Building my own trailer - need some advice

[N8TGK]

Last year I bought a 5x8 utility trailer and upgraded the heck out of it while teaching myself how to weld. Well now I enjoyed that so much I want to try something bigger.
I plan on building a pressure washing, hydroseeding, and fire fighting trailer unit, gonna have a skid mount hydroseeder, a big pressure washer, a water pump, and 2 ibc totes full of water.

The majority of the weight on the trailer will be about 5500lbs of water when its full (assuming 2 full 330 gallon ibc totes), and that plus all the equipment I figure to be safe that's about 7000lbs total, so I'm thinking an 8000 or 9000lb axle.

With leaf springs do I get them by the weight rating on the spring or on the axle? Would I get 2 8000lb springs for a trailer with a 8000lb axle, or would I get 2 4000lb springs for it? What do y'all suggest for the main frame / body of the trailer? Is C channel enough or should I go for square tubing? What thickness? I'm really new to metalworking in general and want to make sure to overbuild everything for safety since I'll be driving it on the road. If I need 3 1/4" angle iron braces I'll put 4 3/8" braces...

Is there some guide or source material I can read that will teach me how to calculate the weight a given profile needs to permanently deform? I want to learn how to pick/calculate what thickness material I need for a given project.

 

[GrifterGuru]

Deleted... Not relevant.

 

[Just for fun]

I can't help on the metal choices. I would go look at a10,000 lbs utility or dump metal they use.

If it were me I would go with two axles.

 

[projectnut]

I think we need more information. A quick check on hydro seeders shows they range in weight from less than 300 lbs. (empty) to over 1,200 lbs. The same is true for a pressure washer. Depending on the size and options they can weigh as little as 150 lbs. or over 550 lbs. The water alone will weigh 5,500 lbs. Don't forget the weight of the totes. They're usually around 150 lbs. each. Add in a small self-powered pump, hoses, nozzles, and accessories and you have another 200 lbs. or so.

Given these approximate weights if you go with middle of the road sizes I would get 2 axles rated at 5,000 lbs. to 5,500 lbs. each. I have a 5'x 10' trailer with Dexter 5,400 lb. axles with electric brakes. I recently replaced the original springs with 5,200 lb. sets from Southwest Spring. They happened to be on sale for $321.00 at the time.

I believe almost all states require brakes, and a break away system for trailers over 3,000 lbs. Most states also require a trailer of that size to be licensed. If its factory built, you'll need to give them the manufacturer name and serial number. If its homemade it will probably have to be inspected before issuing a license.

For fenders I would use 7 ga. diamond plate rather than the cheap sheet metal fenders. My sheet metal fenders rusted though and cracked within the first 5 years I had it. It's nice to be able to walk on the fenders and not have to worry about destroying them.

My trailer frame is made from 4" channel. The tongue and support tubes are 2" x 4" rectangular tube. The weight of the trailer alone is 2,100 lbs. It was originally built by a construction company to haul an 8,000 lb. Bobcat skid steer. Tires and rims are going to be another concern. My trailer uses 15' 6 bolt rims with 225/75R15 load range E tires.

Personally, I would stay away from tube for the trailer frame. I would also leave the ends of the tongue tubes open so they can drain or be washed out. I've seen far too many closed tube trailer frames rust out due to trapped water and mud.

Here are a few pictures of my trailer. It has a wood box installed on it for hauling leaves and trash. The box can easily be removed in sections to haul the tractor or end loader. Loading the tractor or loader requires the ramps which weigh another 120 lbs. each.

 

[o0norton0o]

Sounds like a two axle trailer application to me as well. Also with that much weight, you should be careful of how you position the load on that trailer to keep tongue weight under control. What kind of tow rig are you using?

When I was involved in Dirt car racing, we pulled a 24' race trailer with a crew cab dually with a big block 454. We didn't have a 5th wheel set up so we used load bars on the hook up. It worked, but for that weight it would have been better to be a 5th wheel set up. I think it was a 10,000 lb capacity and it was dual wheeled with dual wheel electric trailer brakes. Those load bars were bent a frightening amount when they were hooked up, but they never broke and helped level out the tongue/hitch connection. My crew chief had done it a million times, so he thought they would hold. It looked like a disaster waiting to happen to me

 

[tq60]

We have many trailer makers here, they also sell parts.

Look in your area to see what you have.

Take photos of everything with weights and then visit them.

They can help you with your design in that they want to sell you stuff.

Frame layout, brakes, wheels, lots of things to consider.

Sent from my SM-G781V using Tapatalk

 

[Eddyde]

IMHO Building a trailer of that weight class is not trivial, welds will be subject to high dynamic stress and the size and shape of materials should be carefully considered. Perhaps there are some plans available for proven frame design that you can use as a foundation for your project?
Here in New York, any home built trailer must receive a special inspection and you must present receipts for all materials used in its construction. I surmise the latter requirement is to prevent people trying to pass off a stolen trailer as home built. (Edit) ensure the state gets their taxes...

 

[N8TGK]

Deleted... Not relevant

What? How is it not relevant?

 

[N8TGK]

IMHO Building a trailer of that weight class is not trivial, welds will be subject to high dynamic stress and the size and shape of materials should be carefully considered. Perhaps there are some plans available for proven frame design that you can use as a foundation for your project?
Here in New York, any home built trailer must receive a special inspection and you must present receipts for all materials used in its construction. I surmise the latter requirement is to prevent people trying to pass off a stolen trailer as home built.

THANK GOD I'm not in New York!

 

[Eddyde]

THANK GOD I'm not in New York!

I would Imagine California, another well regulated state, has similar requirements...