simple frame

[doug hodder]

Don't use flat stock for anything structural other than cutting gussets out of...there is absolutely no strength in one direction, you can bend that size by hand. doug

[angib]

would putting braces like the litewieght trailer be benifical (old tinytears scans of mags).

del,

Sadly, those Tiny Tears scans are now pay-to-view but luckily I saved the Lightweight Trailer (Popular Science Mar 1946) when it was free (but only the first part)! That had diagonal braces running from next to the coupler up to the front of the body:



These were needed because the A-frame is made of 2"x4" wood - and even half of that is notched out where it passes the front of the body!

Those sort of braces would enable an extremely light tongue to be used - probably something like 3/4" or 1" square tube - but to some extent what you save on the A-frame, you pay on the diagonal braces which cannot be much lighter than the A-frame.

Andrew

[dwgriff1]

Andrew you are the engineer, but those braces could be steel electrical conduit or something equally light, since the pressure on them is compression.

That would be a lot lighter than a heavier frame, wouldn' it?

dave

[angib]

but those braces could be steel electrical conduit or something equally light, since the pressure on them is compression.

In theory, yes. In practice I would be worried about someone using one of them as a 'leaning post' or falling onto it - once they've been bent, their compressive strength drops to nearly nothing.

But, yes, it could be made a lot lighter, though you have to design some parts of it carefully, like the points on the body where the braces end - one #8 screw into a 1x2 roof spar would not be enough!

Andrew

[dwgriff1]

Andrew,

Thank you.

If I build again, I'll consider all of that!

dave

[del]

thank you gentlemen

del

[spchytr]

Looking at those diagonal braces I wonder if they are for what you are thinking that they are. The way they are placed they don't appear to support much of the weight of the trailer as much of the weight of this one appears to be primarily in the chassis itself. Rather I wonder if they are to keep the sides of this trailer parallel instead of supporting weight they would keep the trailer sides from leaning ( like / / ) because the top of this trailer, if it's the one I'm thinking of is canvas or some other cloth.

[Esteban]

del,

I forgot to mention that I have a web page that shows what tongue strength is required to pass the Australian small trailer rules.

The maximum weight of a trailer with a 36" A-frame tongue according to these rules is:
2" x 2" x 1/8" angles: 380 pounds
2" x 2" x 3/16" angles: 560 pounds
2" x 2" x 1/4" angles: 710 pounds
2" x 2" x 1/8" square tubes: 1,240 pounds

These Aussie rules are very harsh and it would seem that it's safe to have a trailer weight of double these values.

Gerdo's twin 2" x 3" x 3/16" rectangular tubes are good to 4,300 pounds according to the Aussie rule, so they'd do for a 8,000 pound trailer!

Andrew

Andrew, I printed out your simplification of the Aussie tongue strength rules. Thank you, it's very helpful for planning a frame and tongue.

The weight limit for a 36" A frame tongue built with 2" x 2" x 1/8" square tube quoted above is 1240 pounds. However in your "Even Simpler Look-Up Table" the weight limit for a 36" A frame tongue built with 2" x 2" x 1/8" square tubes is shown to be 1730 pounds. Which is correct the correct weight limit? Is it 1240 or 1730 pounds?

I, too, am planning to build a TD that's about 5' x 10'. At this time I plan to use 2" x 2" x 1/8" square tube for the frame with an A frame tongue 36" long also built with 2" x 2" x 1/8" square tubes...if they're strong enough. A 1240 pound dry weight for a 5' x 10' TD seems to be in the ball park. Loaded up with water, food, bedding, and other camping stuff (maybe 300 to 500 pounds) the tongue would be over loaded if the lower weight limit is correct and fine if the upper weight limit is the OK one.


Steve

[angib]

Steve,

Yeah, I must have got confused. The correct value is 1,730 pounds and I've changed my post on the previous page in case anyone was to look at that on its own.

As I mentioned, for on-road use, I think those weights can be doubled before you will run into trouble.

Andrew