Podmods, Maintenance, Tips and Tricks: trailer tilt

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trailer tilt

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Forum Name: Podmods, Maintenance, Tips and Tricks
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Topic: trailer tilt

Posted By: malkbean2
Subject: trailer tilt
Date Posted: 31 Aug 2020 at 9:00am

Does anyone know the maximum amount of trailer tilt before corrective measures are necessitated under guarantee. ie trailer tilt while setting on flat ground without slide out.

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rpod 178
Grand Caravan

Replies:

Posted By: offgrid
Date Posted: 31 Aug 2020 at 2:55pm

Do you mean how high one side is vs the other? 1/2 inch difference isn't unusual. I'm assuming the slide side is lower?

You might have a bent axle if one side is significantly lower than the other. That is more of a concern than just a difference between the two sides. Do your wheels have negative camber (wheel tilted inward at the top)? Run a string line along the bottom of the axle from one side to the other. You should have a gap in the middle (axle crowned upwards) of about 3/16 inch or thereabouts. If you have noticeable negative camber or no crown in your axle then its bent.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: StephenH
Date Posted: 31 Aug 2020 at 4:02pm

Or, what would be much worse, look at the floor of the trailer from underneath, sighting from one end. Does the floor look level all the way from front to back or is is sagging anywhere? If it is, that is a bigger problem that needs to be resolved before it gets worse. I added two outrigger supports to our 179 because I noticed it was sagging a little under the slide-out. If this is the problem and you don't have the capability (equipment or ability) to add outriggers yourself, you may want to contact Forest River about the problem. If moisture has gotten into the floor, it could have weakened it which would be a likely cause. However, the design is partly to blame also. There is just too much cantilevered floor outside the frame. That is one of the risks of minimizing weight.

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StephenH
Happy is the man that findeth wisdom,...

http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods
Former RPod 179
Current Cherokee Grey Wolf 24 JS

Posted By: offgrid
Date Posted: 31 Aug 2020 at 4:25pm

Good point. Here's a question, not having seen a trailer with a sag in the floor, does a sagging floor look like the whole trailer is tilted to one side? Or does it appear as level trailer with sagging wall/slide on one side? I would have thought the latter?

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: Tars Tarkas
Date Posted: 31 Aug 2020 at 4:32pm

All kinds of possibilities here I suppose, but the first thing to check is the simplest. Are the tires aired equally?

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2010 176
FJ Cruiser

Posted By: mcarter
Date Posted: 31 Aug 2020 at 4:38pm

When I experienced a saggy floor, the trailer never exhibited a tilt. The floor sagged and separated. I would look at frame and suspension, not floor, first, if trailer tilts.

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Mike Carter
2015 178
" I had the right to remain silent, I just didn't have the ability."

Posted By: malkbean2
Date Posted: 17 Sep 2020 at 3:03pm

Thanks for the comments. According to information obtained from Forest River, for the 178 Rpod with the slide in "The unit should not be tilted at all. It should be level. "

To answer some above inquiries.

The slide side is lower by about 1" measured at the rear in various locations.

There is no visually noticeable camber issue at the wheel.

Tires are inflated at 50 psi equally.

The floor looks straight (as much as can be seen without removing the tanks).

From a simple eyeballing view the axle appears to be slightly crowned upward in the middle.

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rpod 178
Grand Caravan

Posted By: offgrid
Date Posted: 17 Sep 2020 at 5:47pm

1 inch is a bit high. I'm surprised that FR would say that the height on both sides should be exactly equal. I've seen other reports that they allow around 3/4 of an inch. It would seem to me that they would be picking up an unwanted warranty liability by stating that they should be equal. For reference my 179 is about 1/2 in lower on the slide side.

You might want to get under there and measure the actual axle crown to be sure its really there.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: Toyanvil
Date Posted: 17 Sep 2020 at 5:49pm

I would measure at the wheels, ground to frame to check suspension. The best way to check camber is with a 24" bubble level, wheels should be plumb with sides of the trailer.

Posted By: malkbean2
Date Posted: 24 Jan 2021 at 10:34am

Final resolution for trailer tilt: Axle was bent. Extended warranty (American Guardian) was useless.

New axle with brakes etc ~$375

Shipping ~$130

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rpod 178
Grand Caravan

Posted By: malkbean2
Date Posted: 24 Jan 2021 at 12:38pm

Opinion requested from engineer type people: R-pod is parked on a 20 degree slope for 6 months. That is to say tilted side to side not front to back. It is supported at 3 points , the 2 wheels and the front screw jack. Is it likely that this would/could permanently bend or twist the frame and/or bend the axle?

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rpod 178
Grand Caravan

Posted By: jato
Date Posted: 24 Jan 2021 at 6:52pm

Noting that the 178 is 'static' not in motion, I personally see no way that from the description you give, that the frame would twist or axle would bend. The only cases I have heard where frame twists or axle bends is when torque or stress is applied to those areas, such as having a correctly loaded or more likely an overloaded situation and then traveling down the road and hitting a pothole, bump, or some large debris causing a situation where two opposing forces come to a point resulting in the weaker of the two to bend, or worse yet break under extreme stress or torque of the metal.

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God's pod
'11 model 177
'17 Ford F-150 4WD 3.5 Ecoboost
Jim and Diane by beautiful Torch Lake
"...and you will know the Truth and the Truth will set you free."

Posted By: offgrid
Date Posted: 25 Jan 2021 at 8:34am

Wow 20 degrees is a pretty steep slope. First question. Can you put leveling blocks on the low side wheel to level up the trailer some?

Here’s what I think the math says, someone correct me if I have it wrong. At a 20 degrees side slope, the center of gravity will shift towards the downhill side by the sine of 20 degrees multiplied by twice the height of the center of gravity above the ground. The factor of 2 is because the cg moves downhill as the trailer is tilted and then the point where a vertical line from the new cg location hits the ground is the new balance points the new cg location. The sine of 20 deg is 0.34. We don’t know how high the cg is but let’s be conservative and say it’s 3 feet. I can’t imaging it’s higher than that. That would shift the cg to the low side by about 2 feet.

The wheel spacing is about 7.5 feet so instead of the load on the wheels being balanced with 3.75 feet on either side we’re at 1.75 feet on the downhill side and 5.75 feet on the uphill side. So we end up with about 75% of the load on the low side and 25% on the high side. The 75% represents a 50% increase in load. BTW this calc would have the rpod rollover point at about 36 degrees which probably isn’t way far off. 36 degrees is crazy steep to get sideways on.

When I looked at axle safety factor before yield failure I found it to be around 100% (2g’s) so you should be ok on the axle tube.

That’s for the steel. Steel is very elastic and won’t retain a deflection as long as you don’t exceed it’s yield point. I’m not so sure about the rubber the torsion arm sits in. Unlike steel, rubber and other polymer materials can take a compression set and not come back all the way when the pressure is released. You could find that the low side ends up lower after long term storage because the torsion arm doesn’t rotate all the way back where it was.

If you can as a minimum I’d suggest parking the trailer with the slide side (which is heavier) uphill. And level up the trailer as much as possible so you don’t have to worry about it.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: EchoGale
Date Posted: 25 Jan 2021 at 11:06am

Unrelated to the frame/axle question but isn't also also a problem for the fridge?

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Julie

Posted By: offgrid
Date Posted: 25 Jan 2021 at 11:28am

If the fridge is left on yes.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: malkbean2
Date Posted: 26 Jan 2021 at 11:42am

Thank you offgrid for the detailed analysis.

So the axle tube is not likely to bend but the rubber inserts have a good chance of deforming. That makes a lot of sense given the long term of the unequal weight distribution, and it might even be detected by comparing the angle of the torsion arms.

And what of the frame? I read somewhere on this site that the frame thickness is 1/10". Would you expect the torque created from the unequal weight loads to impart a twisting force to the frame enough to exceed the yield strength of the frame and create a permanent bend?

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rpod 178
Grand Caravan

Posted By: offgrid
Date Posted: 26 Jan 2021 at 6:35pm

Good question on the frame. It is has roughly the same 2x safety factor (2 g load to read yield) as does the axle tube. So I think that will be ok.

The biggest consideration will be rubber possibly taking a compression set and effecting the torsion arm angle I think.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: malkbean2
Date Posted: 05 Feb 2021 at 7:54am

So takeaway from this is that it is poor practice to park a torsion axle trailer on a sideways slope for an extended length of time mainly due to the uneven weight distribution and possibly permanent deformation of the rubber inserts within the axle. Good to know and thanks.

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rpod 178
Grand Caravan

Posted By: offgrid
Date Posted: 05 Feb 2021 at 9:06am

It’s a possibility is all, I don’t know enough about the rubber compound in the torsion axle to say one way or the other. Not worth taking the risk for me, just to avoid putting some blocks under the low tire.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold