Quote:
Originally Posted by JesseK
It's more about their overall design rather than the WCD-sliding blocks or their custom gears (which I suspect *could* be COTS gears if they chose).
3.5" wheels -- they can't go smaller because of the large gear on the shifting shaft
They can't make the first stage reduction greater because of CIM spacing (2.55 or 2.6" between CIMs) and the internal shaft spacing of the large gear on the first stage. The AndyMark super shifter runs into this same issue.
So they're 'stuck' with 18 ft/s, in a sense. All in the name of removing the 3rd gearing stage from the transmission to increase efficiency.
Then
- For any sort of decent acceleration, they need incredible efficiency on the overall drive train since it's only 4 CIMs (unless there were other motors hiding under the CIMs...)
- Weighing only 100 lbs + battery, bumper, lightweight minibot helps acceleration too
So their strategy, at 18 ft/s for an 'open field' where defense rules were constricting and effective "anti-flow" strategies forbidden, was actually a great idea in hindsight. 7 ft/s would help them get through the average defensive robot in a pinch, though the tradeoff was lack of torque -- which did get them into trouble once.
I'll admit, I didn't count gear teeth, and a bit of this is reverse-engineered estimation; so I don't know the true numbers for their gearing itself. Yet if you design a 2-reduction 2-stage gearbox (I tried the week after champs) you'll see that it's not quite as easy as slapping COTS parts together. So most of us wouldn't be able to do it quite like they do.
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Not to pick on you, but there are quite a few flawed assumptions here.
I can only speak for us, but I would assume 254 has the same reasoning.
We don't gear for top speed, but for a "sprint distance".
Low gear is well past traction limited. 254 was likely pushed in fm1 due to being underweight. There was no lack of torque. 99% of robots would not have been able to do that to them, 469 was really an edge case with their drivetrain.
Using the same geometry, you can easily gear to get a top speed in a smaller range (in 2010 we were 13.5 fps with LARGER wheels...). We're not stuck with 18fps.