Author Archive

Lifting Arm Calculations

Review the PDF linked below for calculations for the lifting arm.  If the PTO is driven on the low gear side (14 to 64), then an additional reduction of approximately 8:1 will be required to drive the arm.  This is easily achievable in two stages.  If the PTO is driven from the high gear side (30 to 48), then an additional reduction of about 23:1 is required – still achievable in two stages, but requires rather large and small sprockets. With 4 CIMS, the lift can occur in about 1/2 second.  With only 2 CIMS, it could still work if geared properly (twice the reduction), but it would take twice as long.

The calculations below are presented in a fashion that should be understandable by the astute high-school student who has completed a Physics class.


Vacuum Suction Testing

Since the ball may only roll 3 inches into the robot, we wished to study the plausibility of a vacuum holding system.  In the 2008 Overdrive game, Team 1771 successfully used a mini shop-vac impeller driven by two Fisher Price motors, to posses and lift the 8lb track ball.  For our test today, a Shop-Vac brand “Hang-Up Mini” model was used.  This is a 120VAC 6.2A model.  As shown in the picture below, the impeller is approximately 4 inches diameter, one half inch thick, and very light weight.

After reassembling the vacuum, a plastic funnel of approximately 4 inches diameter was affixed to the hose.  A small basketball and a rubber exercise ball were used for the test (no soccer balls available at testing location).  No seal was used around the lip of the funnel.  The vacuum held the small basketball very well, and the large exercise ball moderately well.  While seams in the balls did not greatly affect the holding power, we speculate a larger funnel with a lip seal/gasket would improve the results greatly.

A video of the test is shown below:

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We have not yet determined exactly how a mechanism like this might integrate with a kicker.

We also observed the suction power directly from the impeller housing:

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The testing revealed the vacuum produced greater suction and holding power than expected, and could potentially be a successful  soccer-ball holding device.  Further tests would have to be done to power the impeller with KOP motors (such as two Fisher Price motors, as 1771 did in 2008).

Winch Gearing & Performance Calculations

See the linked PDF below, for some important calculations regarding gearing and performance of the winch.  The run-through of the basic calculations should be understandable by the astute high-school student.

Please let Dave know if there are any errors in the calculations, and it will be corrected accordingly.