Homemade Roofracks.

[XJINTX]

OK, a question for you builders and for rack users in general. There is talk about weight and steel being heavy and I agree.
My full length steel rack is a bit heavy. I have cross bars but no flooring. I am / was planning on welding on some expanded steel flooring.
The question is... I don't need flooring much except when actually going on a loaded trip. What do you think about just laying in the flooring when needed? the weight of cargo will hold it in? I do not have space issues with being able to store a floor piece at home.

 

[GeoTracker90]

It all depends on the type of cargo you are carrying up there. If I were to have a removable floor I would just use a piece of 3/8" plywood, but I would be sure to have it fastened down to the rack at a number of places. The wind can generate quite a force on it when driving at speed. You could perforate it with a hole saw to let some of the air through, but what ever you use for flooring I would attach to the rack in some fashion.

As an alternative I have in the past just welded in a series of 1/4" solid rod spaced every 4" to 6". For an arrangement like this I would have a couple main cross bars welded into the rack. These could be 1" square tube with a 0.065" wall like I used in my roof rack. Additional cross bars could be lighter 1/2" square tube in as thin a wall thickness as your local steel supplier stocks.

A floor like this worked well for supporting boxes such as Pelican or Storm cases, or even action packers. It also works well for supporting your umbrella chairs, EZ-Up Awnings, etc.

Correct material selection will go a long way towards helping reduce weight. Estimate how much of each size of material you are going to use and then break out the steel weight chart and figure out how much your design is going to weigh. With this information you can make an educated decision on what if anything needs to be changed to meet your goals for the project.

Mike

 

[mudbutt]

As an alternative I have in the past just welded in a series of 1/4" solid rod spaced every 4" to 6".

This is how my rack is, except I used tubing instead of rod. It works just fine.

Like Mike said, regardless of what you use for flooring, it should be anchored to the rack.

For reference, 3/4 x 13 expanded steel mesh is about 1 lb. per square foot.

 

[bobDog]

Forgot I had this one on my old '85 pickup.

Simple 1" tube for the rack with expanded metal floor.

[/IMG]

Damned nice truck my man damn nice almost makes me want to dump my XJ and build one like this....:victory:

 

[ntsqd]

This is how my rack is, except I used tubing instead of rod. It works just fine.

Like Mike said, regardless of what you use for flooring, it should be anchored to the rack.

For reference, 3/4 x 13 expanded steel mesh is about 1 lb. per square foot.

Just for comparison, plywood weighs between 0.63lbs/sqft and 0.78lbs/sqft per 1/4" thickness. So a square foot of 3/8" thick plywood would weigh 0.94lbs to 1.17lbs. Most of the refs I looked up use the heavier end of the range.

 

[R_Lefebvre]

Interesting comparison, but isn't a sheet of 3/8" plywood stiffer than expanded metal?

 

[Rot Box]

Here is one I whipped out in just a few hours. It is not nearly as nice as some of the other examples here, but hey it works right? :snorkel:

The studs on the passenger side will hold my hi-lift jack and I plan to add some lights too. Aside from the expanded metal this was all made from scrap that I had lying around.

 

[mudbutt]

Interesting comparison, but isn't a sheet of 3/8" plywood stiffer than expanded metal?

I would surmise "stiffer" would be subjective... Everthing I have read about expanded mesh says that it is actually stiffer than the same thickness steel that is not expanded....

I would prefer expanded mesh over plywood. I think it would be stronger.

As far as expanded mesh goes, it has to be anchored (welded, bolted, whatever) in order to work properly.

If I were to start from scratch using expanded mesh as a bottom tray, I would find a way to stretch it during fabrication.

In other words I would clamp the rack to the weld table, weld one side of the mesh to the rack, then attatch ratchet straps or something similar to the mesh and stretch it a llittle. This would put the mesh in tension. It would look much cleaner (flatter) and be less likely to stretch under load.

 

[Backwoods Rambler]

Are guys using FEM or SEM? I picked up FEM, but was thinking that maybe SEM would prevent a load from shifting due to the raised portions.

Just curious

 

[mudbutt]

Are guys using FEM or SEM? I picked up FEM, but was thinking that maybe SEM would prevent a load from shifting due to the raised portions.

Just curious

I would think the FEM would do less damage to your gear....

Your concerned about shifting loads? Are you not anchoring things down??

 

[ntsqd]

I would expect the 3/8" ply to be stiffer than the expanded metal. While it makes the fabrication easier, I have little use for expended metal in the gauges likely to be used for roof rack flooring. At this thickness it is very flexible unless anchored at close intervals. The very nature of the expanding process makes the sheet more easily distorted than a smooth, uninterrupted/non-perforated sheet. At a thickness where it would not be flexible the ply should win the weight contest.

 

[R_Lefebvre]

I would surmise "stiffer" would be subjective...

Not subjective at all. I'm talking engineering terms, deformation of a structure of a given weight by imposition of given weight. On a by-weight basis, wood is actually stiffer than steel. Wood is actually very impressive for many structural measures, and it's biggest downfall is simply that it can't be welded or plasticly formed, and it degrades when wet.

3/8" ply with a Linex coating would probably make a great flooring. Light and weatherproof.

 

[GeoTracker90]

Another option for flooring would be a solid floor (sheet metal) that has been lightened and formed using dimple dies. It would be lots of work but the result would be great.

Mike

 

[R_Lefebvre]

Yeah. Or you could get "perforated" sheet. Basically has tons of tiny holes punched in it. Looks more attractive than "chicken wire" expanded metal too, if that matters to you.

 

[ntsqd]

The way that I see it a rack floor that is not solid presents a whole bunch more edges to the air flowing over it. The aerodynamics can't be pretty. A smooth, flat floor, preferably the same thickness as the rack's frame tube, or at least one with it's top and bottom surfaces flush to the top and bottom of the frame tubes, would present far less air resistance. Only one air separation point (at the front), and a lot less turbulence inducing changes in cross section etc. should make for nearly laminar flow with a much smaller turbulent boundary layer.