So my team just did fairly poorly at a competition and now we are discussing a redesign of our bot.
Our current bot is a 30x30 4 motor drivebase with a 60:36 speed ratio with green cartridges and 4in omni wheels, with 4 bar front lift and 2 bar back lift
Me and my designer have been discussing back and forth about the benefits and drawbacks of using a speed ratio.
In the recent comp, they said that we were getting pushed around a lot and so we should go back to 1:1 ratio so that we can drive around and be able to defend better and also steal mogos better.
I still want a speed ratio for faster manuverability so we can get around the field quicker and grab mogos quicker. I don’t think that our bot actually got shoved around a lot, I think it’s more my unexperienced driving being bad at offence and defence so that it lead to a position where we were easily pushed aside because of our omni wheels. I don’t think that we were pushed back when driving head to head against another robot, so it’s not the torque that’s the issue, rather my driving, since I’m still fairly new. Also I’d like a speed ratio so driver skills is easier for me since we get around the field quicker (im aiming for a 280 driver skills just elevating all 7 mogos and not elevating our bot, because im not sure if it’s possible with our drivebase)
Has anyone else experimented with a speed ratio and have input on what would be better for this competition
If your problem is not getting up the platoform it seems ur running 333rpm on 4in omnis which could be the issue, i would suggest gearing it down a little more to give you more torque and since your relatively new to driving ( as it seems ) i would suggest coding the robot to be a little slower, when you get confident with that speed go back to 100% speed gl!
speed is pretty important in this game, but you might be going a little too high with 5:3 as your ratio. Try out 3:7 on 600 rpm cartridges or 7:5 on 200 rpm.
I’d strongly recommend against limiting the speed of your robot in code. This means your drive can’t using it’s full power, and that will cause your robot to be weaker than it could be. If you find it difficult to drive a fast robot, gearing it slower is much better than coding a limit on the speed because then you at least get more torque out of it.
it depends on the robot (weight, center of mass, what wheels you are using, etc.) it is best to test it with your robot to see
according to the graphs on the robot’s brain, the torque is at its max at about 50% power, so making it slower in the code is a viable solution, especially because you can make the robot reach the neutral goal faster and still be slow for driver control.
Another thing I would recommend doing is switching to 3.25in wheels. 333rpm is very high for 4 in wheels and will definitely not win pushing battles. If you were to switch to 3.25in wheels, you would get 27% more torque and 19% less speed and it would take much less time than switching around all your gears in your drive.
Also, I’m seeing a lot of reversed gear ratios. Speed ratios are always <1 and torque ratios are always >1. 333 rpm would be 3:5 and not 5:3 since the output is greater than the input. Most of the ratios listed here are <200 or >600 rpm which are pretty extreme.
While I don’t think this is 100% true. I do think that giving the motors 12 volts will get the most out of the motor. We can achieve the most “torque” and the highest speeds at the “same time”. If we start to push something the amount of torque the motor has to exert goes up(its takes more Nm or Lb-Ft) to move that object and the robot. This decreases the speed all while allowing the motors to function at the highest level.
As you go slower you are swapping torque for speed, but when the robot doesn’t need the torque the motor should use the power to speed.
most force meaning most power, not most torque. You might get very slightly more torque at lower speeds, but not 50% more torque at 50% less speed, meaning an overall loss in power (torque*speed)
After reading your experiment I think you have the right idea but missed the mark by a little bit. The max power output is very likely at 66% speed but you can only get there by putting a load on the motor, not just by spinning it at a lower speed in the code.
i think there is a flaw in that test because you geared up the ratio to be 200 rpm in both trials, so it would have the same output (this could be wrong, this is just from my limited knowledge on engineering and physics), as well as what @2775Josh said with putting it under load. maybe if you try with a full robot (it wont be the most accurate test, but it will eliminate the problems).
gearing up was the point, in order to test if there were any benefits to running motors at lower speeds but gearing up externally.
The idea was, that if this did turn out to work, you could get a stronger drive by running motors slower but with a higher external gearing. Obviously though it doesn’t work this way.
i thought the point was to see if it gives more output torque at lower power, not to see if when running at the same RPM if it outputs the same. both are useful in this case, but lower power without gearing up was more of what my post was talking about.