Before the end of the year we must build a drill powered cart including a brake and steering mechanism and a seat with a back. our budget is $25 but some materials are already included and do not need to be purchased, these include pieces of PVC, a 4' X 8' piece of plywood, assorted pieces of small wood, and screws. We are being evaluated on speed and maneuverability which will be assessed at the end of a project with an obstacle course and race.
This photo is an example of one of our options for drill attachment.
This photo gave us one idea for our steering that we may or may not use, it at least gives us more options if our current design for steering doesn't go as planned.
For more videos and photos of our design references please follow this link:
Our first step was to brainstorm ideas on a dry erase board, we spent the class drawing up parts we thought would be useful and compiling them on this board.
My partners and I then chose one or two parts to draw detailed sketches on, some of the sketches are not quite so detailed and on the chair parts are missing but I fixed my partners mistakes once we moved on to OnShape.
The image above shows our assembled OnShape pieces, this doesn't include the wheels since we will be buying wheels instead of making them. the brake and acceleration are not attached because they will be fastened on with hinges.
The OnShape files were converted to v-carve files and cut out on the shopbot, the assembled chair is shown above.
The floor of the cart was cut out as one piece and scrap wood was used as the brake and acceleration handles which are shown above on top of the cart floor but are not yet attached.
The chair was then attached to the floor of the cart, however the wheels had not yet arrived and were therefore not attached. As a result the floor of the cart was resting on the ground preventing the brake and acceleration rods from being attached.
As soon as the group started to assemble the steering column around the wheel we noticed that the hole we had cut in the wood was 4 inches too wide. we also noticed that the wood rubbing on wood created a lot of friction, it made the cart very hard to steer. To solve this problem a cloth was placed on the top of the steering column where it contacted the bottom of the cart and a piece of dry erase board was secured to the bottom of the cart with just enough room to put the column through. This solved both problems.
The original location for our handle bars was too far forward and too short for the driver, so we cut the top of the 2x4 at an angle and extended it so it reached the seat and sat at the proper height.
In this picture the cart is almost completely done, all the wheels are attached, there is means to attach the drill and a pedal to pull the trigger. the only thing missing is the drill itself and the brake rod.
Instead of attaching our drill directly to the axle rod, we decided to make a drill bit to rub against the wheel and spin it. The plastic rod had to be replaced with a metal one since it sheered off pretty quick when it was actually tested.
Here Ian is driving our cart, mostly completed. it accelerates pretty well and turns extremely well, you can't turn it as sharply as it is capable of turning though as it is top heavy with a tall driver and fell over, bending the axle rod, during the second test run.