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Direct Link To This Post Topic: Actual Weights as measured
    Posted: 11 Oct 2019 at 5:03pm

If I may ask you, could you run numbers on 1x2x3/16" (7 gauge steel)? That's what my frame repair is and would match up for the tongue support. Yes, it's on the flat..
[/QUOTE]

Will do. I finally got home before the road on the island got shut down due to ocean overwash so I should have time to runs some numbers tomorrow.  

My 179's tongue weight is closing in on 550 with full fresh water, dual GC2's, one (not two) full propane tanks, and not much of anything else heavy forward of the trailer axle. Total weight is about 3800 so that's around 14% tongue weight. So yep, as Podwerks says, FR's tongue weight numbers are really not anything like the real world for anyone who does much boon docking with the bigger rpods.  

You have to be careful though too about moving too much weight aft. If, like me, you are returning with all that water moved to the 179's gray water tank that reduces tongue weight percent to about 11. Get much lower than that and the trailer can be sway prone, so there is a sweet spot for me around 14% outbound and 11% inbound. 
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Direct Link To This Post Posted: 10 Oct 2019 at 4:04pm
Originally posted by Jeepinator

Such a great discussion.  I'm living in the "moment".

Based on documented failures, isn't the weld from tongue to frame one of the most significant points for potential failure?  That being the case, I was considering adding reinforcement there as you would not have to give up any clearance on the bottom.  I did examine the weld and it looks pretty crappy.  A shimmed piece of angle properly welded would significantly increase the strength in my unqualified opinion.

I was also going to weld the bolt-on receiver as it tends to flex with the WDH.  I just have to confirm I can still remove my Jeep bumper.

As we all are due to Offgrid and his knowledge on this. I do thank him for being so willing.

The question of how is important to all of us. We don't want to just weld more steel/weight without knowing just what the benefit will be. I just went through an examination of the tongue with my dealer repair pro. I was amazed at the tongue weight empty (I do mean no tank or battery there) and it read 375# (or there abouts). Base weight, nothing added and we come very close to what is suggested by FR. Deflection according was only 1/4" as weight was placed upon. 

Throw a propane tank (singular) and my dual batt's, I've added close to 100#'s on that tongue. Given we can back load (behind the axle) to compensate, and we add a WDH. What shall we do to compensate?

That becomes the 'moment' / action we need to deal with. 

My Dealer contact had that 'Deer in the headlights' moment when I asked... Pun intended! 

As my experience continues, and that of others continue to figure out, we shall work this through.

I do wish this thread continues!

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Direct Link To This Post Posted: 10 Oct 2019 at 3:24pm
Such a great discussion.  I'm living in the "moment".

Based on documented failures, isn't the weld from tongue to frame one of the most significant points for potential failure?  That being the case, I was considering adding reinforcement there as you would not have to give up any clearance on the bottom.  I did examine the weld and it looks pretty crappy.  A shimmed piece of angle properly welded would significantly increase the strength in my unqualified opinion.

I was also going to weld the bolt-on receiver as it tends to flex with the WDH.  I just have to confirm I can still remove my Jeep bumper.
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Direct Link To This Post Posted: 10 Oct 2019 at 7:49am
Originally posted by offgrid

I'll take a look at the numbers when I get home but I think a 2x2 tube is a good idea. It will add strength without compromising clearance much assuming there is a 4 inch riser at the axle.  I'd probably go a little thicker than 0.1 though, and extend it from forward of the wdh attachment to aft of the front of the trailer box a couple of feet. I do agree that adding a bit of reinforcement to the rpod frame and axle on the heavier units would go a long way to make them more robust. 

If I may ask you, could you run numbers on 1x2x3/16" (7 gauge steel)? That's what my frame repair is and would match up for the tongue support. Yes, it's on the flat..
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Direct Link To This Post Posted: 09 Oct 2019 at 6:04pm
I'll take a look at the numbers when I get home but I think a 2x2 tube is a good idea. It will add strength without compromising clearance much assuming there is a 4 inch riser at the axle.  I'd probably go a little thicker than 0.1 though, and extend it from forward of the wdh attachment to aft of the front of the trailer box a couple of feet. I do agree that adding a bit of reinforcement to the rpod frame and axle on the heavier units would go a long way to make them more robust. 
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Direct Link To This Post Posted: 09 Oct 2019 at 1:42pm
Originally posted by offgrid

 

Re the strength of a weld, a good welder can make a weldment just as strong as the steel he or she is welding (emphasis on good welder using the proper technique for that weld). If we're talking about adding a doubler tube under the existing tube that is a pretty benign thing to weld because the mating surfaces of the two parts will be at or near the neutral axis of the weldment. The neutral axis is the cross section where there will be no stress (in other words, the location where the parts transition from being in compression to tension when placed under load). 

With a bit more research, I find that properly done, the weld can actually be stronger than the parent metal. That does surprise me! I always thought there would be some give in the process. 

Live and learn! Thank you for the input.

Now, for fun of this conversation and how our tongue frame is done. 2x4x.1 steel is everywhere. Being the tongue is welded to the front cross member vs. the tongue being the through member. My mind goes towards the tongue going through would be stronger due to the 'hollow' of the 2x4x.10 cross member. I would think the moments (see, I  am learning.. I think..) happening in the tongue frame are greater than those of the cross member. 

I do think that stacking (not sure of correct term being it would be under) in our existing position would do the deed to enforce the tongue frame. I would also go as far of thinking even a 2x2x.10 steel tube (matching the parent steel) would help in a major way. 
I see far too many folks adding storage boxes, second propane tanks and some many other carrying racks without considering what really happening. Then of course we add a WHD into the mix. 

All said and not attempting to take away from the original threads purpose, I do believe all this is relevant. FR basically is saying their tongue design is meant for (in my case) 385#. 10% of the max weight of the trailer. If over, how do we compensate? I load behind the axle to reduce, yet best I figure, I'm still 15# over. Then comes the action (moments, still tryin' here) of the WDH. 

I'm not saying we own a piece of crap.. We have a pretty decent unit for the dollar and a couple hundred dollars to get it to where it can be is well worth the effort and expense. 

   


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Direct Link To This Post Posted: 08 Oct 2019 at 6:54pm
Originally posted by Olddawgsrule


Here's where I now sit dis-mystifying the magic. And only 'my understanding' of the magic!

Offgrid explained the torque I see as actually being moments of the action introduced by the WDH. I get what he's saying now mostly from watching the video I offered. The magic is being explained.

The down force on the ball from the trailer is not removed. The force (moment/torque) is being displaced by the WDH through it's action. Thus sending X forward and X backwards. Then again that amount being determined by the axle length of the TV (I think I've learned). That again becomes a question of why if the weight of the ball is not removed, then where do we get the addition weight on both the TT & TV? 


The weight on the hitch itself is not removed from the hitch but it is removed from the TV rear axle. Think of it this way:  in a statics problem (where things aren't actually moving around) all the forces have to balance to zero and all the moments (separately) have to as well. If the forces don't balance then things would rise up or sink down and if the moments don't balance things would rotate. 

The weight of an object is of course a force pressing downward and is countered by an equal and opposite upward force from the ground.   So, since tensioning the wdh applies moments which are balanced by increasing forces pressing up from the ground at the front axle and the trailer axle, then there has to be an equal reduction in the force pressing up from the ground somewhere else, because the total force pressing up by the ground has to equal the total weight of the rig, which isn't changing. That somewhere else is the TV rear axle.  So the downward force on the hitch itself doesn't change but the downward force on the rear axle does. The front axle load gets higher and the rear axle load gets lower, both of which are good things for your TV.  

There are some downsides though.  There is now a new downward point force on the trailer frame from the tensioning chain/bracket, and there is more load on the already heavily loaded trailer axle. And there is also a moment placed on the TV receiver and frame which wasn't there before. So the tow vehicle and receiver have to be rated for a wdh and the load of the trailer and hitch have to be within those specs. The trailer frame and axle should be rated for the additional load too, which is where axle and frame reinforcement come in. 
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Direct Link To This Post Posted: 08 Oct 2019 at 6:08pm
Originally posted by Olddawgsrule


I'm certain Offgrid can explain better, yet what we have, I don't consider a true 'A' frame. The way it is done, I consider it a 'V' frame. Maybe even with the way it's done (and the welds being very good) it should be better than a true straight tongue. Yet I wonder..

Speaking for myself, and what I hope to see done to my trailer (in for warranty frame repair),I figure a 2x2x? will be added under the tongue 'A' frame to stiffen it. Under meaning it would travel past the existing frame cross member and be attached (welded) to the side frame member. That would make it a true 'A' tongue frame.

Here's where I go to Offgrid and ask of what percentage of strength is a weld compared to a through section of frame? My assumption, if the welds are good, 80-90% of original. 


I can't explain the detailed design of the rpod tongue attachment, I really haven't gone under there and looked at it. What I am saying is simpler:  if you just assume that the trailer frame was made up of two continuous 2x4 beams running from the hitch to the rear of the trailer, and supported by the hitch and the rear axle, what you would have is a simply supported single ended cantilever. If you then loaded those beams uniformly from end to end (not true for an rPod but a reasonable starting point) you would have the standard structural case of a simply supported uniformly loaded single ended cantilever. For that case you can look up the moments and deflections, no need to do some kind of complex analysis. 

That's this case:


If you look at the moment diagram, there are two points where the moments reach maximum (which is where the frame will bend if the stresses there exceed the yield strength of the steel). One point is partway between the hitch and the axle, trying to bend the frame down, and the other is at the axle itself, trying to bend the frame up. That's why I'm saying that there is a high bending load location near the front of the trailer, but probably under the box a little bit. Not sure without doing the calcs how the two bending moments compare and exactly where and I'm travelling (without my pod unfortunately) so I can't take the measurements right now. 

Re the strength of a weld, a good welder can make a weldment just as strong as the steel he or she is welding (emphasis on good welder using the proper technique for that weld). If we're talking about adding a doubler tube under the existing tube that is a pretty benign thing to weld because the mating surfaces of the two parts will be at or near the neutral axis of the weldment. The neutral axis is the cross section where there will be no stress (in other words, the location where the parts transition from being in compression to tension when placed under load). 
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Direct Link To This Post Posted: 08 Oct 2019 at 2:32pm
Originally posted by GlueGuy

Originally posted by Jeepinator

Given all the smart people on this thread, I’d like to add another element. What is the underlying risk of exceeding tongue weight and will air bags reduce it?  I’ve not determined my exact tongue weight yet but I suspect I exceed the 350# even with the WDH. 

I am aware that sway and receiver/coupler damage are potential risk factors but I assume there are others. 

The TV and trailer are level when the WDH is engaged.
The WDH does not reduce the tongue weight, it distributes the weight. Effectively it will reduce the amount of the tongue weight applied to the rear axle of the TV, and distributes it to the front axle of the TV and back to the trailer axle. The amount that goes to each axle depends on the torque plus the length of the moment arms.

Also, air bags will not reduce the tongue weight. Air bags will increase the weight that your rear suspension can handle, but will not increase the weight the axle/bearings can handle or the weight the frame of the vehicle will handle.

Here's where I now sit dis-mystifying the magic. And only 'my understanding' of the magic!

Offgrid explained the torque I see as actually being moments of the action introduced by the WDH. I get what he's saying now mostly from watching the video I offered. The magic is being explained.

The down force on the ball from the trailer is not removed. The force (moment/torque) is being displaced by the WDH through it's action. Thus sending X forward and X backwards. Then again that amount being determined by the axle length of the TV (I think I've learned). That again becomes a question of why if the weight of the ball is not removed, then where do we get the addition weight on both the TT & TV? My assumption is because of the action of the WDH. My concern is what is happening on our tongue frame for all this to happen. It's only 2x4x.10 steel and is it capable to compensate? 

That to me is a lot going on on our frame.

I do see by the program Offgrid offered, I need to go back to the scales for some accurate readings for it to work correctly. Which I will do.

Does a WDH work? No doubt it does. More to learn and understand.


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Direct Link To This Post Posted: 08 Oct 2019 at 1:50pm
Originally posted by Pod People

I understand what Offgrid is saying. We have a 4x8 utility trailer that had a failure where the tongue met the body. It was a single 3x3 beam and not an A frame, so it had only a single point of connection.  Welding a reinforcement beam under the original beam and adding triangle gussets took care of the issue.
with the RPods A frame, at least there are 2 connection points.
Vann

I'm certain Offgrid can explain better, yet what we have, I don't consider a true 'A' frame. The way it is done, I consider it a 'V' frame. Maybe even with the way it's done (and the welds being very good) it should be better than a true straight tongue. Yet I wonder..

Speaking for myself, and what I hope to see done to my trailer (in for warranty frame repair),I figure a 2x2x? will be added under the tongue 'A' frame to stiffen it. Under meaning it would travel past the existing frame cross member and be attached (welded) to the side frame member. That would make it a true 'A' tongue frame.

Here's where I go to Offgrid and ask of what percentage of strength is a weld compared to a through section of frame? My assumption, if the welds are good, 80-90% of original. 

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