Building trailer...what size steel do I need?

[chrism16]

Hi all I am a golf course mechanic and am looking to build a single axle trailer for a 500gal water tank in order to irrigate some sod and new landscape being planted in a few months. I already have the tank, axle and wheels but I need to start ordering steel and Im not sure of exactly what size and gauge I need. This water wagon will only be pulled at about 5mph by a tractor and the tank wont be filled more then 3/4 full. As far as size I am thinking 6X10 should be sufficient for the tank, pump and small engine along with hoses. The total weight I am figuring should be close to 5000lbs. I have seen some plans on the internet for 3500lb utility trailers but nothing for any heavier. I have a pretty good idea how to build it but I guess my question is should I use channel steel and if so what size? There is not going to be any decking...I am going to bolt the tank directly to the frame and make platform for engine and pump. If anyone can give me an idea of what type of steel I should use it would be greatly appreciated. Thanks

 

[davesl708]

There is a reason you don't find plans for larger trailer online. Moving this much weight requires specific engineering requirements and welding.
Your plan is to not take it on the road or fill it up but in the future someone else may.
I would get some consultation from a fabricator that builds trailers. That is a lot of weight to stop.

Good luck with the project.

 

[LD1]

The water alone will be pushing 4200#. So 6k total weight with trailer, pumps, etc would be a closer target. And for that I would want more than a single axle. Not that you cannot get a single axle to handle the weight, but for load distribution. 6k on two smallish tires of a 7k axle is gonna leave some ruts.

And how is your welding skills? Are you confident you can weld a 500gal tank with no leaks?

Depending on how you do the water tank will determine the room it takes. A 5' x 5' x 3' box will be slightly more than 500gal. That would still leave half of a 6x10 trailer empty.

HAve you considered the 250gallon totes? Or even an old 500gal propane tank attached to the trailer?

Also, size of the trailer frame also depends on size and design. A shorter smaller trailer can get by with smaller material cause you are spanning less distance. Landscape type trailers dont use any heavy steel or channel, cause their strength comes from the 1' high side rail all the way around, basically making a truss.

 

[chrism16]

I have been welding for 15 years that is not my concern. I already have a 500 gal poly tank that weighs less than 100lbs. You can not fill a poly tank to the top without blowing the cap off or damaging it so 400 gals IS the max. While I have never fabricated a trailer, I have done many other things and this is really not that difficult. Yes its alot of weight but I already have a 6k torsion axle and 5k heavy duty wheels. A double axle on grass is not a good idea when you need to back it up and that is the main reason I am keeping it single. This is really a simple rectangle shaped base with cross members and V tongue...thats all I need, nothing fancy. I just definitely dont want to under spec the steel or over build it either for extra weight reasons.

 

[Deere Dude]

I have a 4x7 trailer with a single cheap 6,000# mobile home axle and load range e or g tires, I don't remember which size. Maybe 14-1/2" tires.
But I move a full 350 gallon tank around the yard with no problems for watering trees.
You don't need springs, although I have them. I would just get 2 3" channels for the main frame and the rest out of maybe 1-1/2 angle 1/4" thick. Mine has a thin steel metal floor, don't know the guage but that would be unneeded. Mine has about 24" walls and I used to regularly pile with dirt until it rolls off the sides and haul it around the lawn to fill low spots. I lift the front up with the tractor and use it as a dump trailer with no problems. No ruts as long as it is dryish.
My trailer uses a lot smaller metal than what I described to you before and is 40 years old and is in good shape yet. I have no qualms about pulling it down the road with a truck.

 

[5picker]

chrism16,

I built a trailer similar to what you are wanting to build but mine is a dump.
Much like you, I didn't want tandem axles for backing into yards so I used a single 7k axle on mine.

It is 6' x 9' and would easily haul a 500 gallon tank.
I used 2" x 4" x 1/4" rectangular tube for the box of the frame with 2" x 3" x 3/16" crossmembers.
My floor is 10 ga. (1/8") sheet steel as is the sides.
Best of luck with your project. Let us know how it turns out.

 

[Gary Fowler]

I am not an engineer and have not done any stress calculations, however for a small say 10 foot long trailer, I think 3x3x1/4" angle for the frame is sufficient. I would use 2x2 angle as cross members for the frame. I would think you would want side rails so either 1.5" pipe rails or 2" angle would work for that also (angle being easier to cut and fit than pipe).

My experience with cost of steel, axles, tires, paint, lumber, etc for trailer building is that you can buy one cheaper than you can buy the material and even if your labor and welding supplies are free, you cant break even on the cost.

 

[jenkinsph]

I agree with Gary, I can usually find a used trailer cheaper than I can build one.

 

[LD1]

So you already have the tank. To determine what size you need, I would set the tank, them pump, hoses, etc out on the garage floor in an arrangement that they would be on the trailer. I would try to center the tank over the axle if possible. You width is really gonna be determined by the axle.

after size is determined, you need to decide how you are gonna build. Do you want a landscape type with the side? those are made with lighter material as it is a truss. Or you can do a channel setup with no sides. Angle iron without the sides (even the 3x3x1/4 that gary suggests) still seems light for the weight. Pound for pound, channel will resist bending alot more than angle. 3x3x1/4 weighs 4.9# per ft. A 3" channel iron that weighs 5# per ft is 50% stronger. And 4" channel weighing 5.4#/ft is twice as strong as that 3" channel.

If it was my trailer, I would probably go with 4" channel sides, and 3" channel cross members every 2'.

So a 6x10 square box made from 4" channel would weigh 172#
4 cross members with 3" 4.1lb/ft channel would weigh 100#
2 10' sections of 4" channel for the tongue (extending under the deck back to near the axles) would weight 108#
Treated 2x decking would weight ~300#
Tongue and jack ~#50
Axle and wheels ~#350

So about 1100# complete.

Steel is likely gonna cost ~$350
Jack and coupler ~$75
Decking ~$120
Misc hardware and paint ~$200

So already at about $750 for a single purpose offroad only trailer. I think for the money you could probably find a used trailer to meet your needs that can be registered and hauled on the road if you want. Not trying to talk you out of a neat project, but unless you already have a steel rack full of material, it just dont make sense.

Even of you find one that has 3.5k axle, swap axles since you already have one. Keeping the load of water right over the axle, I dont see an issue doing this.

 

[farmer2009]

Based on your description. I have a feeling that you are looking for something like this.




500 gal tank with boomless nozzles and hand wand.

The only thing that concerns me with what you want to do is your comment that a 500 gallon tank won't hold 500 gal. That tank is rim full in that picture. What kind of tank do you have?