Building a chassis frame

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Building a chassis frame

Postby FloridaWild » Sun Feb 25, 2018 11:57 am

Ready to start a TD build. I've decided to build my own frame. My thought is to use 2x2x1/8 angle steel for the main frame and 2x2x1/8 tube for the tongue. The trailer will be 5x8x4. No traditional galley, just the bed, small mini fridge and a couple upper cabinets. The goal is to be 800# or less. The axle is a 2500#. My question is, would this frame be adequate and how would you suggest I orient the angle. Flat side up makes it easier to mount the floor and body, but presents a problem mounting the leaf spring hangers. Flat side down, allows to mount hangers, but my fear is it presents a few problems, such as holding water underneath the floor and makes sealing the seam between floor and wall more difficult. I've searched the site for answers but not coming up with anything. What do you guys suggest?
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Re: Building a chassis frame

Postby QueticoBill » Sun Feb 25, 2018 12:00 pm

Look at the ultra light chassis in design resources for a solution. http://tnttt.com/Design_Library/The%20U ... hassis.htm
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Re: Building a chassis frame

Postby FloridaWild » Sun Feb 25, 2018 12:13 pm

QueticoBill wrote:Look at the ultra light chassis in design resources for a solution. http://tnttt.com/Design_Library/The%20U ... hassis.htm


Sometimes a picture is worth a thousand words! Thank you! I can build flat side up and weld a 2 ft. section to the frame upside down on each side, to mount the hangers. 8)
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Re: Building a chassis frame

Postby tomhawk » Wed Mar 14, 2018 6:40 pm

I would also like to make my chassis.

I am thinking about building a foamie similar to ghcoe's #1 http://tnttt.com/viewtopic.php?f=55&t=54099 but in a 5' X 9' size. This would be a lightweight build. I expect the final(loaded) weight to be well under 700 lb. I am trying to think airplanes not tanks. I just hope I don't overdo it in the light direction.

Here is my current chassis plan with ideas stolen from various places on this site (for example: http://www.tnttt.com/viewtopic.php?f=35&t=12220)
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  • The top panel is the tongue and axle portion.
  • The middle panel is the rectangular deck support.
  • The bottom panel is the deck support attached on top of the tongue/axle.
  • I will stick to 1/8" steel because I tend to burn through welding anything thinner.
  • I am hoping it will be easy enough to move about my garage during construction.
  • I am unsure about the 1" angle for the deck support. I think this should make the floor stiff enough.
  • I will use 1" angle for a few cross bars to stiffen the floor a bit as well.
  • Andrew's notes say the 2"x1" rectangular tube A-frame should be quite strong.
  • I will probably use 6-8 3/8" carriage bolts to connect the floor to the chassis via some welded on tabs and cross bars.
  • A Dexter Torflex #8 axle is planned that will bolt to the 2X2" square tube portion.

I would appreciate any comments.

Tom
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Re: Building a chassis frame

Postby tony.latham » Wed Mar 14, 2018 7:41 pm

The only issue that jumps out at me on your trailer plan is the tongue angle. If you are planning on using an A-frame coupler, I think they are 50ยบ. But maybe you've already thought this one through and have a solution for it.

Also, that cross member near the axle duplicates the one on the Torflex. :thinking:

:beer:

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Re: Building a chassis frame

Postby tomhawk » Wed Mar 14, 2018 9:47 pm

Getting rid of the cross bar near the axle is good. Saves 4 lb.
I had not thought about the coupler attachment. I think what others did was weld the vertex ends of the A frame to a short 2X2" square tube section with the coupler bolted to it.
Thanks,

Tom
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Re: Building a chassis frame

Postby swoody126 » Thu Mar 15, 2018 7:24 am

tomhawk wrote:Getting rid of the cross bar near the axle is good. Saves 4 lb.
I had not thought about the coupler attachment. I think what others did was weld the vertex ends of the A frame to a short 2X2" square tube section with the coupler bolted to it.
Thanks,

Tom


just remember you will need to join your floor sheets and having a metal brace under that joint is jam handy

sw
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Re: Building a chassis frame

Postby tomhawk » Thu Mar 15, 2018 12:18 pm

I am worried about the floor being too weak.

Alas, 5' x 9' sheets of plywood aren't available. I am planning a sandwich 1/4" ply - foam - 1/4" ply floor. I have made some trials with scarfed joints to extend the ply. I was surprised to find I could do it with my limited woodworking skill set. The advocates say not to be afraid to try. I would agree to that! It makes a really strong joint. I think the joints won't be a weak spot.

The main stress on the floor will be the 300 lb of occupants at the camp site. The cross bar supports therefore should be under the front part of the cabin with less need for the portion under the rear galley.

Tom
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Re: Building a chassis frame

Postby tony.latham » Thu Mar 15, 2018 12:37 pm

tomhawk wrote:I am worried about the floor being too weak.

Alas, 5' x 9' sheets of plywood aren't available. I am planning a sandwich 1/4" ply - foam - 1/4" ply floor. I have made some trials with scarfed joints to extend the ply. I was surprised to find I could do it with my limited woodworking skill set. The advocates say not to be afraid to try. I would agree to that! It makes a really strong joint. I think the joints won't be a weak spot.

The main stress on the floor will be the 300 lb of occupants at the camp site. The cross bar supports therefore should be under the front part of the cabin with less need for the portion under the rear galley.

Tom


I wouldn't bother with scarfed joints. Me? I'd butt 4 x 5' pieces over 1" internal cross ribs and alternate those joints so the top joint isn't over the bottom joint. On my fourth build, I'm planning on doing it the same way. A sandwiched floor made from two layers of 1/4" subfloor ply and stiff foam.

You could rip your floor ribs, glue them up on edge and that would make for a stiffer structure. Or use something other than pine.

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That's how I do my roof spars. :thumbsup:

Tony
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Re: Building a chassis frame

Postby QueticoBill » Thu Mar 15, 2018 6:06 pm

Portable sraging, like that used for rock and roll concerts, uses 4x8 decks with paper honeycomb as the separtor between 3/16 ply. Foam would be better for thermal and do the same as honeycomb.

Check on APA (American Plywood Association) for stressed skin structures. Ive built 16 and 20 ft long platforms with no cross framing. Just use same ply and scab joint 1 ft each side of joint, glue, and clamp.

You dont need to worry about framing under joints.
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Re: Building a chassis frame

Postby KCStudly » Sun Apr 22, 2018 12:07 pm

The original micro light fame concept had no metal floor frame.

I did my floor 64 wide x 9'-8" using 2x2 and 1x2 cedar frame, 1-1/2 thk blue foam, and 5mm ply skins top and bottom all glued to be a structural panel. It weighs about the same per sq ft as 3/4 ply, but at 1-7/8 total thickness is much, much stiffer.

Don't forget, the walls and bulkheads (even the cabinets) on your camper box are like very deep section beams, they will hold the floor up at the perimeter and greatly stiffen the whole assembly. Don't think of it as the trailer frame supporting the walls, think of it as the very rigid walls stiffening the trailer frame. Think of it like a railroad bridge; the road bed is the trailer frame and the trestle is your side walls. All of the strength comes from the trestle.

Once my foamie hybrid cabin had the roof on, there was zero flex to it, and that was off the trailer. I could lift any corner and it moved everywhere at once, no sagging or twisting. The trailer frame, being such a short section depth will never be as stiff as the cabin, no matter what reasonably sized material you make it from. Mine is 2x2x1/8 sq tube and still flexes a little with the cabin not installed yet.
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