Intro: Single Wheel Bicycle Trailer
This all started when I decided that I wanted to do some touring and needed some extra space for camping equipment. In order to do this I wanted to build the trailer myself and I was going to recycle as much stuff as possible. So I started to research... and the list of requirements started to grow:
- It would be a single wheel trailer as I was not going to spend several hundred Km with one wheel off the pavement
- I wanted all of my wheels to be the same size (700c) to simplify tubes and tyres etc. I wanted a 700c wheel as well to avoid any shopping trolly effect.
- I discovered the Extra Wheel trailer and thought it was a good idea but I was not impressed with the fact that it boasted that you could use the wheel as a replacement. How often would your front wheel go? It is always the back, so the extra wheel was going to be a rear wheel.
When I finally got the trailer made I went down to Tasmania and rode down from Devonport to Hobart via the west coast. The trailer was faultless, worked fine on pavement, dirt and gravel surfaces and most importantly very stable at speeds up to 55km/hr (I didn't really feel the need to test it beyond this point).
Unfortunately I am not good with taking pictures as I work so I have had to come up with some alternate images, you will no doubt get the idea. What you see in these pictures is actually the third version.
Step 1: Step 1 - the Frame (Part 1)
I started off with this old womens step through frame. It actually worked out quite well as I was able to keep the head tube and bottom bracket fully intact, lugs and all. All of these joints were brazed, which meant a lot of time mitering tubes.
From the picture which shows how I cut the frame up:
- I got rid of the upper half of the seat tube and the upper downtube that was joined to the seattube. I left the lower downtube connected to the bottom bracket. Both the upper and lower downtubes were left attached to the headtube.
- With the chainstays sitting as horizontal as possible, I orientated the headtube so that it was pretty much vertical. This is necessary for handling, if it is on an angle the trailer will want to lie down when it corners. As you can see in the pictures the tubes coming from the headtube ended up almost perpendicular to the seat tube and the downtube that had been left attached to the bottom bracket had to be cut at a very acute angle which left a very long joint to be brazed, which added to the strength and stability of the front end.
- The seatstays were bent back so that they were pretty much vertical.
- I managed to get some Dueter panniers cheap and found that the attachments could take up to a 16mm pipe which was convenient as this is the smallest steel tube that the hardware store stocks. When I couldn't recycle bike bits I ended up using galv steel conduit (Warning - it is always a good idea to get rid of as much zinc as possible before heating and do so in a well ventilated space...) You can see in the fourth pic, to make the pannier rails I have bent and brazed the pipe at a height appropriate to the panniers that I bought. I made a point of getting them as low as possible without them dragging along the ground when cornering.
Step 2: Step 2 - the Frame (Part 2)
The first pic here gives you another view of the pannier rails. The pics also show the top rack, this is specifically designed to hold a tent with the minimum of fuss tying it down. Each morning I would have to go to great lengths to make sure the tent was secure and wasn't going to come off, so I thought this design up as I was riding along.
- The rails are made of the 16mm conduit and the clamps are made of 19mm conduit with the arms also made of 19mm conduit. The clamps are basically a barrel with two arms brazed on at right angles. It works when the tent is forced down onto the lower arm which in turn rotates the vertical arm and presses it against the side of the tent. I made the clamps first, fitted them on and then brazed a few rings in place to keep them where I wanted them. I ended up buying some end plugs to make it look fancy.
- The fourth pics shows some bits of tube I had to add to stop the panniers from flapping about
Step 3: Step 3 - the Forks
When it came to the way of attaching the trailer I was looking for something that would not twist. The way the Extra Wheel and the Bob trailers work was appealing in this respect.
For this part I was determined to utilise the forks that came with the frame. On the first attempt I simply cut the blades near the crown at a 45 degree angle, swapped them around and reattached them so they were at a 90 degree angle and brazed some steel around the join to strengthen it. Later I added a pair of stiffeners which travel up to the gooseneck that I pinched off an old BMX. The stiffeners are just long enough that the clamp on the goosneck can be disassembled and the gooseneck twisted around so that it can be removed which allows for the entire fork assembly to be removed as one piece.
The rod ends have a standard M10 thread, I realised that I could use an M10 threaded rod connector (pictured) and grind off the outside angles to make it round enough to fit inside the conduit, then brazed it in place. This allows me to fine tune the alignment of the fork arms by giving the rod ends an extra turn if necessary.
Step 4: Step 4 - the Hitch
This part was inspired by the three point hitch on my father's tractor. The cleavis pins are fixed in place with a split pin and are easily removed whch makes taking the trailer off a piece of cake.
The brackets consist of a 3mm plate with an L welded on at the end. Another piece is welded perpendicular to the plate along its length to add stiffness. A final piece is welded at an angle which will rest on the inside of the seatstays to stop any rotation.
On this particular bike there is only on set of lugs for panniers (some bikes have one set for pannier racks and another for mudguards) so the brackets were fixed to these and also clamped on with the skewer. Basically there is a 5mm hole on the non-drive side bracket and on the drive side I had to drill an 11/64" hole so that I could tap a 5 x 0.8mm thread (I welded another 3mm of plate to make it 6mm of thread to bite into - see pic 3). This seemed the best option because the 3mm plate on either side meant the standard skewer wasn't going to be long enough. Once this was done it turns the rear wheel into a 5mm bolt through setup, because the skewer is basically fixed at either end it also removes the need to clamp it really tight as would normally be the case.