How to prevent trailer hitch bracket rotation?

Question

I am using a croozer kid bicycle trailer with a solid rear axle (shimano nexus 7). The hitch is the kind that goes on the rear axle between the left nut and the anti-axle-rotation nut for the gearhub.

The problem I'm having is that seemingly no matter how tight I tighten the rear nut, I am unable to prevent it from loostening and allowing the hitch bracket to rotate about the axle.

Has anyone else had success with this on similar trailers? I am fairly certain the nut will strip if I tighten it any further, and I'm very worried the bracket (and frame) are doing damage to the axle if I ride with it while loose.

We are carrying only a newborn baby; the trailer is not overloaded.

Does anyone have a solution for this rotation problem? Thread lock? Anti-lock washers? Maybe a split nut?

Answer 1

Based on the image of their hitch that I found and added to your question, you're going to have to modify the hitch to make it work. It's designed to rotate (I don't think that's a good decision, but that's what they did).

If you have enough clearance between the trailer and your rear wheel/mudguard, you could rotate the hitch forward and clamp it to the chainstay. I'd use a jubliee clip (hose clamp), and leave it there permanently. The problem with that is that you won't be able to remove the rear wheel without removing the clamp. If the chainstay sticks out past the dropout it's also going to bend the hitch when you do the axle nut up, which I would not do.

The other option is welding a bump/tab onto the inside of that clamp as described by solson. I strongly suspect that mount is steel, so it's easy enough to weld onto. If you don't have a welder it's going to be 10 minutes work for a metalworker to do it, plus you will need to repaint the hitch afterwards. I would buy a second hitch for this, since Croozer sell them, and that way if you stuff it up you can still use the existing hitch. If you're paying, clean as much paint as you can off the whole hitch (welding will heat the whole thing up and burn off paint over much of the hitch, which is stinky, so if you don't do it you're going to be paying someone else to do it). Then work out exactly where you want the tab and scratch marks along each edge, from the hole in the middle right out and down the outside edge (so they're visible after the weld covers the scratches on the inside surface). The welder will put a blob that extends past the scratches (molten metal doesn't sit in nice box shapes), then you will file it back to get nice straight edges that will lock in place nicely. If the metal place is able, oil quenching after welding will harden the bracket which will be helpful.

What you're trying to get is the red blob added on the dropout side of the hitch, so it sits on the slot in your dropout when the wheel is installed.

Answer 2

Trailer mounting hardware sometimes has a tab that is supposed to fit into the slot of the dropout to to keep it from turning.

Likely causes I can come up with:

1. Your trailer mount doesn't have that tab. That means you probably need to tighten the nut more, but you're worried it will strip. If you make sure the nut and axle are free of dirt and rust, and then possibly lubricate the threads, you might be able to get it tighter without risk of stripping.
2. If the nut itself keeps loosening, try a nylon insert locknut. This might be something of a desperation measure, as I don't think they can be infinitely re-used. They can be found at decent hardware stores.
3. You didn't get the tab into the dropout.
4. The anti-axle-rotation nut for your gearhub doesn't allow the tab to get into the dropout slot.

My solution for a different brand of bike trailer involved fabricating a trailer mount with some electrical conduit and welding it directly below the dropout, but that's not likely to be an option for most people.