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Unread 27-02-2016, 18:16
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Joe Johnson Joe Johnson is offline
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Re: Help Needed With Vex Ball Shifter

Quote:
Originally Posted by MysterE View Post
Ok -

So - I'm going to post the info I have. I'll be honest - I'm not sure how to calculate the gear ratios.


Ball Shifter is 3 cim Ball Shifter using 2 Cims with a 2.65 spread. The pinion gear attached is 12 tooth and the wheels have a 30 tooth gear on them.

The Single Speed is a WCP with 2 motors with a 44:30 ratio attached to the same gears on the wheels.

Wheels are 12 inch pneumatic taped to reduce friction.

As far as we can tell the air actuator is working correctly - we are using another to launch our catapult and that is working properly.

Let me know what else you need.

Thx,
Daniel
Vexpro 3CIM Shifter with 2.65 spread:
CIM Shaft=Motor to ShifterShaft1:
12:50
ShifterShaft1 to ShifterShaft2 = Output:
50:34 High Gear
34:50 Low Gear
ShifterShaft2 to Wheel
12:30
Overall Ratio (High Gear):
(50X34X30)
------------- = 7.1:1
(12X50X12)
Overall Ratio (Low Gear):
(50X54X30)
------------- = 18.8:1
(12X30X12)
WCP with 30:44:
CIM Shaft=Motor to ShifterShaft1:
12:50
ShifterShaft1 to ShifterShaft2 = Output:
30:44
ShifterShaft2 to Wheel
12:30
Overall Ratio:
(50X44X30)
------------- = 15.3:1
(12X30X12)
Plugging these numbers into JVN's spreadsheet (again, I say, this spreadsheet should be required to buy a gearbox from AndyMark or Vex) with a 12" wheel you are going to have (adjusted top speed) of

Shifter Low Gear: 12fps
Shifter High Gear: 31.8fps
Single Speed: 14.8fps

That 31.8fps is MONSTER. WAY TOO FAST. Seriously. That is almost certainly your problem. I suppose that the clicking you heard was the CIRCUIT BREAKERS not the shifters. You should probably get ratios more like 19:1 in high gear and 50:1 in low gear with those 12" wheels.

Dr. Joe J.
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Last edited by Joe Johnson : 27-02-2016 at 18:24.