Teardrops n Tiny Travel Trailers

I built my teardrop body independent of my chassis. The metal chassis has 4 corner mounting points, designed to take M12 bolts.

The base of the teardrop body is 3x1/2 ply sandwich on the corners (ft square on each corner) so in other words the body has 4 mounting points which are 1 1/2 plywood thick. The body is approx 150kg.

Do you think these 4 points will suffice or should I consider other mounting options?

What is the size?. I am a big believer in more rather than less attachment but that is dependent on how much you are holding down

8x4 standard 4ft high about 100-150k weight

I am not sure I would be comfortable with only 4 mounts. Mine have 8. May be over kill but I would rather not lose it on the road.

suppose a couple of extra bolts through the overhanging side walls would help?

If you use m12 bolts and dock washers above the plywood to distribute the load it shouldn't be an issue. The plywood is the weak part. A bolt with a regular washer could pull through if there was an accident, but highly unlikely in general normal use. With a dock washer it'll likely stay attached in an accident. Dock washers are just large diameter heavy washers. You could make your own from a short piece of strap iron, and just drill a clearance hole in the middle. I'd use 1.5" wide 1/4" thick mild steel strap iron, or anything with a net higher tensile strength. You could use a carriage bolt on the strap iron, and then have the nut below. That will give you a wide flatter top surface to the fastener. Use low strength thread locking compound to keep the nut from loosening, and to prevent corrosion in the threads.

Another option would be to use elevator bolts. They have a large diameter head, and would present a relatively smooth surface inside. Elevator bolts at McMaster-Carr: http://www.mcmaster.com/#elevator-bolts/=lgwlrl These are only standard grade strength. I've never seen elevator bolts in higher strength grades. Looks like they only have up to 10mm. I'd maybe go for two or three at each corner. You could put one where the frame's hole is, and another three inches away along the side.

Many thanks for the detailed reply bogo!

Ill probs go down the dock washer method as I can get them from my local fixtures/fittings place.

Im gonna add 2 additional centre fittings so at least ill have 6.

My trailer is designed to be bolted onto the chassis but I have no plans to take it back off once fitted. Nice to have the option though.