Hensley Arrow: How does it REALLY work?

jdwhittaker wrote:
Tim,
Excellent drawings(Figs. 1-3), they depict the only movement that the HA is capable of, well except for the opposite motion of course. It should also be noted that this type of motion can only be created by the TV, as in the case of a TV initiated turn...unless something is very wrong. Big hockey puck, or unsafe travel on very slick roadways or the like. It seems that alot of people posting in this discussion are interpeting other peoples posts as absolute statements...ie. can not happen, or can only happen this way, when in fact I think most people are trying to say something can't happen, or can only happen a certain way under normal circumstances.

I agree, but you've got to admit that Milt has not been so open to acknowledging those exceptional circumstances that result in a behavior that he hasn't himself seen or experienced.

jdwhittaker wrote:
My interpetation to the forces and motion associated with sway are different to the forces and motion in the figures above. I see sway as a rotational moment with it's center at approximately the center of all of the axles on the TT, and it's affect on the TT and TV.

How is that different than the moment diagram I posted a few days ago? The simple result of a 1000 foot-pound counterclockwise moment about the center of the TT's axles on Will's trailer is the 45.5 pound force I showed in Fig 1.

jdwhittaker wrote:
The HA all but eliminates that type of motion except in the case of extreme conditions.

I completely agree.

jdwhittaker wrote:
I'll attempt to make and post a little sketch of the forces that I'm describing, as well as a short video of the HA moving while mounted only on the stinger(as Milt and I have done). I think the video will really clear up alot of misconceptions about the motion of the HA.

I'm looking forward to seeing that.

jdwhittaker wrote:
I am still looking for an explanation of the Virtual Pivot Point, and it's role in all of this, that I can follow. Anybody?

Here's an earlier post where I showed the path of instantaneous centers inherent in a HA and linked to an interesting page of links discussing some of the many uses of 4-bar linkages. We're using the term Virtual Pivot Point to describe these Instantaneous Centers. Here's an interesting example of instantaneous centers in a prosthetic knee.

jdwhittaker wrote:
Tim, you must have 40 or more hours invested in this discussion, I don't know where you find the time. Thanks

Well, I haven't been counting, but I'd guess its probably closer to 10 hours reading and 5 hours generating posts. Thankfully, it's been spread out a little over the course of nearly a month. I feel that being a non-Hensley owner and an engineer gives me a unique and objective perspective, but I'd be delighted to step back and let an engineer who's taken a Hensley apart take over :D.

Tim