Quadricycle Fun

UPDATE: Check out our replacement vehicle, the DateTrike!  For all the alternative bike builders out there,  if you get inspired and build something similar, please send me a note and a picture!

There is nothing like a trip to Burning Man to open your mind to the endless possibilities of human-powered transportation. The main mode of transport in Black Rock City is the bicycle, but at Burning Man the imagination rules, and all manner of craft are to be found.  After a couple of years of using first just bicycles, then bicycles fashioned with canopies, it became time to invent a more appropriate vehicle for the playa.  The result was our quadricycle, a surprisingly robust construction made from a pair of girl’s used mountain bikes that were fashioned into a truly sociable transportation vehicle.  The quad, as it became known, saw us through three Burning Man trips as well as countless travels on the bike paths around Eugene.  It is not a craft made for speed, but it excels as a leisure vehicle, when enjoying the ride with the person next to you is more important than getting there quickly.  The quad provides a place to sit in the shade when you want to stop and enjoy the view.  There is even room for an extra passenger on the bench seat.

Just in case someone else gets inspired to make something similar, I will mention a few of the details.  The construction was fairly simple, inexpensive, and required no welding.  Rather I fashioned most of the assembly out of scraps of wood and used bolts and clamps as fasteners.  For the bikes, we had one girl’s mountain bike that had been through a couple of kids and was pretty solid.  A garage sale landed us a real “cheapy” second bike for  a few dollars.  The bikes were only approximately the same size, so each attachment point provided a unique challenge.  If you can find two bike that are the same your life will be easier.

Rigidity comes when the joining beams form triangles.  The attachment between the rear axles and across the frame under the seat provides the best opportunity to add cross rigidity to the bike pair.  I fashioned a couple of metal straps to attach a wooded triangle frame near the axles to the lugs on the bike frames that are there for attaching bike racks.  Try to make this attachment as skookum as possible because it will take a fair amount of stress as the bikes try to rack.

The main cross coupling beams were made with scraps of wood.  I fashioned clamps for the frame attachments using a few long bolts and other pieces of wood.  Because the bikes were  different sizes, one clamp ended up on the top and one under the bike’s frame.  Do whatever works!   The distance between the two bikes was set at 26″ on centers. This allowed just enough clearance between the handle bars that they did not interfere with one another without the craft becoming too wide.

The front coupling I just made from a 2×4 and attached it to the front head stock with a pair of U-bolts on each bike. The U-bolts joints need to be as solid as possible to counteract the forces that want to make the bikes splay in or out at the front wheel.

The last connection between the bikes is at the seats.   I clamped a couple of 2×4’s together and drilled a hole where the two boards came together just the right size so that I could clamp it tightly to the seat post.

Then I screwed a couple of boards across the two post mounts to make up the bench seat.  I used various forms of padding to build up a cushion for the seat, but despite my best efforts it wasn’t the most comfortable for pedaling long distances.  This is mostly because on an upright bicycle you need clearance for your thighs.  Ellen can attest to a certain amount of chafing.

The trickiest part of the design was the steering, but if you know the trick then it’s easy too. When you turn, the front wheel on the inside of the turn needs to be turned tighter than the outside wheel because the inside turning radius is smaller than on the outside. If the two wheels steer equally you will quickly discover that there is a lot of scuffing and fighting of the wheels on a turn, especially on pavement. The key is steering compensation, and it is really pretty simple. All you have to do is line up the tie-rod pivot, and the steering pivot with the center of the back axle.

My steering tie rod was just another piece of wood, in this case a piece of closet rod.  To make the tie rod brackets, I just fashioned clamps from wood and bolts that attach to the handlebar.  A pretty robust clamp can be made by clamping together a couple of pieces of wood and drilling a hole the same size as the handlebar along the joint – similar to the seat post clamp.  I reinforced the clamp with a couple of metal straps.  For acceptable performance, all you have to do is make sure the distance between the tie rod pivot and the steering head stock pivot is the same for both sides, and line up those two pivots so they point to the center of the bike midway between the rear wheels.  (Note the arrow in the photo.)  For the tie rod pivots, I just used bolts with extra washers and a crimp on the nut so it wouldn’t come loose.

That’s about it.  Hop on and have fun!  The baskets, canopy and lights were a must for Burning Man.   The decorations are where your creativity can run wild.

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