Trailer balancing spreadsheet

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Trailer balancing spreadsheet

Postby Homebrewer25 » Fri Feb 16, 2018 11:35 am

I've been playing around with the trailer balance spreadsheet a bit this week, and had a question about using a Dexter torflex axle. The spreadsheet requires a measurement from the back of the trailer to the axle, and of course with leaf springs it is also the wheel center. But with a torflex the wheel center is approx 6" behind the axle center, and I'm not sure which measurement to use in the spreadsheet.

I'm planning on using a #9 Dexter torflex with 14" wheels/tires on a customized NT 5x8. I plan on extending the tongue similar to how Zach did it on the X-Cubed, then extend the frame at the back end. I'm planning to extend the trailer frame by using 2 of the 5' cross rails to extend the side rails, overlapping by approx 2' to achieve 11' total. I was figuring on centering the Dexter axle mounting brackets on that overlapped area. This would leave only the wide cross member on the frame, but the torflex should add some rigidity. If necessary I can add a couple of pieces of angle iron as new cross members.

This would put the axle center about 48" (36%) from the back of the frame, but the wheel center would be about 42" (32%) from the back. Using some very rough estimates I've found that the tongue weight will be a bit high ... somewhere around 250 lbs ... when using the actual wheel center as the distance from the back of the frame.

So which should I use ... axle center, or wheel center? My intuition is to use wheel center, and my reasoning is this: Imagine that the axle location is the perfect balance point of the trailer when it is raised off the ground ... the resulting tongue weight would be zero. Then lower it to the ground ... the wheels are 6" behind the balance point, so the tongue weight would increase considerably.

Any thoughts on this?
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Re: Trailer balancing spreadsheet

Postby aggie79 » Tue Feb 20, 2018 8:49 am

Wheel center.
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Re: Trailer balancing spreadsheet

Postby tony.latham » Tue Feb 20, 2018 10:49 am

aggie79 wrote:Wheel center.

Yep. The thing with bearings on it. It'll be the same for Timbren axles.

Thanks for doing this. :thumbsup:

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Re: Trailer balancing spreadsheet

Postby troubleScottie » Tue Feb 20, 2018 6:32 pm

The trailer is pivoting around the axle.

Hence like a simple teeter totter or a simple lever, this calculator is computing balance point and expectation of how much weight will end up on the hitch.

Technically, the wheel offset and how that is attached to the frame does alter the weight distribution. By how much, I would not hazard a guess.

Of course, the model assumes the walls are evenly distributed -- most likely not with doors, windows and skeletonization and wall curvature.

Similarly, the ceiling weight is assumed to be evenly distributed which it is not -- especially in designs with vertical fronts or skylights or if the roof curves under itself. The rear door/galley hatch is often constructed differently (denser) than the rest of the roof.

Same for the floor weight -- biggest culprit is the mattress. It is adding weight to only part of the floor.

The placement of the big heavy things eg lead battery(s), spare tire, full cooler, cabinets, air conditioner, generator, water tank(s) and/or propane tanks really do effect the outcome.

Finally, you will be adding static and consumable supplies to the trailer, which can alter the weight over the course of your travel.

Given that lots of people have been reasonably successful with this calculator, one might surmise, there is room for error.

Of course all of this is an estimate. Your actual numbers may vary.
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