Calculating beam size for a trailer.

[MrBeast]

I am designing a goose neck trailer, it is going to have a 36 foot deck and an 8 foot neck.

I want to make the trailer durable, it will have a tandem dual setup, but at the same time I don't want to make it too heavy.

Does anyone know the formula for determining the strength of an I-beam?

[Fegenbush]

I am thinking that you are going to want more of a design than just the main beams. My recommendation is to hire an engineer to come up with some sizes and maybe drawings. I know that there are quite a few engineers who would size the beams and goose neck for you for a couple hundred bucks. Drawings would be a couple hundred more. There are a lot of things to take into consideration when designing these things, and you want to make sure you are doing it safely.

Let me know if you need help locating someone, or want me to do it.

Fegenbush

/Currently my stamp is for Kentucky only, but that shouldn't matter for this job.

[MrBeast]

did some research, going with 12"x19 lb wide flange beams, 2x5" box tube for the edge of the deck, C4x5.4 channel for the cross members, setting them on 16" centers.

http://i40.photobucket.com/albums/e215/DigitalTA/36%20Foot%20Trailer/RENDER2.jpg

http://i40.photobucket.com/albums/e215/DigitalTA/36%20Foot%20Trailer/RENDER1.jpg

[ed mac]

you can buy trailer plans from northern tools
there good plans and DOT ap.

[SundownIII]

Yeah ed,

And I think Northern also offers a DVD on Welding 101.

You ever check it out?

Just thought it "really strange" that you would be the one to chime in on "trailer design".:rolleyes:

[Lanse]

Good lord Sundown, have you ever said a positive thing to anyone on here? Seriously man, why do you insist on criticizing these folks at every chance that you get?

[CEP]

Mr Beast, all you need to do when building trailers, is take a protractor, tape measure, pad, and pencil to a couple trailer sales lots. Measure, and write down the dimensions of all the trailers that are in the category of what you want to build.
Sometimes the salesmen don't like this, go ahead ask me how I know. :laugh:

[Rick V]

Ed Mac spotted something good. Here's the closet plan Northern Tool has to what you want to build - a mite shorter than your 36 footer. It's for a trailer of dimensions 32 x 8ft. 6in.
http://www.northerntool.com/shop/tools/product_200308241_200308241
I like what one review said, "I used these plans to build a 32 ft. hydralic drop tail trailer. My trailer differs from this one , but I used the plans for the construction details in the gooseneck, axels, and main frame." Seems a good investment for $40.

A bit of surfing on the Internet did not quickly turn up much more but maybe a more determined search could reveal something - certainly worth a try.
I kept running across comments on making sure you had local state DOT approval before you built your trailer - else you might not be able to run it on the road.

[CEP]

I have seen those drawings from Northern Tool, they sure make it easy, any 3rd grader could build a trailer with their drawings.

[SundownIII]

Lance,

Just so "I stay with tradition", you've sure got a lot of mouth for a young punk who can't make it more than one day on a job.

Maybe ed hack should buy one of those sets of plans from Northern and learn to weld. Then, maybe the gates wouldn't fall off his trailers.

Maybe after you've graduated (or at least spent a little time there) from the school of hard knocks, you'll have a little better understanding of why guys like Fat Bastard, me, and several other guys get a little fed up with the crap we see posted on the boards.

I'm beginning to think that maybe you just don't have thick enough skin to be hanging out on a welding forum. Maybe you should be looking for a job with the Democratic Party.

Really got little use for whiners. Signed on at 11 years old as a "carpenter's helper". Learned real quick what a shovel was for (digging ditches/cleaning up trash). Then I learned how to hang fiberglas insulation overhead in a crawlspace in the middle of the summer in 95 deg weather. You know what, I did anything/everything that was asked of me. By the time I was 13, I really was working as a carpenter's helper. By the time I was 15, I was running my own crew.

I'm 63 years old now, and I sure as HE11 don't need any advice from a "wet behind the ears, smart mouth punk" about how to be "politically correct".

[MrBeast]

I am not going to use the Northern Tool designs for one because those designs are not suited to my needs, for two, every tom dick and harry has built one, and they are hardly unique.

For me there is a challenge and a learning curve involved in this project, I do have the skill necessary to build it, and I am smart enough to figure out a design that will work, and I am well enough aware of my limitations that I will not be getting in over my head.

That being said, for me doing this project is as much about the experience and knowledge if not more so than the final outcome, although you can bet your bottom dollar what ever that final outcome is, it is going to be done right.

I really look at the northern tool designs as taking the easy way out.

[AMC724]

Have you ever seen the movie "Grumpy old men"?

Me either, just thought i would ask.


X2 on going to a retail lot with a tape measure, pencil and note pad
if for nothing else, to determine a main beam size

[MrBeast]

Have you ever seen the movie "Grumpy old men"?

Me either, just thought i would ask.


X2 on going to a retail lot with a tape measure, pencil and note pad
if for nothing else, to determine a main beam size

That is actually what I did, found a couple of manufacturers who listed the beam size, and it was the 12x19 W beam.

[Rick V]

Maybe I am missing something here... but can anyone just design and build their own trailer (yes, a 36 footer) and put it on the highway? Really?
I'd of expected there were are a pile of rules and approvals required - more than just on lights and brakes.

[MrBeast]

Maybe I am missing something here... but can anyone just design and build their own trailer (yes, a 36 footer) and put it on the highway? Really?
I'd of expected there were are a pile of rules and approvals required - more than just on lights and brakes.

Si Seinor. All it needs is a home built trailer inspection.

[Boostinjdm]

Si Seinor. All it needs is a home built trailer inspection.

They don't even ask to see them around here if the empty weight is less than 2000 lbs. Interpreting the rules above that can be almost impossible in some cases. They don't want to see it till it's done either so I keep mine under the limit just to avoid some jackass telling me to move my light 2" forward or back after it's been hole sawed into the outer rail. I once even asked if an officer could stop by on the way through town and view the construction so I could get it right. Didn't happen...

There is a lot of absolute junk going down the roads, so I don't even know why I worry about it.

[MrBeast]

They don't even ask to see them around here if the empty weight is less than 2000 lbs. Interpreting the rules above that can be almost impossible in some cases. They don't want to see it till it's done either so I keep mine under the limit just to avoid some jackass telling me to move my light 2" forward or back after it's been hole sawed into the outer rail. I once even asked if an officer could stop by on the way through town and view the construction so I could get it right. Didn't happen...

There is a lot of absolute junk going down the roads, so I don't even know why I worry about it.

There is a lot of junk, but here is how I look at it, as a fabricator, I am going to do the best job I know how, I am going to constantly look to improve, and I'm not going to worry about the standard because after all that is a minimum that I feel should be far exceeded.

As well I will not worry about what the other guy is doing, I will just do my best in the hope that it takes the business away from him and brings it to myself.

On the road there are no guarantee's, I have traveled over a million miles on America's highways, and the thing I have learned is that what is more important on the road is not being in a hurry, take your time, do your stuff right, don't get stressed and keep an eye out for the other idiots, and you will be alright.

[wnywelder]

In New York at least, trailers over 2000 pounds have to be taken to a DOT inspection station before they can be titled and registerred. I would hope that they know what to look for to keep some of the dangerous stuff off the roads.

[wnywelder]

Double post.

[SundownIII]

MrBeast,

The problems with designing/building your own "one off" trailer are many.

Today's larger trailers (ie 36') are really "engineered" to give a design load capacity, while at the same time minimize weight and use the most economical materials available.

The "one off" builder simply does not have these tools at his disposal. As a result, the conscientious fabricator (which I think you are), will tend to "overbuild" his trailer. That results in a reduction of "load carrying capacity" while at the same time increasing costs.

I understand that this build also has a degree of "I can do it" involved, but realize that it's extremely difficult to compete with the "big guys" when it comes to design and buying power. For instance, you're buying a couple main beams. They're buying the stuff by the ton. Same thing applies to axles, brakes, etc., etc.

One option you may want to consider is finding a used trailer in good shape that "comes close" to what you really want. Buy it and modify it to meet your exact needs. Think you'll find that you're far ahead of the game both in capacity and costs.

[AMC724]

My momma always said "give credit where credit is due"


I would have to agree with sundowniii's suggestion about buying a used trialer.

[Donald Branscom]

I am designing a goose neck trailer, it is going to have a 36 foot deck and an 8 foot neck.

I want to make the trailer durable, it will have a tandem dual setup, but at the same time I don't want to make it too heavy.

Does anyone know the formula for determining the strength of an I-beam?

Machinerys' Handbook has strength of beams from pin to pin when weighted in the center.etc.,but with a trailer, the WAY the weldment is constructed must be taken into account.

Probably the juncture or attachment point of the 8 foot beam to the trailer frame would be one of the main concerns. Why not use plans that can be bought, or are available from an approved source? Take the strain off of yourself.

HERE IS A SET of plans for $66.00 29ft. tandem 1500 lbs hitch weight.
http://www.glen-l.com/campers/queensbury.html

[MrBeast]

Machinerys' Handbook has strength of beams from pin to pin when weighted in the center.etc.,but with a trailer, the WAY the weldment is constructed must be taken into account.

Probably the juncture or attachment point of the 8 foot beam to the trailer frame would be one of the main concerns. Why not use plans that can be bought, or are available from an approved source? Take the strain off of yourself.

HERE IS A SET of plans for $66.00 29ft. tandem 1500 lbs hitch weight.
http://www.glen-l.com/campers/queensbury.html

Are you serious? That is a camper.

[CEP]

Does anyone know the formula for determining the strength of an I-beam?

Mr Beast these may help you, for this project or in the future.

[MrBeast]

Mr Beast these may help you, for this project or in the future.

That is exactly what I was looking for! Thank you very much!

[CEP]

You're welcome.
You need one these.

[MrBeast]

You're welcome.
You need one these.

Definitely, I know for as much as I use my pipe fitters blue book those look like they will come in very handy, I am going to order them up!

[Donald Branscom]

Are you serious? That is a camper.

You did not tell us what the trailer was to be used for.
Are you going to be transporting a backhooe?

Then you could look up plans for a backhoe trailer. Free or low cost.
A person was asking the same basic question on the Miller welding forum and a guy that has built 500 trailers said he could help.
Equipment trailers.
http://www.millerwelds.com/resources/communities/mboard/showthread.php?2646-Looking-for-good-equipment-trailer-plans

[MrBeast]

You did not tell us what the trailer was to be used for.
Are you going to be transporting a backhooe?

Then you could look up plans for a backhoe trailer. Free or low cost.
A person was asking the same basic question on the Miller welding forum and a guy that has built 500 trailers said he could help.
Equipment trailers.
http://www.millerwelds.com/resources/communities/mboard/showthread.php?2646-Looking-for-good-equipment-trailer-plans

See previous post:
I am designing a goose neck trailer, it is going to have a 36 foot deck and an 8 foot neck.

I want to make the trailer durable, it will have a tandem dual setup,

When I specified "deck" that would denote that this is going to be a flat bed trailer.

[DSW]

Keep in mind that the charts CEP posted are for what engineers refer to as "simple" beams that are supported on both ends uniformly. A trailer is a much more complex design issue. These charts are the basics engineers use to dertemine structure designs. Figure 1 is what CEP's tables are based on. Figures 18-22 are the closest they show to a trailer.

http://www.awc.org/pdf/DA6-BeamFormulas.pdf

Actually a trailer is a beam with multiple supports ( each spring hanger would be considdered a "support" and the equalizer between them complicates the issue) and a cantileavered overhang. Add in that there can be uniform loads or point loads, or a combination of both. You don't have to understand the math and exactly what the diagrams mean. The moment curves ( bottom diagram of the 3 shown) are generally what is used by engineers to design a beam against bending. The higherst point on the curve is the point where the most bending is likely to occur and is the point that generally determines how tall or heavy a beam needs to be. Note that the area changes from above and below the line in many cases. Any area above the line shows bending in the down direction, similar to what most people think of when you apply a load to a beam. Like putting blocks on a board supported on both ends, the beam bends down, and the moment diagram shows a curve in the up direction over the line. And curve or area BELOW the line means the board is bending UP not down, something many people don't realise.

The diagrams give you an idea how complex this can be depending on how the load is applied, and these are the "simple" ones. Your's is more complex. That's why engineers get paid the big bucks and why there really is no simple answer to your question.

[wmgeorge]

To be honest, the only trailer I have seen that came apart was welded and designed by guess what? My :PHD brother in law, and his friend who did the welding who was an engineer! They used a little 120 volt MIG welder. After it fell apart on the first trip out they took it back home and re-welded.

When I saw it after the trip from Georgia to Maine I was surprised it made it, even after the re-weld. All the welds looked like c**p. Nice little camping trailer, but scary.

[Donald Branscom]

To be honest, the only trailer I have seen that came apart was welded and designed by guess what? My :PHD brother in law, and his friend who did the welding who was an engineer! They used a little 120 volt MIG welder. After it fell apart on the first trip out they took it back home and re-welded.

When I saw it after the trip from Georgia to Maine I was surprised it made it, even after the re-weld. All the welds looked like c**p. Nice little camping trailer, but scary.


It is always scary when engineers try to build something.
I have worked on projects that were "engineered" that failed.
I am not going to type the whole list.
Just read the newspaper.
Bridges that are designed have teams of engineers. I think there is a reason.

Once I was asked to look a plans for a 35 foot aluminum boat.
When I saw the drawings I knew the boat would fail. The thicknesses of the plates and structure were too small. Transitions too abrupt.
I told them it would not work.
The big bosses told me in a condescending way to go back to work.

3 months later the boat went out for sea trials and the keel folded up.
Then the lawsuits started flying.
I just sat back and watched the show. Hey what does a stupid welder know that has already built several boats - right?

It seems to me like some engineers(not all) skipped the build a go kart or something phase and went straight to the math part. Later on they tried building a small project at home and it failed. I think it is very important to build things and get a feeling of the strength of materials and understanding of other problems that can happen in addition to just learning the math.
When building things larger than 6 feet high then you have to do the math or people will get hurt.
Remember when the Hubble space telescope was sent into space in two halves and would not fit together?
Engineers form two different countries. And we all know how tight the tolerances will be when Germans machine things.
Same thing with the new Boeing 787 being built with many countries participating. over 3,000 fasteners had to be replaced.
Also the young inexperienced workers just thought the fasteners would work without any problems and put them in without checking.
Older more experienced workers may have prevented that from happening.
Same thing with the 380 airbus wing center section box. Engineers kept building larger planes with the same computer program or data but the wing sections kept getting larger. Now there is evidence that the plane broke up in a storm.

Like I said just read the newspapers.

[Donald Branscom]

See previous post:


When I specified "deck" that would denote that this is going to be a flat bed trailer.

I understand but all trailers have decks.
The load to be placed on the deck can vary.

And you still have not told us what this trailer with "deck" will carry.

[Sandy]

Build your own version of airbus with no engineer/engineering. That'll show 'em. ;) You'll be a billionaire. :)

Do not buy a trailer that has been designed by an engineer.

Only buy cars that have a tag "no engineering no design involved".

[Donald Branscom]

I have been welding for many years and I would invest in the $40 plans .
RICK V has good advice. You can always make custom modifications but at least the structure will be correct.

Once I went online and got simple plans to build a wood workbench.
You know what? I am still using that bench after many years and it does not wiggle or squeak. The plans were free too. My ego was not damaged.
Matter of fact I felt good that I could follow a set of plans, and get a good result.

OR...Take Sundown III's advice and buy a trailer and modify it for your needs.
I would sit down and see which costs less. You may save a lot of money. Like maybe a $1000 or more.

[Country Metals]

The problems with designing/building your own "one off" trailer are many.

Today's larger trailers (ie 36') are really "engineered" to give a design load capacity, while at the same time minimize weight and use the most economical materials available.



I agree with Sundown. I priced around for a 14,000 lb trailer that was a low boy that can handle my JCB520 and my 2646E3 Scissor Lift (not at the same time but they have different loading needs). After getting prices for building it myself and prices for it delivered, I seen that I can't build it for the price I paid for it. Plus it is powder coated, DOT approved, and I didn't loose any time building it. There are many trailer places around and Texas has the best pricing if you can travel that far. A buddy of mine just bought the same trailer you want to build 3 years ago new for $4,800. I doubt you can buy the steel and axels for that price.

[Dualie]

A couple of years back i got a wild hair up my azz and started designing a gooseneck style lowbed out of T-1 with some ideas stolen from murray lowbeds. I got about 1/4 the way through design and said screw it and bought a walton. I think i threw the drawings away.


IT was going to be a outside frame rail gooseneck with completely fabricated beams, dual tandem.

[AndyA]

Be careful designing from those tables. Remember you are trying to support a dynamic load, not a static load as you would see in a structure. What factor should you use to convert dynamic loads into something you can look up in the tables. Probably 2x, but I don't know. I'm an electrical engineer, not a muck-anical.

[Fegenbush]

You're welcome.
You need one these.

Be warned, CEP. The 8th Edition of the book has been superseded by the 13th. They combined the ASD and the LRFD books into one and they are phasing out ASD from what I can tell. ASD is more conservative when the live load is 25% of the dead load or less. Otherwise, LRFD is the more conservative approach. With the case of a trailer, I would assume that the live load would be at least equal to the dead load. I'd use the LRFD, were I designing it.

Moving away from engineer mode, building a trailer from scratch can be a DIY project, but it really depends on the person doing it. Without specific calculations of length, load, etc. you likely won't be getting the best deal. The trailer will weigh more for it's rating than one from the factory. That's just money down the drain every time you haul something with it.