and Range Rover that make
one tow better than others, such as wheel base and hitch to rear axle distance. IT
would be fun to do the stability test with the same profile tire on vehicle. I
know at least one pilot that improved the stability of his towing by putting low
profile tires on the glider trailer, which is cheap and easy - worth trying if the
other factors (tongue weight, tire pressure, etc) don't help enough.

--
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

On Monday, December 16, 2019 at 3:03:02 PM UTC-5, princiar wrote:
Anyone has experience towing a trailer with a car with the trailer sway mitigation installed?

An important factor is the tire slip angle; ratio of side to vertical load.
Radial tires have a low slip angle, which is what you need on the trailer
and rear tires plus stiffening the side walls with increased pressure.
Dropping the front pressure also helps.

Something to check; PIK factory trailers had a tip angle adjustment,
a large turnbuckle at the hitch. If this is not tightened down hard,
the side cheek flex allows an extra degree of freedom in the control loop.
The result is dramatically bad as I found out when I neglected this.

Weight at the trailer back is bad, as has been said. Many of us us
are in the habit of stuffing odd items into the rear end; bad idea.

Something to test; a rudder on the tail box controlled by a mechanism
driven by the car/trailer error angle. ( in the right sense of course)
Cables or fly-by-wire ?

John Firth

john firth wrote on 12/18/2019 8:09 AM:
Something to test; a rudder on the tail box controlled by a mechanism
driven by the car/trailer error angle. ( in the right sense of course)
Cables or fly-by-wire ?

Hmm, we could call it a "yaw damper". Mechanical units exist, like the optional
Cobra trailer hitch that clamps onto the ball, so the friction can dampen the
trailer's swaying. Works well, I'm told, and a relatively easy fix, but you must
use a ball that is truly fixed on the hitch, not just bolted on. Follow the
instructions.

--
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

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.