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Old 11-14-2013, 04:08 PM   #127
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Ron

It has been 50 years since I had any strength and materials classes and really had little use for them while working, thus I did not attempt to show the math.

However I do remember that a cantilevered beam, the tires to the hitch, has a uniformly increasing bending moment along the beam. A beam designed for that would have no problem supporting the load we are talking about here. My point is the trailer frame was not designed with this type of load in mind and thus I suggested looking at point where displacement would be most likely to show up.
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Old 11-14-2013, 05:23 PM   #128
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I agree with what you say.

What part of what I posted do you think might not be true?

I think we're saying the same thing.

Ron
It seemed that you were saying there is a smaller limit of the angle then with other hitches.

Unless you just meant people need to be told sheet metal damage might not be the limiting factor with this type of hitch.
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Old 11-15-2013, 07:56 AM   #129
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Unless you just meant people need to be told sheet metal damage might not be the limiting factor with this type of hitch.
That is what I meant to convey when I stated, "And, as Steve's photos show, the hitch limit can be reached with good remaining clearance between TV and TT and with no obvious interference between hitch components."

IOW, you can reach the hitch limit before there is any sheet metal damage.

Ron
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Old 11-15-2013, 11:51 AM   #130
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Fifth Wheel hitching problem

A buddy of mine has a Silverado. I met him when I asked "What on earth happened to your truck? I thought a tree might have fallen across it as the sides of the bed were all crushed down.

Somewhat redfaced, he told me that he had been towing his fifth wheel when it came off the hitch and KA-Boomed on his truck. He hadn't yet left the campground and was only going about 5 mph... but Oh the humiliation and drama! Then he said he normally lies and says he just got it super cheap with a salvage title!

Now there's a story that makes me even happier I never considered a fifth wheel. I hate to ever be on the side of more government regulation but has anyone ever seen an RV dealer that offered a "newbies guide to towing?" It's kind of remarkable how few of us DON'T get hurt or killed making newbie mistakes on our first few trips.

I remember years ago that a local municipality decided to save vehicle costs for road and sewer maintenance trucks by putting utility trailers on them The idea was that carrying a lot more equipment per vehicle would allow the crews to get to work faster and that they could send one or two trucks out to a project instead of three or four and still have everything on hand they needed to do the job. Worked fine, except for the number of accidents the (almost totally male) crews started having. The city concluded that they'd just all assumed that the men could "handle it." $40K in damages convinced them that no one is born knowing how to hitch, tow or back up safely (surprise surprise). So they put in a 3 day seminar with classroom and real driving/backing practice. The accident rate went back down to pre-trailering levels.

Brings me to a hijack - we ask for volunteer inspectors. How about a "forum manual" of good hitching practices and safe towing suggestions" - or even have volunteer mentors for the newbies? I say that with a grain of caution as a "geezer" told me to simply twist my chains to shorten them when I first started. BAD advice. Even my new EB Airstream came with the emergency breakaway cable threaded through the chains... (Another BAD idea.) I left it alone for the first trip... and sure enough the chains were a tad too long and got a tiny bit of road rash. I shortened them one link. The cable looked badly damaged so I took it out of the chain and "tested" it by pulling on each end. D'oh, it popped apart. Got a nice replacement one - it is six feet long, but it sprials so it rides well clear of all the things that can pinch or sever it. It's also covered in red plastic so it's easy to notice that it's hooked up right.

Paula
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Old 11-15-2013, 03:12 PM   #131
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Maybe the topic for another thread but a serious question for a customer...

Would you recommend that we cut the stop shorter, increasing the turning radius, so that anyone using a 3P hitch will come in contact with the frame or the trailer in those situations?

I'd have to test how much shorter I can get it.
Good question. I always thought the turning angle was limited mainly by the inherent geometry of the hitch. I don't think I've ever hit it but I have had the yoke dislodged when maneuvering in difficult (hilly/muddy) terrain. One of the things I want to try is painting marks on the hitch somewhere so I can determine without unhitching how much turn angle is left.
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Old 11-15-2013, 03:43 PM   #132
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A back-up camera, a hitching stick on the receiver,
.... use the stick as the vertical crosshair, when the tank becomes un-covered, get out and check, continue increasing the angle, repeat as needed. Burn it in the memory banks.

Bob
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Old 11-15-2013, 04:27 PM   #133
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Quote:
Originally Posted by Foiled Again View Post


Brings me to a hijack - we ask for volunteer inspectors. How about a "forum manual" of good hitching practices and safe towing suggestions" - or even have volunteer mentors for the newbies? I say that with a grain of caution as a "geezer" told me to simply twist my chains to shorten them when I first started. BAD advice. Even my new EB Airstream came with the emergency breakaway cable threaded through the chains... (Another BAD idea.) I left it alone for the first trip... and sure enough the chains were a tad too long and got a tiny bit of road rash. I shortened them one link. The cable looked badly damaged so I took it out of the chain and "tested" it by pulling on each end. D'oh, it popped apart. Got a nice replacement one - it is six feet long, but it sprials so it rides well clear of all the things that can pinch or sever it. It's also covered in red plastic so it's easy to notice that it's hooked up right.

Paula
Well stated Paula. I received a very small amount of instruction from the technician that setup my first new SOB. The rest of my skills were learned the hard way and on this forum and the rv.net.
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Old 11-15-2013, 04:45 PM   #134
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Guess how dealer initially installed chains? I noticed immediately and corrected

I'm staying at dealer tonight and reading the manual before we pull off
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Old 11-15-2013, 04:54 PM   #135
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Originally Posted by Jammer View Post
Good question. I always thought the turning angle was limited mainly by the inherent geometry of the hitch. I don't think I've ever hit it but I have had the yoke dislodged when maneuvering in difficult (hilly/muddy) terrain. One of the things I want to try is painting marks on the hitch somewhere so I can determine without unhitching how much turn angle is left.

Jammer, I think you're correct about the turning angle being mainly limited by the inherent geometry.

The above plots were generated for the Hensley Arrow linkage, but I think they apply to the ProPride as well.
At 0 degrees you can see the slightly greater center-to-center spacing of the rear pivot points.
This gives the hitch the "converging" geometry which causes the trailer's pivot point to be "projected" forward about 52".
At 19 degrees, the ball has reached its maximum lateral displacement of about 4.8".

The geometric limit for the hitch occurs at about 83.5 degrees when the right-hand linkage bar has rotated more than 180 degrees and becomes parallel with the left-hand linkage bar.
At this angle, the hitch is attempting to push the trailer sideways.

It looks as though the physical limit for the linkage would occur at about 88 degrees when the left-hand WD bar swings far enough to make contact with the right-hand WD bar.

Relationships for the ProPride 3P might be slightly different from those shown above.

Ron
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Old 11-15-2013, 04:59 PM   #136
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Quote:
Originally Posted by Jammer View Post
Good question. I always thought the turning angle was limited mainly by the inherent geometry of the hitch. I don't think I've ever hit it but I have had the yoke dislodged when maneuvering in difficult (hilly/muddy) terrain. One of the things I want to try is painting marks on the hitch somewhere so I can determine without unhitching how much turn angle is left.
This subject has also got me interested!

I too assumed that at some point the four bar link would just reach the end of its travel and lock up - never really checked it though or gave much thought to what the result of that might be!

I just quickly went through our Hensley manual and didn't see any advice or warnings about backing up - I went through it quickly and might have missed something - I will re-read!

At times, I have backed at some pretty sharp angles and always thought it was a bonus that the extra length of the Hensley setup allowed me to do that.

But now I have some new concerns about maybe causing damage and how to know when i am close to doing that!

Annie - it is an ill wind that blows no good! You have got many of us thinking!

Brian.
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Old 11-15-2013, 06:07 PM   #137
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But now I have some new concerns about maybe causing damage and how to know when i am close to doing that!
Brian, according to former Hensley Arrow owner, Steve Rankin, and as shown in the above photo,
when the corner of the orange cover lines up with the center of the draw bar,
you have reached the limit.

In the photo, the limit has not quite been reached.

I have not verified this. You might want to check it out.

Ron
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Old 11-15-2013, 06:29 PM   #138
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Thanks Ron,


Looks like pretty darn near a ninety degree angle! Not often I back up that sharply I don't think so maybe I don't need to worry after all!

Reminds me of a time when we checked into an RV park at Apache Jct. It was one of those places that are 90% park models with the odd spot open for rent in amongst them.

Roads seemed pretty narrow and I'm not the best backer-upper and so I was a bit concerned about my ability to get into the tight spot that was oriented ninety degrees to the road (why, oh why, do they design RV parks like that!?).

Anyway, they sent an older gent with me to help me back in. He was a gruff old guy a bot like a drill sergeant (but all in good humor), and instructed me to do exactly what he told me.

He had me execute a whole series of first cutting the wheels full lock one way, backing up a bit, then cutting the wheels to the opposite lock, going forward a bit and then repeating this cycle many times.

I was very impressed how well the trailer went in and decided to remember that technique next time I encountered such a situation.

Mostly been in pull-throughs or well angled back-ins ever since. but i still remember how well that worked in a spot I thought was going to be a real challenge!

Brian
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Old 11-15-2013, 07:03 PM   #139
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Guess how dealer initially installed chains? I noticed immediately and corrected

I'm staying at dealer tonight and reading the manual before we pull off
First - congrats!

Second - spot on! Put those chains under!

Third - you might also want to take up a little slack on them. They look pretty close to the ground.

Enjoy!
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Old 11-15-2013, 07:40 PM   #140
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First - congrats! Second - spot on! Put those chains under! Third - you might also want to take up a little slack on them. They look pretty close to the ground. Enjoy!
Also, the chain coupler may not be the correct strength for the job at hand and you might be able to stretch your cord a bit so it doesn't pull out in a tight turn? All fun stuff to muck with in the rain. Jim
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