Hensley Arrow: How does it REALLY work?

BurbMan wrote:
I'll go out on a limb and say that both Will and I agree with everything you have said to this point. However, what we are saying is that in addition to all that, the tension that exists between TV and TT as the TT is being towed adds additional resistance to ANY movement of the 4-bar linkage, particularly inputs from the TT.

Don,

As I stated before, if your phrase "adds additional resistance to" means "locks out", then I do not agree with the statement. I do agree that added tension requires that added force be applied to swing the TT. I already have stated that a tension of 1000# would require a force of about 17.5# to swing the TT to an angle of 1 degree.

Can you formulate a proof that shows that these forces do not affect the behavior of the HA?

Let's give it a try. It's either do this or go back outside and paint.

When the HA is in the "straight ahead" position, the left side link is angled to the left at the rear and the right side link is angled to the right. The angles are equal and are about 4 degrees. If the TT is producing a tension in the tongue, then both links will be in tension equal to about one half of the tongue tension.

If the tongue tension is 1000#, the left link pin will have a rearward load of 500# and the right link pin will have a rearward load of 500#. The tension in each link will be 500/cosine(4 degrees) = 504.9#. The left link pin will have a right-directed load of 504.9*sin(4 degrees) = 70.3#. The right link pin will have a left-directed load of 70.3#. The net lateral force produced by the tongue tension if zero.

Now, let's swing the TT so the rear link moves right. Lets assume the left link now has an angle of 3 degrees and the right link has an angle of about 5 degrees. The left link pin would have a right-directed load of about 503*sin(3 degrees) = 52.5#. The right link pin would have a left-directed load of about 508*sin(5 degrees) = 88.2#. The net lateral force would be a left-directed 15.7#. Therefore, to get the TT to swing the prescribed amount, we would have to exert a force of 15.7#. The harder we push, the more it swings.

Yes, there is resistance. I made this point in a reply to one of MacMan's posts very early in this thread. We can quantify the amount of resistance. Now, you might ask, "If the resistance is so small, why don't TTs swing more than they do?". The answer, as I have tried to explain many times, is that the TT's tires provide nearly all of the resistance -- not the hitch.

I don't know how to explain it any simpler than that.

Ron

On Edit: I referred to a post by Don early on. It was a post by MacMan instead. Sorry.