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Unread 26-05-2013, 03:33
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Re: Shifting while not going straight

Quote:
Originally Posted by Joe G. View Post
1. Depends on how quick the shift is. For the most part though, I can't imagine it being that much of an issue with any pneumatic-based shifter.

2. I would not want to build a shifting mecanum. The idea of a mecanum drive is to avoid pushing matches rather than to win them, which negates nearly every situation in which one would use low gear. Additionally, four seperate shifters add up in weight real quick.
I guess one question I have is how long the shifts typically are. I know that with some of the teams at the championship I could watch them and tell when they were shifting as they drove, which suggests to me that they aren't super quick.

I don't intend to build a two-speed mecanum, but I'm interested in hearing how it worked because it might be more sensitive to what the dynamics of the shifters are.

I don't know if there's anyplace that does this, but it would be cool if there was some data about what output you can get about what the dynamics are. For example you might get something like:

t=0 is when a shift command is given
The original gear remains engaged until t=a
The wheel is free until t=a+b
When t=a+b the new gear is engaged

a=50ms, b=100ms

Or you might get: a=75ms with a stddev of 25, and b=100ms with a stddev of 50ms

Does anyone have data that could allow you to say something like: Supershifters take 150ms +/- 75 while the vexpro ball shifters take exactly 200ms every time. Then if you had some application where you needed things better synchronized you would know which one to pick.

I guess another good question to ask is: Is the output shaft being totally free a good model for what's happening during a shift in the sort of gearboxes that FIRST teams are using?