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Unread 01-12-2018, 09:40 PM
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Gear Ratios on the ToughBox Mini (KOP): benefits and risks of changing the KOP ratio

This is a similar thread to https://www.chiefdelphi.com/forums/s...d.php?t=161392, but we thought it would be appropriate in the Strategy forum as well.

With the KOP come this gear ratio table: (these values are at 75% free speed according to the published table)
We would like to know from other's experience what the trade-off is to go from the included 10.71:1 which is rated at 10. ft/sec, down to the 5.95:1 rated at 18.0 ft/sec.
How much slower will the 5.95 accelerate off the blocks?
Is there a greater battery amp consumption?
Do the motor controllers get hotter?
Can you "brown out" the bot in a shoving match sooner?
...and any other considerations we haven't yet thought of?
Thank you for your assistance.

We are asking, because we have neither the time nor money to order the interchangeable gears AND try them out sufficiently to be confident that the above and other issues not mentioned might show up.
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Unread 01-13-2018, 09:41 PM
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Re: Gear Ratios on the ToughBox Mini (KOP): benefits and risks of changing the KOP ra

Check out the JVN calculator for your specific case.

In general, if you have a light robot, you can get away with gearing faster and still have decent acceleration and acceptable current draw. Heavier robots with the same gearing and wheel size will accelerate more slowly at the same current draw, or draw more current with the same acceleration.

Remember to consider how long you think your average "runs" will be. Last year, gearbots had to cycle gears from one end of the field to the other and had about a 50' run. For STRONGHOLD, the runs were much shorter, and there were ramps and obstacles to overcome. This year, there are short runs and long runs, depending on where you anticipate sourcing and scoring cubes; how to best gear is greatly dependent on how long you think your typical runs will be (short runs should gear low for acceleration, long runs gear a bit higher for top speed)

Edit: OK, what is acceptable current draw? Of course, this depends on what risks you are willing to take. 3946 does our calculations based on 50A current draw on each CIM to minimize the possibility of breaker trip or motor smoking during a match. Battery considerations also suggest a 200-250A max current draw across all the systems in operation at any given time. YMMV
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Last edited by GeeTwo : 01-13-2018 at 09:46 PM.
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Unread 01-13-2018, 10:04 PM
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Re: Gear Ratios on the ToughBox Mini (KOP): benefits and risks of changing the KOP ra

Last year we ran the 5.95 gearing with 4" wheels on a 118LB robot. It got off the line extremely fast but the breakers had a tendency to break when in a pushing match. The robot could hold it's ground, but not actually push any other robot back. The speed and handling was great (keep in mind 4" wheels not 6"), but if you want to ever push then don't use them. We didn't notice any battery drain problems even when using four full CIMs on drive and two full CIMs for a cimber winch. Just don't try to push anything.
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Unread 01-14-2018, 09:28 AM
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Re: Gear Ratios on the ToughBox Mini (KOP): benefits and risks of changing the KOP ra

Quote:
Originally Posted by KingOfDemise View Post
Last year we ran the 5.95 gearing with 4" wheels on a 118LB robot. It got off the line extremely fast but the breakers had a tendency to break when in a pushing match. The robot could hold it's ground, but not actually push any other robot back. The speed and handling was great (keep in mind 4" wheels not 6"), but if you want to ever push then don't use them. We didn't notice any battery drain problems even when using four full CIMs on drive and two full CIMs for a cimber winch. Just don't try to push anything.
5402 ran the same setup last year, with black HiGrip wheels, and it worked great once we got through some teething problems that weren't caused by these choices.

That said, I find pushing gets into diminishing returns quite quickly in recent years. Knocking a robot askew, occupying protected zones, and disrupting their flow takes a lot less current.
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Unread 01-14-2018, 09:42 AM
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Re: Gear Ratios on the ToughBox Mini (KOP): benefits and risks of changing the KOP ra

If you're not sure, the stock ratio is a really good mix of good acceleration and top speed for a divided field game like this. I would stick with it.
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