Trailer hitch between a bike and trailer?

Question

I want to make a bike cargo trailer. It seems to me that making the hitch will be one of the most difficult parts so I opened a separate question for this.

How would you attach the trailer to the bike? Would you attach it at the seatpost (high) or near the wheel axle (low). How would you allow the trailer to pivot both up and down and side to side?

See also: How to make a cargo trailer.

Answer 1

Not a full answer, but I'll get started with the attachment point part of the question:

Attaching to the seatpost is more convenient, and recommended for trailers that are carrying very little in the way of weight.

Attaching at the axle is far less convenient, as you have to bend down to attach and reattach, but can potentially carry a lot more weight.

Axle hitches also face the choice of attaching on one side (the non-drivetrain side, usually) or on both, like a BOB touring trailer does. A double-sided attachment is also going to be harder to engineer.

Answer 2

I found this solution on Instructables: http://www.instructables.com/id/Building-a-strong-flexible-bicycle-trailer-coupler/ which uses two large casters to give you a large degree of movement between bike and trailer.

Answer 3

I have 3 trailers and have previously owned a fourth (which was my first) each of which has had a different attachment mechanism.

You have 3 issues to address:

1. Attachment to the bike
2. A "quick" release mechanism so you can, if you want, separate the bike from the trailer
3. Achieving a universal joint of some sort (or at least sufficient degrees of freedom to avoid any unpleasantness

The crudest connection I have is for my shopping trailer (a Christiana from Denmark) - this is a substantial lump of stiff rubber that has a hole for the seatpost and a long "tongue" that goes to the trailer drawbar over the back wheel of the bike, there's then a pin through the drawbar to hold it in place. This is not a particularly elegant solution, but it works. You get rotation of the rubber round the seatpost and then both up and down and twist from the rubber tongue. I've managed to put the trailer on its side with a combination of a pothole whilst being a bit too keen when the trailer was empty and the bike stayed upright...

The other three all attach to the bike around the rear axle/chainstay.

First was a Winchester child trailer which had a j clamp to go around the seatstay and, I think, something springlike to provide the articulation - not quick to attach/detach but pretty effective when on. Contemporary trailers often use "Weber" connection components for which are, I believe, available for purchase.

Third is the attachement for our Bike Friday Triplet - a plug and socket arrangement, plug clamped very firmly to the rear seat stay and the socket on the draw bar. Right here, right now I can't remember how it articulates (but it does).

Second - and last because its by far my favourite (simple, elegant and effective!) is for my Radical Cyclone. Bike end is a ball on bit of bent metal that goes over the rear axle and is clamped in place by whatever holds you back wheel on already. Trailer end is a polymer cup with a sprung steel cap to hold it in place. You can see both on their accessories page. I've used this trailer for touring - you barely know its there apart from the fact that you go more slowly (even more slowly in my case).

All of the above work more than adequately well. Articulation can be provider by a ball and socket, by a universal joint - multiple "hinges" (this is how a BoB trailer works horizontal through the axle, vertical at the trailer and no need for "twist" to cope with the lean of the bike as its single wheel and therefore will lean with the bike) or by having something that will physically bend and twist (spring, rubber).

Answer 4

It makes sense to me to buy this part of the setup or scavenge/cannibalize discarded old trailers.

Answer 5

I would also go the commercial route, buying the hitch and building only the trailer itself. The handling (during cycling) of an axle attached trailer is much better than if you attach it on the seat post. Handling is best if the hitch parts can move as little as possible relative to each other. The Chariot hitch is pretty good, especially considering the fact that only one axle/quick release module fits a wide range of dropout designs.

Still, everything can be improved: The German company Weber makes a hitch system with the following highlights:

• extremely rigid connection
• very simple and fast to use
• fits most frames perfectly by providing different frame/quick release attachment parts, even for geared hubs etc.
• fits basically any drawbar, by providing inserts for any commonly used tubing size
• can easily be locked (although the lock won't scare a good lock picker)
• an integrated bike stand is available
• quality and safety are top notch, and the parts last a long time

Weber hitches are easy to get hold of in Germany. It should be possible to get them exported to almost everywhere. Unfortunately the information is in German only, and the system is rather complex with all the different frame and drawbar fittings.

Answer 6

The Chariot brand trailer hitch is the best one I've ever seen, and you can buy it independent of owing a Chariot trailer. They are the safest, easiest to use, and just simplest trailer hitches you can find. You just mount it on your axle like a washer, hitch the trailer into the cup part, and slip in a retaining bolt. You have exactly no worries about the hitch coming off the bike unless the hitch arm or "lollipop" break somehow, and even then there's a backup strap.

It looks like this:

You can buy this kit for about $50 at places that sell Chariot stuff, or you can buy the parts separately. I'd go for the full kit, especially if you're building your own trailer.