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GlueGuy View Drop Down
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Posts: 2628 		Direct Link To This Post Topic: RPod Axle Issue....why?
    Posted: 16 Jun 2019 at 10:31am
Originally posted by crankster78

Greetings:
I have a 2015 179 which has been on many a rough road and has about 12 k on it.  So far no problems. I have the lift blocks installed, and have 8 ply tires at 65 psi.  I try to be very careful making turns and not running over curbs.  This year I installed a Eaz Lift R3 Weight distributing hitch due to my truck being a bit old with 124K on it.  I wish I had done this a long time ago.  It really improves handling and levels the whole combo.  I have enjoyed the 179 and had few problems.

Crankster78  (now 79)
A lot of people resist the thought of using a WDH, but I really don't understand why. It's not really that big a deal getting it hooked up, and it does make a significant improvement to the ride quality.
bp
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offgrid View Drop Down
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Posts: 5290 		Direct Link To This Post Posted: 16 Jun 2019 at 11:31am
I did the axle tube load calc awhile ago (there is a thread on this) and came up with something around a 2x safety factor (for bump loads) at 3500 lbs. From everything I've read about vehicle design this safety factor is typically in the 2.5+ range. So its certainly a bit shy of what one might want to see. 

But there isn't a published standard for it and vehicle manufacturers treat their designs as trade secrets. So as lostagain says it might  be hard to prove that this was a design defect.  There is the specific reason for the tube to bend on the rPod which is the unusual inboard mounting location, which may not have been taken into account properly.

By "heavier" I'd say anything with a axle load that reduced the actual bump load safety factor below around 2.5X.  That would be trailers with an axle weight over about 2800 lbs. So in practice that probably means "heavier" is anything with a slide, but its going to depend on how you load it, and whether you use a wdh. 

The axle tube reinforcement helps with the bent tube problem, but remember that the whole axle is rated at 3500 lbs by Lippert, so there are other parts that can and I'm sure sometimes do, fail. If I had to get a new axle I'd buy a 5200 lb one, which is the next size range up. 
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David and Danette View Drop Down
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Posts: 1214 		Direct Link To This Post Posted: 16 Jun 2019 at 11:57am
     I think it was Toyanvil explained the main problem with the r-pods is the mounting points of the axle there is to great of a distance from the mounting point to the wheel. If there was a greater distance between the two main channels of steel under the floor and they were closer to the sides of the camper there would be less of a chance of axle failure. This is what I seem to understand is the main problem.
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offgrid View Drop Down
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Posts: 5290 		Direct Link To This Post Posted: 16 Jun 2019 at 12:03pm
Yes, of course, I just stated that:

"There is the specific reason for the tube to bend on the rPod which is the unusual inboard mounting location, which may not have been taken into account properly."  

That is what all the tube reinforcement designs are intended to address. but that doesn't mean that that there haven't and can't be other axle problems.
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GlueGuy View Drop Down
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Posts: 2628 		Direct Link To This Post Posted: 16 Jun 2019 at 12:19pm
Plus, they could have mounted the axle tube as a square instead of as a diamond and gotten a bit more vertical load bearing (not to mention a very slight increase in ground clearance).
bp
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David and Danette View Drop Down
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Posts: 1214 		Direct Link To This Post Posted: 16 Jun 2019 at 12:24pm
  Sorry offgrid I missed that. You are right there may be other problems. The axle on our Vibe was replaced but it ended up that too may have been bent from the factory a few months after it being replaced it was replaced again under warranty. It is a Lippert axle and thankfully so far it has not been a problem
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offgrid View Drop Down
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Posts: 5290 		Direct Link To This Post Posted: 16 Jun 2019 at 1:00pm
No probs. 

Just as a wild guess the FR/Lippert engineers probably did their job correctly originally when they spec'd that axle with the inboard attachments for the lighter rPods, then as pressure mounted from sales for bigger and bigger trailers they just kept using the same axle. 

I know it sounds like it should be obvious but not going back and properly revisiting original design constraints when you change stuff later is a pretty common engineering fail. Sadly, the consequences can be disastrous. The Boeing 737Max comes to mind... 
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lostagain View Drop Down
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Posts: 2587 		Direct Link To This Post Posted: 16 Jun 2019 at 1:09pm
All this sure makes me glad I have one of the older and lighter 172 rPods.  If I was going to go out and buy a new trailer I think one of my top choices would be the Starcraft 17RB.  With the leaf spring suspension, it sounds like it would be a lot sturdier than heavier rPods of comparable design with the overstressed axle.  We'll see what the market says when people are confronted with axles that are iffy on one model and a leaf spring axle on the other.  
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StephenH View Drop Down
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Posts: 6288 		Direct Link To This Post Posted: 16 Jun 2019 at 2:15pm
Originally posted by podwerkz

I was in an RV dealership about a week ago and spotted the StarCraft Satellite....which is very similar to the r-pods. I looked underneath and it had a leaf spring axle.

Only if the frame is wider so the attachment points for the axle are closer to the wheels. If there is still the large space between wheel and frame, the difference in suspension would not necessarily remove the problem if the weight rating of the axle remains the same.
StephenH
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lostagain View Drop Down
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Posts: 2587 		Direct Link To This Post Posted: 16 Jun 2019 at 2:49pm
StephenH, do you know the distance from between the frame rails of the Starcraft compared to the rPod?  Is the overhang the same?  They don't show any info in their web site regarding the axle or it's sturctural elements.
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