My Trailer Build Plan W/Questions (1 Viewer)

[LFD2037]

I'm going to start my offroad camping trailer build soon. Similar to @Box Rocket but some differences. It will carry ~ 500 lbs of stuff & maybe a RTT in the future. It'll never exceed 1,500lb. 4x6 w/~20" tall walls. Frame will be 2x3x1/8" and have a 'combination' A frame tongue (center tube, that hitch mounts on, will go under & back to the 2nd cross brace & A sections will be angled about 35* & go under and back to 2nd cross brace). Walls will be 2x2x14g w/16g sheet over them. I plan on using a Dexter 3,500 lb axle w/ 1K lb springs & some cheapish shocks. Wheels/tires the same size as my 80. ~20gal H2O tank/pump/heater. My questions are:

Is the 2x3x1/8" strong enough for the A frame tongue?(I can do 2.5sq. x 3/16" if need be)
Is there a complete axle kit w/axle, springs, hangers, hubs, etc.? (they all seem to have 3,500lb springs)
Any brand axle to stay away from?

 

[ntsqd]

Page 29 in this book gives you the tools to figure out your tongue question for yourself: http://www.amazon.com/Trailers-Desi..._sim_14_4?ie=UTF8&refRID=08PCWF594T0TPHM0AW9W

There are also some really good links & pages on the topic on the tear-drops & tiny trailer forum.

 

[greentruck]

Bigger is usually better in a place like this as far the tube goes. Those numbers seem smallish to me, but I'm not an engineer, so the cited reference is likely worth a read.

As for complete axle, the axle itself can come complete, but that's never with spring, etc AFAIK. The suspension it too application dependent, but I'd bet any of the big parts houses would be glad to discuss your needs and suggest solutions. If it were me and no starting point for a fresh build, I'd still go with something common, like a M416 spring. Another choice that makes sense is to use some Jeep springs (IIRC use of Jeep front springs is not uncommon). You can often leave leaves out if the full capacity isn't needed, but not sure that's workable if you plan to carry that load.

An option to consider is a braked axle. The Dexter can be done this way with electric brakes and IIRC was around $350 a few years ago when I first spec-ed. If it's still less than $500 by the time I get around to it, I'll have no complaints, as it'll still be cheaper than buying the parts to upgrade my M101 CDN's axle from parking brakes only. That much weight in a trailer will horse you around and if you plan any trips to the mountains, you'll consider them worth the small cost.

 

[ntsqd]

Wall thickness of the tongue tubes is secondary, the vertical dimension is most important to load carrying capacity.

I'd say that if you're going to buy a braked axle that you should spring the little extra and get one with a parking brake option.

btw, the book is pretty good, but not so good that it's worth the new price. Buy it used.

 

[greentruck]

SNIP
I'd say that if you're going to buy a braked axle that you should spring the little extra and get one with a parking brake option.
SNIP

IIRC, the Dexter comes with the parking brake as an option. That's important to me, as I want to preserve that feature on our M101 CDN. Here's more info:
http://dexteraxle.com/i/u/6149609/f/600-8K_Catalog/2300-4000_Lbs.pdf

It turns out that Dexter is selling complete assemblies with springs. Don't know if I just missed that when I was doing research or if it's a new thing. In fact, it's available in both leaf spring and torque arm variants.

Lots more Dexter info here:
http://www.dexteraxle.com/literature1

10" brake options:
http://www.dexteraxle.com/10__brake_assemblies

 

[LFD2037]

Does the tongue need to be 2.5sq x 3/16"?
Also, did a little more research on the frame tubing size:


the moment of inertia of the 2X4 14ga. is 1.94 in^4
the moment of inertia of the 2X3 1/8 is 1.47 in^4

so the 2X4 14 ga. is a little stronger but it will weigh less and cost less

I'd prefer to use the 2x3x.120 but if y'all don't think it'll be sufficient (I personally think it will because I've seen many a car hauler built with it) then I'll go 2x4x.120.

Thanks for the input!

 

[ntsqd]

What you might want to consider is to make at least the very forward-most portion of the tongue from receiver hitch tube.

If you understand MoI then perhaps you also understand Shear-Moment Diagrams? It's just a combined point & distributed loading that is part cantilevered and part simply supported.

 

[LFD2037]

Okay, I've decided tongue will all be 2.5"sq 3/16". All the frame will be 2x3 .120. Wall upright beams will be 1x2" 14g. Now I need to figure out what springs I can get to go with the 3,500lb axle. I found Dexter 20" & 23" 1K (each) springs but they seems short, but then again the trailers only 6' long. Any specific spring length?

 

[greentruck]

The eye to eye length of the springs on my M101 CDN is about 36". If you're getting 20" or 23" as the best options you may want to talk to them to find out what's up.

They're not torque arm springs, are they? Those would be shorter.

 

[LFD2037]

No, just regular leaf springs. Those are the lengths I found with these spec:
Dexter 1K lb springs (1K each)
Fit a 2 3/8" round axle tube
Front and rear eye mount
20" or 23" eye to eye

I'll keep searching.

 

[LFD2037]

It appears the popular spring choice is YJ or CJ front springs. I'll check more into that tomorrow.

 

[greentruck]

Yeah, that sounds about right. BTW, the springs on the M101 CDN are 2" wide.

 

[LFD2037]

Yeah, that sounds about right. BTW, the springs on the M101 CDN are 2" wide.

Got woke up to put out a car fire so my search continues tonight. Well, this early morning. It appears the common replacement for your trailer is front CJ 5 springs.

 

[greentruck]

That's good to know. I suspect I'll never need replacements, but if I do those should be easy enough to find -- and cheap.

The foot difference in length between recommendations for a general use trailer axle from Dexter and the rather more specialized set-up on the M101 CDN is rather telling. I think Dexter's focus is on road trailers, many of which have multiple axles, so the shorter leaf spring length helps pack two or three axles closer together. Our short off-road trailers are almost always single axle, along with a need to be overbuilt in order to handle the trail, so a longer spring comes into play.

If a longer leaf spring isn't an option that Dexter offers in the 3500 lb axle, then probably worth looking into Jeep springs or something similar. I did see there are longer springs available in configuring some of the heavier capacity Dexter axle choices, so it may simply be a matter of consulting with them to special order and produce a complete 3500 lb. axle and suspension package with the longer springs. If not, then something like CJ springs might be worthwhile to incorporate in the design of your trailer.

 

[ntsqd]

Typical trailer springs are short and stiff. This is because then the ride height doesn't change much between unladen and fully loaded, and that stiff of a spring rarely if ever needs a damper.

I'm assuming the plan includes dampers? If it doesn't, it needs to.

I don't think that you can go wrong with longer springs. Within reason, the longer the better. You can go too slinky with trailer springs and have something unstable at speed. Start with a stiff leaf spring that has lots of thin leaves and remove the shortest leaves one pair at a time until you get to a spring rate that you can live with.

 

[LFD2037]

There's a spring company about 20 miles from my house. I'm going to give them a buzz and see what they say about making me a set that's ~36" long with a weight rating of 1K each and have 7-9 leafs per spring.

 

[LFD2037]

There's a spring company about 20 miles from my house. I'm going to give them a buzz and see what they say about making me a set that's ~36" long with a weight rating of 1K each and have 7-9 leafs per spring.

That spring company doesn't make springs anymore. Said the closest he could get me was a 30" rated at 2,400lbs each. Uh, no. There's a set of free CJ5 springs on CL but they're an hour away and 35 years old. Search continues!

 

[ntsqd]

Got a dedicated 4x4 service shop anywhere close? They'll have take-offs. For that matter, assuming a U-pull-it within a reasonable distance can take a wander thru and find something that looks to work.

 

[LFD2037]

Got a dedicated 4x4 service shop anywhere close? They'll have take-offs. For that matter, assuming a U-pull-it within a reasonable distance can take a wander thru and find something that looks to work.

I don't. There is a junk yard in my town that might have a YJ. Maybe. I rebuilt a set of leafs many years ago. IIRC, I just take the center pin out, sand each leaf, repaint, new friction pads between each leaf, new pin bolt & put back together?

 

[greentruck]

I don't. There is a junk yard in my town that might have a YJ. Maybe. I rebuilt a set of leafs many years ago. IIRC, I just take the center pin out, sand each leaf, repaint, new friction pads between each leaf, new pin bolt & put back together?

Yep, that's pretty much it.