Drop frame van RV

I am penciling out a 48' RV conversion and have a few questions regarding weight distribution. I fully understand that in trucking the axle group weight on the trailer and drivers should be close and, weight behind the trailer axle group should be avoided. I have a Peterbilt 387 that I tow a camper with now, it is a 24K trailer, my truck is single rear axle. The 48' van will end up being around 34-36K

That said, in looking at RV trailers and light weight car trailers a lot of them have the trailer axles much further forward. The trailers I am looking at have sliders and if I were to have the axles all the way forward to keep more weight on the trailer and say keep the king pin weight to 12-14K and, 20K on the trailer axles, how would that trailer handle? My truck has flex air rear suspension so I am likited to 17K on the back axle.

This is where I add another wrench in the works, the rear 15' of the trailer including 8 or so feet behind the trailer rear axle will have a car and, couple motorcycles. The weight of the car and bikes 4500 and, 2500 behind the rear axle.

I don't have any real way to try this without buying a van and ballasting it. Before I invest a lot of time and money into this I want some feed back from folks who have more experience with this kind of loading if possible.

Thanks,

Steve

 

So you're making an old potato chip van or something into an rv?

 

Sounds about right

 

Not Frito vans but close, there are some 07' Trailmobile plate vans with 20" drops. I want to put 4 slide out in the trailer and have a garage in the back. These vans are 53', I am limited to 48' as an RV so the back of the trailer will be cut as well. The trailers weigh about 14K empty, estimating I will take 1000-1200 pounds off with the 5' removed. I will fab a ramp back door, cycle deck and lift system.

The bill of materials and infrastructure for RV conversion is right at 16K, add 5K in in toys and the whole thing should scale 34K. That is with gen fuel and 1/4 fresh water. I have water tanks in several locations to trim weight per loading.

Steve

 

I would think you should be fine park your car in there as close to the axles as you can you oughta be fine. Make a heck of a camper

 

How would trailer stability be with 20-24K on the trailer axles and 12K on the drivers? I have considered doing a fixed spread axle arrangement on the trailer IF I can't get the axles forward enough to keep the pin at 12-13K.

I have to scale the trucks back axle with the Holland hitch, I have an air ride RV hitch on the truck now. With the RV hitch and bodywork my back axle weight is 4800. I could lighten it up 7-800 pounds moving batteries and water, flex air is rated at 17K single axle.

I would really like to have 12K on the pin ready to roll, that could put as much as 24K on the trailer for 33/66 kin pin / trailer tandem loading.

Steve

 

With 48 foot trailer you can run the wheels all the way back, put 19 inch rubber on it to retain the garage.

 

These trailers have 17.5 tires now, how does running the wheels back change anything? The question or concern is with FORWARD axle placement to get more weigh on the trailer. Did you read and understand the above posts? I am not worried about king pin to back axle distance.

Steve

 

Weight behind the rear axle does not necessarily have to be avoided. If I'm understanding your concerns correctly, I think you're dealing with a "fulcrum problem". The added length out to the steer axle in relation to the length behind the drive axle affects weight distribution exponentially as you go out away from the fulcrum point (rear axle in this case)

You might refer to this for some guidance.

Balanced on a fulcrum (net torque and equilibrium) - Math Central

Lever Mechanical Advantage Equation and Calculator Case #2 | Engineers Edeg | www.engineersedge.com

Me, I would try and insure that my expected maximum weight load behind the drive axle group center would not lighten the normal unladen steer axle weight any more than about 5%. It will be up to you to determine about how the cargo weight at the rear of the vehicle might be roughly distributed. It may or may not be even, depending on a lot of factors, and obviously, the more weight you add the further back, the bigger potential problem you may be dealing with but I can't imagine any scenario where it would be much variance between "about equally distributed"

 

Running the wheels all the way back puts more weight on the drives, no I wouldn’t run 24 on trailer and 12 on the drive