6 Cim Drive-Train

[Massako]

Would a 6 sim drive train with an overall gear ratio of 19.64:1 and 8 inch wheels be an ok setup for this years game. esimateing the total robot weight at 120 just to be safe. one issue we though of was the current and if it would exceed the limit and if that is the case what would be an ok substitute. instead would it be a better idea to run with the same overall gear ratio and use a 4 cim drive train instead?

Thanks

[Procolsaurus]

The max robot weight is really 120lb for the robot + 14lb for the battery + 11lb (can legally be up to 20lb) for the bumpers.

[Massako]

Originally Posted by Procolsaurus

The max robot weight is really 120lb for the robot + 14lb for the battery + 11lb (can legally be up to 20lb) for the bumpers.

I know and i expect it to be higher i was just wondering if that would be a usable solution.

[Lil' Lavery]

What is your wheelbase and track width?
What other motors will you be running simultaneously with your drive system?
Are you going to be using a compressor?
Are you going to monitor your voltage in any fashion?
Are you going to dampen your acceleration with your software?

[Breadbocks]

You can run the exact numbers in the JVN spreadsheet, but when I was looking at a 10:1 ratio on a 6 CIM drive train pushing match I couldn't break 80A of current. Unless you get into a pushing match and try to shoot the ball and climb all at the same time you probably won't break 120A.

The bigger concern should be battery life, which you'll be best suited to figure that part out yourself. 6 CIM is definitely a possibility, teams have done it before, but what your specific design winds up being will decide whether your battery can handle it.

[Massako]

Originally Posted by Lil' Lavery

What is your wheelbase and track width?
What other motors will you be running simultaneously with your drive system?
Are you going to be using a compressor?
Are you going to monitor your voltage in any fashion?
Are you going to dampen your acceleration with your software?

we will msot likely be useing 2 or 3 bag motors and a mini cim. no compressor and we will have the max speed reduced in software. voltage monitoring will be done just in drive station.

[Massako]

Originally Posted by Breadbocks

You can run the exact numbers in the JVN spreadsheet, but when I was looking at a 10:1 ratio on a 6 CIM drive train pushing match I couldn't break 80A of current. Unless you get into a pushing match and try to shoot the ball and climb all at the same time you probably won't break 120A.

The bigger concern should be battery life, which you'll be best suited to figure that part out yourself. 6 CIM is definitely a possibility, teams have done it before, but what your specific design winds up being will decide whether your battery can handle it.

i put all those numbers in a swell and i got 38.35 pushing amps per motor.

[cmwilson13]

WithThe battery's legal for first use I personally see no scenario where 6 cim drive does anything but hurt your performance. The internal resistance of the battery is too high, the voltage drop causes too many issues. 2 speed transmissions do more then enough. The greater benefit is a good automatic shifting algorithm.

[Massako]

Originally Posted by cmwilson13

WithThe battery's legal for first use I personally see no scenario where 6 cim drive does anything but hurt your performance. The internal resistance of the battery is too high, the voltage drop causes too many issues. 2 speed transmissions do more then enough. The greater benefit is a good automatic shifting algorithm.

so then would a 4 cim drive train with the same overal gear ratio be a better solution

[cmwilson13]

yes. i might speed it up a little bit, but with the obstacles on the field the extra power can be beneficial

[asid61]

Originally Posted by cmwilson13

WithThe battery's legal for first use I personally see no scenario where 6 cim drive does anything but hurt your performance. The internal resistance of the battery is too high, the voltage drop causes too many issues. 2 speed transmissions do more then enough. The greater benefit is a good automatic shifting algorithm.

Those would be issues regardless of the number of CIMs, if I'm not mistaken. I always took away that a 6-cim could push harder and accelerate faster. They risk brownouts for the extra current draw.
If you gear your drivetrain down that much, there is little or no purpose I can see to having a 6-cim over a 4-cim.

[IronicDeadBird]

Originally Posted by asid61

Those would be issues regardless of the number of CIMs, if I'm not mistaken. I always took away that a 6-cim could push harder and accelerate faster. They risk brownouts for the extra current draw.
If you gear your drivetrain down that much, there is little or no purpose I can see to having a 6-cim over a 4-cim.

We had a 6 cim drive base and a fly wheel one year it was always interesting seeing the lights being slightly dimmer when the flywheel was fully rev'd and we were traveling at full speed.