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

[jclaudii]

Have you thought of doing a wagon style instead of a trailer? Meaning it pulls behind a truck/tractor but has front wheels that turn with the hitch bar. We have a 500 gal setup on an old truck frame of some sort, like '40 or '50s. The thing uses the truck frame, front axle beam, rear drive axle, and even the very very old 18wheeler style wheels/tires.

You could build the same thing but just using f350/f450 parts from a junk yard, heck perhaps just cut the frame off behind the cab. Perhaps you can even find an old fertilizer wagon or spreader that is rusted out, but most of those have dual ribbed floatation ag wheels on the rear and prolly haul several tons of fertilizer.

I see your in Florida so you may have trouble finding these, but another option is a hay wagon. Like this trailer

 

[muddstopper]

First off, a 500gal poly tank needs a saddle to set on, or it subject to bust from the weight of the water sloshing around. The saddle can be nothing more than some 14guage metal formed to the shape of the tank and welded to you trailer. Straps can be used to attach the tank to the saddle and trailer. One axle is perfectly fine. My old 600gal Finn hydroseeder just used one axle and it was a metal tank with an agitator inside. If fact, I still have the old tank, but the axle is long gone, and no engine, if your interested in something ready made that will handle what you want to do. Even has the pump, ( been sitting for a few years so might not even work),but probably to big for your needs any ways If interested, pm me, I'll let it go cheaper than you can buy the steel to build your trailer.

If you build a trailer, You dont need that heavy of material. I think my old jet hydroseeder used 2x4 rectangle tubing, Thin wall. The tube was laid flat, so it was only 2inches tall instead of 4 inches, which sounds like it is opposite that it should be, but it worked. The tongue did extend under the tube back to the axle and pump/engine was mounted on tongue, much like the one in the above picture. I dont remember the size of the channel used for the tongue. The poly tank was supported by the saddle and the saddle was attached with flat bar to the frame. The frame did have angle welded in between each side, dont remember how many, what size, or how far apart. It met Oklahoma Dot specs or they couldnt have sold it for highway use.

 

[franklin2]

I will give my opinion, including some of the comments already made;

I think you are correct in building your own trailer. It's going to be hard to find a heavy duty single axle trailer for your use.

I agree with some of the others, the metal doesn't need to be as thick and heavy as you would think. I would price it out. Rect tubing is much stronger than angle. But I would compare price and availability, I am notorious for using what I have laying around or can get cheap. If you are going to use any type of angle iron, I would stick with 1/4" stuff. If you are going to use some sort of tubing, you can go thinner.

I am not sure I would center the tank over tha axle. I would always want a little tongue weight with it, and I would be afraid as the water sloshed back and forth, you would go from no tongue weight to a lot of tongue weight as the water went forward and backward.

 

[muddstopper]

I am going to disagree with Franklin on tank placement. Yes you will get sloshing of water from forward to back, but placing the trailer forward of axle is not the proper way to get tongue weight. If the axle is centered in the trailer and the tank is centered on the axle, yes you will get a tendency for the tank to lift up and down on the hitch. Simply mowing the tank forward only creates tongue weight when the trailer is full of water. When its empty, your going to get even more bouncing on the trailer ball. Rule of thumb for axle placement is 1 inch back for every foot of trailer lenght. 10 ft trailer, axle placed ten inches back of center. This will give you right at a 60/40 split on weight distribution. Placing the axle properly under the trailer and then centering the tank over the axle will make sure you have proper tongue weight empty and full. Water sloshing will only transfer 40% of the sloshed weight to the trailer ball, not the full weight of the amount of water that moves to the front of the tank.

 

[David Devuono]

A bunch have beat me to the punch. The Op sounds like he has a big Kubota so 500 or 1000 lbs on the tongue would not be an issue. The only single axle HD compact trailers are ones that haul cable reels. Since the Op has everything but the steel, I just happen to be building a 4x6 foot tandem dumper this weekend with independent walking beam axle for off-road hauling. I bought (in canada so will be way cheaper in the USA) 30 feet of 4" channel today for 200 bucks. You likely will not need longer then a 4x6 foot trailer. For those in colder climates, I have a trailer made of tubing where some of the tubing is now round because water froze in the frame so I went with channel for this build (plus channel was 80 bucks cheaper then 2x4 3/16 wall tubing. Farmer2009 that is a nice rig. I want to set up a firefighting rig like that -minus the pto pump when I build my country home.

 

[Cord]

Northern has some trailer plans, perhaps one of them could be adapted to your needs. The issue I've seen in the past is that the cost of materials and parts nearly equals what you can buy a pre-made trailer for. Knowing you need some capacity (400 gallons of water weighs 3300lb) and want to use it off road I'm wondering if a hay wagon wouldn't be a good choice for you. Shorten up the center tube to the length of the tank, balloon tires and a long tongue to clear tractor tires would make it perfect for the job. Plus you can get a good used one for $500. If buying a used one, just make sure the steering isn't worn out or the thing will hunt terribly. If you can find the running gear off a old mobile propane tank, they use a king pin type steering that will track better than the automotive style used on the hay wagons.