I want to be able to hear other people’s insight on something I have considered myself?
Would it be practical to go a 6 Motor v5 (600rpm) drive for a defensive oriented bot?
And if so, how effective do you think a 6 motor v5 600rpm drive would be in comparison to 2 and or 4 motor drives?
If you are solely a defensive robot, 6 motors actually sounds like a good idea. For a non-defensive oriented robot, is overkill.
However, it might be smarter to utilize 4 motors for a drive base, saving 4 motors for extra functions, that is, external mechanisms.
Good luck figuring this one out!
600rpm on 4" wheels is a very fast robot. But also a robot hard to control. (I have hard-enough times controlling a 200rpm robot, but … I am a mentor, not a driver :-)).
Do you think you’d ever had a chance to apply the full throttle in this configuration? Maybe external gearing for 300rpm would be more reasonable…
When considering your gear ratios remember that it is a common mistake to confuse top speed with actual speed.
You actual speed is how long it takes you to go from being stopped at point A to being stopped at point B. Unless you travel a long distance most of that time is spent accelerating and decelerating. When you are accelerating and decelerating you actually want a lower gear ratio, rather than a higher one.
You might find that it makes sense to gear down to speed up.
Jason
That’s right, though the V5 motors have significant power and torque.
Let’s do some back-of-envelope calculatiuons, assuming a very heavy robot (10kg → 22lb) and little losses
with about 10W for each motor.
Full speed (600/60pi4") is about 3m/s and the robot would have 45J (or Ws) of kinetic energy, delivered from the 60W of motors in about 0.75s. During this 0.75s acceleration, you’d travel slightly over 1m (1/2 * 3 * .75 = 1.125), so you’d have a pretty good chance to reach the top speed in under half the filed length to actually benefit from the higher top speed.
(the reality would be a little worse than that due to friction and lower maximum power at the lower motor speeds)
But 300rpm, or maybe even 200rpm would be more beneficial IMO, due to higher static push capability (fighting for the center platform, for example)
If you can manage the rest with 2 motors then sure. Go for it. But I don’t think I personally can manage it.
I think it would be perfectly reasonable, especially early season, to have a 6 motor DB that would guarantee the park and use the other 2 motors to handle one of the tasks, either caps or flags.
A 6 motor 600 rpm bot could get pushed by a 4 motor 200 rpm bot though…
600 rpm is a bit much and probably nearly impossible to drive.
Seriously, 600 rpm is way too fast unless you’re using really little wheels, and little wheels would make it hard to climb the platforms.
But compare 200 rpm with 6 motor to 4 motors. Assuming you have the traction to handle it, the 6-motor version could out-push and out-accelerate the 4-motor version, meaning the 6-motor version would be faster on average as well as winning pushing contests if everything else is equal.
You can use 600rpm motors, but it is best to gear them down. A reason to gear them down is to achieve soeeds that direct drive motors can not. For instance, you can do 600rpm geared 3:5 to get 360rpm or you can do 600rpm geared 3:7 to get 240rpm.
This would definitely be the main reason to use 600rpm on 6 motors. Both of these have more torque than a 4 motor 200rpm and are faster than it too. I would personally recommend the 3:7 x600rpm for a 6 motor pushbot if you were aiming for defense. I think that you would be able to outpower pretty much every feasible robot in competition with that.
Not quite. They don’t both have more torque. 6 motors run at 360 rpm with less torque than 4 motors running at 200 rpm. Yes, at 240 rpm the 6 motors would be both running with more torque and running at higher speeds. The cut-off without worrying about friction and the like would be 300 rpm.
Oh yeah sorry, I did the math wrong there, thanks for the correction