On Monday, October 10, 2016 at 9:53:59 PM UTC-7, Eric Greenwell wrote:
Charlie M. (UH & 002 owner/pilot) wrote on 10/5/2016 7:59 AM:
I've wondered if adding a small (1/4" - 3/8") anti sway bar to the
trailer axle would help in most situations. Granted, proper weight is
best, but the anti sway bar may widen the margin. Thoughts?

It's unlikely it will change the dynamics of a single axle trailer.
Ante-sway bars are used on cars and similar to change the roll stiffness
about each axle: generally, an anti-sway bar on the front axle increases
"understeer" and makes the vehicle more stable. A rear bar does the
opposite.

The place to change anti-sway bars is on the tow vehicle. I suspect a
bigger front bar would increase the towing stability, but I think it's
better to get the trailer balance and tire pressures right (ditto for
the tow vehicles tire pressures).

--
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
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

The most stable trailer configuration is a semi where about half the trailer weight is on the tongue. This is not possible for autos which can't support that kind of tongue weight. Even fifth wheels don't put the trailer wheels in that position, and they are accepted to be the most stable trailer configuration.

I have come to realize that there are two moment of inertia of interest; one referenced to the trailer axle and the other referenced to the hitch. Why is MOI important? The answer is if you have an oscillating body it will be harder to stop the larger the MOI. This is why engines have flywheels. If you want to minimize axle MOI you would put as much weight as possible near the axle, which may decrease tongue weight. If you want to minimize hitch MOI you move weight forward, which increases axle MOI. Clearly there is something contradictory about these two MOIs. All trailer towing guides I have seen emphasize maintaining a tongue weight that is 7 to 10% of the total trailer weight. Remember that MOI is calculated as the sum of the weight times the radius SQUARED, so any weight is a long distance from the reference point has a major influence on MOI. If the trailer's tires are maintaining traction with the road the axle MOI is of interest, but if the tires loose traction then the hitch MOI dominates. For certain, putting weight at the rear of the trailer aggravates both MOIs, but increases the hitch MOI four times as much as the axle MOI.

The moral of the story is to manage the hitch weight properly. Merely adding weight to the front of the trailer is not the solution: you should adjust the axle position to get the proper tongue weight. I have done this on one trailer and experimented with trailer transient response as a function of tongue weight. More tongue weight was better.

Tom