Yeah when people bend stuff its usually much harder to fix than it was to bend.

I can draw it up to submit to the customer and include dimensions but I do appreciate the offer.

I might make the top a little heavier or put some angle across the 14ga for grip and because I found out the tractor is a 3 wheel type.

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Actually the pipe In the center is just under six inches long.

When I said two arched skins I was saying for ultimate strength arching both skins makes it indestructible. But that single arch is extremely strong.

You could probably get away with a smaller O.D. Tube for the hinge as well. Maybe some gate hinge stock. I always put in grease fittings when I have the time. I just drew it so the guys could visualize the structure.

The arch is a mad crazy phenomena created by God. Accidentally over the years things became arched and we could not bend it with any force. Funny stuff looking back, at the time not too funny. It makes you feel darn helpless.

Usually to layout the arc or arch I draw it in cadd and just measure where the pipes are from one end and the length of each pipe. But before cad and even still today I just take a piece of metal and bend it into an arc, in the center I bend it to 6 inches off the straight skin maybe tack it to the layout table and then just measure and cut all the pipes.

I drew that up in about 10 minutes it is all good fun to me. I love guys that build their own stuff. We are a dying breed. If you finalize a design I can easily draw it and output the pipe lengths. And the angle it will meet the arc at if you like.

Sincerely,

William McCormick

 

This design looks to be the lightest yet. Not sure what you mean by two arched skins though?

Since the tubes just run vertically to connect the flat bar together, would they also need to be tied together horizontally? Is it about 2" of height change per tube? (8" middle, 6" each side and so on)

P.S.

I really thank you for taking the time to draw that out.


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If you look at a lot of trailer ramps they are bent and distorted. Part of the reason is that sometimes the weight ends up right in the middle of the ramp. The machine bounces, or gets stopped when it hits the center of the ramp and great forces are created. Three inches of material thickness is light over eight feet. Because when you move an object in theory for a few seconds here or there the machine could put the full 3,000 pound load all to one side right in the middle of that side. That is what your ramp will not be prepared for.

As someone mentioned the angle helps. But with movement you can undue that advantage.

Ultimately eight inches over eight feet is perfect. I understand how that would be unwanted. But everything from there down is a gamble. The lightest eight inch beam made will outperform the heaviest three inch beam made. Without a large skin to keep it from bending, three inches is light. The best design would be two arched skins, with a tapered trusses inside. That could be light and very strong. But just one arched skin would do it in this case. Something like this. This is what I would do.

 

I have made a set out of 3 inch channel it worked great n the guy that own trailer hauls a 6 ton crawl a hoe on that dang traiker up n down em ramps I made for him.

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I guess seeing the ramps on goosenecks has me set on going heavy. Friend of mine suggested 3"x1/8" channel which braced in the middle would be sufficient for such a light load.

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Good point

I was just adding up material weight and was originally planning on skinning the top but think leaving it open and doing as you suggested will work better.

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After more research, I have decided to replicate bobcat trailer style ramps.

(4) C3x5# channel runs with (6 or 8) 2"x2"x3/16" angles running width wise flush with the top of the channel to connect them and provide support for the top skin. 1"x1"x3/16" angle will be welded across the top skin/channel to give grip for the tractor tires.

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As for the angle in between , maybe consider 3'' channel instead. The the channel toes up, it will give more gripping surface than the angle. My opinion.

 

Like BD1 said, it's more complicated than a simple beam. Do some reverse engineering, copy other known designs and make them a tad better.

 

That sounds heavy. I would locate a manufactured trailer which match your needs and see what they designed. It could make life easier and no guess work.

 

A basic understanding of engineering and structures is essential. Angled ramps can be a bit complicated, but flat beams are simpler. If the "beam" won't deflect flat, you will be good on an angle.

A few things all come into play with stuff like this. #1 is loading. Simple beams are loaded either with uniform loads ( same load over the whole length, say a stack of lumber on a flat bed) or point loads, where all the weight is located at a certain point, say weight of a tractor on it's tires. Worst case on simply supported beams is usually the middle, so you'd figure max load being applied at that point for deflection.

With C channel, you also have to worry about side buckling since the material shape is asymmetrical. You solve that with side bracing on something like a ramp. Buckling is when you apply enough force that the "beam" wants to twist. It may still be able to support the load as long as it stays straight, but as soon as it twists, it looses it's strength and can collapse. If you use I beams or wide flange sections, because they are symmetrical, they are less prone to buckling unless loaded only on one side.

Resistance to bending comes from height of the member usually. You can often find beams that are taller but weigh less than a smaller beam, but can support a lot more weight. It's the same principal as a truss, put the material as far from the neutral axis of the beam as possible and you'll get the most efficient use of the weight of the steel used. For example you can get C channel in 3" x6 lb weight. You'd get more resistance to bending however by using 4"x 5.7 lb channel, but the steel will be lighter. You could also jump up to 5" x 6.7 lb channel with some gain in weight, but significantly more resistance to bending.

There are some simple charts out there that show basic load ratings over given spans. Usually these charts are for wide flange sections as they are the simplest to calculate and have the least number of variables. Asymmetrical shapes like angle and channel are more difficult to calculate because their strength alone is usually limited to buckling. How far apart your support is and how strong it is changes what the channel will carry by how much force it can resist in buckling.

All of this info came from several semesters of basic structures we were required to take for Architecture. It only covers very basic structural designs. A good structures text book will help, assuming you can understand it. ( I never could, I aced all my structures courses solely because my instructor had a great knack for explaining things in a way I could easily visualize, and I've yet to find a good text written the same way.)