Tuesday, 1 May 2012

Hitch installed (without a hitch)

Despite the title pun, this has been one of the trickier parts of the build. There are a lot of different requirements that make up the ideal hitch, and attempting to accomplish all of these in a DIY hitch is a difficult task. We needed our bike trailer hitch to:
  • Have movement in every plane (including twisting)
  • Be easily detachable
  • Be interchangable between different bikes
  • Be very strong
  • Be able to withstand pushing from behind (when breaking with a heavy load)
  • Not interfere with the rear rack or panniers
  • Not attach to the axle (we both have quick release skewers that couldn't handle the load)
  • Not place too much strain on any one part of the bike frame
So no easy task...
The making of the hitch is one thing that no one agrees on. Every one seems to be different, even with off the shelf trailers. With homemade trailers (and also some bought ones), many opt for flexible couplings such as pneumatic hose or a heavy duty spring as this allows the required movement in all planes. However, I'm not really keen on the flexibility, especially if the trailer is pushing from behind.

I have trawled through the internet looking at every design I could find, but none really seemed perfect for the job... but fortunately I have a mechanical engineer for a father. I planted the seed of the problem in his mind and sure enough he managed to produce two amazing options for the pivot. One was a ball and socket, turned on the lathe, and a beautiful piece of work, but the angle of rotation turned out to be not quite enough.

However, his second creation is not only beautiful but functions perfectly. It is based around a door hinge, but with lathe turned and milled parts, and with a rotating nylon sleeve on the shaft to allow for the twist. This took care of the movement, but I still had to sort out the attachment...

So I have spent the last couple of days staring at the bikes, and playing around with bits of wood and metal and trying to accomplish all the above bullet points with limited tools and materials. Today I took the plunge and started drilling, cutting, bashing and screwing and unexpectedly finished with a strong functioning hitch that seems to tick all the boxes.

The attachment is sheet aluminium with a shaped piece of wood sandwiched between

A work of art!

No comments:

Post a Comment