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Replacement axle?

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lostagain View Drop Down
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Post Options Post Options   Quote lostagain Quote  Post ReplyReply Direct Link To This Post Topic: Replacement axle?
    Posted: 09 May 2019 at 9:20am
I've been following the axle issues with interest.  It appears that strengthening the axle outboard of the frame rails is pretty good idea if you are carrying weight approaching the capacity of the axle or are traveling on roads that could stress that weakness to the point of failure.  The three designs by offgrid, Toyanvil, and marwayne all offer creative and viable solutions to reducing the risk of bending the axle while loaded under normal conditions.

On the other hand, I have my doubts about the value of going to a larger capacity axle.  Not that it wouldn't be stronger, but rather that that if you loaded the trailer consistent with the capacity of the axle you'd be overloading the basic frame and would just be moving the risk of failure to another weak point.  The frame and the axle, I suppose though I'm far from an engineer, function as a single unit and like a weak link in a chain all you are really doing by going to a heavier axle is moving the weak link to a different location.  

The Pod is a lightweight trailer that has its limitations and appeals to a specific market nitch.  It shouldn't be overloaded beyond its design capacity.  Attempting to increase its design capacity, in my opinion, is asking for problems.  If you are unsatisfied with the GVW of the Pod, a better solution would to be invest in a travel trailer that will handle the loads you wish to carry.  
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Fred & Maria Kearney
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offgrid View Drop Down
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2019 at 9:47am
I agree. I wouldn't suggest or consider a heavier axle in order to add load beyond the 3500 lb spec. I'd consider it f I have an axle failure at my current weight (just under 3500) even though I reinforced my axle. 

One of these days I'll take a look at the frame load again and see how much safety factor there is in that. But regardless of where the frame comes out you'd still be picking up liability if something bad happened and you were knowingly overweight on your trailer.  
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marwayne View Drop Down
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Post Options Post Options   Quote marwayne Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2019 at 10:32am
I reinforced my  frame about 7 years ago. I took out all the screws out of the outer rails and inserted a 1 1/2" by 2 1/2" tubing and bolted them together.
If you want something done right, do it yourself.
2011 RP172, 2016 Tundra 5.7 Litre, Ltd.


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offgrid View Drop Down
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2019 at 11:42am
Originally posted by marwayne

I reinforced my  frame about 7 years ago. I took out all the screws out of the outer rails and inserted a 1 1/2" by 2 1/2" tubing and bolted them together.

Do you have a photo of what you did marwayne? 


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marwayne View Drop Down
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Post Options Post Options   Quote marwayne Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2019 at 11:47am
The tubing you see here goes all the way to the front.


If you want something done right, do it yourself.
2011 RP172, 2016 Tundra 5.7 Litre, Ltd.


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offgrid View Drop Down
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2019 at 12:30pm
Ok, got it. Just to confirm, your 172 frame tubing is 2 x 4 x .01 inches, right? 
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marwayne View Drop Down
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Post Options Post Options   Quote marwayne Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2019 at 12:38pm
My tubing is 2x4 1/8 wall, the insert is 1 1/2 x 2 1/2 1/8 wall. I added shims where ever it is bolted together.
If you want something done right, do it yourself.
2011 RP172, 2016 Tundra 5.7 Litre, Ltd.


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offgrid View Drop Down
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2019 at 7:25am
Ok thanks marwayne, I recall my wall thickness was 0.1 inch vs your 0.125. I'll mike mine today and try to run an estimate of the load capacity of the frame. 
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2019 at 8:23am
I finally got around to this this morning.

First, my frame tubes were 0.1 inch when I mic'd them, so marwayne, you might want to check your 1/8 inch number again. If FR/Lippert went from a 0.125 thick tube to a 0.1 thick one between 2012 and 2015, on a heavier rPod (179 vs 172) then that's truly annoying. 

I ran the load calcs on the frame. To keep things simple I  just assumed a uniform load from tongue to rear bumper. This tends to overestimate the weight on the tongue but I don't think that changes the end result too much, because the highest stress load on the frame occurs at the axle. 

Using my 0.1 inch frame thickness figure, I got a  bending stress at the axle of around 22 ksi assuming a trailer loaded to 3900 lbs. That only provides for a 1.65 bump load safety factor. Not real good. The other peak stress point is up front about 78 inches back from the tongue, but that point has an adequate safety factor of around 3. 

In reality, its not going to be that bad because the load on the frame from the axle is spread out somewhat and the trailer box will add stiffness. But either way, its a good idea to avoid putting heavy junk in the back of your trailer and an even better one to drive slow over bumps. 
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dcholden View Drop Down
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Post Options Post Options   Quote dcholden Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2019 at 2:02pm
I do not see any posts about using leaf springs and axle to replace the torsion axle. Is there any reason why leaf springs and new a axle would not work to replace the torsion axle? We live full time in Baja Calif.,Mexico and most of our use is on very bad roads.
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