Quote:
Originally Posted by matt2081
Has anyone made an effective suction rig that does not involve using a CIM motor? With the limit on 5 CIM motors, we were looking at using four on the wheels and the last one on a propulsion mechanism. But if the vacuum requires a CIM motor, then we would have to re-design something.
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The power rating on shop vacs is very misleading. I have a shop vac at home that claims "5 PEAK HORSEPOWER". Is this a real number? If we assume that the machine is 100% efficient (violating several physical laws). 5 HP is equivalent to ~3750 Watts. Since power is defined as V*A, and my vac runs on 110 volts, it would require 33 amps to run the vac. In reality, these really cheap universal motors are horribly inefficient, so the actual current draw for a motor that produces 5 HP would be over 40 Amps. My vac runs fine when plugged into a 15 amp circuit.
The power number on the vac is only sales hype. The real power is closer to 1/2 HP, if that. A single CIM or two Fischer Price motors will work just fine. In 2008,
1771 powered a very large, two stage shop vac impeller with two Fischer Price motors with excellent results. In fact, we had to reduce the speed with the speed controller to get the ball off the manipulator. Also keep in mind that power requirements go
down when you choke off the flow. So, once you acquire, and are holding the ball, the impeller will speed up, generating more vacuum.
As for manipulators, the holding force is dependent on two things: pressure differential, and area of the low pressure zone. In 2008, we had a 20" circular zone, so with a delta P of 1 PSI, we had 300 lb.s of holding force. This year, the balls are smaller. The maximum size for the holding area would be about 8" in diameter. so with 1 PSI delta, you would generate about 50 lb.s of holding force.
You don't need a perfect seal, vacuum cleaners are designed to flow a lot of air, so even with big leaks, you can get decent delta P.
In conclusion, a vacuum is an excellent method of manipulation a spherical object. For more force, go with the largest circular opening you can fit within the rules, and look for a vacuum device. that generates a high static pressure differential.