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  #16   Spotlight this post!  
Unread 31-10-2014, 07:17
Lil' Lavery Lil' Lavery is offline
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Re: Fastest FRC Robot?

Without any standardized benchmarks to test completed drivetrains, I have no problem with "geared to" comparisons. It's still the most useful shorthand to compare different drive speeds.
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Unread 31-10-2014, 10:41
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Re: Fastest FRC Robot?

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Originally Posted by Lil' Lavery View Post
Without any standardized benchmarks to test completed drivetrains, I have no problem with "geared to" comparisons. It's still the most useful shorthand to compare different drive speeds.
The problem is robots that are "Geared to [x]" will not even theoretically reach that speed. If I say I geared my robot to 25 ft/s, it will never reach close to that. In fact, if I say I geared my robot to 20 ft/s, it will actually go faster than the one "geared" to 25 ft/s. A more useful metric would be something like "it goes covers 20 feet in 2 seconds from a stop". That's something that's actually somewhat easily measurable and useful.
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Unread 31-10-2014, 12:31
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Re: Fastest FRC Robot?

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Originally Posted by Michael Hill View Post
The problem is robots that are "Geared to [x]" will not even theoretically reach that speed. If I say I geared my robot to 25 ft/s, it will never reach close to that. In fact, if I say I geared my robot to 20 ft/s, it will actually go faster than the one "geared" to 25 ft/s. A more useful metric would be something like "it goes covers 20 feet in 2 seconds from a stop". That's something that's actually somewhat easily measurable and useful.
The value of everyone using free speed to talk about gearing isn't in being able to literally use the number as is to know the robot's top speed. The problem with using adjusted speed is that everyone uses different constants and parameters to define what their adjusted free speed is. Geared free speed puts everyone on the same page, and the reader can apply their own constants to adjust that free speed if they so choose. It's just a known benchmark that's easiest for everyone to agree on in order to compare robots to each other.
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Unread 31-10-2014, 12:49
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Re: Fastest FRC Robot?

Quote:
Originally Posted by Michael Hill View Post
The problem is robots that are "Geared to [x]" will not even theoretically reach that speed. If I say I geared my robot to 25 ft/s, it will never reach close to that. In fact, if I say I geared my robot to 20 ft/s, it will actually go faster than the one "geared" to 25 ft/s. A more useful metric would be something like "it goes covers 20 feet in 2 seconds from a stop". That's something that's actually somewhat easily measurable and useful.
No one disagrees with the point you're making about robots not hitting their free speed.

The point others are making is that in absence of good data on friction, teams should report free speed as that is a more clear comparison to others.

TLDR; I'd rather have someones idealized (frictionless) numbers than their BS guess at friction.
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Unread 31-10-2014, 13:08
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Re: Fastest FRC Robot?

Fastest means something quite different on our team:

How long does it take to travel X ft from a standing stop?

Where X depends on the game as each one has a different typical "sprint" length.

I don't think we've geared for a specific top speed in a long time.

As a result, we probably have some of the "slowest" robots in FRC...
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Unread 31-10-2014, 13:46
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Re: Fastest FRC Robot?

Quote:
Originally Posted by Mr. Lim View Post
Fastest means something quite different on our team:

How long does it take to travel X ft from a standing stop?

Where X depends on the game as each one has a different typical "sprint" length.

I don't think we've geared for a specific top speed in a long time.

As a result, we probably have some of the "slowest" robots in FRC...
To be fair, if all teams reported this measurement, then all robots would be the "fastest" robots, however they would all be the "fastest" for different sprint lengths.

That being said, I would be surprised if the highest top speed of a robot was not one of the sprint bots of '08. Those little fellas looked nigh-uncontrollable.
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Unread 31-10-2014, 15:16
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Re: Fastest FRC Robot?

I think I remember playing with a team last year who told me their robot was geared for 26fps. I am also pretty sure that they only had a single speed transmission.

What I definitely remember was how long it took them to travel short distances. Frankly, I was not impressed.

Their reasoning was that, even though they knew they would never reach this speed, that the increased acceleration from this arrangement would be beneficial. Unfortunately, I didn't get a chance to explain to them why their reasoning was flawed. What I should have done is asked them why, by that reasoning, they didn't gear their robot for 100fps.
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