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Topic ClosedAxle Riser/Lift Kit

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Olddawgsrule View Drop Down
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Direct Link To This Post Topic: Axle Riser/Lift Kit
    Posted: 13 Aug 2019 at 7:20am
I'll defer to Offgrid. He explained it well to me and I don't wish to mis-state anything.

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mjlrpod View Drop Down
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Direct Link To This Post Posted: 13 Aug 2019 at 7:41am
The frame on the 195 is made from 2 x 5 x .100 thk rectangular tubing.  The axle mounts are located 10 inches from the inside edge of the tire, to the center of the mount.  As far as any concern about a lift kit, the only factor I can think of being an issue is, are the lifts made from atleast equally structural steel. I would think that Simply placing a shim between two contact points should not compromise the structural integrity of something unless the shim is inferior.
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Direct Link To This Post Posted: 13 Aug 2019 at 7:43am
Will the thickness of a nickel help?  Don't have anything that can do it accurately. Sorry.
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Olddawgsrule View Drop Down
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Direct Link To This Post Posted: 13 Aug 2019 at 8:13am
Originally posted by mjlrpod

The frame on the 195 is made from 2 x 5 x .100 thk rectangular tubing.  The axle mounts are located 10 inches from the inside edge of the tire, to the center of the mount.  As far as any concern about a lift kit, the only factor I can think of being an issue is, are the lifts made from atleast equally structural steel. I would think that Simply placing a shim between two contact points should not compromise the structural integrity of something unless the shim is inferior.

Well the sizing is better, thickness still low. 
Your modulus #'s are 1.421
Mine (2x4x.1) is 1.001

Your are also at 4740 max weight.

What axle is under there?


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offgrid View Drop Down
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Direct Link To This Post Posted: 13 Aug 2019 at 8:27am
Originally posted by Jeepinator


I’m no engineer, but I’m a curious how raising the height would add more force?  Perhaps a smidge of downforce (original height times 1.X where X equals additional height?) but I wouldn’t think it was even measurable.  

The lift kit won't add more force but it will add more moment (think torque). The vertical load on the frame from gravity or from getting lifted by a bump or dropping into a hole won't change.  The moment from the arm of the torsion axle getting pushed up also won't change. What will change is the moment caused by braking or by hitting a curb. That is because torque is force x distance. The distance is the height difference between the contact patch and the frame, which is increased by the lift kit. If it helps to visualize this imagine the extreme case where you bolt 10 foot stilts on your trailer and then you run it into a curb. The stilts would act as a long lever and immediately twist the frame where it is attached.

Is it a significant increase? With my lift kit the distance from the contact patch to the frame is 14 inches. Without it it would be 10.5 inches, so it adds 33% to the stress on the frame from braking or hitting a curb. So yes it is significant. 

Is it enough more to cause a frame failure? The only reported frame failure I know of is Olddawgsrule's and he doesn't have a lift kit on his trailer. There are lots of owners who have lift kits, including all the HRE's until FR started increasing height by changing the start angle on the torsion arm, not sure when that was. So I'd say that there is no hard evidence that adding the lift kit increases the stress on the frame enough to cause frame failures in the real world. 

For me, if I can come up with a simple and inexpensive way to reinforce the frame at that weak point I will just do it rather than risk a failure, but I'm not giving up my lift kit.  For where I camp the standard height trailer is just too low to the ground. 




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Olddawgsrule View Drop Down
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Direct Link To This Post Posted: 13 Aug 2019 at 8:42am
Thank you Offgrid! I knew you would explain it better!

I offer my statements due to the frame failure I have incountered. Adding the additional support to the frame is a minor cost and reduces the chance of failure. 

Axle failure and replacement is much easier than what has to happen to mine. I do wish I had caught it sooner or knew what I do now earlier.


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Direct Link To This Post Posted: 13 Aug 2019 at 8:43am
Originally posted by mjlrpod

The frame on the 195 is made from 2 x 5 x .100 thk rectangular tubing.  The axle mounts are located 10 inches from the inside edge of the tire, to the center of the mount.  As far as any concern about a lift kit, the only factor I can think of being an issue is, are the lifts made from atleast equally structural steel. I would think that Simply placing a shim between two contact points should not compromise the structural integrity of something unless the shim is inferior.

a 2x5x0.1 tube is 74% stronger in bending than a 2x4x0.1 tube so without having done all the detailed equations for the 195 I think it's frame would probably be no worse if not better than a smaller rPod's.  

All this material is going to be fabricated from mild steel for cost reasons so there isn't any reason to be concerned about the strength of the lift kit compromising the frame because of that. The lift kit does add to the stress on the frame from hitting a curb or from hard braking, see my post above.  


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Olddawgsrule View Drop Down
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Direct Link To This Post Posted: 13 Aug 2019 at 9:02am
Originally posted by offgrid

Originally posted by mjlrpod

The frame on the 195 is made from 2 x 5 x .100 thk rectangular tubing.  The axle mounts are located 10 inches from the inside edge of the tire, to the center of the mount.  As far as any concern about a lift kit, the only factor I can think of being an issue is, are the lifts made from atleast equally structural steel. I would think that Simply placing a shim between two contact points should not compromise the structural integrity of something unless the shim is inferior.

a 2x5x0.1 tube is 74% stronger in bending than a 2x4x0.1 tube so without having done all the detailed equations for the 195 I think it's frame would probably be no worse if not better than a smaller rPod's.  

All this material is going to be fabricated from mild steel for cost reasons so there isn't any reason to be concerned about the strength of the lift kit compromising the frame because of that. The lift kit does add to the stress on the frame from hitting a curb or from hard braking, see my post above.  



Scary, I had 71% 

Curious, I see the 2x5 having greater strength the 'hard way', yet wouldn't the added height (without added thickness) make it more susceptible to bulging? 

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Direct Link To This Post Posted: 13 Aug 2019 at 9:15am
Greetings:
I've owned 2 pods, a 171 and now a 2015 179.  I have had the factory lift kits on both.  I have driven many miles on rough 2 lane roads in MN and WIS plus gravel and hayfields for dry camping.  I've had no problems with the frame or axle on either pod. I try to avoid running over curbs etc. but have at very low speeds.  I have dual LP tanks and a group 27 battery, and usually a full tank of water.  Several pod owners have gone to Alaska and back with pods.  I do think the axle is a bit light.  I've looked at some other RV's similar to the pod that had frames with smaller square tubing.  I wonder how they work out.  

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Direct Link To This Post Posted: 13 Aug 2019 at 9:25am
We have to keep in mind that FR sells the lift kit which is designed(supposedly) for our trailers. If in fact the use of risers causes frame damage, then FR could be liable. Bent axles and frames would be a hard thing to prove in court due to the many variables involved. That being said, I'll take my chances since dragging hard parts on the ground may cause just as much damage. If the collective comes up with a reasonable reinforcement that can be welded in place I'm all for it. 

What stumps me is that many members here drag their Pods all over the country with zero issues with the frame or axles. I have to wonder if the few failures we have seen are caused by poor metallurgy or installation errors? 
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