I built this trailer to use on my recent ride down the C&O Canal Towpath. The trail is 184.5 miles and runs along (you guessed it!) the C&O Canal, from Cumberland, MD, to Washington, DC. For the most part, the trail is hard packed dirt, although there are places where it's mulch, crushed rock and even paved in a spot or two. I decided to build this after having gone online and found that, while two-wheeled trailers would work, single-wheeled ones are recommended. I looked at buying one, but at ~$325, I didn't look too long.
That's when I decided I could do better. I think I did...what do you think?
I wasn't sure how to go about building it and thought of a couple different ways to do so. PVC was considered, as was copper tubing, but I finally settled on electrical conduit after seeing I could get a 10' length for $2.50! I settled on brazing the pieces together after perusing the conduit connectors and realizing they probably weren't going to be strong enough. The only problem with brazing was that I had no idea how to go about it. (Sure, I learned in 8th grade shop, but that was ages ago!) I did some searching on the web and finally decided to just go for it. In the end I found out it wasn't that difficult (looking at the trailer, you can tell which joints were brazed early in the project and which were done last -- the learning curve isn't' that steep).
Excluding tools, this can be made for less than $20. What you do with the savings (~$300) is up to you.
Step 1: Ingredients
4 x 10' 1/2" electrical conduit
front fork of junker bike*
rear wheel triangle of junker bike*
head tube and seat post of junker bike
wheel (16" or 20" -- I used a 20" tire off my daughter's old bike)**
1" to 3/4" conduit step down washer
1/2" screw-type conduit connectors (3)
*This was made using a 26" mountain bike since it's going on to be used behind 26" mountain bike. I recommend using the same size (or larger) fork/rear triangle as you have on the hauling bike.
**While you could use the wheel from the junker bike if absolutely necessary, having the smaller diameter tire allows the trailer to be parallel to the ground.
brazing torch and rods (I used MAPP vs. propane for a quicker job)
hack saw (w/ metal blade)
*This is used to cut the holes in the fork. A metal bit is required. I used a Lenox 3/4" Arbored Hole Saw Drill Bit and it work liked a champ.
And now, a word of warning, courtesy of Fletcher:
A word of caution about working with electrical conduit: Conduit is generally galvanized, meaning it's got a thin coating of zinc. Zinc is toxic; grinding, welding, brazing, etc. will vaporize the zinc, raising the risk of inhalation. Before working with galvanized pipe, remove the zinc layer (it's thin, so sanding/use of a wire wheel or brush will do it) in an area with good ventilation. A fan would be a good idea, as would a quality respirator (a simple filter mask won't do.) Conduit is a good, inexpensive basis for building all sorts of things ; just remember to take the proper safety precautions.