Newbie Chassis Questions

[cpucampin]

Hi newbie here, brand new builder and teardrop fanatic. I am going to drive myself nuts and jump head in. I am planing a 5 X 10 approx. 1500lb tear build from the ground up. I have been learning and researching the fantastic threads on chassis material, axles, placement, etc. but I still have some basic questions.

The thread on tongue strength answered all my questions about material and design for the tongue but I am still at a loss on what material I need for the frame. Weight is a concern for me but I know I need to haul 1500lbs. I have gathered that 2X3 is the right material for the outside frame but I still unsure on thickness and also on what material I can get away with for cross memebers. I am also still unsure on cross member spacing. Using some of the threads here and my calculations, if I used 2 X 3 3/16 for everything I will be very strong but very heavy. Some of the pre made 5 X 10 frames are coming in at 420lbs and under. Any help figuring out how much I need and how light I can go? I just can't bring myself to pay $1,000 bucks to get a frame and get it shipped.

Btw, am I now destined to lay awake everynight trying to figure out how to fit a 10lb RV in a 5lb trailer?

-Ken

[ErikF]

Im new too.

You might want to consider something like this.

http://www.tnttt.com/viewtopic.php?t=20145

its a 5x8 ready made from norther tool. $300 or so

I think at a good price, you would have trouble bulding a trailer for cheaper, unless you basically had free access the a good deal of the materials.

Plus a prebuilt avoids alot of titleing hassles.

Unless of course you want to build the chassis, to know you built it.

[Podunkfla]

Ken... The trailer frame doesn't have to be all that heavy compared to an all purpose utility trailer. A well built "box", as in a teardrop or standy, acts as a tortion box structure when all together. This can and does add substantial strength and rigity to the trailer when attached. So, you can use somewhat lighter materials under the box. Even 2 x 2 -1/8" angle iron may be all you need. Or, you could use tubing for the perimiter and angle for the cross members and still save some weight. I wouldn't skimp on the tongue or axle mounting parts though. Just my thoughts on the subject. Good luck with your project.

[sdtripper2]

Ken:

You might find help here at Doug & Rich's Trailer Tutorial.

[madjack]

Steve, I believe that is what they used for the tongue...for the frame, they used 2x16ga tube...on our present build we are using 1x2x3/16 C chanell for the frame and crossmembers and 2x1/4 tube for the tongue...a TD, when properly built is a torsion box and needs no steel frame under it except to tie the tongue to the axle and provide a place to mount the "torsion box"..............
madjack

[doug hodder]

Yeah Jack...the frame perimeter and 2 cross members are 16 ga. 2x material. I did the tongue in .120 2x3 tubing with 1/8 angle. I think I could do without the angle, but the plan is that in the future, I can put a rack on the front on any tear I want to keep with a small scooter on it, fair amount of extra weight. I may or may not get a scooter, but at least I've got the option built in for it. In the meantime, some treadplate makes for a great platform for a water jug.

For anyone wanting to scratch build a frame, check the weights/ strengths of the materials that you are wanting to use via the info from Andrew. Like previously mentioned, the torsion box aspect of the build will add a ton of strength to it. You don't need to build it like you are going to haul a D-9 cat on it. It's just a lot of extra weight to drag around, not to mention the price of materials....Doug

[asianflava]

Like the other posts say, the tear is a box that sits on top it provides the rigidity. The frame mostly serves as a way to join the tongue and axle to the box. You could attach them directly to the wood but that doesn't save much weight since you have to beef up the attachment points with hardwood.

I think that 2X3X3/16 is a bit of overkill for the frame. The only place you'd need that is for a single tube tongue. Even for the tongue you could get away with 2x2x3/16 or 2x3x1/8. My entire frame is made of 2x2x1/8 square tubing. In retrospect, I think that I should have gone with a more beefy tongue but it's been fine so far.

You only really need 1 crossmember, it provides 2 places to attach the tongue. If you use a torsion axle, it will serve as another crossmember although it doesn't make contact with the floor. You can add another one if you like but I feel that any more than 2 is excessive for a tear. Your weight is spread out by both the mattress and your butt.

[Esteban]

I'm kind of a newbie, too. I had a local welding shop build my 5'x10' frame. It cost $500 for labor and steel. I supplied the axle.

The outside of the frame is made from 2"x2"x1/8" square tube. Cross members, on 2' centers, are made from 2"x2"x1/8" angle - because it's lighter than square tube and because I could drill through them for the floor bolts. The 48" long A-frame tongue is made from 2"x3"x1/8" rectangular tube - it's about 10 lbs. heavier than a 2"x2"x1/8" tube A-frame tongue, but much stronger (in other words it's way overbuilt).

I decided to go by the Aussie Rules for tongue strength even though Andrew says they may be twice what a teardrop trailer really needs. I wanted my tongue to be good for at least 1500 lbs. per Aussie Rules.

The axle is a 22 degree down angle Dexter #9 torsion axle with the rubber rated for 1700 lbs. As a bare frame sitting on 14" tires it has about 17" of ground clearance. With a teardrop on top and loaded with gear it'll come down a little. It's about 2-3" more ground clearance than I wanted or initially planned for...especially to get the right height of the galley counter I want to build.

The number of cross members on my frame, 4 of them, is probably excessive just for frame strength. I figured they'd help stiffen the floor and there'll be one at each 4' joint of the plywood floor. Initially I was going to build a ladder floor with 1/2" plywood for the top of the floor, a nominal 2x2 inner wood ladder frame with foam insulation (actual height 1 1/2"), and 1/4" plywood on the bottom.

I'm now thinking about using 3/8" plywood for the top of the floor to save about 20 lbs. of weight compared to 1/2" plywood. The 2' on center frame cross pieces should help stiffen it enough with the wood floor's ladder frame cross pieces laid out above them.

I may change the inner wooden ladder frame to 3/4" high to lower the floor and save a little more weight. Partly that depends on the quality of foam board insulation I can buy locally. Home Depot's bead board is about R4 per inch. There's another kind that's about R6-7 per inch I'd prefer to use if I can find a local supplier. Depending on the floor thickness and insulation quality the floor could be insulated from about R3 up to about R10.

This is long and wordy. Maybe it'll help you figure out yours.

Could have shaved off some weight by using a lighter tongue, lighter gage tubing for the outer frame, and fewer frame cross pieces. All in all I'm very satisfied with how mine came out.

Kerry, I edited the spacing of the cross pieces.

[toypusher]

....... Cross members, on 2" centers,............

Seems a bit extreme to me! Would make it tad heavy, I think!