Introduction: Bike Trailer
If you only want details of the build without the background; look for the different stages/parts in bold.
Ever since I started biking I had wanted to expand my options and make a trailer and then when I started kayaking I found the perfect excuse to make a trailer - for my boat. This would mean I could get my boat quickly and easily to and from the club house/surrounding rivers.
So before Christmas I made a prototype out of a few wooden pallets I had lying about. I was just experimenting at this point and so the result was a bit of a mess. I tried it that evening (late at night when the roads were clear!) and to me (and the family's) surprise it went a treat! I ended up using it for the next few months. It broke a couple of times but nothing too serious. At this point it was strong enough to carry over 80kg!
However, I still was not satisfied, particularly with the make-shift wooden drawbar which had a tendency to flex. So my priority was to replace the drawbar. I did this by taking 1”Ø steel piping, cutting it to length and then slowly bent the remaining shorter sections for the 90° bends. Then, I made two ‘O’ rings for this to slot into with the end ‘O’ ring being a sleeve with a drilled hole for securing the drawbar with a pin. I then screwed these ‘O’ rings onto the wooden frame and this improved the handling and reliability tremendously.
Having now made the step from ‘just wood’ to ‘half-wood/half-metal’, I started a design for a metal frame. I designed one on the computer (using Google SketchUp) with removable upright pillars. In the end I used 2” steel box section which had the strength but was still fairly light. I could have used lighter stuff but it wouldn’t have had the strength that I was looking for. I came up with a design which could be used not just for my boat but for transporting, giving lifts, etc also I wanted it to work with more than one bike. I had made it narrower by 6” making it 2’ wide, but slightly higher (by 3”) making the base of the frame 1’ off the ground.
Consequently, in testing it became apparent that this was too high making it unstable along with the fact the wheels were too close together after reducing the width. So I cut the frame down the middle and welded in place some 6” of left over box section (making it 30” wide) with some plates to strengthen it/hold everything in place. Also I swapped the orientation of the ‘tabs’ where the wheel attaches. This lowered the frame by 3” making it only 9” off the ground. Upon a second test, the trailer performed beautifully! However, because I had widened the frame the boat did not sit quite right so I had to insert blocks of wood as spacers as you can see in the pictures.
Because my primary use of the trailer would be for transporting my boat, I had designed the drawbar and uprights (and their placement) specifically to fit my kayak but left a flat base so other objects could transported on it. The natural shape of my kayak (a playboat) meant it sat at an angle so for safe transportation and an even spread of weight I would have to make one side of uprights angled. I had 1’ of box section on each corner already so using an angle grinder I cut into it at an angle and welded on plates for it to sit on. I then added rubber padding and later (after widening the frame) wooden blocks to take up the extra space.
I left the hitch until last. Looking at other Instructables I saw a range of ideas most of which connected to the side of the rear wheel. This surprised me as it seemed impractical for tight turns and accessibility. I came up with the idea of riveting the drawbar to two strips of stainless steel which then held a ‘U’ shaped nylon block. This would fit around my 1”Ø bike seat stem/shaft. A pin through it would ‘complete the circle’ which is fully secured by another pin. I have found this quick and easy to attach/remove especially on dark winter nights.
Wheels were the biggest problem but they were also most influential towards the whole of this project. I had considered using ‘fatter’, barrow type wheels as well as solid rubber wheels. These would have lent themselves to a lighter, shorter and generally weaker trailer. This was not a compromise I was willing to make so my bike from when I was about ten suffered the loss of its 20" wheels and now just the frame remains. It was a good sacrifice as it allowed me to make a much bigger, stronger and heavy duty trailer. I have found them to perform better slightly deflated so they have a bit of bounce; they are after all the trailers only suspension.
I was very pleased with my creation and whilst everyone may not be able to access the materials I have used, I hope this will inspire, influence or even just provide interest to someone and/or their project.
Please feel free to ask a question, provide feedback or add suggestions below :)
Update Feb 2012: I was returning from a club night at about 10pm and got stopped by the police. All they wanted was a chat about the trailer. It turns out it is road legal but they just wanted a closer look at it. They took a picture of me with it for a laugh. Hopefully I will end up on Cops With Cameras ;)