Building my own trailer - need some advice

[rabler]

Why do I need tandem axle if I have a 9000lb axle with 8000lbs of weight towed by a vehicle with a capacity of 9500lbs. All those numbers seem to line up. Why would I pay so much more for materials to go with 2 say 4500lb axles instead of 1 9000lb one?
I get that that might be the case given how many people have told me that I need multiple axles, but purely based on the numbers I don't understand why when I can just buy a 9000lb axle... And nobody has said why, aside from possibly safety or redundancy.
How exactly is there a problem with 1 9000lb axle with electric brakes?

I'm not trying to be rude, but this is the Internet. You've been given some advice. There are times were I still struggle with doing so myself, but I believe your choice at this point is to take the advice or ignore it. I doubt you'll get more clarity on the issue.

 

[FOMOGO]

Tandem axles also help mitigate tongue weight issues, among the other already mentioned benefits. Mike

 

[projectnut]

Repurposing or refurbishing an existing trailer may not cost nearly as much as you think. I paid $100.00 for the trailer in my first post. As mentioned, it has two 5,400 lb. Dexter axles with 12" electric brakes. It didn't look quite like it does today when it was purchased almost 20 years ago. It needed new lights, brake shoes, tires, fenders, and a good cleaning. The lights and brakes came first at around $200.00. I used it with the old tires and poor fenders for a few years before upgrading.

Tires were next on the list. They didn't cost anything since I traded a local tire dealer 4 rims and tires, I had from an old Bronco for new trailer tires. After using it for about 5 years the wife suggested I put on some new fenders. They cost about $500.00. Nothing more had to be done for over 10 years when I decided it was time to replace the springs. As mentioned earlier they cost about $325.00. Not counting labor, I only have around $1,250.00 invested over close to 20 years, In those years it's traveled around 20,000 miles with loads from 1,000 lbs. to well over 6,000 lbs. with no problems.

When traveling with no load in the trailer I lower the air pressure to 40 psi. That keeps it from bouncing all over the road. Most roads it travels on are paved. Without paved roads and a single 8,000 lb. or 9,000 lb. axle the trailer may hard to control on unpaved roads or off road. I much prefer electric brakes to surge brakes on a trailer that's used off road. The uneven terrain often causes the surge brakes to engage. When using a trailer with surge brakes in construction sites it was a good policy to lock them out. The only problem then is to remember to reengage them when going back on the road.
Looking on Facebook Marketplace there are well over 5,000 trailers for sale in or near Montana. Many are outrageously priced for what they are, but other show some possibilities. This one struck me as a good possibility, and the asking price is only $750.00. It's been listed for a while, so the owner may be willing to negotiate.

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Another thing to look at might be military surplus trailers. They're tougher than anything on the commercial market, and usually go for around $500.00 or so.

ON Edit: A dual axle trailer will also reduce the tongue weight on the truck. The recommended tongue weight for a single axle trailer is 10% to 15% of the load. The recommended tongue weight for a dual axle trailer is 5% to 7% of the load. That's roughly half the weight needed on the tongue to keep the trailer stable.

Here are a couple pictures of the trailer early on its life. As you can see t's been a work in progress.

 

[projectnut]

Personally I'd prefer two axles over single dually. Many things like cracks in the road run across the road so with a dually both tires take the impact at the same time. That's harder on the tires, and the ride. (My big trailer is a dual axle dually tires, 22k gooseneck). Keep in mind that without a dually pickup, dually axles extend wider than your truck. That's just asking for problems.

I see this all the time. A half ton pickup truck pulling an empty equipment trailer with tandem duals. More often than not the driver doesn't realize how wide the trailer is. They're coming at you on a 2-lane road with one set of the duals a foot or more across the centerline. I've also seen them turn corners not realizing the trailer needs far more room to make the corner than the truck. On country roads they often get sucked into the ditch. In town they jump the curb and ruin a tire or two.

 

[N8TGK]

I see this all the time. A half to pickup truck pulling an empty equipment trailer with tandem duals. More often than not the driver doesn't realize how wide the trailer is. They're coming at you on a 2-lane road with one set of the duals a foot or more across the centerline. I've also seen them turn corners not realizing the trailer needs far more room to make the corner than the truck. On country roads they often get sucked into the ditch. In town they jump the curb and ruin a tire or two.

That's driver error though not a fault of the trailer itself. If you have enough brain cells to pay even a small amount of attention to the road and your mirrors that isn't a problem.
Retard drivers exist everywhere, from teenagers to little old ladies, to contractors.

I'm not surprised that you've seen it plenty though, it seems to me like the majority of drivers shouldn't be anywhere near a road.

 

[RJSakowski]

I have built five trailers over the years. IMO, building a trailer is not where you want to improve your welding skills. There is a lot that can go wrong and the road isn't the place where you want to find that out. This holds true for designing your own as well.

I have pulled trailers that weighed close to the tow vehicle weight and a heavy trailer that starts to fish tail will get you religion in a hurry. In one case, I was pulling my boat on a divided highway and a passing semi grazed the back of the boat. The trailer started to fishtail and began whipping the truck around as well It became greater as I tried to come to a stop. The trailer ended up upside down and pointed 45º to the rear. It had popped off the hitch but fortunately, the safety chains held. The boat sheared its safety chain and pulled the winch axle from its bearings. It skidded down the shoulder about 100ft, ending up parked parallel to the road and right side up with the 25 ft of nylon strap extended perfectly straight in front. That trailer was someone else's homebuilt. When I returned home I designed and built a replacement trailer.
The original trailer didn't have brakes which didn't help my situation. I installed Surge brakes on the new trailer which made it a dream to pull. The dropped axle lowered the center of gravity by 6 inches making it more stable and cutting wind resistance.

When pulling a liquid load, there is a lot less stability. A sudden change in direction or forward motion will cause sloshing in a partially filled tank which can result in an uncontrolled oscillation that can turn serious in a hurry. All things to consider in your design. BTW, if I were building , I would opt for a double axle.

 

[lordbeezer]

I’ve tried hard not to say anything. I’m all about people building what they need or want BUT if you’re not 100 percent sure your welding skills can take the stress of road conditions I wouldn’t build something being towed on public roads that if it fails it could hurt or kill others. I overbuild trailers. Gussets. Brackets. Overlaps til I’m positive in worse cases it won’t fail. And I’m perfectly happy with my welding skills.

 

[verbotenwhisky]

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.

A lot depends upon whether you are building a true flat deck or a truss type bed. If you are building a flat bed I would consider using a C6x8.2 member toes pointed out, for the front and side rails with the tung as C4x7.25 with the toes pointed out welded to the bottom of the side rails and front rail; and, deck supports spaces at 24" back to back and one welded to front channel L2 1/2"x 2 1/2"x 3/8" with 1 toe pointed aft and 1 pointed down spaced 2" below side channel I would use 2 10K axles with a set of 3500# springs on each located 75% of the distance back from the center of the ball to the tail of the trailer. I would floor it with 2"x 8" #2 yellow pine boards bolted down with galvanized carriage bolts (oak is better but 5X the price). I would use a 2" bulldog ball hitch.

If you want a truss style trailer you cannot buy the materials much cheaper than you can buy a new commercially built trailer because everyone builds 3 more than they can sell in a season and get bulk discounts on the materials. If your hearts set on building one though let me know and I can explain it.

If you build it make certain you check your local laws on home builds and carry towing insurance on your vehicle (its actually wise to have the insurance anyway and most folks do not even realize it is a separate part from your auto insurance)

 

[verbotenwhisky]

I have built five trailers over the years. IMO, building a trailer is not where you want to improve your welding skills. There is a lot that can go wrong and the road isn't the place where you want to find that out. This holds true for designing your own as well.

I have pulled trailers that weighed close to the tow vehicle weight and a heavy trailer that starts to fish tail will get you religion in a hurry. In one case, I was pulling my boat on a divided highway and a passing semi grazed the back of the boat. The trailer started to fishtail and began whipping the truck around as well It became greater as I tried to come to a stop. The trailer ended up upside down and pointed 45º to the rear. It had popped off the hitch but fortunately, the safety chains held. The boat sheared its safety chain and pulled the winch axle from its bearings. It skidded down the shoulder about 100ft, ending up parked parallel to the road and right side up with the 25 ft of nylon strap extended perfectly straight in front. That trailer was someone else's homebuilt. When I returned home I designed and built a replacement trailer

The original trailer didn't have brakes which didn't help my situation. I installed Surge brakes on the new trailer which made it a dream to pull. The dropped axle lowered the center of gravity by 6 inches making it more stable and cutting wind resistance.

When pulling a liquid load, there is a lot less stability. A sudden change in direction or forward motion will cause sloshing in a partially filled tank which can result in an uncontrolled oscillation that can turn serious in a hurry. All things to consider in your design. BTW, if I were building , I would opt for a double axle.

Yeah, if he tank doesn't have baffles and a DOT approval I would not put it on a trailer. If you do place it on the trailer it should be centered over the front axle or forward of it by a foot or two and the bulk of your weight should be in front of that.

Trailer waggle or fish tail is generally a load issue but a strong gust of wind or a semi will get your attention. surge breaks are okay but I always put a break controller on my tow vehicles the newer pendulum types work as good as the old hydraulic over electric controllers and do not require a tap into your break system. if you get waggle for any reason you reach down and manually pull the breaks to tension the trailer without breaking the tow vehicle and the weight of the trailer will straighten you out. If it is a load distribution issue (usually is) you'll need to stop, clean out your shorts and redistribute some weight forward of the axle.

 

[Barncat]

Are your totes baffled? We have 2 brush fires units at my work, a 300 gallon baffled and a 250 gallon unbaffled. The unbaffled one feels like you got rear ended if you need to stop quick, it will push the vehicle ahead. I would not want that on a single axle trailer, I bet it would feel like a 1000lbs of tongue weight was added very quickly on a fast stop. Even the baffled tank 300 gallon can move the truck. A double axle wouldn’t rock as much. Have you price checked double vs single axle? I know 7k axles can be cut down and shortened to get your 4’ width, can a 9 or 10k axle be easily shortened? A blowout on a single axle with a lot of water sloshing around is a recipe for disaster. Also plan on at least a ton of trailer weight, which of course reduces the capacity of the trailer. My 14k trailer weighs 3800lbs, resulting in an actual capacity of 10,200 lbs.