bettered
UpCountry SC
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BurbMan wrote:It's all in good fun! I appreciate the opening nonetheless.
MPG runs about 9-10 around town, 13 on the hwy, 8 or so towing. Oh well....
Donb
Don - (I like that better than Burb, too)
That's why I made the 'classy' remark.
I've got an '00 1500 GMC p/u with a CGW capability of 13,000. The truck is 5,700 so I'm about maxed out. My engine is the 4.8L with the 4:10 so around down I get 15, maybe 17 on the highway (and maybe not) but towing doesn't suffer so much - still getting about 12 or 13. I'll know more after our trip to the No. GA mountains over the 4th. I've looked at the new trucks, but have decided that I can buy quite a lot of gas for $30,000, even if I had it...
Tim - That is really an eye opener, but I just made a Margarita for my wife and jumped in with her (made one for myself too, that is) so I'll have to study the pictures in more detail when I'm able. One thing that's immediately obvious is that all the action is between the front and rear bars so it's challenging to see what's really going on in there.
Stay tuned.
Ed
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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Don, FWIW..
Over on SKP's website is quite a discussion about the 8.1L and fuel milage, both towing and not. One fellow was claiming some remarkable results, but I didn't study why.. Most aren't having such luck.
Tim,
I've examined the new picture. (Thanks, I'd forgotten how relatively easy it is to make such a picture.) That's what I'm seeing, and now I understand the hitch operation much better(ed). It's a bit difficult to see on the actual hitch because the sheer size of the front and rear bars mask much of the action of the short links. But the stick figures are accurate.
I assume you used the 165 degree figure to show the limit of travel. Extrapolating what the actual hardware looks like, in the purple view I can envision where the ears are relative to the collapsing short link (on the left in your picture). Given the width of the link and the position of the ears, this appears to be the same point (in the purple figure) where the ears will contact that link, stopping further rotation.
Well done. Ron G will be proud (or will have forgotten us altogether). I think we're ready to go to press with this one.
* This post was
edited 06/11/05 05:49am by bettered *
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tluxon
Kirkland, WA
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bettered wrote:...I assume you used the 165 degree figure to show the limit of travel. Extrapolating what the actual hardware looks like, in the purple view I can envision where the ears are relative to the collapsing short link (on the left in your picture). Given the width of the link and the position of the ears, this appears to be the same point (in the purple figure) where the ears will contact that link, stopping further rotation.
Yes, the purple position represents the last degree I could rotate the rear bar on the model without the linkage stopping itself.
I think the videos and illustrations have really helped uncover some of the mystery of the HA. Before we go into consolidation phase, I'm wondering if anyone can think of anything that might be missing that would help the curious understand how the hitch really works.
If I consolidate to a new post that links to this thread, I probably won't include EVERY video, picture, and illustration. If anyone has a favorite video or image in this thread that they would want to make sure gets into the "consolidation" post, please add a post with the video or picture in it or link to the post that contains it. You can get the address (needed for the link) of a specific post by going to it and selecting the "Link" label on the right side of the post's header. Then just paste that address into your new post.
Thanks,
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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Obviously your Figure 5 qualifies, and I like the video of the hitch - which shows what I was doing with mine to make the observations in the last few posts. The movie of the hitch in action from the back of a TV is difficult to appreciate because of the relative lack of any points of reference - except for that yellow line that moves in and out of the frame...
Ron's calculations and the actual data that was plugged in were helpful.
I also liked the commentary on the perceived differences between the PR and the HA. I'll go back and try and pick out a few posts that are really meaningful and list them.
Ed
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willald
NC
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I'd like to dredge this topic back up, to discuss something I've been thinking about, that I'm not sure we took into consideration before, in all the models discussed before.
There seems to have been some 'disagreement' in this discussion previously, about whether or not the Hensley truly is 'locked' in a straight position (from the trailer's standpoint), or if its completely free to pivot, but strictly pivot through the arc/angle that the Hensley allows.
After some thought, I'd like to submit, that perhaps BOTH are true. Stressor was of the firm belief that there was indeed a 'lock' from the trailer's perpective, where as many others disagreed with such. It is my belief, that perhaps BOTH are correct. I'm not really able to put together the illustrations like others have, so I'll try to put it into words. Here goes..
Look closely at the video clip several posts back, where someone put a camera above a Hensley, when it was travelling down the road. This is the one that shows the Hensley going through its entire path of pivoting, when going down the road. Watch this video closely, a couple of times. After doing such, is when I came to a realization.
Notice, that the part of the Hensley affixed to the trailer (orange head), when it does pivot, it has to pivot through an ARC. And, notice that when the trailer/Hensley is in a straight line, its in the BOTTOM of this arc, such that in order to pivot either way, it has to move UP the arc in either direction, if you will.
Maybe one way to think of it, is to picture your truck and trailer suspended vertically by a crane or whatever, with the trailer hanging down below the truck. Gravity represents the same force pulling back on the trailer, that is normally pulling back on it when towing. Friction, air resistance provide this force when towing.
NOw, think of this dangling trailer, and you try to push it either way to make it pivot. In order for it to pivot, it would have to move up the arc the Hensley forces it to pivot through, hence it'd have to overcome the force pulling it back (gravity). Bottom line: It would NOT move/pivot. It would basically be LOCKED, from the trailer side. Thats exactly what Stressor(Milt) was trying to suggest.
Now, think about the truck pulling a trailer, and realize that there is tension/pulling between the truck and the trailer, similar to the way gravity pulled on it if suspended vertical like I just mentioned. It is this very 'pulling'/tension, that makes it almost impossible for the trailer to induce any pivoting. In order for the trailer to pivot, it has to move up the arc I mentioned above. As long as the truck is pulling the trailer, there is a TON of force the trailer would have to over come, in order to move up this arc. Hence, it cannot move up the arc, and the trailer CANNOT induce any pivoting. Basically, the Hensley is using the wind/friction resistance that a trailer has, to force it to stay in the straight position
Now, once the 'pulling' on the trailer goes away (as in, when braking and brake controller is not set aggressive enough), this whole effect goes away, and the Hensley pivots just like the previous models suggest - similar to a 5th wheel for first few degrees, getting more and more like a conventional TT the further it goes. Thats why its so crucial to have your brake controller set right, when using a Hensley, to get the full effect of the Hensley's design.
Anyway, I think in all our models/discussion before, maybe we did not take into account the fact that there is pulling/tension between the truck and the trailer/Hensley, which makes it nearly impossible for the trailer to induce any pivoting.
Thoughts? Ron Gratz, I'm sure you have a 3 page Physics model that may confirm or destroy my thoughts here, so go ahead - lay it on me. I'm ready. ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/smile.gif "smile")
Will and Cheryl
2021 Newmar Baystar 3014 on F53 (7.3 V8) Chassis ("Brook")
2018 Jeep Wrangler JK ("Wilbur")
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BurbMan
Indianapolis, IN
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Will, exactly correct (until Ron proves me wrong....).
The visual of the suspended truck with the dangling trailer was brought up early in the thread. The pivot arc created by the HA only allows the TT to move laterally if it also moves closer to the TV, which, as you pointed out, is almost impossible in normal driving due to wind resistance and rolling friction.
The struts "lock" the HA to the trailer for purposes of eliminating any possible rotation around the ball, forcing all rotation to occur through the arc you describe.
FYI, just came back from a week in VA Beach, and was thinking about this thread while cruising at 70 mph with one finger on the wheel. Pouring rain on the way back, I never had to worry about what the TT was doing, because it only does what the truck tells it to.
I LOVE this hitch.....if every TT had one, 5er sales would be in the toilet.
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willald
NC
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You know, Don, I said at the very beginning of this discussion, that I suspected there was more to the Hensley's design/benefit, than just the fact it projects the pivot point close toward your rear axle. That was what I had hoped to bring out from this discussion.
I remember saying in the beginning, that in my case, it would imply the pivot point is about 20" behind the rear axle. Given what we have experienced with the Hensley (similar to your travelling 70 mph with no concerns about the trailer), I never could really 'buy' that this was all there is to how the Hensley works.
Perhaps this is the other piece to it - the fact that the 4 bar linkage, due to the way Hensley has designed it, makes it such the trailer just cannot induce any pivoting AT ALL, when its being pulled on. Not just that the pivot point is projected toward the rear axle, but more, the pivot is made impossible, from the trailer's perspective, as long as the TV is 'pulling' the trailer.
Will
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BurbMan
Indianapolis, IN
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I agree, I think we put too much emphasis into the physics of the virtual pivot point, and not enough on the practical application of the 4-bar linkage.
The fact is that the ONLY way the TT can move to the side is if it also moves forward, something that can't happen unless the TV is braking or slowing down.
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willald
NC
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BurbMan wrote:The fact is that the ONLY way the TT can move to the side is if it also moves forward, something that can't happen unless the TV is braking or slowing down.
Minor point, but even when slowing down or braking, its still unlikely the trailer can move forward and pivot (assuming the brake controller is set aggressive enough).
Even when coasting to a stop (no brakes being applied), which is providing more wind-related stopping power, the trailer, or the truck? You guessed it - the trailer is. Sooooo, even when coasting to a stop, the tow vehicle is still 'pulling' on the trailer, so the lock-up is still there. Probably not as much, but its still there.
Will
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Ron Gratz
full time RVer
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Will,
Thanks for reopening your thread. This is even more fun than fishing.
Will and Don,
If the "can't swing because it can't move toward the pivot point" theory is correct, then no pendulum can swing because gravity would not allow the mass to move upward. Galileo Galilei could not have invented the pendulum and we would have had no pendulum clocks.
Worse yet, no one would need a Hensley Arrow because no TT could swing. Even with a conventional hitch, a TT must be able to move forward (against the force of wind and tire drag) if it is to swing. If the force prevents the conventionally coupled TT from moving forward, then it cannot swing and no sway control is needed.
The problem with the theory is that the drag forces on a TT, whether it is coupled with a conventional hitch, a HA, or a PR do not prevent it from moving forward when the TT is subjected to lateral forces. If the force were that large, you would not be able to tow it -- even with an Excursion. Similarly, gravity does not prevent a pendulum from moving upward when it is pushed to the side.
Of course the ball coupler on an HA moves forward when the TT swings. That is because the ball coupler and TT are swinging as though they are pivoting about the virtual pivot point. The ball coupler and TT also move forward when the TT is coupled to a PR. That is because the coupler and TT are pivoting about the actual pivot point which is up close to the TV's rear axle.
Neither a HA nor a PR have any way of "locking" to prevent the TT from swinging. Well, actually the PR does; but you would not want to tow a TT with it in that mode.
Ron
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