2-Speed vs 1-Speed drivetrain

[Orion.DeYoe]

Originally Posted by Abhishek R

I searched some old threads but couldn't find a clear answer.

What is it about a single speed drive train that allows it to accelerate faster than a two gear one? I don't see why it does, but it seems like there should be a technical reason that I'm missing as to why it does accelerate faster.

As most people have said, it's the gear ratio (or number of motors).
However there is one other thing that makes a bigger difference on acceleration than most realize. That would be the number of rotating components (gears) in the gearbox. Typically a good 1-speed gearbox will have 1 or two stages and have 3-5 gears (2 small pinions). Most shifters have 2-3 stages with 6-9 gears (3-4 small pinions). Not only do the motors have to get the robot moving they also have to get the gears spinning. And in the early stages of the gearbox they don't have the mechanical advantage of multiple gear reductions to increase torque. This is made worse when the gears are steel not aluminum.
Now whether or not that actually creates a noticeable difference, maybe not. However it certainly is something to keep in mind when designing a gearbox.

[JesseK]

There is a lot of talk about speed in this thread.

There is no talk (yet) about designing for speed and still being able to turn well. There are extra variables in play here would make the fastest robots worthless without special consideration:

• Weight distribution (want it slightly off-center from track center-of-area)
• Wheel Base (want it wider than track length)
• Track Length
• Wheel Tread Composition
• Drive Train Frame Rigidity (want it STIFF)
• Center of Mass (want it LOW)

[Andrew Schreiber]

Originally Posted by JesseK

There is a lot of talk about speed in this thread.

There is no talk (yet) about designing for speed and still being able to turn well. There are extra variables in play here would make the fastest robots worthless without special consideration:

• Weight distribution (want it slightly off-center from track center-of-area)
• Wheel Base (want it wider than track length)
• Track Length
• Wheel Tread Composition
• Drive Train Frame Rigidity (want it STIFF)
• Center of Mass (want it LOW)

Well, I wouldn't say WORTHLESS. There are times when you don't want to turn and that might be a feature.

But it is important to remember that your gearboxes/motors are merely part of your drive system. It is comprised of several parts (incomplete list):

• Main Breaker
• Motor Breakers
• Battery
• Motors
• Gearboxes
• Wheels
• Drive Surface
• Frame
• Controller

Each of these systems plays a HUGE role in the overall effectiveness of the system. While the gearbox and wheels may be big parts of it please make sure you analyze the whole system instead of simply saying "we wanna go fast".

Ricky Bobby didn't design his car, he just drove it.