Wednesday, May 22, 2013

New Bicycle Trailer

Have been busy for the past few weeks designing a trailer for the Bicycle Cafe business I want to start this summer. The trailer has to be strong enough to haul about 100 - 120kg and be wide enough between the wheels to fit a Taiwanese-style steel icebox.

Had originally thought about making a trike after seeing this picture of Dr. Szmodics online. The attention to detail and quality of construction is really quite amazing. Finding a trike like this in Taiwan proved quite frustrating, as many of them are made here, but are unavailable for sale domestically.

The closest I could find for sale in Taiwan was this trike made by Ta-Han; a restaurant supply business based in Tainan. $55,000 a unit was more than I wanted to pay though, and they wouldn't sell me just the bare trike.

Then, I saw this picture of Bicycle Coffee in Oakland and it gave me the idea to do a trailer instead.

The icebox I have is 50cm wide , 67cm long and 70cm tall (without the wheels), so I decided upon a width of 65cm between the wheels. Combined with 2 x 10cm axles and 2 x 2.5cm square tubing on the outside, this gave a total width of exactly 90cm. Too wide to go through a standard door, but still safe enough to maneuver in traffic.

The closest I could find to a design I liked was this one from instructables:

The metal fabricator I found to build the trailer turned out to be really good at his job and a cycling enthusiast himself. He gave me some very helpful suggestions to modify my design. Specifically, to move the wheel axles further to the back to reduce swing on the rear corners and make it track behind me better. Nice one.

A few days later he delivered the trailer to me to try, so I loaded it up with my 45kg icebox and took it out for a spin; handled the load no problem.

The only problem has been the hitch. I decided to connect at the seat post because I already have a hitch there that I use for my son's Trail-a-bike. Also, it makes the cart easier to maneuver like a handcart than when you connect to the rear axle.
The problem is that the trail-a-bike has only one wheel and can lean with the bike. The 2-wheel trailer can't and was putting a lot of twisting pressure on the hitch. The builder explained his idea to fix the problem and drew me a picture of it, only to show up a couple of days later with something completely different.

It works, and can allow for a full range of movement, but the tiny bit of slack between the two metal loops makes quite a racket when rolling along. It'll do for now, but I have to think of another solution. Maybe a rod-end (heim joint) like they use in Japan. Anybody with suggestions, let me know.

Now, off to see my carpenter friend to build the wood box.