Weight Distribution hitch |
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Rpod-Couple
Newbie Joined: 21 Jun 2021 Online Status: Offline Posts: 37 |
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Topic: Weight Distribution hitch Posted: 20 Nov 2021 at 9:36pm |
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The WDH bars are 1” diameter making a cross sectional area of 0.785”. The yield point for mild steel is about 50,000 pounds-per-square inch x 0.785 inch-squared = 39,000 lbs for each bar. I don’t see how 600 lbs spring bars are going to yield anywhere near 1200 lbs. They have a huge safety factor.
I have run this on-line WDH calculator and everything is in the green for my CX-9, with 600 lbs WDH, and R-pod 171. https://www.ajdesigner.com/apptrailertow/weightdistributionhitch.php |
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Steve & Elaine
2021 R-pod 2023 VW Atlas Cross Sport |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Post Options Quote Reply Posted: 21 Nov 2021 at 3:23am | ||
The link to the towing calculator is down at the bottom of my post.
Re when the spring bars will fail you need to consider them as if they were cantilevered beams, fixed at one end with a point load at the other end. That beam configuration has a moment at the fixed end of M = F x d. d is 18 inches and in my case F is about 750/2 = 375 lbs (2 bars) , so M = 6750 in-lbs. Assuming a 1 inch bar, the section modulus is 0.098 in^3 so the stress is M/S = 6750/.098 = 68 ksi. Way past the yield of mild steel. And that is before we add a 2x factor to handle 2 g bump loads, which are common. I don't have my trailer or wdh anymore but I'm sure the bars on my 1000 lb wdh were larger than 1 inch dia. Unlikely they are mild steel either, spring steels are around 100 ksi or better in order to not be to stiff in deflection. I did eventually find a statement that my bars were rated at 1000 lbs each max. In any case, the point is that you can for sure bend your wdh spring bars under bump loads if they are too light for the application. So run the calculator for your actual load case and get wdh bars rated for that. Might be 600 lbs for a light rig but not for a heavier configuration set up for boondocking. In my case an 800 lb rated wdh would have worked but been marginal. The ride was quite comfortable will 1000 lb bars so I went with that. And you are not going to bend your TV frame by using a wdh with a higher rating because if you have it set up properly the max load on the bars, frame, and trailer will be the same regardless of the wdh rating. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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smedleyludlow
Newbie Joined: 26 Oct 2016 Location: Huntsville al. Online Status: Offline Posts: 19 |
Post Options Quote Reply Posted: 21 Nov 2021 at 8:56am | ||
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Projects take longer than expected, cost more than expected and will go wrong at the worst time.
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