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Author Topic: Question about roto-flex and similar 5th wheel pinboxes  (Read 171 times)

Boonieman

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Question about roto-flex and similar 5th wheel pinboxes
« on: September 29, 2017, 02:48:47 PM »
Iíve looked at several Fifth wheel campers that have a pivoting head on the pin box where the pin is attached, such as roto-flex and others.  I canít find any internal views of this mechanism. Surely these two 5/8 bolts arenít carrying the weight of these big campers. Iíve asked two different sales guys, and they said yes, these bolts are what holds it on, but they are ďheavy dutyĒ bolts. ????? Thereís some high tech lingo for ya. I see a lot of them on the road, so the design must be ok, but I sure would like to know how the internals are constructed. 5th wheel hitches pivot anyway, so is there any real advantage to this system, or is it just a gimmick?
2016 Chevrolet Dually/Duramax
2011 Fuzion 322
2016 Harley Trike
3 cherished dogs, Moo, Molly, Mia the one eyed pup 😊
Originally from South Dakota, reside in Kentucky

Rene T

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Re: Question about roto-flex and similar 5th wheel pinboxes
« Reply #1 on: September 29, 2017, 02:52:26 PM »
Iíve looked at several Fifth wheel campers that have a pivoting head on the pin box where the pin is attached, such as roto-flex and others.  I canít find any internal views of this mechanism. Surely these two 5/8 bolts arenít carrying the weight of these big campers. Iíve asked two different sales guys, and they said yes, these bolts are what holds it on, but they are ďheavy dutyĒ bolts. ????? Thereís some high tech lingo for ya. I see a lot of them on the road, so the design must be ok, but I sure would like to know how the internals are constructed. 5th wheel hitches pivot anyway, so is there any real advantage to this system, or is it just a gimmick?

What they should have said is that they are probably Grade 8 bolts which are stronger than the standard steel bolt which may be Grade 2.  If there are no markings on the head they are Grade 2. If there are 3 lines on the head, they are Grade 5.  If there are 6 lines on the head, it is a Grade 8 bolt and nearly 3 times stronger than a Grade 2 bolt.
« Last Edit: September 29, 2017, 02:56:54 PM by Rene T »
Rene & Lucille & co-pilot Buddy
AKA  Pep N Mem
2011 Chevy Duramax 2500 HD 4X4
2011 Montana High Country 343RL
From the Granite State of NH
& Florida Snowbird in Lakeland FL

Boonieman

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Re: Question about roto-flex and similar 5th wheel pinboxes
« Reply #2 on: September 29, 2017, 03:50:18 PM »
Thanks Rene. I am familiar with the bolt grading system, but I was hoping there was a solid internal pin that the assembly pivoted on besides a couple bolts. Maybe thereís not though. Most things on RVís havenít impressed me as far as the engineering goes. It seems to be designed to be adequate, but nothing more. From axles, to tires, to A/C capacity, it all seems ďjust enoughĒ barely. In all fairness, Iím often teased about my ďindustrial strengthĒ projects I do, so I plead guilty to overkill. Maybe itís just me. 😄
« Last Edit: September 29, 2017, 03:53:25 PM by Boonieman »
2016 Chevrolet Dually/Duramax
2011 Fuzion 322
2016 Harley Trike
3 cherished dogs, Moo, Molly, Mia the one eyed pup 😊
Originally from South Dakota, reside in Kentucky

Gary RV_Wizard

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Re: Question about roto-flex and similar 5th wheel pinboxes
« Reply #3 on: September 30, 2017, 11:22:17 AM »
The entire pin box is bolted to the trailer in the same way whether a movable head or fixed and its only about 4 bolts per side. I've never looked closely at a Rotoflex, but the actual pivot in the Reese Sidewinder appears to be a pin. However, the pin assembly is just bolted together. I'm sure it could break off, but reports of failing 5W hitches are scarce and what reports there are rarely have the circumstances and history of use/abuse documented.

If you look at the other half of the hitch mounted to the truck, major parts of that have only a few bolts as well.

Looking at a photo of the Rotoflex, I'm guessing you are talking about the pair of bolts that mount the movable front section. It does indeed seem "light" considering that the entire force of towing gets transmitted through them, and its a movable joint as well.

Unlike RV builders who work mostly via "shade tree engineering", most real hitch manufacturers (Curt, Reese, etc.) actually do have mechanical engineers on staff who understand things like shear strength, tensile strength, fastener elongation, etc. Doesn't mean they never make mistakes, though.  Whether that applies to Trailair is harder to judge. Trailair is part of Lippert now, and Lippert is not well known for top flight engineering. Cheap components seems to be their specialty.
« Last Edit: September 30, 2017, 11:24:21 AM by Gary RV_Wizard »
Gary
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Boonieman

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Re: Question about roto-flex and similar 5th wheel pinboxes
« Reply #4 on: September 30, 2017, 02:15:14 PM »
Thanks Gary, that was kinda my take on it too. I only asked because my better half occasionally gets a wild hair about trading ours in on on newer model, and she keeps looking bigger too. I like to have a comfortable margin on error, weight-wise, and some of these triple axle monsters they are putting out now are getting close to outclassing a dually and I refuse to go any bigger than that for a TV. But a lot of the new 5th wheels are coming out with the pivoting pin and are really being touted by sales people as preventing chucking. I like do do my own repairs when possible, so now that Iíve seen some of the innards of these RVís, I try to look past all the beautiful interiors and all the bells and whistles. I dig a little deeper and try to see how well built they are, provisions for maintenance access, etc. Not only that, over the years in the chemical industry Iíve noticed materials of construction doesnít seem as consistent as it use to be. Before I retired we had an expansion project and some of the valves they bought for a very corrosive service called for hastelloy c internals. Well, I guess due to price and a bidding process, the valves came from Russia. Had all the appropriate API stamps and symbols on the valves, but after only 3 months they all started leaking thru and eventually all had to be replaced. We had other valves of that material in service for 20 years with no problem. Not knocking Russia either, thatís just one example Iíve seen. Makes me a little leery just because a bolt is stamped as grade 8, itís only as good as the quality control and manufacturing process it comes from. I donít like buying anything that has serial number 0000001, or anywhere close to it. 😄 Moot point for now since sheís decided to hang on to what we have......for now. Agains, appreciate the reply, and yes, the two bolts you describe were my concern.
2016 Chevrolet Dually/Duramax
2011 Fuzion 322
2016 Harley Trike
3 cherished dogs, Moo, Molly, Mia the one eyed pup 😊
Originally from South Dakota, reside in Kentucky

 

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