Trailer Design Iterations

It's nice to now think only about bike trailers and not pooper scoopers, but anyway...

So, after totally being called on just emulating (a nice way to say, knocked off) the Burley Travoy, I'm back to the drawing board on the frame design. I'm still aiming for the same set of parameters for the trailer when I initially set out on this project,

• walkable and bikeable
• lightweight
• stable w/ load (riding or walking)
• customizable bag options

So initial ideas all followed the Travoy model of flat bed, foldable, support structure around the bed. I played with ideas for adding a third wheel for walking as I perceived the Travoy to be a bit tippy when standing upright (especially when loaded) as it stood on two wheels and a small leg. My goal was when walking to have at least 3 wheels on the ground for stability.

My methodology for joining the metal tubes (plastic housings basically) also was derived from the Travoy. In my trailers new form, I'll mostly likely use a similar joint as this seems to be the best and most elegant method. Also, this drawing came out well.

In sketching for the new frame I decided to work off of a single main tube as the backbone of the trailer with the main support wheels moving in towards the frame for riding and out to create a tripod with a castored wheel for walking. Walking stability was a high point with this iteration.

A guide slid up and down the main tube, keeping the wheels lined up.

The sliding guide however took up quite a bit of space on the tube that could other wise be used for mounting a frame for cargo. Thus only the top and bottom of the tube could be used for mounting, with a aimed cargo weight of 60 lbs, this would create quite a bit of stress and would need large amounts of reinforcement at the junctures adding complexity and weight.

To combat the sliding ring, a grooved guide was added to the side of the main tube, keeping the wheel struts in alignment and clearing room for more cargo supports. The raising and lowering of the legs would be accomplished by a lever on the top of the main tube connecting via cables and pulleys inside the tube to the wheel struts. Pull the cable up and it would pull the wheels in to the frame for riding. An issue with this was locking the wheels in place and the extra complexity of the pulleys and guide wheels. The more moving parts mean the more to go wrong. I realized I was moving away from Dieter Rams 10 principles, and was making the trailer more and more complex. The more complex, the greater the possibly of a mechanical failure.

So, in this vein of simplicity with stability, I'm working on elimination of as many moving parts as possible. Goodbye cables and pulleys.

This is the latest scanned sketch I have (I know, its super rough), moving the two main support wheels to be stationary (to eliminate as much stress on a joint as possible) and moving the castored wheel to the fold down third wheel. This is the direction I'm currently moving the trailer in, presently in Rhino, with the aim to be making a physical model out of pvc pipe starting the 8th.

Thanks for reading.