The Obligitory Planning and Eventual Build Thread

[JeepinJensen]

Howdy folks. Been lurking here for a while now, and have some ideas (quite a few actually) floating around in my head that I intend to put down on paper sometime today. I do have a few questions right off the bat though, seeing as I am a complete n00b when it comes to these amazing trailers that a lot of you have. I fully intend to build this entire trailer from the ground up by myself, simply for the satisfaction that one gets from looking at something and saying, "Yeah, I built that". I haven't fully decided if I want to build it in the M416 style, or straight box style yet, but that will probably be flushed out in the design process. It will have a hinged top lid, in order to facilitate the mounting of a RTT.

My tow vehicle with be my 2003 Jeep Wrangler with a 4.5" lift and 33" tires. I'd like to run the same wheels and tires on the trailer as I do on the Jeep, mainly for aesthetics, but also a SHTF spare if need be. Now come the questions...

- What would be the ideal axle size (WMS to WMS) to maintain the same track width as my TJ?
- In order to keep the weight down (not trying to overbuild the frame and box too much) what would be the best square tube size to use?

I would also greatly appreciate some of the more experienced individuals to chime in with some nuggets of wisdom in regards to fabrication tips, design nuances, and amenity implementation.

 

[JeepinJensen]

This is my tow vehicle:

And this is the initial sketch of the frame layout:

 

[indiedog]

Hi Jensen, looking forward to seeing how your design and build develops. One comment on your frame design. If you are using leaf spring suspension then all the load/shocks/bumps are ultimately transferred through the shackles to the side rails and then back to your tow hitch. The more direct link you have between those two points the less you rely on welds etc for strength. In your frame sketch imagine the wheels staying still and the tow hitch moving forward to deflect the frame. Currently you will be bending the cross rails and relying on the welds to the side rails to transfer the loads to the wheels. Looking at the frame and how it will deflect under various loads will go a long way to helping come up with a strong and efficient layout.

So possibly revise your tongue storage to include a more triangular layout which comes back to the front of each side rail. Hope that helps.

 

[JeepinJensen]

Indie-

I see what you are talking about. This is what I think you mean about triangulating the tongue a bit more to transfer the load to the outside frame rails and in turn the leaf springs and axle, or am I way off base here?

 

[rnArmy]

Here is my nugget of wisdom in regards to fabrication tips, design nuances, and amenity implementation. Before you start buying square tubing and such, read this:

http://www.jeepforum.com/forum/f27/...ype-trailer-ultimate-build-up-thread-1180456/

It is very long, and there are lots of links (check out the links). It might help answer some of your questions, and give you some ideas for things you might not have thought of. It may also save you some money and frustration in the long-run.

 

[indiedog]

Indie-

I see what you are talking about. This is what I think you mean about triangulating the tongue a bit more to transfer the load to the outside frame rails and in turn the leaf springs and axle, or am I way off base here?

View attachment 274596

Looking good. :victory:

 

[JeepinJensen]

ArmyRN, thanks for the link, lots of good info in there. I appreciate it. Much more reading to commence.

 

[rnArmy]

ArmyRN, thanks for the link, lots of good info in there. I appreciate it. Much more reading to commence.

You're welcome. A lot of folks have had input into that thread. Pay particular attention to the link from jscherb on modifying a HF HD (not the folding one) 4x8' trailer for a more trail-friendly size.

 

[JeepinJensen]

You're welcome. A lot of folks have had input into that thread. Pay particular attention to the link from jscherb on modifying a HF HD (not the folding one) 4x8' trailer for a more trail-friendly size.

Will do, oh and BTW I was born at Campbell.....

 

[nnnnnate]

My tow vehicle with be my 2003 Jeep Wrangler with a 4.5" lift and 33" tires. I'd like to run the same wheels and tires on the trailer as I do on the Jeep, mainly for aesthetics, but also a SHTF spare if need be. Now come the questions...

- What would be the ideal axle size (WMS to WMS) to maintain the same track width as my TJ?

You need to measure the axle width on the TJ to figure this out. To be able to use your TJ wheels (5x4.5) you'll need to run spacers to clear the hub on the trailer axle. With my JK I needed to get a 3500# axle to get the bolt pattern to match, not sure if that is the same with the TJ though.

In order to keep the weight down (not trying to overbuild the frame and box too much) what would be the best square tube size to use?

This is a quick run down of what I've done, not saying its the best choice out there but its what I've come up with as I've figured things out.

2.5" square 0.120 wall for my frame
1.5" 14 GA for the vertical wall supports
2" 14 GA for the top box rail
18 GA sheet for the floor and walls. (kind of wish I would have gone 16 GA but it'll be fine)
3500# axle without brakes, hubs to match my JK stock rims
48" outside frame measurement
just over 11' tip of the tongue to rear
with mainly just paint left to buy I've spend just under $800 so far

This is my first fabrication project and I bought my welder just before Christmas. I've had a few bumps along the way but nothing too terrible. My more complete build thread can be found here. I've asked a ton of questions and gotten some really good feedback from the local guys.

 

[rnArmy]

Will do, oh and BTW I was born at Campbell.....

Hooah. Now I'm at Ft Hood, Texas (your post reminded me I needed to update my profile). While at Ft Campbell I was section chief of the inpatient wards (to include L&D and the mother/baby unit).

You'll need both your trailer's tub width and the tires/wheels you're planning on running to deteremine your needed axle width. The classic WWII military trailer had a tub base measurement of 40" wide by 72" long. And if you look at some (most) of the aftermarket off-road trailer specs, that's pretty much what they're using too (40" x 72" tub). Mine is 40" x 50" (as it was built on a HF-type 4' trailer frame).

And you may or may-not need to run spacers on your axle depending on if you're running factory alloy rims or steel or aftermarket rims. A 5 on 4.5 is a very common bolt pattern for trailer axles, but if you're wanting electric brakes you might have to step up to a heavier duty axle that has a welded brake flange on the ends.

And for what it's worth, my Jeep is running 33" tires (285/75/16") and the trailer is running 205/75/15" tires. What's interesting (to me anyways) is the trailer has 3" MORE clearance under the axle than the Jeep's rear Dana 44 pumpkin. Three of my trailer 205 tires and rims are almost the same price as just one of my Jeeps's tires and rims; plus I can carry a dedicated spare on the trailer itself.

 

[JeepinJensen]

Well here is a better frame design, this time I broke out Google Sketchup to get my rough idea down.

From the tip of the tongue to the back edge of the bumper, it's just a hair over 150". Outside frame rail to outside frame rail is 59 1/4".




Since this will be the main load bearing portion of the frame, I wanted to make it a little beefy, so it's (draft-wise) made from 2" x 2 1/2" square tube. I left the tongue to frame reinforcement (as well as the tongue storage platform) in white just to illustrate that and make it a bit more obvious. Next bit I'm hoping to accomplish is the actual box and lid portion of the trailer, which will most likely be made out of 1"x1" square tubing, and skinned with 16 gauge sheet metal.

Comments/critique is more than welcome, and highly encouraged.

 

[JeepinJensen]

Realized that some of my measurements looked a little off, so I redid some of the tubing, and this is what I came up with.

Outside frame rail to outside frame rail is 59 1/4"; and the tip of the tongue to the rear of the bumper is now 166 1/16", and the main box area in 96" from front to rear.



Those odd looking orbs are "supposed" to be my 33x12.5 tires.

 

[nnnnnate]

59" is pretty wide, adding the tires is going to make it 74" without any room for tire/frame clearance. I'd guess your TJ is in the low 60" range as far as axle width. If I remember right my JK axle is 64".

Have you planned out the tub of the trailer (kitchen, water tank, etc) which is necessitating it being this wide? How did you land on that dimension?

 

[indiedog]

Looking good Jensen. Just wondering if the 59 1/4" width is right as that will make your wheel track a fair bit wider than your Jeep. I have a KJ and my trailer box width of 48" makes for a pretty good track width match to the car. I tow a bit on beach where track width is a bit more important, really depends on where you are going with it.