steel, how strong would this be?

[titanmike]

I am making a bed extender that comes out of the hitch to carry longer loads. I have 2" solid steel and 2" 1/4" wall steel. I'd like it to stick out about 3' to 4'. How much weight to you think it could hold?

[Timmyo2L]

lund makes one, and it fits into a reciver hitch it sticks out what looks like 3-4' with 1/4" steel it holds 750lbs.

[Titan1080]

Is it mild steel or stainless? Cold or hot rolled? I'll just assume mild steel and head home and do a quick calculation.

[Boone-Titan]

Originally Posted by titanmike

I am making a bed extender that comes out of the hitch to carry longer loads. I have 2" solid steel and 2" 1/4" wall steel. I'd like it to stick out about 3' to 4'. How much weight to you think it could hold?

Titanmike,
There are several factors that come into play in calculating load bearing capability for someting like this.
1. The rise up to level of bed.
2. The type and strength of junction between the rise and the beam coming out of the hitch.
3. I assume you'll have a bar running horizontal at the top of the rise to rest things on. The placement of the load along this bar could matter due to torque.

I can give you an idea of the strenght of the beam in terms of deflection assuming it sticks out of hitch 4 feet and a load is place on the end of the beam. In engineering terms a "canilevered beam" calculation. Also will assume the hollow tube is used since the solid tube welded assembly would likely weight to much to move. This should give you a general feel for the weight it might carry. Keep in mind that typically you should design things like this 2 times stronger than you expect to load them for safety margin.

The numbers are load in LB then the deflection (amount beam bends down) in inches.
1000 - . 78
800 - .62
500 - .39
250 - .20

Hope this helps!

Other assumptions:
E=30000
I=.911
F=LB
L=Ft

Calc - F(deflection)=F*(L*L*L)/(3*E*I) (couldn't figure out how to get a qubed for L)

[titanmike]

Well i would like to use 2 x 2 x 1/4 if its strong enough. I was planning on coming out 4' if i can. The rise up to the horizontal support is about 16". On that joint i was going to weld two triangular plates on both sides for support. The horizontal support is going to be 4' with two 2 x 2 x 1/4 45 degree supports going down to the 16" riser piece. If that setup can hold around 750 pounds like the Lund brand can and not be too much weight for the receiver then i'd like to do that.

[TitanBlue]

The tube should be plenty strong, def don't use solid in that application. The hitch is rated for 1,000. Extension is far at 4 foot, don't forget Red Flgging the load and the turn or swing radius. A lot of weight behind the wheels. Worth doing, easy fab job.

(27 years Certified Weldor)

Hot rolled Carbon Steel is ideal, Stainless would be a waste of money for this object. GitRDone.

[titanmike]

are you saying that the extension is far at 4' meaning that its too far to support weight or just to watch out for turning ect.?

[TitanBlue]

A little of both. I wouldn't go beyond 4 foot, you don't need to:

Actual use will determine what is ideal for what you are using it for. Consider the support does not have to be at very end of load, further in may give better balance to reduce sagging of material between support arm and bed or tailgate. Allow some material to overhang support arm, maybe a foot or two. Too much overhang past support would cause bouncing. Experience will guide you as you see your particular load applied. I believe the commercial unit is adjustable for just such a reason. Looks like you could haul upto 12' long material if properly loaded. What do you plan for securing the load? Strap points welded on bottomside of crossbar could make for easy securement without interfering. Then attach hooks from ratchet straps when needed.

I think making your own is a great idea, I'm all for what your doing. Simple, cost effective, personalized; great combination. Post pics with it in use if you don't mind.

[Krodad]

Depending on what you are doing with it, you might consider making a "bed extender" that lays on the bed floor and extends past the open tailgate. If you have the utilitrack, you can lock the extender down using the bottom tracks. You could even make it fold so that when the long items are unloaded (or you are on your way to Home Depot) it will be folded up inside the empty bed. Now you just have a cantilever load, but spread over a couple steel bars and plywood, and no eccentric loads which are part of the problem with the hitch design.
For locking it down to the bed, I think you might be able to use the little nubs that come with the track hardware, add longer bolts to go through the steel bar and back into the nub that is locked into the track.

Just a thought, but it's something I'm planning on doing myself. Wish I could explain it as well as I have it thought out in my head. You could even get real fancy and put a low profile trailer 3 light cluster on the bottom of the backside and plug it into the trailer light harness wired to the brake or running lights.

Sorry for the book, I'm bored.

[Titan1080]

Here's a short book:

Assuming annealed 1020 steel, yield strength Sy = 43000 psi

Simplifying the bed extender to a single beam of 2x2x1/4 tubing 48" long from the hitch receiver. For a design stress Sd = Sy/N where N is a safety factor. For static loads, use N=2. Now used the Flexure Formula for beam bending plugging in the design stress and known values and solve for the moment about the receiver hitch:

Sd = M*c / I where I is the moment of inertia, and c is the distance to the outer-most fiber from the center axis of the beam. For the 2x2x1/4, I = 0.766in^4 and c = 1.414in. Solve for M:

21,500psi = M*1.414in / 0.766in^4

M = 11,645 lb*in

Now divide the moment by the length of the beam to get your maximum "safe" load. For 48", your load would be 242.6 lb, not including the weight of the beam or anything you weld to the end of it.

[Boone-Titan]

Originally Posted by Titan1080

Here's a short book:

Assuming annealed 1020 steel, yield strength Sy = 43000 psi

Simplifying the bed extender to a single beam of 2x2x1/4 tubing 48" long from the hitch receiver. For a design stress Sd = Sy/N where N is a safety factor. For static loads, use N=2. Now used the Flexure Formula for beam bending plugging in the design stress and known values and solve for the moment about the receiver hitch:

Sd = M*c / I where I is the moment of inertia, and c is the distance to the outer-most fiber from the center axis of the beam. For the 2x2x1/4, I = 0.766in^4 and c = 1.414in. Solve for M:

21,500psi = M*1.414in / 0.766in^4

M = 11,645 lb*in

Now divide the moment by the length of the beam to get your maximum "safe" load. For 48", your load would be 242.6 lb, not including the weight of the beam or anything you weld to the end of it.

Come on! 242 Lbs is the limit on a 2X2X1/4wall tube 48" Long. I don't think so. Better try that again.

[Titan1080]

Originally Posted by Titan1080

For a design stress Sd = Sy/N where N is a safety factor. For static loads, use N=2.

Originally Posted by Boone-Titan

Come on! 242 Lbs is the limit on a 2X2X1/4wall tube 48" Long. I don't think so. Better try that again.

Note the Bolf-faced type in the quote. I never said it couldn't take more. Besides, would you put a 1000 ft*lb moment on your receiver? I sure wouldn't. Our hitches our designed for a maximum tongue weight of 1000 lbs at what is assumed to be a standard location, probably within 12 inches, not 48.

[titanmike]

If i can safely carry about 500 pounds on the extender i should be fine. I also thought about making a bed extender type that uses the bottom utili tracs, but thats a little more work than what i'm planning and i don't need to use this that often.

[Titan1080]

I suppose I could have made myself more clear, the numbers I put up are conservative numbers that designers have to account for because they have to assume that a customer is going to use it constantly. At 48" long it will start to bend plastically around 485 lbs. I would shorten the length as much as you can to raise that yield load up over what you plan on loading it up with. Other than that, you should be good for how often you plan on using it.

[titanmike]

I guess i could shorten it up to three feet and still support what i carry. At 3' that would have the extender at about 10'4". I carry stuff from 12' to 16' So i think i should be ok. The only thing i carry up to 16' is lumber and not that heavy.