When I moved back to uni, I visited Tescos and bought all the neccessary bits and peices of food for the next week or so. I came to cycle the 1.5 miles home, and found it a bit of a strugle. A large backpack with all my uni stuff in, and bags of food hanging off every surface.

On the way back, when I was not fully occupied keeping the bike balanced I realised that a trailer would be a helpful addition to my random collection of bike parts, and decided to look into making one.

When I got home I did some research on the legality of using trailers on bikes, and there did not seem to be much, other than reflectors and lights being needed at night.

Then my attention turned to ebay. There were new bike trailers selling for £30 + £10 postage, and I did not think that I could make one for less than that even with the generous amounts of bike parts in my back garden. It also came complete with a towball, and had a rating of 50kg. Now I will not mention names, but I have a small female housemate who weighs in at 45kg, so even she could sit in my trailer, being pulled around like a dog.

A few weeks later, and a very large parcel arrives from Germany. Carefully unpacking it yeilded a large grey box, lots of steel tubing, two wheels and a pile of bolts. The instructions that came with it were useless, and I resorted back to my intuition and managed to get something that looked roughtly how it should. The bolts that were supplied were of very poor quality, and I sheared a lot of the threads off when tightning things up. I was not using a torque wrench, but I know that bolts should not be loose.

The next problem was the towball. It was all nice and shiney, but I could not figure a way to fix it on. After hitting it with a large hammer, I got it to fit around my seat post stem. However, when the trailer was loaded it tended to bend the ball downwards, putting a large force on the locking screw keeping the trailer fixed to the ball.

About a week later, I realised how the ball was meant to be fixed on. Of course it needed some modification to work, but it was a much better solution. All I needed to do was saw through the 3mm steel bracket with my junior hacksaw with 50p blades. Needless to say, the blades took most of the impact and my trusty swiss army knife saw to the rest of the bracket. Once I had taken the right amount of steel off (and replaced the poor quality bolt that had sheared) the bolt was threaded though the seat post bolt, and the bottom of the bracket rested on the top of the A frame, as shown in the picture. This resulted in a horizontal ball that was fairly sturdy. However, now the beam of the trailer could potentially interfere with the pannier rack, and so I lowered the back of the panier rack to give plenty of clearance.

I have used the trailer for quite a few shopping trips, and have found it very useful. It allows me to save on plastic bags, as the items go straight in the grey box. However, the trailer does have some problems associated with it, which I will now consider.

When you have a load in the box, perhaps greater than 15kg you can feel the affect on your bike brakes. The trailer wants to continue going forward and if you primarily use your front brake to stop yourself (which you should!) it creates a moment above the center of the rear wheel, and so helps you go over your handlebars. If the trailer was fixed onto the bike at the centre of the rear wheel, as in the photo on the right you would still have to brake harder but you would not get the turning moment to help you over your handlebars.

The grey box is loose, and it rattles around a lot, especially when ridden on the lovely Coventry roads. I fixed this issue with a few bungie cords strapped around it, which also help stop your shopping dispensing itself on the road.

When you are cycling with it on, you have to be constantly aware that it is there – otherwise you could find yourself stopped abruptly by a bollard. There can be no weaving in and around traffic, and you have to be careful when turning because it turns a little later than the bike does and tends to catch on things. I improved the design slightly by insetting the capped nuts for the wheels by a few milimeters, just to take them to the inside of the main sidebar. This reduces the amount of paint I knock off things when I get too close.

The final problem with the trailer is keeping it. When I take it shopping I have to take two locks with me, as my one D-lock is not big enough to go around both my bike and trailer.

Despite the problems, the trailer is very useful to me and although I get some funny looks when it is attatched to my rear end it was well worth the money in novelty value and usefulness.

This entry was posted on Tuesday, November 14th, 2006 at 12:22 pm and is filed under Engineering, General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.