RPod Axle Issue....why? |
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GlueGuy
Senior Member Joined: 15 May 2017 Location: N. California Online Status: Offline Posts: 2629 |
Topic: RPod Axle Issue....why? Posted: 16 Jun 2019 at 10:31am |
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bp
2017 R-Pod 179 Hood River 2015 Ford F150 SuperCrew 4WD 3.5L Ecoboost |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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David and Danette
podders Helping podders - pHp Joined: 24 Nov 2009 Online Status: Offline Posts: 1214 |
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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2018 Vista Cruiser 19BFD (2018-
2012 Vibe 6503 (2014-2019) 2009 r-pod 171 (2009-2014) Middle Tn 2014 Ram 1500 Quad cab |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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GlueGuy
Senior Member Joined: 15 May 2017 Location: N. California Online Status: Offline Posts: 2629 |
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).
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bp
2017 R-Pod 179 Hood River 2015 Ford F150 SuperCrew 4WD 3.5L Ecoboost |
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David and Danette
podders Helping podders - pHp Joined: 24 Nov 2009 Online Status: Offline Posts: 1214 |
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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2018 Vista Cruiser 19BFD (2018-
2012 Vibe 6503 (2014-2019) 2009 r-pod 171 (2009-2014) Middle Tn 2014 Ram 1500 Quad cab |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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lostagain
Senior Member Joined: 06 Sep 2016 Location: Quaker Hill, CT Online Status: Offline Posts: 2587 |
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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Never leave footprints behind.
Fred & Maria Kearney Sonoma 167RB Our Pod 172 2019 Ford F-150 4x4 2.7 EcoBoost |
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StephenH
podders Helping podders - pHp Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6288 |
Posted: 16 Jun 2019 at 2:15pm |
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.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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lostagain
Senior Member Joined: 06 Sep 2016 Location: Quaker Hill, CT Online Status: Offline Posts: 2587 |
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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Never leave footprints behind.
Fred & Maria Kearney Sonoma 167RB Our Pod 172 2019 Ford F-150 4x4 2.7 EcoBoost |
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