Designing subframe for camper... advice anyone?

[adam88]

I'm about to have my aluminum subframe constructed. I've designed the subframe with wheel wells to keep it as low as possible to ground. The camper will be attaching directly to this.

If anyone has any engineering background or experience with this type of stuff, I am wondering if my design will be strong enough. I am using 3"x2" rectangle aluminum probably 6061-T6. I haven't decided on 1/8" or 1/4" wall yet. According to my design, I am going to be using roughly 77 feet of aluminum total. At 1/8" wall this would weigh 110#. With 1/4" wall, it would weigh 208#. I could also go with a compromise in the middle at 3/16". I don't want it to be too weak, but also don't want it to be overkill. The 208# doesn't seem like much, but once the storage compartments are added and misc items it would end up heavy. The total load will be around 2000 to 2500# maximum, spread out evenly, with most of the weight at the front center. The overall dimensions of the subframe is only 8' long x 6'6" wide.

Any advice or comments would be appreciated. Thanks. Adam

 

[UK4X4]

Is this the base for the camper ?

or this is only the bed and the camper goes on top with its own frame ?

Presuming the 3'2 1/2" dual rails follow the vehicle chassis rails full length and are fully supported by the vehicle chassis ?

That's where your main support is.....

By the way 3/8" is heavier wall than 1/4"(2/8)

What would the platform be used for if the camper has a separate chassis when the campers not in place

 

[adam88]

Is this the base for the camper ?

or this is only the bed and the camper goes on top with its own frame ?

Presuming the 3'2 1/2" dual rails follow the vehicle chassis rails full length and are fully supported by the vehicle chassis ?

That's where your main support is.....

By the way 3/8" is heavier wall than 1/4"(2/8)

What would the platform be used for if the camper has a separate chassis when the campers not in place

Oops, I meant 3/16".

Yes, the flatbed longest rails follow the chassis the whole way. They will be connected directly to the frame using 4 mounts (2 front, 2 rear). The 2 rear mounts will be spring mounted. Most of the weight will be sitting on these two rails as well.

Camper will be in place all the time. So it's not really a flatbed, guess I shouldn't call it that. This is going to be a SUBFRAME. The camper is going to attach directly to this now.

I am leaning towards the 1/4" / 0.250" wall, at 3"x2" thickness.

 

[adam88]

After looking things over, I think the above might be too many crossmembers. Some of the gaps are as little as 7". I took out several of the crossmembers... and it looks like this.... not sure if this is better or worse. If I went with this version, then it would definitely be 1/4" wall.

 

[IdaSHO]

depending upon how it is attached to the chassis, you will probably be well served by adding a torque tube to the flatbed.

 

[Martyn]

A few thoughts.

Does the camper need this much support? Could you make the frame even more spartan?

How are you joining the aluminum tubing together? Aluminum welds can be brittle and crack. Have you thought about bolting it together with gussets?

Along the sides above the wheels should be close din with plate to stop mud and dirt from getting lodged in these areas.

 

[southpier]

frequency of framing members can be modified with thickness of sheathing. fewer = thicker or vise-visa

 

[heimbig]

Designing subframe for camper

I'm not an engineer but looks like you are heading in the right direction. you might look to others who have done this sort of thing, have a similar camper, similar load, and will use the rig in a similar way.

A big factor is the camper, what is it? is it torsionally stiff? or flexible? the more flexible the camper the stiffer you need the sub-frame. I'd also recommend a torque tube.

Is the front mount a rigid mount? or just not having springs. If front mount is a 'rigid' hinge then the distance between the cabover and cab will get smaller as the sub-frame 'floats' above the frame rails. Even if it isn't a hinge in the front and all 4 points can float up and down then the cabover to cab distance could get smaller.