jdwhittaker
York, SC
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bettered wrote:The HA does not lock in any position unless the side links interfere. It never locks in any other position as long as the hitch bar is in place. Ever.
Ed
Ed, is the statement above a reference to my statement below found on page 23 of 25?
"...that shows the motion of the HA lock to lock..."
If so sorry about the poor choice of words, I should have said stop to stop, since the hitch definately has a limited range of motion. If you listen closely to the video that Tim posted for us you can clearly hear a clunk as the hitch stops moving just prior to the end of the video. I was in a hurry when I made the video and have not had a chance to investigate exactly what made the sound. I believe that it was the sound of the side links hitting each other, as you said above.
If your statement above was in reference to something else, then please excuse my paranoia.
Dave
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tluxon
Kirkland, WA
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In my model the side links never come close to hitting each other, and the Hensley patent says something about offsetting the linkage so it doesn't hit itself. I think the sound must be from the pins when they reach a point where the links themselves would have to be a different length in order to keep moving.
Refer to the picture immediately above.
Tim
Tim -
wife Beverly & 2 boys who love camping
2002 K2500 Suburban 8.1L 4.10 Prodigy
2005 Sunnybrook 30FKS HP Dual Cam
Replaced 2000 Sunnybrook 26FK on 8/6/04
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bettered
UpCountry SC
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I will repeat, there is no lock. The thunk on the video appears to be the point at which the side links interfere. In effect it's a stop determined by the width of the links when they hit each other. This doesn't lock anything, it's simply as far as the physical limitation of the design will allow it to turn. My hunch is there will be other factors causing interference in most cases before you could get the hitch to this point. I'm thinking tongue to bumper kind of thing.
Now as to the locii of the instantaneous VPP's, you've got me really confused here. Because the side links cannot 'pass' each other the points on one side of CL are mirrored on the other, tracing an ellipse. There cannot be any points behind the (whatever?) except on paper, where lines are of zero height (off the paper). These are great theoretical points but they don't appear to be meaningful, unless we have some EE's in the crowd dealing with imaginary numbers (square root of -1)
Ed B
BetterEd
DW + 2 grandkids + Mini Schnauzer
2005 Chev 3500 Crew D/A 6.6L LLY, 6 x 6 DRW, 3.73
Tru-Flow + Banks, 2005 Flagstaff 831FKSS
Hensley + Prodigy
"Genius may have its limitations...." E. Hubbard 1856 - 1915
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bettered
UpCountry SC
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The side links operate in the same plane. They're about 3/4" thick and they will interfere at the limit of travel. I think that's the thunk.
The front bar and top bar are displaced from each other vertically. The front bar cannot hit the back bar (orange and black parts) as clearly seen in the video.
Ed
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tluxon
Kirkland, WA
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bettered wrote:I will repeat, there is no lock. The thunk on the video appears to be the point at which the side links interfere. In effect it's a stop determined by the width of the links when they hit each other. This doesn't lock anything, it's simply as far as the physical limitation of the design will allow it to turn. My hunch is there will be other factors causing interference in most cases before you could get the hitch to this point. I'm thinking tongue to bumper kind of thing.
Now as to the locii of the instantaneous VPP's, you've got me really confused here. Because the side links cannot 'pass' each other the points on one side of CL are mirrored on the other, tracing an ellipse. There cannot be any points behind the (whatever?) except on paper, where lines are of zero height (off the paper). These are great theoretical points but they don't appear to be meaningful, unless we have some EE's in the crowd dealing with imaginary numbers (square root of -1)
Ed B I'll take a video of my model's movement until it can go no longer. I believe it will change your opinion.
Tim
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bettered
UpCountry SC
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LIB!
I am mistaken. The links DO pass each other. That's why they're shaped a little like a figure 8 - to provide clearance. This design is cleverer than I thought.
The thunk is also identified. Earlier I talked about the drop down gravity bar that holds the hitch straight when the hitch bar is not in place. That bar is held in place by a pin which is mounted in two ears on top of the black piece. At the limit of travel, one of the side links interferes with the nearest ear. The ears and the drop down bar are all pretty hunky, so the overall width of the 'stop' is about 1 1/2"
The fact that the links pass each other also explains the s-shaped locus of VPP's. Tonight I learned that the original creator of this design was very clever indeed.
Apologies for the earlier misinformation.
Ed
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tluxon
Kirkland, WA
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I wasn't able to get a video of my model going through the rotational range that was even nearly good enough to post. Maybe I can figure out how to convert it to Macromedia Flash. If anyone knows, please clue me in.
Here's a video of two short segments on the Hensley marketing video where a camera is looking directly at the hitch while angles are changing at relatively slow speed.
http://home.comcast.net/~tbluxon/Hensley_Hitch_cam.WMV
Tim
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tluxon
Kirkland, WA
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bettered wrote:LIB!
I am mistaken. The links DO pass each other. That's why they're shaped a little like a figure 8 - to provide clearance. This design is cleverer than I thought.
The thunk is also identified. Earlier I talked about the drop down gravity bar that holds the hitch straight when the hitch bar is not in place. That bar is held in place by a pin which is mounted in two ears on top of the black piece. At the limit of travel, one of the side links interferes with the nearest ear. The ears and the drop down bar are all pretty hunky, so the overall width of the 'stop' is about 1 1/2"
The fact that the links pass each other also explains the s-shaped locus of VPP's. Tonight I learned that the original creator of this design was very clever indeed.
Apologies for the earlier misinformation.
Ed On my model, the rear bar passes over the side link on the side it's pivoting toward just about the time it's beginning to cross over the front bar. Is that what you're seeing? At no time does the side link opposite the direction of pivot cross over any of the other bars - well, outside the area around the two joints anyway.
Tim
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bettered
UpCountry SC
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That's sort of the problem. It's very difficult to discern exactly what's happening with the side links because you can almost never see them. I was running my hitch back and forth and trying to determine exactly what the links were doing when I concluded that they (being shorter than the distance between the bearings) can and do fold over each other (the lines of action cross) during the last (tightest) part of the turn. That's what gives the hitch the 165 degrees of travel.
Clearly the front and rear bars overlap at this point, but it's the action of the side links "meshing" that makes it possible.
Ed
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BurbMan
Indianapolis, IN
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Joined: 09/20/2001
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zzzzzzzzzzzzzzzz
*snort*
Huh? Wazzaat??
Oh, hi guys....Tim, I'll jump in and answer your question to Will...I think we pretty much beat the concept of the 4-bar linkage to death. I'll go out on a limb and say that we all agree that the creation of the VPP by the linkage is the cornerstone of the HA design and largely responsible for its effectiveness. Recent conversation has largely been focused around the specifics/details of this.
We did start to touch on a secondary component of the hitch, a point that you brought up Tim, about the HA's ability to reduce lateral forces on the TV based on the moments created by the 4-bar linkage. I think we got off track before we sufficiently quantified that concept.
All we need now is a little differential calculus to show that the 4-bar linkage not only changes the force moments, but also affects that rate at which those forces build on the TV in response to forces applied to the TT. (dv/dt=?)
I would also suggest that we could summarize for the Les the Moderator the relevant posts to keep in the thread and condense to a sticky.
Thanks to all for much time spent on this! Ron, enjoy your fishing trip!! Last time I had 3 weeks off in a row, I was unemployed....
Don
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