Roof rack sugestions?

[Clark White]

i am looking to build my own roof rack to mount on my Tacoma. It's large (hence why I'm building my own) so that I can pitch a tent up there and have my own cheap version of a RTT. I don't plan on putting too much weight up there, just kayak, bike, bulky gear, maby a pair of gas cans and thats about it. When in camp, most of that stuff would come off, and I will pitch a tent up there where my girl friend and I will sleep (if we even need a tent). I'm planing on using expanded metal for the flooring.

Here are my plans (done on paint, so parden their simplicity). The black is thick wall tubing, red is thin wall for weight savings. I'm undecided on putting the third bar down the middle of the bottom, but other then that I think these are about final. Does anyone have any changes they would recomend before I pass the point of no return on this?

Thanks!
Clark White

 

[rickc]

Take a peek at mine. It's huge; 9' long by about 7' wide all in aluminum tubing. The big bars are 1 1/8" and the smaller triangulation material is 1/2".

The most critical things to consider other than total weight is how the weight will be distributed and how the thing is fastened to the truck. The more contact points the better, particularly at the truck pillars as you do not want excessive stress put on the truck leading to crumpling.

How are you planning to support the back end?

Aaaghhh! PITA! we still can not post pictures.

try this link:
http://www.hummernetworkforums.com/viewtopic.php?t=197734

 

[rickc]

Me again Clarke:

Note the square section ally tubing for the base.

some details:

 

[Clark White]

Take a peek at mine. It's huge; 9' long by about 7' wide all in aluminum tubing. The big bars are 1 1/8" and the smaller triangulation material is 1/2".

The most critical things to consider other than total weight is how the weight will be distributed and how the thing is fastened to the truck. The more contact points the better, particularly at the truck pillars as you do not want excessive stress put on the truck leading to crumpling.

How are you planning to support the back end?

Aaaghhh! PITA! we still can not post pictures.

try this link:
http://www.hummernetworkforums.com/viewtopic.php?t=197734

The site you linked to unfortunately needs a user name and password. I have a smaller basket attached to a Yakima roof rack on my camper. I'm thinking of adding a third cross member to the roof rack, but this probably would not be necessary since I don't think I will be carying too much more weight up there then I do now.

Here is the best picture I can find of what I have now.

My only real concern as far as weight distribution is if I get too much weight out over the cab, it will put too much weight on the front feet and damage the camper (the rack will be free floating over the cab to allow flex in the bed).

How much does your rack weight? I don't have a weight for the flooring, but I figure my rack will weight 60-70lbs empty.

Clark

 

[Clark White]

Wow! That is an awesome looking rack! I looked at AL for materials, but it looks VERY expensive to go this way?

Clark

 

[rickc]

Hi again Clarke:

I have never weighed it but I can easily move it around by myself. Note that the main frame is in four sections so it can be set-up as a 3', 6' or 9' length.

You may want to consider using a plastic floor mat instead of metal. There was a thread here recently about doing this using animal cage flooring.

Sorry about the bad link. I thought that viewing the forum was open to all.

 

[absolute]

Clark,
I think you would want to use an extra bar in the middle. On my yak rack w/extension it stiffened it up a lot for extra support!





*Thread Hijack*

That is one nice Hummer!!:bowdown:

*End Hijack*

 

[Clark White]

Hi again Clarke:

I have never weighed it but I can easily move it around by myself. Note that the main frame is in four sections so it can be set-up as a 3', 6' or 9' length.

You may want to consider using a plastic floor mat instead of metal. There was a thread here recently about doing this using animal cage flooring.

Sorry about the bad link. I thought that viewing the forum was open to all.

I am considering that plastic flooring, as it would be cheaper and lighter. The only reason I'm thinking of the expanded metal is because I was told welding that in would stiffen the rack up quite a bit.

Clark

 

[Clark White]

Clark,
I think you would want to use an extra bar in the middle. On my yak rack w/extension it stiffened it up a lot for extra support!





*Thread Hijack*

That is one nice Hummer!!:bowdown:

*End Hijack*

Yes it is a nice hummer!! :bowdown:

For that middle support, would you use the thicker walled tubing, or thin walled?

Clark

 

[ntsqd]

I would scale the 3/4" up to 1" minimum and consider going to 1-1/8"
You get more strength from tube dimension than you do from wall thickness.
I used 1-1/8 x .080 square steel tube to build the 99" x 56" rack below. With the 3/4" plywood deck installed I can move it around by myself, though it is too awkward of a shape to put up or take off the vehicle by myself.
My goal was low air resistance when not carrying something on it and to be able to walk on it for use as an observation deck.

How and where you support the rack/deck is of crucial importance, as is what you attach it to. I would not expect expanded sheet metal to offer much in structural strength.

If you do the calcs on aluminum vs. steel you can't come out ahead on weight for strength with aluminum unless you opt for a design that does not use structural shapes. You have to use formed sheet metal shapes, essentially a monocoque type design. Staying with normal structural shapes (rounds, squares, rectangular box sections) requires really large cross sections and wall thickness'. If you do the latter you haven't saved any weight over steel. BT, done a thorough Engineering analysis on it. When things get large enough then the strength of aluminum is enough and the additional strength of steel is unnecessary. I do not think a roof rack is large enough to qualify, needs to be more the size of a flat bed truck bed.

 

[rickc]

Some flex may be a good thing depending on how you attach the thing to your Tac. The cabin roof and rear truck bed are already separate components both fixed to the chassis so if you have a very stiff rack that is attached to both you may run into problems as I'm sure there is some differential movement between the truck bed and cabin.

You could add a couple of support bars providing some triangulation to your design for extra stifffness.

 

[ntsqd]

I would not attach to any part except the bed or the frame under it. Trying to attach to both the bed and the cab is asking for trouble.

 

[OTR]

Why not make the rack two seperate pieces. 1 part of the rack is attached to the truck cap and the other is attached to the cab. I would have the gap be the same width that seperates the cap and cab. You could add a filler piece to the rack when if you need a continous "floor" while camping that can be removed while traveling. This would allow the truck & rack to flex, increase mounting points to distribute the weight (4 total), make it easy to remove (2 pieces), and give you the ability to use one rack if you don't need both.