Trailer dropout suggestions?
 

I made a trailer, it mostly works, I like it. Today I put a pretty heavy load on it (bookcase, maybe 90 pounds) and the dropout brackets came loose (before I started riding). They look like this:

http://sccs.swarthmore.edu/~cbr/imag...MG_2936-tn.jpg
(bigger image)

The connections between the metal and the 2x4s is what's wiggly. It's held together by screws.

I'm thinking maybe If I took it apart and replaced the screws with bolts it would do better. Maybe I need to put bushings in the 2x4s to put the bolts through? (I know bushings are usually used with rotating parts, but they would also help keep the bolt stable in the 2x4.) Suggestions?

Bolts would likely be stiffer than screws. Bushings would not be good.

To my eye those brackets look too thin. I'd look for something around 1/8" thick or so. Then a couple of 1/4" bolts with flat washers on the metal, and flat/lock washer combo on the wood should make them nice and stiff.

The wheel is 28 inches, so the brackets are thicker than they look. They're 12 gauge galvanized steel, which looks to be .1082 inches, or 7/64. Almost 1/8.

You're dependent on the wood fibers that the screws are biting into to hold everything together. If you replaced the screws with through-bolts and locknuts (say, 1/4" diameter), with fender washers on both sides to distribute the force, you'd be in better shape.

I'd go along with the recco to have heavier metal. That galvanized sheetmetal isn't very stout. You can bend it with your bare hands. Steel bar stock would be a lot sturdier.

A fender washer is a big washer with a small hole, right?

I can't actually bend those with just my hands; I guess I'm pretty weak.

I wonder if the screws I used in the rest of the build are likely to be a problem too -- the rest of the frame is all 2x4s glued and screwed together. The forces there are somewhat different, though.

I'll be putting less weight on it after I fix it too; I was foolish thinking that the bookcase was reasonable.

Use a shelf bracket like this in at least the 4" size. Cut down one end to 1-1/2" so that it hooks onto the bottom of the stud. Use epoxy, then 2 screws into the inside face and a screw into the bottom to clamp it until the epoxy sets. Done.

:)ensen.

http://www.carinya.com.au/e107_plugi...kets_group.jpg

Stop messing around dude! Get two eye bolts(PER SIDE) long enough to fit the 2x4 edgewise then drill holes through the 2x4 drop the eye bolts in with the eyes on top strip off the chain ring from the wheels then stick the axle through the two eyes bolts each side and install/tighten the nuts.

When done the whole assembly will be a lot stronger. Mine can carry a 300#+ load easy.

Consider yourself fortunate.... I've had an eyebolt straighten out under load. Unless I've welded it shut, I wouldn't trust it vs a solid plate.

:)ensen.

Must've been really crappy steel in that eye bolt or you loaded it wrong. Either way the way mine are installed the load is on the shaft not the eye.

Carriage bolts are what you want. Those are the ones with a round head with a square section under it. The square locks into the wood when you tighten them. Make sure you use lock washers under the nuts so they do not work loose.

I drilled new holes and put two 1/4 inch bolts on for each plate. It feels very solid. Thanks for the advice!

I have trouble imagining how you load the eye bolts such that there's no load trying to straighten out the bolt.

Looking at this table:

http://www.smithfast.com/eyebolt5_6.htm

Perhaps a 3/8 bolt would be reasonable for a 2x4? They give a maximum vertical load of 1400 pounds, assuming "a straight vertical lift in a gradually increasing manner". Which a trailer on potholes won't be providing. Hmm.

No lifting load at all in my application. The loading was under the 2x4 causing the load to press upwards on the shaft. Either way the 2x4 (pine) is the weak link. I used hardened
white oak for my wheel runners. Can't hardly drill that stuff! :eek:

Got it, thanks.

As these are big wheels, I like that the frame is below the axles. This does make it less sturdy, though.