Off Road Design Considerations

[GATORB8]

Flamesuit on.

I hate to do this before I’ve really explored all the knowledge y’all have already put time into here. Please bear with me, I’ve watched days of YT videos and done a ton of research.

Tow Vehicle:
21 Wrangler Rubicon 4xe (hybrid), 3500 lb rated, Curt has a 4K/400 available.
Basically a street competent rock crawler. 10+” of travel at each corner. Hitch is at 23 bottom 25” top unloaded, expect 2” squat (will aim the headlights), 17” to skids at breakover.

Although it’s probably not the best idea, I want to match the tow wheel setup. 37” BFG KO2 (OWL if that excites anyone), 17x8.5” Racelines at +18mm offset.

My initial mock-up proved I want at least 5x9 for a Queen and reasonably deep galley, still awaiting approval from the Boss. Although not an SE, I do have collegiate level structual(statics) classes and have a reasonable understanding.

I’ll calc before construction, but thinking 2x2x .120 wall steel.

Initial questions:
1. I want a tongue as close to the tow vehicle as possible, with as much clearance for tow vehicle to trailer breakover as possible. Is a “backbone” design the recommended solution? What about a lower trailer (for access/COG) and stepping the tongue up for clearance?
2. My gut is telling me Timbren Tonnes, as the extended travel for the same weight would likely soften the suspension. With 17.5” ish of hub height, and the HD/extended spindles. How critical is matching the tow vehicle track width? I would need to elevate the bed and squeeze the mounting frame in to about 4’ to make this work.

I’m sure these are dumb questions, but appreciate any comments.

[tony.latham]

I want a tongue as close to the tow vehicle as possible,

I think a 4' long tongue is about right.

Is a “backbone” design the recommended solution?

What's a backbone design?



And BTW, that's 2" .120" tubing. It works fine.

What about a lower trailer..?

Our chassis is at 18" above the ground. It allows for plenty of clearance and makes getting in and out about right. You're building a bed on wheels and the edge needs to be at a reasonable elevation for this. Not too high and not too low.

How critical is matching the tow vehicle track width?

For us, it's not. And we travel over many-many miles of unimproved roads.

I want at least 5x9 for a Queen and reasonably deep galley

Another foot in length is a mile when it comes to galley depth. Toy with a 10' long 'drop. Take a look at my galley and it might give you a sense of what that extra 12" does:





Tony

p.s. I've been at that spot where your selfie was taken.

[GATORB8]

I want a tongue as close to the tow vehicle as possible,

I think a 4' long tongue is about right.

Is a “backbone” design the recommended solution?

What's a backbone design?



And BTW, that's 2" .120" tubing. It works fine.

What about a lower trailer..?

Our chassis is at 18" above the ground. It allows for plenty of clearance and makes getting in and out about right. You're building a bed on wheels and the edge needs to be at a reasonable elevation for this. Not too high and not too low.

How critical is matching the tow vehicle track width?

For us, it's not. And we travel over many-many miles of unimproved roads.

I want at least 5x9 for a Queen and reasonably deep galley

Another foot in length is a mile when it comes to galley depth. Toy with a 10' long 'drop. Take a look at my galley and it might give you a sense of what that extra 12" does:





Tony

p.s. I've been at that spot where your selfie was taken.

Thanks for the reply.

I should have clarified I meant tongue height, but I’m anticipating needing about 4’ of straight to tongue to clear the Jeeps rear door. By backbone, I meant running the member for the tongue front to back through the box of the frame. One obvious concern with that is that it makes all welded joint for the transfer of forces between the two independent suspension connections, and it’d be nice to not have to install the lower tieing 2x2 the timbrens allow.

So, although I feel 18” of clearance would be adequate for the trailer itself with skid plates, That would mean a 7” drop hitch of of the Jeeps wimpy Class 2, 2” receiver. The Jeeps receiver is only bolted to a crossmember and has no tie in to the frame rails. Taking a hit to the front of the drop hitch at speed would do some significant damage.

I feel like the perfect frame would have a lower box, around 18” like you recommend, and a step up to the tongue to get it up around 22”.

[tony.latham]

...to clear the Jeeps rear door.

It sounds like you need a taller tongue to deal with your lift issue, eh?

Make sure you go with a removable rotating jack. Our previous teardrop had an A-frame jack that was problematic with our Tacoma tailgate --if the trailer was at an angle. It needs to be removable so you can take it off when the going gets rough. Otherwise, you can bend the foot. I know that to be a fact.

Tony

[GATORB8]

...to clear the Jeeps rear door.

It sounds like you need a taller tongue to deal with your lift issue, eh?

Make sure you go with a removable rotating jack. Our previous teardrop had an A-frame jack that was problematic with our Tacoma tailgate --if the trailer was at an angle. It needs to be removable so you can take it off when the going gets rough. Otherwise, you can bend the foot. I know that to be a fact.

Tony

Definitely, I’ve had several work trailer jack failures. My boat trailer has a rotating one, and just the reduced effort is worth it.

[tony.latham]

My boat trailer has a rotating one, and just the reduced effort is worth it.

I'm talking about one of these:

https://www.amazon.com/gp/product/B004QEM7HK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Tony

[GATORB8]

My boat trailer has a rotating one, and just the reduced effort is worth it.

I'm talking about one of these:

https://www.amazon.com/gp/product/B004QEM7HK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Tony

Very similiar, Karavan (Wisconsin) made our boat trailer, and their jack rotates 90 with a pull out spring u bolt pin. I’ll shoot a pic next time I’m at the lot, but definitely the same setup you are talking about.

[twisted lines]

Now I’m second guessing my bolt pattern,
The wheels and tires are unsprung so that weigh doesn’t count right?

[GATORB8]

My boat trailer has a rotating one, and just the reduced effort is worth it.

I'm talking about one of these:

https://www.amazon.com/gp/product/B004QEM7HK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Tony

Ordered your book today, BTW.

I mocked up some basic wall panels this weekend with some Masonite, like most gotta get approval from “the boss”.

[twisted lines]

p.s. I've been at that spot where your selfie was taken.

Me too! My Grandpaw Told me I needed to see it
Not far away, I hear the fishing's good.

[GATORB8]

p.s. I've been at that spot where your selfie was taken.

Me too! My Grandpaw Told me I needed to see it
Not far away, I hear the fishing's good.

That was taken last month during a 5 week, 8k mile trip visiting national parks and offroading through WY, UT, and AZ.

If it's been a while since you guys have seen Horseshoe Bend, the current setup may be news. The city of Page saw an opportunity and built a pay parking lot on their property (complete with toll attendants and tire spikes) at the vista, you could still see the restoration efforts at the old access on public land. New enough it's not showing on Google's satellite images.

[GATORB8]

Conceptual mock-up approved. Missing the additional foot in rear.

I’m planning on 2200 lb long arm timbrens. With 280 on the tongue I sag an inch. So I’m looking for 22” bottom of frame to be dead level. Unfortunately the Timbren “tonne” only comes in 0 or 4” lift spindles. The 0 puts me at 20” BOF, and the 2” puts me at 24” BOF.

I’m guessing best bet is to go with an undermount tongue structure to drop it the 2”. Unfortunately, that’s the opposite of what I wanted, really wanted a lower entry for the trailer

[tony.latham]

really wanted a lower entry for the trailer...

Keep that height in mind for the galley countertop too.





Tony

[GATORB8]

really wanted a lower entry for the trailer...

Keep that height in mind for the galley countertop too.





Tony

Yes, at this point if I do a departure miter, I’ll need the counter at deck height. The clearance I’m looking for will definitely negatively effect the ergonomics.

BTW, your Amazon Shipper is killing me, lol.

[GATORB8]

Tony,

I’m not used to the picture limits here. Is that because I’m new, or is there a workaround?

It won’t allow me to attach a file larger than 1 MB.