Engineering Projects/StrandBeest/Howard Community College/fall2012/p3-550-ocm

Problem Statement

Build and design a walking strand beast. A walking mechanical machine.

Look through the different designs, formulate a way to fabricate the required parts and build it.

Team Members

Summary

In the first week of this project we worked on making crank shafts from different materials. We are making a crank shaft from steel and bolts and We are also working on a legos crank shaft. Previous teams have been unsuccessful in making a working crankshaft. After week one we have made one crankshaft that we believe will work. We are moving forward to begin designing and building the legs and body.

Poster

Story

Starting out, we had a dilemma, to use the previous groups Lego crank, or redo the work of custom building a crank, such that our design is conformed to the dimensions, or "holey numbers" configured by Theo Jansen as seen here. Currently we are making the new crank out of a different material such that it did not have the bending problem of the previous model.

Old bent crank
Marking where to drill the holes with a punch, denting the metal
Drilling the holes
We switched to using the drill press to make more precise holes

After we finished cutting out each part, we assembled the crank. We now need to set the correct angles for each leg

Cutt up and drilled tabs for the shaft
All of the parts for the crankshaft
The fully assembled crank, though the angles need to be measured precisely and secured with lock tight

After we add the finishing touches to the crank and body of the StrandBeast, we will start designing the legs.

Each of the 3 team members will independently conceptualize their own ideas for the legs of the mechanism over the weekend. Other electronic designs can be seen by clickinghttp here or here The design that is closest to the design that we are building can be seen here

Progress of work with the Lego's.

It is a propeller which we attached with the crank shaft to spin it.
These are some of the parts including Lego's bearing.
This picture shows the Lego bearing are attached with the leg of crank shaft. It will help to mobilize the legs of strand beast easily.

These bearings are very useful because we can attach the legs on it easily. we made four legs from the legos, and attached them together at 120 degrees, and made a complete crank shaft. It can be seen below in the picture. After making the central crank shaft we made a rectangular frame for the crank shaft. For the frame we took two 6.50 cm bares which had eleven holes with the diameter of 4.80 mm. we put the crank-shaft's axle in the middle hole. After that we measured the length of crank shaft which is approximately 42 cm, and we took two plastic rods with the length of 45 cm. From the ends of these plastic rods we turned them down to 4.80 mm so they can fit in the holes of 6.50 cm long bars.

This is a complete central crank shaft with four legs.
All pieces of crank shaft.

At the end we just put all the pieces together. Now it is a complete crank shaft, and it can be spun easily.

This is a complete crank shaft made of legos.

Progress of work with the wood leg. Tips and tricks are described in the image description.

A drawing of the initial design of the wooden leg, turned out to be wrong.
An idea for a joint in which the middle piece can pivot through the full 360 degrees
The corrected schematic, with part quantity and dimensions included. the joint no longer needed.
The cardboard model finished and pinned.
Cutting out the triangular bits of the incorrect cardboard leg model.
Measuring and pinning each of the joints
All of the supplies I utilized for making the cardboard leg... minus my hands, those were kind of important.
Stuck washers to some electrical tape in order to press them flat to remove any inconsistencies from drilling them out.
pressing the washers on the tape
Using the drill press to punch out the washers
A few examples of failed attempts at drilling out washers.
First, I used a hand drill for the job, but it turned out to be too irregular.
When/if using the hand drill, always keep it on setting one, setting two just shreds the aluminum.
The first two successful washers made
All of the tools for making the washers.

Continued work with the wooden parts. We decided for the sake of time not to use the aluminum can washers, punching out hundreds of them would prove time consuming.

The failed slab, side view
The front view of the failed slab, showing the variance in width
The piece of wood which I found that fits the correct dimensions, a resource I did not know I had till I went looking for it
The first mark to be drilled, turned out to be too close to the edge of the stick
A correction of the first point such that the wood would not splinter
Taking the measurement of the second hole with my vernier calipers
IMPORTANT: Stack the sticks to drill multiple at once, and wrap them in masking tape to ensure clean holes and prevent shifting of the sticks which will result in inaccurate measurements.
progress
more done
Fin!
finished piece, pivoted to one limit of movement
finished piece, pivoted to the other limit of movement

Some useful videos found here:

http://www.youtube.com/watch?v=tkV7Bym_qiU

http://www.youtube.com/watch?v=CufN43By79s&feature=em-share_video_user

A successful toy model from kickstarter found >>here<<

A funny hamster powered strandbeest: http://www.youtube.com/watch?v=A3iP0NGDDao

Decision List

List all formal decisions made with links to their documentation such as a decision tree or decision matrix.

Material List

Materials- A 3 foot X 1/8 inch by 2/3" inch welded steel bar was purchased at Lowes at a cost of $3.57 2-packages of 4-40 1 1/4 inch bolts with nuts, 10 pieces/each, each package. At a cost of $1.18 each. Various parts from a previous project.

A material needs to be determined for the legs and body of the strandbeest.

For each leg: 7 popsicle sticks

2 long screws of undetermined length ~12mm

2 screws 2mm shorter ~10mm

2 screws 2mm shorter ~8mm

14 washers? presuming washers are used

2 triangles built to specs

6 locking nuts/ 12 regular nuts

Software List

One of the team member used SAI paint tool to render some of the conceptual designs but other than that, there was no software used in this project short of a calculator.

Time

59 hours

Tutorials

All projects create new tutorials of technical details future participants are going to want to know. They are going to be separate pages that are linked to here.

Next Steps

The next steps to this project are to complete the prototype and begin working on methods to reduce the friction in the legs so that the beest can walk. Also, testing using a rivot gun to assemble the legs. The design worked on during this project, has 6 sets of legs. After assembling 1 set to the frame and crakshaft it was determined that 6 sets would have too much resistance. A design needs to be created that minimizes friction in the legs. Also another area that could be worked on is a design and method for a one wire design for the crankshaft. A method for bending a small steel wire in a precise manner to create a sturdy and stable crankshaft.