Carbon Fiber/Aluminum build for a family of 5

[John61CT]

I use the Timbren Axle-Less suspension system. I love it, but it's a little more finicky than a traditional axle. Not using a thru-axle with the Timbren puts an ENORMOUS amount of stress on your main rail.

The topic here is a purpose-built custom frame. Cross-members at the same height as the main rails, right at or close to the mount points will be fine, long as the sizing and build quality are good.

[John61CT]

With your tongue being aluminum I don't think it will be strong enough without support.

Yes I would do the usual A-frame reinforcement at least.

What are the registration / inspection / insurance issues like in your state OP?

[FM82]

Your pictures are very blurry on my end. Like the resolution is really low. I'm enjoying the progress, but I'm having trouble making out what's going on in the pictures. Are they showing up the same for everyone else?

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[StrongFeather]

The tongue will be beefed up with angled A-frame beams. I hope to work on that today.

In my state, Colorado, the trailer will be registered as a home built trailer. A state trooper does an inspection, and from what I understand, they care more about lighting, safety chains and brakes (if over 2k GVWR?). Sadly, I don't think structural integrity is on the list. With that said, I believe that most custom frame TNTTT builders overbuild their frames (and shells). Not that there's anything wrong with that. My goal is to build a safe, only slightly overbuilt, light weight custom trailer. If I'm ever at the point of feeling that it is not safe, or if I see structural damage, I don't have a problem tearing it apart and adding strength.

As it sits right now, the outside of the frame is pretty rigid, but the floor cross members are still somewhat flexible. They're 1x1.5x0.125 6061 aluminum. The significance of this is that the main tongue's fore/aft movement is tied directly to the front frame rail and 2 floor cross members. If left as is, I'm sure the trailer weight would tear the tongue from the bottom in no time. But, as they say, "something about strength is the sum of all of the parts, blah, blah, blah", and by connecting every piece of the frame to a rigid floor, and adding the A-frame beams to the tongue, and a rigid shell on top, I'm making an uneducated assumption that it will actually be slightly overbuilt when done. Only time will tell.

Regarding the axle, so far, I'm very happy with the Flexi-Ride torsion axle. Mainly because; (A) it's not a leaf sprung axle, and (B) the shafts and spindle arms are splined, giving me the ability to adjust trailer height in a matter of minutes. Not to mention there is a cost savings over Timbren, and surprisingly it only weighs 55 pounds.

Time to build!


Steve

[StrongFeather]

Your pictures are very blurry on my end. Like the resolution is really low. I'm enjoying the progress, but I'm having trouble making out what's going on in the pictures. Are they showing up the same for everyone else?

I've been changing the resolution to 640 pixels to be able to add them to the gallery. Maybe I'm doing something wrong. Any suggestions?

[StrongFeather]

Let's see if this is better...

DSC09863.JPG (159.12 KiB) Viewed 2860 times

[FM82]

Your pictures are very blurry on my end. Like the resolution is really low. I'm enjoying the progress, but I'm having trouble making out what's going on in the pictures. Are they showing up the same for everyone else?

I've been changing the resolution to 640 pixels to be able to add them to the gallery. Maybe I'm doing something wrong. Any suggestions?

Ah! I see. That must be issue. If you've maxed your allowed resolution out, per the restrictions for gallery images, there may not be a way around it. Just guessing, but to have them in the gallery, but have the higher resolution in your thread, you may have to upload twice. Higher resolution for one, lower for the other.

Not sure how it looks for everyone else, but on my end, this is how I'm seeing it.

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[FM82]

Let's see if this is better...

DSC09863.JPG

Much better!! Thanks!

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[StrongFeather]

Thanks for letting me know, FM'. I'm glad someone said something early, instead of a couple months from now. I'll go back and change the previous images and upload the higher resolution images in the thread from hear on out.


Steve

[StrongFeather]

Another good day on the build. The A-frame/tongue angle thingys whatever you call them are pretty much installed.

And as an added bonus, it snowed inside the shop nearly all day long! It was totally awesome!

DSC09879.JPG (237.1 KiB) Viewed 2800 times

Okay, it may not be as glamorous as saw dust, but hey, aluminum shavings are pretty cool, too.

Here are a couple of pictures of the furthest aft tongue & cross member mount.

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DSC09865.JPG (130.28 KiB) Viewed 2800 times

Only 3 attachments per post, so... To Be Continued...

[StrongFeather]

Mocking-up the A-frame tongue beams, the coupler (upside down, I know) and the tongue jack.

DSC09867.JPG (216.67 KiB) Viewed 2835 times

And the front cut on the A-frame tongue beams.

DSC09868.JPG (143.93 KiB) Viewed 2835 times

Nothing too exciting, but I've heard people like pictures...

MTF...

[StrongFeather]

Here are a few of the fruits of today's labor.

This shot shows the A-frame tongue beam connection to the 1st floor cross member. The tongue is on the left and the main side rail is on the side. Once the floor is in place, a bolt will go through the brackets into the T-nuts in the floor.

DSC09877.JPG (219.19 KiB) Viewed 2834 times

And the rear attachment to the sister and main side rails, as well as the 2nd floor cross member.

DSC09876.JPG (166.88 KiB) Viewed 2834 times

And finally, a shot of everything almost done.

DSC09873.JPG (169.45 KiB) Viewed 2834 times

Steve

[FM82]

Thanks for letting me know, FM'. I'm glad someone said something early, instead of a couple months from now. I'll go back and change the previous images and upload the higher resolution images in the thread from hear on out.


Steve

No problem, Steve. The updated pictures look great! The framing is moving right along.

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[John61CT]

An inspiration.

Anyone out there qualified to reco the size angle, tubing and bolts to scale this design up to say 15,000 lbs?

Some joins can be welded, but the A-frame definitely needs to be detachable so the box part fits in a conex.

[Andrew Herrick]

An inspiration.

Anyone out there qualified to reco the size angle, tubing and bolts to scale this design up to say 15,000 lbs?

Some joins can be welded, but the A-frame definitely needs to be detachable so the box part fits in a conex.

That's a hornet's nest.
The OP is doing a great job. He's put in a lot of research, and it shows in the quality. A lot of what he's doing is an adaption of what's on the market, which reduces his design burden.
But a similar design rated to carry 15,000 lb? There isn't much like that on the market. So there's less to borrow off of.
And sadly, you can't "scale" a trailer design. The loads don't increase proportionally. You're really talking an entirely new trailer.
The fact that it's aluminum adds a layer of complexity few hobbyists are familiar with. For instance, welding 6061-T6 aluminum anneals the metal in the HAZ from a T6 to a T0 temper, meaning it loses almost 80% of its yield strength. And the fatigue strength of structural aluminum is around 11 ksi ...

I'm not saying you can't build a bolted aluminum trailer rated for 15,000 lbs. You most certainly can. And there's nothing wrong with borrowing concepts from this trailer. But I'd pound my gavel loudly on the notion that what you're wanting needs to be designed in conjunction with a licensed engineer or trailer builder. You don't have an industry-tested template to build off of. If you're planning to build with aluminum, you'll already be spending a small fortune - may as well add 10% for expert help!