Dynamic Base Prototype

Prototype Description

This prototype consists of three grooves on posts, a section of the fixed base, and a section of the axis 1 structure that rotates.  Each of the grooves is attached to the base sections using a slight press fit.  One groove uses only a slip fit so it can be removed for inspection.  Alignment of the grooves is obtained by 2mm diameter pins securely pressed into the base sections.  The prototype can be operated as shown in the movies below.  Two balls on the side plate should be placed onto the two groove section.  The other ball should be slowly lowered onto the third groove to prevent the magnet from hitting the grooves. Care must be take with the magnet to prevent damage.  The two base sections can be rotated to demonstrate the coupling's dynamic action.

Pictures and CAD Files

base_inner_disc_1.jpg
base_inner_disc_1.jpg		 Front view of inner disc prototype.  The inner disc represents the moving part of the base (axis 1)  Radius of the curve shown is approximately the same as the actual base.
base_inner_disc_2.jpg
base_inner_disc_2.jpg		 Rear view of the inner disc prototype.
base_outer_edge_1.jpg
base_outer_edge_1.jpg		 Front view of the outer ring prototype.  This ring represents the outer part of the base, which is fixed to the ground.  Radius of the curve shown matches the curve on the inner disc.
base_outer_edge_2.jpg
base_outer_edge_2.jpg		 Rear view of the outer ring prototype.
groove_1.jpg
groove_1.jpg		 Picture of a groove on a post.
groove_2.jpg
groove_2.jpg		 Picture of a groove on a post.
groove_3.jpg
groove_3.jpg		 Picture of the bottom of a groove on a post.  Note small hole for alignment pin.
groove_connection.jpg
groove_connection.jpg		 This picture shows the groove  connection interface on inner disc.  The groove post is press fit into the large hole and aligned using the protruding pin.  Specific dimensions for these items (ie radius) are not crucial and can be changed for ease of use.
ww_unit_on_base.jpg
ww_unit_on_base.jpg		 Assembled unit
  Download Solid Works 2000 or IGES CAD Files (No assemblies for IGES)

Drawings of Parts

   Detailed drawings of inner disc in Solid Works 2000 or PDF format
   Detailed drawings of outer ring in Solid Works 2000 or PDF format
   Detailed drawings of groove on post in Solid Works 2000 or PDF format
  Drawings of Wonder Wyler Unit plate available in Side Plate Prototype Section

Movies

movement_of_base.mpg
movement_of_base.mpg		 This movie shows the movement of the inner disc to the outer ring without the Wonder Wyler unit in place.  These grooves would be the only exposed item on the robot during normal usage.
unit_moving_no_magnet_1.mpg
unit_moving_no_magnet_1.mpg		 Shows assembled unit in operation without the magnet.  Maximum rotation is approximately 5 degrees in either direction.
unit_moving_no_manget_2.mpg
unit_moving_no_manget_2.mpg		 Shows assembled unit in operation without the magnet. 
unit_moving_no_magnet_fail.mpg
unit_moving_no_magnet_fail.mpg

Shows assembled unit in operation without the magnet. If the unit is rotated more than 5 degrees either way, the balls on the Wonder Wyler unit will lose contact with the grooves.  This failure will invalidate results and possibly damage the unit.  A solution is to have physical stops (either magnet or alignment pin).

complete_unit_moving_1.mpg
complete_unit_moving_1.mpg		 Shows assembled unit in operation with the magnet.  With the magnet installed, the unit can only rotate ~2 degree each way.  This limited motion can be fixed by reducing the diameter of the magnet or by removing material from the grooves.
complete_moving_unit_2.mpg
complete_moving_unit_2.mpg		 Shows assembled unit in operation with the magnet.  

 

Description of Special Parts

The special parts required for this prototype are hardened steel dowel pins, which are available from McMaster-Carr.  Two sizes were ordered: 2mm and 5mm diameters.  The 2mm diameter pins are part number 91595A203 and are US$16.71 for a package of 100 while the 5mm diameter pins are part number 91595A424 and are US$35 for a package of 100 pins.  The McMaster catalog page is here: mcmaster_pins.pdf.

The other special part required for this prototype is a 90 deg. Drill/Mill used to machine the grooves.  The mill is a 7/8 inch diameter, 90 degree high speed steel mill.  This tool is available from McMaster-Carr as part number 2957A56, at a cost of US$50.51.  A copy of the McMaster catalog page for this tool is available here: mcmaster_tool.pdf.

 

Manufacturing of Prototypes

Manufacturing of the dynamic plate prototypes  was the most complex of the prototypes.  The outer ring and inner disc required translation of the Solid Works CAD files into CNC instructions using Master CAM software.  The following steps were taken for the outer ring and inner disc separately:

  1. Material cut to size 

  2. Material fixtured in CNC milling machine and end surfaces are milled to meet dimensions and smoothed

  3. Contoured curve is milled using end mill

  4. Holes are drilled through slightly undersized

  5. Holes are reamed

  6. Part is deburred and polished

  7. Dowel pins are pressed into corresponding holes using arbor press

Manufacturing of the groove on a post was performed using a lathe using square stock and standard mill.  To increase rotation of the prototype, the groove was later trimmed in a standard mill.  The following simplified steps were taken for each groove:

  1. Fixture bar stock into lathe

  2. Turn end of stock down to 1/4 inch diameter rod

  3. Cut off part at top of groove (~16mm)

  4. Refixture part in mill

  5. Machine 2mm off of a side

  6. Refixture part in mill

  7. Machine groove into part using 90 deg. drill/mill

  8. Drill hole slightly undersized

  9. Ream hole to proper dimension

  10. Deburr part

  11. Press onto corresponding part using arbor press if needed

 

Back