Custom trailer, chassis and all, from scratch

[john61ct]

I am a noob, please be gentle. I have lots of ideas, many I'm sure overly ambitious, aka "unrealistic", but that's all part of the learning process.

Which is what this thread is for, so rather than get into my "big picture" design dreams, I'd like to focus on practical questions to start, about some details I'm not sure about.

Starting with this great idea from JKChad:

I would suggest spec'ing your axle dimension to allow for the extra width of using a 1.5" wheel spacers/adapter. . .

This method would also allow you to use a different wheel and/or adapter if you change your tow vehicle. . .

Just make sure the adapter has the proper stud size/thread pitch for your wheels and lug nuts.

Does this mean I could in effect use a wide range of different tire sizes on a given trailer? Obviously there will be a min and max size per given hub pattern. . .

My plan is to build the trailer platform first, rent the TV to start with, and in some contexts, maybe even just pay for transport.

When (rarely) the total load is very heavy, as with a 30' boat, maybe 14K#, requires larger HD tires.

But normally travelling slowly, living out of a modular camper pod, total maybe 3-5K# load, can use a regular truck, and I will want to match the TV tires.

Seems do-able?

 

[Mccool]

Tire size isn't dependant on hub bolt pattern. The reason for the wheel spacers is to allow the use of the center cap on the wheels. Without the spacers the dust cap on the hub will protrude too far for the center cap to be used.

I'm not sure what you're asking about the 30' boat.

 

[Charles R]

He's suggesting that you could use a spacer/adapter on your trailer to match the bolt pattern to the one you have on your TV. Then, if in the future, you change vehicles that have a different pattern, you can just change the spacer/adapter.

 

[john61ct]

Which also means can vary tire size, correct?

Boat was just an example heavy load

 

[john61ct]

The reason for the wheel spacers is to allow the use of the center cap on the wheels.

Sorry, I thought spacers and bolt pattern adapter were like a set.

But it is the adapter that makes the spacer necessary?

 

[Mccool]

Sorry, I thought spacers and bolt pattern adapter were like a set.

But it is the adapter that makes the spacer necessary?

The spacers can change the bolt pattern if you need them to, they don't have to though. My trailer axle has 6x5.5 hubs and I use 2" spacers, but the spacers don't change the bolt pattern.

 

[Charles R]

I just re-read your original post. Let me see if I get this straight...

You want to make a sort of "universal trailer" that can be, with a few bolt-on changes, used for everything from a fairly lightweight living space, on up to a pretty massive 14,000# boat.

My short answer is that anything universal, is usually universally poor at everything.

To me, a trailer built properly for something upwards of 30ft and 14k is going to be far too heavy to use spacers and adapters.

 

[john61ct]

OK, thanks.

Yes I realize I'm shooting for a lot here, but planning on getting help with the engineering.

The foundation frame + suspension will be as light as possible.

Then for carrying the boat(s) a custom cradle + "secondary frame" that also adds a lot of the strength needed, extra weight only carried when used for that purpose.

Another "secondary frame" will adapt it into a car carrier, insert the full floor into that it becomes a generic deckover flatbed.

Utility "bin" frame for sand, gravel, soil.

A frame to support a 20' conex shipping container, likely empty, or at least only loaded up to the 14K# GVWR.

A tank for hauling water, another for propane.

The living pod is just a lightweight shell, designed to work supported on posts, so the strengthening frame is integral not external.

 

[Buffalobwana]

OK, thanks.

Yes I realize I'm shooting for a lot here, ...

The foundation frame + suspension will be as light as possible.

... Utility "bin" frame for sand, gravel, soil...

A frame to support a 20' conex shipping container, likely empty, or at least only loaded up to the 14K# GVWR.
.

Are you talking about three different trailers here?

You may have some unreasonable expectations of a light suspension, light frame trailer. I have built a few from scratch, and never have I conceived such a beast. The springs have limits, tires have limits, axles have limits. All the components of a trailer are designed to withstand certain loads, all the way down to the coupler.

You need to do some research on axles and spring capacity. Go to eTrailer or southwest tire and wheel. Good sources of info.

If you want to design a 14k trailer, we can help, but it won’t be light. 2K + maybe? I have one that weighs 4K it’s a hefty gooseneck though. Could be a 21k with different axles.

 

[Buffalobwana]

You will not be using spacers on these wheels. You have to use 8 on 6.5 bolt pattern. That’s the only wheel that will accommodate the axles you want to put on your trailer. It will have to be a tandem axle 7k axle setup. Unless you buy an older 3/4 ton that happens to run the same bolt pattern ... but let’s be realistic. You don’t need to be using your trucks spare on your trailer. You need to buy a spare tire dedicated to this trailer.

The spacers the others are talking about are for lightweight camping trailers. They do not apply to your situation.

 

[furbucket]

Tire size and frame strength aside- I would think that any suspension that could handle the heaviest proposed loads would be all but solid (useless) under the lighter proposed loads. Unless maybe some over engineered air bag solution could be devised maybe...


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[Bullseye240]

OK, thanks.

Yes I realize I'm shooting for a lot here, but planning on getting help with the engineering.

The foundation frame + suspension will be as light as possible.

Then for carrying the boat(s) a custom cradle + "secondary frame" that also adds a lot of the strength needed, extra weight only carried when used for that purpose.

Another "secondary frame" will adapt it into a car carrier, insert the full floor into that it becomes a generic deckover flatbed.

Utility "bin" frame for sand, gravel, soil.

A frame to support a 20' conex shipping container, likely empty, or at least only loaded up to the 14K# GVWR.

A tank for hauling water, another for propane.

The living pod is just a lightweight shell, designed to work supported on posts, so the strengthening frame is integral not external.

It would be far easier and likely cheaper to build or buy three different trailers for the proposed loads you suggest. Building a subframe for the heavier loads would do little to nothing to strengthen the light weight frame used for the lighter loads. Hub spacers or adapters would not work for this situation as the light duty hubs would not be up to holding the weight the heavier tire wheel combo could hold. Yes you could design an overly complicated air suspension to carry the weight but it would add a considerable amount of cost and weight into the build as well as needing a compressed air supply in order operate the trailer. Seriously this is one of those "just because you can do something doesn't mean you should do something" situations.

 

[john61ct]

Yes the hub pattern adapters idea is now well shelved.

 

[john61ct]

Are you talking about three different trailers here?

You may have some unreasonable expectations of a light suspension, light frame trailer.

No on all counts, sorry if I wasn't clear. But the target design GVWR of 14,000 lbs should have made that clear.

The only "light" requirement is that the primary frame and chassis be "as light as possible" within that target requirement.

To the extent the target load keeps the total well under that maximum, their secondary frame does not need heroic engineering design efforts, a bit of extra weight is NBD for I think everything but a heavy boat.

A 20' connex is usually only ~6K# for example, and I'm talking about hauling light fuel-efficient passenger cars, not heavy trucks.

 

[john61ct]

I'm hoping specialized engineering / design talent combined with structural aluminum framing will help with the chassis weight vs max load capacity issue.

The secondary frame / cradle for boat, connex or big tanks will help spread the load out more evenly along the primary rails rather than it being too concentrated.

And that primary / secondary framing design is inherent to the modular multi-use requirement anyway.