Welcome to the NMBGMR Stick-slip model page

This model was developed by Dave Love at the New Mexico Bureau of Mines and Mineral Resources. It is simply an extension of the models developed by FEMA and Michelle Hall-Wallace (University of Arizona). This model uses a small motor to pull the brick along the board. Also, instead of a spring scale attached to the brick, it employs a force sensor connected to a laptop computer to plot the force exerted on the brick against time.

List of materials

Computer
We used an old 386 laptop and DOS-based software from Vernier . A high-speed machine is not necessary.
Force sensor and serial box plotter
These, along with the software, were purchased from Vernier soft- ware company. The cost for these was about $250
Board
We used an eight foot 2x10 inch board purchased from the local lumber store. This cost about $10.
Motor
This is a small motor (cm reversible-gear) that was ordered from MSC Industrial Supply Company. The part number is 36690471. The price of the motor was $55 plus shipping.
Wooden spool
A plastic spool that thread comes on will also work just fine.
Four conductor wire
We used a trailer light wiring harness that cost about $12, but four regular wires will work as long as you keep them straight as to which is which.
Two L-shaped brackets
These came from our local hardware store (ACE Hardware) and cost about $1.25 each.
Steel cable
This is a fine steel cable like the kind used to hang pictures.
Switch
This also came from the hardware store and cost about $2.50 The switch is a single-pole double-throw switch. It is used so that we could make the motor turn in both directions (forward and reverse).
Project box
This is a small plastic box available at Radio Shack for about $2.00. This is what we used to house the switch so that no bare wires are exposed.
Three-conductor extension-cord wire
This also came from the hardware store and cost about $0.50 per ft. This is used to supply power to the switch.
Electrical plug
Also from the hardware store, it cost approximately $2.50. This was used on the end of the extension cord wire. You can use a short extension cord and simply cut the female end off to avoid wiring the plug.
Small pulley
This came from the hardware store as well and cost about $2.00. The pulley wheel is about 5/8" in diameter.
Wood block: 1x3x3 inches
This was used to mount the pulley above the board. This was just wood scrap.
Assorted springs
More items from the hardware store. These were under a dollar each. A variety of springs of different stiffness can be used to see how each effects the final plot on the computer. Small S hooks are also very useful.
Brick or wood block
I would suggest using a wood block (~ 2x4x8 inches) as it is easier to drill into and fasten things to. Bricks can be placed on top of the block for added weight.
Bracket to connect brick to force sensor.
3" T bracket about $1.50 from the hardware store. This is the reason that I would suggest using a wooden block rather than a brick. It is much easier to fasten the bracket to a wood block than to a brick.
Ring stands and metal rod
These are used at the motor end of the board so that the motor is fully suspended. The ring stand came from our lab and was not purchased for this project.
12 inch piece of 2x4" and 18 inch piece of 1x6" lumber
These are used to make a foot at the end of the board so that when the board is level it will sit higher than the motor and can be secured to the table. The wood was avialabel scrap.
Hinges
These were attached to the foot and the board. These allow the board to be inclined and still have the foot secured flat to the table.


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Instructions
  

This is what the finial project will look like

 Force meter mount:

The T bracket will have to be bent in two places. First bend it at the point where all the arms of the T come together. Then bend it about an inch and a half lower on the base part of the T. This will allow the force meter to be screwed to the wooden block and will keep it from dragging on the sandpaper. Then attach the force meter to the bracket using the screws that came with the force meter.

Ramp construction:

 

 Motor mounting:

Start by drilling a 1-inch hole through the 2 x 10 inch board about 1 foot from the top edge. Then drill a ½ inch hole about 6 inches from the larger hole (this small hole will be used to run the wire through). The motor should then be attached to the L brackets so the legs of the L face out parallel to the motor shaft (see pictures). The motor and brackets should then be screwed down to the board with the motor shaft directly over the hole. The shaft should be perpendicular to the long side of the board. Be sure to push the wires from the motor through to the other side so the switch can be wired.
  


 
 

                                               Motor mounting
 
 

Switch and pulley mounting:

The pulley should be screwed to the small wood block and then the block should be positioned over the 1-inch hole. After the block and pulley are lined up with the hole screw down the block. Then screw the switch box down next to the pulley and wire up the switch


 
 

Wiring the Switch:

All connections made should be done when the unit is unplugged or electric shock will occur!!

There will be four wires coming through the ½ inch hole from the motor and three wires from the power plug. The instructions, which came with the motor, should be followed very carefully when the switch and motor are wired.

Base hinge mounting:

First screw the 2 x 4 to the 1 x 6. The 2 x 4 should be centered on the 1 x 6 for best results. Then mount the hinges to the 2 x 4 about 2 inches from each end. Lastly measure about 6 inches from the bottom of the ramp and attach the hinges as shown.

Cable and sand paper attachment:

The last task is to drill a small hole (about 1/8 inch ) through the wooden spool and tie the cable to it. Then put the spool onto the motor shaft and run the cable through the hole and over the pulley. Lastly tie the free end of the cable to the eyehook on the force meter. If springs are being used tie a loop in the cable and use S hooks to connect the spring to the force meter and cable.

The sandpaper can be attached using Velcro or just double-sided tape.


Created By Dave Love, Chris Durand and John Van Der Kamp

NMBGMR

last modified: 19 May, 2016