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Post from O Falafel

O Falafel | Projects | Chassis | Portfolio

  • Currently, there are not any high quality falafel carts in the Cambridge area.  We set out to solve this issue by creating a very efficient and interesting design that also had amazing falafels.  Our group focused on the chassis.  We designed the whole structure and frame, planning everything out to be the most efficient, appealing cart.  One of the most interesting things about it is the shape.  It is a circle, with an inner semi-circle.  This shape allows the vendor to roll the entire cart, end over end, while the inner half-circle stays level.  That inner circle, where all of the table space is, always stays parallel to the ground.  This alluring design makes the cart very portable and attracts the attention of pedestrians, as an added benefit.

    We felt like we could make very good falafel, and we wanted to maximize the number of people who could experience it.  We decided that the best way to do this was by making a falafel cart.  We chose to make it round, in the shape of a falafel.  There are two sections: the outer circular frame and the inner semicircle.  The two outer circles are constructed using four sheets of 1/2-in plywood.  They all have an exterior diameter of 6ft, 7in.  The outermost circle (the one that everybody sees) is 6in thick, while the ones behind it are 4in.  This allows us to make a track for the wheels on the semicircle to rotate.  The inner semicircle is sandwiched in between the outer two circles.  The outer circles are held, equally spaced, by support rods that are 28in long and threaded through holes in the circles.  There are four wheels placed in optimal locations, on each side of the semicircle.  When the cart rolls, the wheels on the inside spin, allowing the countertop to stay level.  It was a challenge to design the chassis, but we steadily worked through the issues.  The biggest problem we faced was time.  We did not have enough time to build the cart in full scale, which was the original goal.  It also took a while to check over all of our work.  We had to sure make everything was perfect before sending the files out to get cut.  In the end, we sent our pieces to be cut and created a fully assembled, 1/4 scale model.

    In our first iteration, we made a 1/8 scale model out of cardboard.  This really helped us get all of our basic ideas into a physical structure.  In this version, we did not talk much beforehand about the materials that would be used to build it, so there were not many layers of cardboard.  We made two, big, 7ft diameter (full scale) circles for the outside, and planned to join them using 2x4’s.  About half of the inside of the circle was cut out to leave room for the counter space.  We made notches on the outside of the circle, so there would be a bigger surface for the wood to attach.  We also had a retractable awning that would come out of the top of the circle and shade the people below.  At this point, we did not plan on the whole structure rolling, so we did not make an inner circle.  This version just had wheels on the bottom that allowed it to move.  We also wrapped the space in between the outer circles with a thin piece of cardboard.  This iteration also had a counter that protruded in an arc on the customer’s side to give the person room to place his or her belongings while waiting.  We did not have a great storage option at this time; we only had two cabinets in the back.

    In our second iteration, we made a 1/4 scale model out of wood, and fixed many of issues.  While discussing the previous model, we decided to make the whole circle roll.  We wanted the center part of the cart to stay parallel to the ground, though, so we had to make two sections.  We also decided that the wheels on the inner semicircle would need a track.  We created 3D modeling files for all of the pieces.  We knew that we would have to send the files away to produce the parts, since we do not have the equipment to do it ourselves.  Accordingly, we created our model based on the restrictions of those outside machines.  We were only able to cut 1/2in boards, so we decided to layer multiple sheets.  We made the outer two circles identical.  We designed the circles to be three sheets of wood thick.  Each circles had a diameter of 6ft, 7in in order to safely fit through the door and elevator.  The outermost circle was 6in thick, while the inner two were 4in.  This allowed a narrow track where the wheels could spin.  We also had to fit the circles on sheets of wood that were 4ft by 8ft.  This is why we divided the circles.  The outmost circle was divided into halves, while the inner ones were in quarters.  We did this because we wanted to have as few seams as possible on the outside, but also wanted the pieces to fit on the few number of sheets.  The inner part of the circle was positioned in the middle of two outer circles so that the wheels were in each of the tracks.  The wheels fit into grooves in the inner semicircle, where they were put on an axle (which, in this case, was a nail).  This allowed the inner section to roll freely.  We also changed the supports in between the two outer circles from 2x4’s to metal rods.  We made them 28in long in order for them to go through all three layers of wood on each side and still have plenty of space.  This way, it would hold them all together, in addition to supporting the cart.  In this version, we did not make any storage space.  We just left the back open, knowing that we would come up with a storage option later.

    Our third iteration was a quarter sized model.  This model was made out of wood, paper, and 3D printed parts.  There were many subtle changes on this one compared to our last one, but the most important was the shelving.  The first way to do this was to just have containers in the bed of the truck.  This would be accessible and easy to use, but the bottom of the truck is circular so it might not work.  Using shelves with this idea would be to complicated. The shelving we ended up making holds extra tubes filled with condiments so they can easily be accessed when a certain condiment runs out.  For example, the cook would just pull out an entire tube of cucumbers and snap it into the dispenser holder when he ran out of them.  To actually hold these tubes up in the inside, we designed little boxes that were built back into the cart.  We also needed shelving to hold the cardboard sandwich packaging.  The sandwich packages are very big, so we made this as large as it would go.  Because of this, everything was really packed together in an unattractive way.  Soon we started changing this design because we didn't was the extra weight of a box per tube hole.  We just made a support system that stacked on top of each other and held everything up.  In between there layers we added little pieces that could hold the tubes in place.  We also made some changes to the dispenser rack, wheels, outer covering, inner covering, and outer circle.  With the wheels, there are two triangular pieces that rest at the top.  The bottom of those are connected to a small wood rectangle, so that they are not causing friction when the wheel is spinning.