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Topic ClosedGVWR>GAWR and Stabilizer Issues

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offgrid View Drop Down
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Direct Link To This Post Topic: GVWR>GAWR and Stabilizer Issues
    Posted: 05 Jan 2019 at 11:23am
I just checked the current rPod specs and the 171 and 172 do appear to have a 3000 lb GAWR. All the rest of the product line is 3500 GAWR, and the GVWR is in all cases the stated (low) tongue weight plus the GAWR, following the letter of the DOT requirements. 

So there might be a difference in the actual axles on the 171 and 172, or it might be purely specsmanship. By stating a lower GVWR FR can more easily sell the lighter trailers to folks with lighter tow vehicles.  So there is a strong motivation for manufacturers to derate both tongue and axle weight. 

Or it might be limited by tire and wheel ratings. Someone with a 171 or 172 might be able to confirm by looking at the axle sticker and the OEM tire stampings. 

Regarding numbers of customers that have actually experienced bent axles, I'm not so sure its really a high percentage, You're going to tend to hear from the folks who have had problems, not the thousands who haven't.  It would be interesting for someone to take a count on this forum and see what the incidence here has been. 

I certainly do agree that the axle is not as heavy as it could be. OTOH, if a heavier axle was selected, the trailer empty weight would also go up, which would either limit CCC or tow vehicle selection. This is a typical engineering problem, you reengineer to remove one constraint and another one gets worse. Like playing whack-a-mole. There ain't no free lunch...

For this reason and because I don't view a potential axle failure as a safety issue, while I know I have a heavy 179 I opted not to change the axle, but I did upgrade tires and wheels, which I see as a significant safety improvement. The upgrade caused little or no weight penalty.  I'll see if that was the right decision over time.  




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mjlrpod View Drop Down
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Direct Link To This Post Posted: 05 Jan 2019 at 2:18pm
I have a 2017, 172 and I haven't had any issues. I usually put more weight toward the tongue. The bunk area tends to be a great place to put stuff, and it tends to stay put.  Especially since the large storage space is under the lower bunk. So far, I bring whatever I want. I also have the truck bed I pack up also, and if i really need to, I can throw a travel bag on the roof racks, although I haven't ever done that. My biggest issue is when i bring my sewer caddy. If i am over packed in the truck bed, I find it fits perfect right ontop of the tonneau cover, tucked right up to the cab. I use a ratchet tie down that goes under the tonneau cover and hooks onto the tie downs in the bed. I've never had issue with my stabilizers, maybe they dragged on an uneven road. If you go up, or down a small rise on the road, or a parking lot, they can hit. Good luck and camp the hell outta your 172, i LOVE mine. 
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lostagain View Drop Down
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Direct Link To This Post Posted: 05 Jan 2019 at 5:20pm
Our 172 appears to have a 3000# axle.  The gross cargo capacity is stated to be 920 lbs. with a maximum weight of 3179 pounds.  We generally travel with tanks empty, but when the tanks are kinda sorta full [black is nearly always empty], it doesn't make any noticeable difference in handling except the mountains seem to be a little steeper.  We run D range tires, a swap out from the C's that were on it, but that was more for ride comfort, speed, and economy than cargo capacity.  We load the back of our TV, which has a wedge roof camper shell on it, with most of the heavy stuff like extra propane and gasoline [I hope we never catch fire], fire wood, extra drinking water etc.  I've never had the trailer feel overloaded or on the edge of comfortable control.  

As stated in prior posts, we've removed the upper bunk, raised the lower one with more storage below and have done some other things to lighten the load as we live simple lives when traveling.  
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GlueGuy View Drop Down
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Direct Link To This Post Posted: 05 Jan 2019 at 5:45pm
Everyone knows that FR de-rates the actual axle capacity by 500 lbs because the mount points are ~~ 8" inboard of the normal mount points? I think it would be reasonable to fab a support that attaches to the frame, and just wraps around the outboard 8" of the axle. It doesn't need to be welded to the axle, juts have a yoke that wraps around the top. I'll try to draw something up.
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Direct Link To This Post Posted: 05 Jan 2019 at 9:10pm
Originally posted by offgrid

The DOT regs limit the manufacturers to a trailer GVWR no higher than the GAWR plus the manufacturer's lowest listed figure for tongue weight. For my 179 that is exactly what is on my sticker. 
 

Thanks Offgrid, This is exactly what I was trying to confirm.  Also good to hear from other 172's that they too have the 3000lb and this is iaw spec from FR, although it appears earlier 172s have 200 lbs more cargo capacity, I'll chalk that up to the #!@*^& microwave... (no need to correct me on this).

I expect an upgraded axle will be required since I am already at limit, considering the destinations and resulting punishment I hope to put ours through, also an eventual enclosed basement for 4 season camping.  I read the 6000 or 6500 lippert may allow for the same wheel/bolt pattern as my TV (16"/6x5.5 lug), so will look into going as high as that if it presents no other issues.  

Please let me know if anyone else has done this heavy an axle.

Regarding class action, would assume a number of similar issues would certainly be required given FR is, at least on paper, within ratings allowed by DOT.  I hope not to be one of those statistics, but will certainly speak up if anything occurs.

Lastly regarding the stabilizer issue I had-- yes the bolts broke at the trailer mounting location, if I had to guess my driver clutch rating would have certainly been less than 5 on scale of 20, but I did it old school/with 2 turns of the wrench after stabilizers made contact.  It was literally my first time putting them down and I was overly cautious to not lift.  Looking at the bolts again where they broke, there is a good deal of pitting/appeared to be very porous/low quality material-- so at this time will assume that was primary factor and not my incompetence (didn't hear from anyone that the stabilizers required a level ground to avoid additional stress).

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Direct Link To This Post Posted: 06 Jan 2019 at 7:48am
Originally posted by lostagain

Our 172 appears to have a 3000# axle.  

Ooops. 

My bad (memory). I crawled under, our 171 is also 3000# (Just to keep the record straight)
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Direct Link To This Post Posted: 06 Jan 2019 at 7:58am
During my original discussion with Lippert on this issue I was told that they could sell me a 4400 lb axle which was identical except the label to our 3500 lb ones.

I guess perhaps not surprisingly, when I called back to confirm I got a different sales engineer and a different answer (nothing higher than 3500 lbs unless I went to the next size 5200 lb) axle. The second person also made the comment that they had been told not to tell people that a 4400 lb version was available. Hmmm.

So if indeed the first sales engineer was correct then there are really only two sensible explanations:

1) the axles are really good for 4400 lbs and are being derated to 3500 for reasons of specsmanship
or 
2) the mounting points on the rPods are resulting in the derate from 4400lbs to 3500 lbs. 

StephenH, I believe you have been given explanation 2 by FR? So it that is correct than we could potentially pick up 700lbs of load capacity. 

Regardless, from an engineering perspective I think GlueGuy's proposal is a good one if we can make it work. The axle is a essentially a double ended cantilever beam with equal loads at the ends of the overhanging supports. The stress calcs for this load case are here:

https://www.engineersedge.com/beam_bending/beam_bending7.htm

What we see is that by reducing the overhang (c) we can make the axle bending stress lower, in fact with zero overhang the stress goes to zero. Interestingly this is true both for the axle sections outboard and inboard of the mounting points.  So, this is one of the few design changes in engineering where you're not just moving the problem somewhere else, its all to the good, for the axle at least. 

We do have to consider that we would be applying a new torsional stress to the rPod frame rails (because the new axle brackets would need to carry load back to the frame rails), but box tubes are very strong in torsion so that's probably not going to be much of an issue. 

I'm still puzzled though about the 3000 lb axle rating for the 171/172. Lippert's lightest torsion axles appear to be the 3500 lb units so is there really any difference in the actual axle and/or mounting points on those trailers or is the 3000 lbs just a derate for specsmanship? 







e
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lostagain View Drop Down
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Direct Link To This Post Posted: 06 Jan 2019 at 10:01am
I should clarify my comment that " our 172 appears to have a 3000# axle."  That is a number I found on the data plate in two places.  The print was so small and worn that I cannot be sure the 3000 number is really what it seems to be.  I took a picture of the data plate and here it is:
Unfortunately, my line cleat obscures one segment of the data plate, but I don't think it was the critical info.
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Direct Link To This Post Posted: 06 Jan 2019 at 1:16pm
Here is the label from my 16-171:

---
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lostagain View Drop Down
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Direct Link To This Post Posted: 06 Jan 2019 at 1:40pm
So, if you weigh the tongue weight with one of those little Sherline tongue weight scales, and weigh each wheel weight with same, you'd have the total trailer weight by adding the results?  Seems that for the price of that scale, a lot of uncertainty could be clarified and you could easily balance the trailer if you were in doubt about the balance and total weight.  In my imagination, which is very fertile, one could complete this process much faster than going to a public scale.  

Ok, our Pod Board engineers, will this work, or do I need to lay off the arguardiente again?

michaeln, our posts crossed in cyberspace.  So, how come your data plate looks so nice and new.  Could it be my trailer is a 2009 and yours is nice and new?
Never leave footprints behind.
Fred & Maria Kearney
Sonoma 167RB
Our Pod 172
2019 Ford F-150 4x4 2.7 EcoBoost
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