Actobotics hole locations

[Ollie]

When I saw the Actobotics channel first time, the hole patterns seemed to be quite irregular. Now I have learned the geometry and would like the other teams to take benefit of the Actobotics regular hole patterns.

The foundation is in two concentric circles with diameters 0.77" and 1.5". Most holes are located on the circles at the diagonals. Four additional holes are on the smaller circle at the vertical and horizontal axes.

The holes in the diagonals are at the corners of two squares. The smaller square side is 0.544472" long (= 0.77*sqrt(2)/2) and the larger square side is 1.06066" (= 1.5*sqrt(2)/2) long.

To calculate the locations of the holes, we need to know that the channel width is 1.5" and the patterns are repeated on every 0.75". These numbers are combined with the half side lengths (0.272236 and 0.53033).



The 0.5” holes in the center of the squares are repeated on every 0.75”.

On the 1.5” ring there are 0.14” holes in the 4 diagonals at rows R1 & R7 in columns C1 & C11.

R1 and C1 at 0.75 – 0.53033 = 0.21967
R7 and C11 at 0.75 + 0.53033 = 1.28033

Additional 1.5” ring holes from neighbor patterns in columns C5 and C7.

C5 at 0.53033, C7 at 1.5 – 0.53033 = 0.96967

On the 0.77” ring there are 0.14” holes in the 4 diagonals and in the 2 vertical center-lines at rows R2, R3, R5, and R6 in columns C4, C6, & C8

R2 at 0.75 – 0.77/2 = 0.365
R3 and C4 at 0.75 – 0.272236 = 0.477764
R5 and C8 at 0.75 + 0.272236 = 1.022236
R6 at 0.75 + 0.77/2 = 1.135
C6 at 0.75

Additional 0.77” ring holes from neighbor
patterns in columns C2 and C10

C2 at 0.272236, C10 at 1.5-0.272236 = 1.227764

The holes shared on the 0.77” horizontal line are not matching like all the other holes between the patterns.
For that reason the holes have a larger 0.16” diameter.

R4 at 0.75, C3 at 0.75/2 = 0.375, C9 at 1.5 – 0.75/2 = 1.125

[Ollie]

A simple screw plate can be made from 1/2" wide 3/16" thick aluminum bar with the following steps:
- cut off 3/32" from the left bottom side at 45 degree
- cut off 3/32" from the right bottom side at 45 degree
- cut the bar to 2" length
- drill three 7/64 holes at 0.75" distance
- tap 6-32 threads in the 3 holes

The cuttings can be done with a table saw. For smoother surfaces, you can put some oil in the blade. Here are the numbers for the hole locations.



The laser settings in typical drill are not accurate enough for these holes. I did use a wiggler to reset the origin in the XY-table. The wiggler uses 0.1" offset. That is compatible with the XY-table movements; 0.1" per screw turn.

To make it easy to turn the XY-table screws, the drawing shows both the absolute values and the screw settings.

For example 0.25" requires 2 full turns plus setting the screw into position 50. In theory, the table allows 1000 unique postions per turn for 0.0001" accuracy. The actual accuracy is 0.0005" and that requires that all postions are approached only in positive direction.

For teams that have CNC machines available, all these numbers can be simply enetered into the system.

This 2 inch screw plate can be used to attach Actobotics C-channel to 80/20 series 10 beam so that the edges are completly aligned.



The long diagonal allows 45 degree connection.



All kind of offsets are available.

[Ollie]

The series 10 beam can be attached inside the C-channel.

[Ollie]

The 1.5 inch screw plate is made in smae way as the 2 in screw plate.

The first hole is common for all distances. The distances are:
- short distance of 0.5445" for the smaller square
- medium distance of 0.77" for the small circle
- long distance of 1.607" for the larger square



The long distance can be used for two intermediate angles at 30.36 degree and 59.91 degree for distance of 1.057865.



The four main options for long distance screw holes are the following



Here are some of the options with short and medium distance holes

[Ollie]

The large block is made from 2 inch long aluminum bar that is 1 inch wide and 0.5 inch thick.

The essential part of the large block is that it has two large holes (1/4") on the largest face for attachment to 8020 bar.

On the long face it has three 6-32 holes for the two vertexes of the large 1.06" squares and one vertex on the 0.77" circle.

On the short face there are two pairs of 6-32 holes for a large square vertex and 0.77" circle.



The large block can be attached to an end of 8020 bar using two 1/4" screws.



An Actobotics C-channel is attached to this construction keeping all sufraces aligned.



This can be combined with a 2 inch screw plate for added strength.

[Ollie]

The 3 holes in the large block long face provide several connection options for Actobotics C-channels and 8020 bars.

The basic connection is between parallel channel and bar keeping the surfaces aligned.



The orthogonal connection can be done with large connection area



Or, with small connection area.



This can be combined with a second block for added strength.