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Originally Posted by pbuck1
I find this an intriguing subject, so I decided to go back to first principles and work out what happens with a WDH. So, I've produced two spreadsheets which I've attached (hopefully successfully). I'm an electrical engineer not a mechanical one, so I had to try to recall my high school applied math (levers, moments, etc.) which is pretty rusty, so I cannnot guarantee the accuracy. ......snip.....
One thing I found interesting using the first spreadsheet is that the WDH bars really have to work hard to compensate for trunk contents for only a little benefit at the front axle. For my vehicle combination, 200 lbs in the trunk instead of 50 lbs unweights the front axle by only 24 more pounds, not really significant overall, but the WDH tension has to increase by more than 200 lbs to compensate, taking the bars into a higher load category. I'm not convinced it's worth it in most cases.
Of course, all this is all moot if my spreadsheets are not good.
Paul
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Your calcs look fine to me. Numbers reveal that going from 50# in the trunk to 200# raised the spring bar force be a total of 160#. Not real smart use of a WDH. It would be better to move the CG of the weight as close to the rear axle as possible.
The disturbing effect is the additional down force on the trailer axle. If one were loaded to 3300# and had an axle limited to 3500#, the 305# down force (200# trunk wt.) on the trailer causes the axle limit to be exceeded. To me, that looms as the bigger problem when attempting to compensate for a heavily loaded trunk.
I tried 400 lbs in the trunk and 914 lbs on each spring bar so that the front and rear axles had the same additional load. The down force on the TM axle increased to 358# (compared to 305 at 200# trunk load), whilst the front axle was loaded an extra 54#. Doesn't seem a useful tradeoff to me.
Additionally, one would need to be knowledgable of the max static torque load which can be applied to the Class 3 hitch.
BTW - nice work.
Denny_A