And away we go....

[LarryJ]

I will be purchasing the steel for my trailer this week and will be using the three day weekend to start fabrication. The plan is to construct a 5x9+ 'standie', keeping unloaded weight less than 1000 lbs (750lbs would be nice).

Here is a sketchup of the the frame. Any constructive feedback/criticism will be much appreciated.

<img src="http://www.lrjonline.net/media/blogs/lrjonline/Projects/teardrop/thumbs/trailer_small.png">

I haven't completely decided on axle type yet, though I am leaning towards a Torsion axle as setup and maintenance looks to be less troublesome than a sprung axle.

Thx

LarryJ

[bobhenry]

Everyone is different and I don't want to step on any toes
but if it were me I would eliminate the 1st and 3rd cross
member and run the tongue tube all the way to the rear.
If you feel the floor needs additional support in the now
2 bays you could shim directly over the tongue tube to
plane out under the bottom of the floor. The reason for letting
the tongue continue thru is to reduce the downforce that
is now being exerted on the 2nd crossmember in your
drawing by reducing the almost 3 to one mechanical
advantage your tongue design has. Remember junior
high physical science as the weight of the trailed pushes
down on the tongue you tow vehicle is lifting at the coupler
therefore creating a down force it the opposite end as the
front crossmember acts as the fulcrum. By lengthing the
tongue you reduce the mechanical advantage.

As an added bonus by shimming inside the tube with some thin
flat stock you can create a class 3 ( 1 1/4 " ) Receiver.

Great for bikeracks , tote platforms, removable spare tire
rack , and on and on and on. In some stares where
tandum towing is legal you can even do this...............

[LarryJ]

Everyone is different and I don't want to step on any toes
but

Since this is my first build, I plan on having my toes stepped on many times, so no worries here.

if it were me I would eliminate the 1st and 3rd cross
member and run the tongue tube all the way to the rear.

Hmmm... I would be removing 10lbs of weight and adding almost 30 going this route. Also, I am not real familiar with Torsion axle setup, would the axle sit far enough off the frame for the tongue tube to go over it if the tongue were to go all the to way back? Though I guess I could go with half axles, but this would require adding one of the crossmembers back to replace the axle.

[parnold]

I think others will chime in, but if your weight goal is even close to realistic, the worry about the tongue design might be a moot point. The great thing about Bob's design is the rear receiver. I often wish I had welded one on my trailer.

[bobhenry]

larry J quote: I would be removing 10lbs of weight and adding almost 30 going this route. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`

2x2x.083 is 2.143 #/lf 2 pcs. of 5 foot crossmembers = 21.43

6 additional feet of 2x2x3/16 @ 5.4 #/lf = 32.40

so the corrected math shows an added weight of not quite 11 #

I did missed the fact you were shooting for a 1000 lb limit !

That is a rather ambitious goal and you are right every pound counts....

but , but , but where ya gonna put your bicycle

[LarryJ]

DOH - my bad. Was only calculating weight of one cross member - that's what I get for doing math so early in the morning.

11 lbs. would not be a big deal. This just leaves the question about clearance between the tongue tube and the axle. If clearance shouldn't be an issue then this looks like a good suggestion to me

[dh]

Dexter torsion axles have a nice big bow in them, you will have clearance issues. Flex ride axles do not have the bow, but are pricy...

[aggie79]

Dexter torsion axles have a nice big bow in them, you will have clearance issues. Flex ride axles do not have the bow, but are pricy...

As DH said, the Dexter torsion axle is "bowed" upward to give camber to the wheels. You can see the bow in the picture below. (I don't weld very well so I had my teardrop frame fabricated. It is the frame sitting on top of my HF utility trailer.)



I think a receiver is a good idea. On my frame, the receiver extends from the end cross tube to the interior one. If you're not going to carry much weight on it, you probably could just weld one to the end tube. Whatever you do, think about how far out you extend it. You don't want to create a shin knocker.

Take care,
Tom

[angib]

Nice illustration!

I think continuing the centre tongue is pointless as it is the two angle braces that will be carrying most of the tongue load anyway - load follows the stiffest path and stiffest path from the coupler to the side rails is through the angled braces.

Using the Australian trailer design rules your current tongue design is good for a GVWR of 1790 pounds where it goes down to a single tongue (ie, front end of the angled braces) and 2040 pounds at the front cross member. I think it's reasonable to double those capacities for a teardrop that won't be abused like the utility trailers the Aussie rules were written for. So I think the tongue is way overstrength at present.

You could reduce the centre tongue to 2x2x.083 and it would still pass the Aussie rules for a 1330 pound GVWR (say, a 2600 pound teardrop).

Why 2x3x.083 for the main frame - this is more lightly loaded than the tongue so even as much as 2x2x.083 is more than is needed here, but won't come to any harm. The third, fourth and fifth cross members could be swapped for 2x2 angle and still be plenty strong enough - they are only holding up the floor, unless you want the rear receiver.

[LarryJ]

Nice illustration!

Thx. I have more experience with AutoCAD, but seeing some of the sketches others have created on this site, I decided I would have a go at using Sketchup.

You could reduce the centre tongue to 2x2x.083 and it would still pass the Aussie rules for a 1330 pound GVWR

Won't that put me above the 90% mark - I like to have at least 10% for safety margins. 2x2x.120 should do, it will be easier to weld also, as it's closer in thickness to other tubes.

Why 2x3x.083 for the main frame

The original plan was to go with 2x2x.120 for the main frame, as many of the campgrounds that we go to are only accessible via unimproved roads - no serious off-roading, but definitely not as smooth as a paved road. Reading the Off-Road section, I learned that the 2x3x.083 is stiffer/lighter than the 2x2x.120 so I figured that was a better route to go.

[angib]

Won't that put me above the 90% mark - I like to have at least 10% for safety margins.

For off-roading, a stronger tongue certainly won't do any harm and the weight/cost penalty is small.

But I don't think the Australian rule would consider a 10% safety margin as adequate - the tongue rule is that it must be able to withstand a force on the coupler equal to half the weight of the entire trailer, so I think they've got at least a 100% margin in there

Reading the Off-Road section, I learned that the 2x3x.083 is stiffer/lighter than the 2x2x.120 so I figured that was a better route to go.

My point was that the main frame of a teardrop is not subjected to much load - it is the tongue that is more highly loaded than any other part. I cannot think of any example where a main frame rail has broken. Sure it will happen sometimes on things like utility trailers, but not on a teardrop. Even 2x2 angle would be strong enough for the main frame of a teardrop.

[Dale M.]

Personally the whole design is pretty good but prefer a 3x3 inch tongue.... Failure point will be between where two diagonal braces meet tongue and hitch (coupler) ... Or bring diagonal braces further forward...

Dale

[LarryJ]

I have listened - I have evolved

<img src="http://www.lrjonline.net/media/blogs/lrjonline/Projects/teardrop/thumbs/trailer_b_small.png">

I like the final weight of this plan (about 130 lbs of material). Cross member 3 is mainly for framing out the foot well, and cross member 4 is there for adding things like a dropped battery box and/or water tank.

[LarryJ]

Well... I wasn't able to get all my metal this weekend because all the people I know with trailers were still at Burning Man.

I was able to get a piece of 11ga 2x2 for the tongue (yea, yea, changed my mind again) and some 2x2 angle, and now that I have it I'm kind of glad I didn't buy the material for the main frame yet.

I don't usually work with this size of metal (usually only flats and rods) and once I saw the size of the 2x2 I could see why you guys say these things are usually overbuilt.

Which leads me to more questions:

Not counting the tongue, what would be the smallest tube that can be used for the rectangular part of the frame (green in sketch above)? Just going to 1.5x1.5 would shave another 20lbs. This is for a large tear (5x5x10) that will be taken on short (5 - 15 miles) jaunts down unimproved roads.

Does it make a difference depending on which type of axle you go with (torsion or sprung)?

I still don't think I could go with angle, it just raises more questions and I would just have more confidence (in structural strength and my skills) with it being made of tube.

[angib]

Yep, 1.5x1.5x1/8 would be enough for the main frame and the two diagonal braces. I would want the tube for the first two cross-members and the two side rails - all the other cross-members, including the back one can be angle.

With a 2x2x1/8 centre tongue, this passes the Aussie trailer rules for a 1360 pound GVWR - and I think that means it's enough for a 2700 pound teardrop on surfaced roads.