For a GN trailer, can I put the planking right on the I-beams?

[cjmdjm]

The rails are slotted so that the cross members are the same depth as the thickness of the deck boards. Once the boards are attached they are flush with the exposed frame rail.

Ok. So if I were to use my 3" thick bridge planks, I would want to set the channel iron (cross members) down 3" from the top of the H-beam, so the H-beams (rails) would be part of the deck surface. Although, in the interest of saving weight, I may not use such thick lumber.

I looked online at some trailers like this. It seems they typically use 3" C channels on 16" centers. And they usually have 10000lb axles and 20000 gross weight. So if I only want 15000lb gross, then 3" channel iron on 16" centers should be plenty strong.

Also, like I said above, I am a bit concerned about the strength of the H-beam for pierced beam construction. The C channels pierce through the vertical (web) section of the H-beam. But this part of the H-beam is only 5/32" thick, and would have to carry all the weight of the C channels. Does this sound reasonable?

Thanks again guys!

 

[Tdawg]

cjmdjm, sorry if I sounded harsh, but like I said you wouldn't believe some of the contraptions I've seen.
Timster2 has a very good point. 16" is the depth of your beam, you need to measure the width and also the thickness of the web. Google I beam specs to find a calculator to give the weight per foot. You're probably looking at 50-55 lbs/ft. For a 20' trailer plus the gooseneck, you'll have say 70' of beam-that's 3500-4000 lbs. That's before you add crossmembers, siderails, springs, axles, decking, etc. Leaves very little for payload.

Also, because of the height of the beams you should stay away from a deckover design-when loaded you would have a very high center of gravity. If you went between the wheels, would there be enough deck width to fit a tractor?

 

[Tdawg]

Ok. So if I were to use my 3" thick bridge planks, I would want to set the channel iron (cross members) down 3" from the top of the H-beam, so the H-beams (rails) would be part of the deck surface. Although, in the interest of saving weight, I may not use such thick lumber.

I looked online at some trailers like this. It seems they typically use 3" C channels on 16" centers. And they usually have 10000lb axles and 20000 gross weight. So if I only want 15000lb gross, then 3" channel iron on 16" centers should be plenty strong.

Also, like I said above, I am a bit concerned about the strength of the H-beam for pierced beam construction. The C channels pierce through the vertical (web) section of the H-beam. But this part of the H-beam is only 5/32" thick, and would have to carry all the weight of the C channels. Does this sound reasonable?

Thanks again guys!

1) Yes, you would set the crossers on the beam to match the thickness of your decking.

2)Semi trailers use 3" channel 16" inch on center-so yes it will be plenty strong

3)You don't have to slot the beams, but if you do and you know how to weld, this method gives you the strongest frame-you can weld the channel on both sides of the beam.

 

[s219]

First, I'd suggest calculating the weight of those I-beams -- you may be spending a good portion of your axle payload just to drive the beams around.

Second, maybe step back and understand how I-beams work. As a beam, it's the vertical web of the I-beam that carries the load. Don't get hung up on how the web compares to the flanges in terms of size, thickness, or load capability. Do get hung up on any mods or welds to the beam that can affect the web. You need to be careful about the web.

I'd echo other suggestions that you need more structure to support that planking. Being attached to two massive I-beams still leaves a lot of the planking unsupported, and the planks have a lot of freedom to act independently. You could easily get in a situation where a single plank is supporting a load without a way to distribute or share it with the rest of the structure.

 

[LD1]

You have got some good info so far. But the first order of business in to find out EXACTALLY what you have for I-beams.

There are two types, S-type and Wide-Flange type. S-type are the ones with the narrower flanges but the under side is tapered. Like channel iron is. WF type is all squared. Also known as H-beam. This: wide flange steel beam specifications, 16 inch to 36 inch WF beams
is a good website I use for sizing. And looking at both S-type and WF, I dont see ANY with less than a 0.250" web. So can you take som accurate measurements on everything else and maybe we can help.

Because I am now wondering if you actually have a true beam. Because to save cost and weight, a lot of buildings these days are using thinner but larger steel plates welded together to form the "beam". And that may be what you have.

Also, even if it is 1/8", either piercing or welding channel directly to it evert 16" should still be pleanty strong. because it would take ALOT of force to actually "crush" the 1/8" web of the beam.

The easiest way you are probabally going to build would be use the channel BETWEEN the beams and welded in, and then use shorter peices welded to the outside with a small gusset or peice of angle Iron running back down to the bottom flange. Gussets like you see in this link Redirect Notice

Second, maybe step back and understand how I-beams work. As a beam, it's the vertical web of the I-beam that carries the load.

Incorrect. The vertical web only acts to keep the Flanges spaced appart, because the Flanges are what carry the load. Top Flange in compression, and bottom flange in tension. It has to do with how far appart these are spaced that gives the beam its strength. The farther they are appart, the MORE the flanges have to "stretch" and "compress" for the beam to deflect.

So a deeper beam is stronger, but not because of the web. The web is just there to hold the flanges appart.

Think about how trusses work:thumbsup:

 

[rambler]

Safety messages are always good.

However, if you are using good sound 3 inch wood planking, look up Donahue or John Deere implement trailers - they are 8 or 10 feet wide, and 28 feet long to transport long planters sideways. Anyhow, they have 3 inch planking 7 feet long segments running lengthwise supported on each end by angle iron. Rated for 10,000# I believe.

If you are going crossways with the planks, with 2 Ibeams under with perhaps a 4 foot span, compared to the 7 foot span of those trailers.....

As others say, I'm concerned about the weight of your trailer, seems you are using some heavy stuff to make a low gross weight trailer, end up pulling more trailer than load around. If you go with the 16 inch spacing, I sure hope you plan for a smaller plank to save a bunch of weight!

--->Paul

 

[cjmdjm]

Wow, I woke up this morning and theres like 5 new replies. Thanks for all the help!

As others say, I'm concerned about the weight of your trailer, seems you are using some heavy stuff to make a low gross weight trailer

Yeah, if I do pierced beam, I'll probably go with lighter lumber. 3" thick planks are overkill if I'm not trying to span between the H-beams.

The H-beams aren't that heavy. They are Wide Flange (H-beams), not tapered at all, everything is square. The web is 3/16", the flanges are 3/8" thick. They're 16" tall. The bottom flange is 3.5" wide, and the top flange is 6" wide. The top flange has slots for stake holes and chains. I suspect they were originally intended to go along the edges of a flat bed semi trailer, as side rails.

Using the table LD1 suggested, they couldn't weigh more than 26lb/ft. Probably more like 20, since the closest match on the table has a slightly thicker web, and wider average flange width. So thats about 1400lb for 70'. So hopefully with lighter lumber, the weight will be reasonable.

Also, because of the height of the beams you should stay away from a deckover design-when loaded you would have a very high center of gravity.

Yeah, I am looking at some designs for between-the-wheels, and I'll measure my tractors tonight and see how that would work. I probably wouldn't be able to use my H-beams in that design, right? But the lower CG sure would be nice.

But with pierced beam construction, the deck shouldn't be any higher than a trailer with 12" H-beams, with the C channels above the H-beams. The pierced beam design will make up for the taller H-beams, right?

Thanks again guys!

 

[s219]

Incorrect. The vertical web only acts to keep the Flanges spaced appart, because the Flanges are what carry the load. Top Flange in compression, and bottom flange in tension. It has to do with how far appart these are spaced that gives the beam its strength. The farther they are appart, the MORE the flanges have to "stretch" and "compress" for the beam to deflect.

So a deeper beam is stronger, but not because of the web. The web is just there to hold the flanges appart.

Think about how trusses work:thumbsup:

I understand what you're saying, and you are 100% correct. But the web is what handles the gradient between compression on the top and tension on the bottom, and is ultimately what carries the day. Try removing the web and see how those flanges do on their own -- not so good!

There is strong shear throughout the web, with maximum shear plane right down the middle axis of the beam, halfway between the top and bottom flanges. Right at the edges of the flanges, the shear goes to zero. So while the flanges carry heavy tension/compression, the web carries almost all the shear.

If you look at the beam equations for a W16x26 I-beam with 5.7" wide flanges, a web thickness of 0.25" and a flange thickness of 0.35", each flange handles about 37% of the load while the web handles 26% of the load. So the flanges do handle the majority of the load when they are connected by the web. But if you were to take the web away, the flanges by themselves suddenly can only carry 0.01% of the original load! By itself, the web would still handle that 26%.

So it's important to keep in mind that the flanges and the web are a system, and must work together. If you compromise the web on an I-beam, then the flanges are essentially worthless. I didn't mean to imply that the web was the main load carrier, but rather, that it was the essential part that makes the I-beam work.

 

[LD1]

So it's important to keep in mind that the flanges and the web are a system, and must work together. .

I agree with that. And it sounds like you know what you are talking about here. But all too often, people think the web is what makes the strength of the I-beam. Like if you cut one of the flanges off, the beam will be just as strong, or a 1/4" plate 16" deep would be just as strong as a 16" Ibeam in the vertical direction, and that just isnt the case.

If you compromise the web on an I-beam, then the flanges are essentially worthless.

Not necessarily true. In fact if you want to lighten a beam with the LEAST amount of effect on its strength, the web is where to do it. (think a truss). Just so long as you have enough material to hold the flanges appart. Think of those I-beams you see, (like some equipment trailers) that have holes (or triangle sections) of the web removed.


And anytime someone (and there have been many times in the past) someone trys to say the web is what makes the strenght, I like to use the following example to prove the point:

Look at a beam that has the same flange width as depth. The W8x31 works well. It is 8" depth with 8" flanges. And has a web of .285" and a flange thickness of .435".

In the xx direction (convention I direction) you have ONE vertical .285 plate with the flanges on top and bottom.

In the YY direction, you have TWO vertical plates that are .435, yet the beam is about 3 times weaker in this direction.

Or compare the W8x21 to the w8x24. The 8x21 is actially about 1/4" TALLER, and has a thicker web, but the flanges are only 6" whereas the w8x24 has 7" flanges. That extra inch of flange not only overcomes the thicker web and 1/4" taller depth of the W8x21, but it is about 10% stronger to boot.

But either way, I think we both understand the physics of how a beam works.:thumbsup: But after your first post, It sounded like you were one of those that thought the web did it all:confused2:

 

[moored4]

If I'm reading this right, you want to use these I beams for frame rails and then use boards for cross members/decking???? And you want to put a license plate on it and pull it down the highway??? How are you going to attach the boards-deck screws??? Carriage bolts??? And you want to put a tractor on top of it??? Think about it...would you want your family following this rig down the road???

Look, I'm new here and I'm sorry if I ruffle feathers, but I've spent a lot of years building and fixing trailers and you wouldn't believe some of the things I've come across. As strange as it may sound the roads are for everybody, not just guys looking for a cheap (and dangerous) way to haul their stuff around. If you want to build a proper trailer I'll be the first guy to help you out but not if you want to cobble something together out of stuff you have laying around in the yard.

Cheers,
Terry

X2! Its not real clear to me what he/op is trying to do, but does not sound like a good desine to me!