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Originally Posted by Swampdude
I assume your figuring on 6" wheels?
I think our assy weighs around 40lbs
I'd like to see what you're using from John's spreadsheet that adds the loss in weight.
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Dan,
Allow me to perform an analysis for "our viewers at home".
My calculations match your analysis:
The weight will have minimal affect on the top speed. The only difference will be an increased normal force on all wheel/wheelshaft bearing surfaces, which will increase friction slightly.
This increase in parasitic loss is negligible.
Therefore, we can simply eliminate weight from our analysis.
Please refer to the attached spreadsheet.
This sheet shows the speed of the robot at 8.47fps (assuming 100% efficiency). From here, we can increase the "speed loss constant" to 60% which then shows an output speed closer to what Dan is experiencing.
This means, (as Dan stated) the CIM motors are either spinning slower than expected, or there is a large parasitic loss in the gearbox.
If we assume no parasitic loss, we need to find out reasons for a slower spinning CIM.
Some reasons:
-Voltage provided to the motor is closer to 7.2V
-Motor is wound differently, and top speed is limited.
I would almost immediately rule out a motor flaw.
Dan, please recheck your voltage. If that fails, replace the Chip motors and see if the problem persists.
Thanks,
John